release: 0.6.5

Local-only changes since 0.6.4 (no wire change; PROTO planes unchanged),
so this is a PATCH bump per VERSIONING.md.

Ships the low-latency screen-share live-edge fix (4bfc184), which landed
three hours after the v0.6.4 tag and was therefore never released.

Also adds the missing CHANGELOG entry for the participant "Advanced audio"
foldout (26d6600), which shipped without one.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.agents/AGENTS.md

@@ -0,0 +1,21 @@
+# PeerSpeak Codebase Layout and Architecture Rules
+
+When working in the PeerSpeak repository, adhere to the following architectural boundaries and layout:
+
+## Code Layout
+- `src/main.rs`: The application entry point (initializes Tokio and the Iced GUI).
+- `src/app/`: The UI layer (Iced). Handles themes, views (Home, Room, Settings), and visual state. Must communicate with the core via message passing (`UiEvent`/`CoreCommand`), not direct function calls.
+- `src/core/`: The central orchestrator. 
+  - `mod.rs`: Manages the session lifecycle, ties together network and UI, and manages the async mixer tasks.
+  - `jitter.rs`: Houses the adaptive playout delay JitterBuffer and Packet Loss Concealment (PLC) logic.
+- `src/network/`: The "Dual-Plane" transport layer.
+  - `gossip.rs` (Control Plane): Built on `iroh-gossip`. Manages room rosters, verified membership, presence, and chat via cryptographically signed envelopes.
+  - `iroh_impl.rs` (Data Plane): Manages raw QUIC endpoints and peer connections. Forwards UDP voice datagrams directly to peers for minimum latency.
+- `src/audio/`: Hardware audio backends.
+  - Interfaces heavily with `cpal_impl.rs` (Windows/WASAPI) and `pipewire_impl.rs` (Linux). 
+  - **CRITICAL RULE**: The RT audio callbacks are strictly lock-free. They communicate with the async core exclusively via Single-Producer Single-Consumer (SPSC) ring buffers (`HeapRb`). Never allocate memory, log to stdout, or lock Mutexes on the RT threads.
+- `src/codec/`: Audio compression abstractions, standardizing on Opus at 48kHz mono (`opus_impl.rs`).
+
+## General Directives
+- **Security**: Audio admission is strictly derived from the verified gossip roster (S8). Never trust raw UDP sender IDs without validating against gossip.
+- **Latency**: Preserve the deterministic dialer vs acceptor logic in the QUIC layer to prevent connection loops.

.cargo/audit.toml

@@ -0,0 +1,11 @@
+# cargo-audit configuration. Keep the ignore list in sync with deny.toml,
+# which carries the full justification for each entry.
+[advisories]
+ignore = [
+    # quick-xml DoS advisories: build-time only, reached solely via the
+    # wayland-scanner proc-macro parsing trusted vendored protocol XML.
+    # Fix (0.41.0) is semver-incompatible with wayland-scanner's `^0.39`;
+    # drop once wayland-scanner bumps. See deny.toml.
+    "RUSTSEC-2026-0194",
+    "RUSTSEC-2026-0195",
+]

.gitea/workflows/cargo-deny.yml

@@ -1,34 +0,0 @@
-name: cargo-deny
-
-# Enforce the supply-chain policy in deny.toml (advisories / bans / licenses /
-# sources) on every push to main and every PR. Runs on a *locked* tree so the
-# pinned, vetted versions in Cargo.lock are exactly what get audited — see the
-# deny.toml header and VERSIONING.md. A new poisoned release of a dependency
-# cannot reach CI until Cargo.lock is deliberately updated.
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-
-jobs:
-  cargo-deny:
-    runs-on: ubuntu-latest
-    # rust:1 provides the cargo toolchain that cargo-deny shells out to for
-    # `cargo metadata`. Adjust the runner label if your act_runner uses a
-    # different one.
-    container: rust:1
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Install cargo-deny (pinned prebuilt)
-        run: |
-          set -euo pipefail
-          version=0.19.9
-          curl -sSfL \
-            "https://github.com/EmbarkStudios/cargo-deny/releases/download/${version}/cargo-deny-${version}-x86_64-unknown-linux-musl.tar.gz" \
-            | tar -xz -C /usr/local/bin --strip-components=1 --wildcards '*/cargo-deny'
-          cargo-deny --version
-
-      - name: cargo deny check
-        run: cargo deny --locked check

.gitea/workflows/ci.yml

@@ -0,0 +1,44 @@
+name: CI
+
+# Runs on the self-hosted host-mode runner on the desktop (label `arch`). The
+# gitbutter VPS only queues the job; all compile/test compute happens locally.
+on:
+  push:
+    branches: [main]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  check:
+    runs-on: arch
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Toolchain versions
+        run: |
+          rustc --version
+          cargo --version
+          cargo clippy --version
+          cargo deny --version
+          cargo audit --version
+
+      - name: Format check
+        run: cargo fmt --all -- --check
+
+      - name: Clippy (all targets, warnings as errors)
+        run: cargo clippy --all-targets -- -D warnings
+
+      - name: Tests
+        run: cargo test --all-targets
+
+      - name: Doc tests
+        run: cargo test --doc
+
+      - name: cargo-deny (advisories, bans, licenses, sources)
+        # --locked so the pinned, vetted versions in Cargo.lock are exactly
+        # what get audited (the lockfile-as-review-checkpoint model).
+        run: cargo deny --locked check
+
+      - name: cargo-audit
+        run: cargo audit

.gitea/workflows/windows-build.yml

@@ -7,11 +7,20 @@ name: windows-build
 # alias) so a Unix-only assumption can't sneak back in and break Windows.
 #
 # RUNNER REQUIREMENT: this needs a Windows act_runner registered with the
-# `windows-latest` label (the Linux `cargo-deny` job's container approach does
-# NOT apply here — Windows jobs run on the host, not a Linux container). If your
-# runner advertises a different label, change `runs-on` below. Until a Windows
-# runner exists this workflow is simply skipped/queued, not a failure of the
-# Linux CI.
+# `windows-latest` label (a Linux-container approach does NOT apply here —
+# Windows jobs run on the host, not a Linux container). If your runner
+# advertises a different label, change `runs-on` below.
+#
+# MANUAL-ONLY until that runner exists: with push/PR triggers enabled, every
+# push queued a run no runner could claim and Gitea auto-cancelled it ~24h
+# later, littering the Actions page with cancelled runs. Restore the push/PR
+# triggers when a Windows runner is registered:
+#
+#   on:
+#     push:
+#       branches: [main, "windows-port-**"]
+#     pull_request:
+#     workflow_dispatch:
 #
 # BUILD-HOST REQUIREMENTS (validated by the opus spike, see
 # peerspeak-windows-opus-spike.md):
@@ -23,12 +32,7 @@ name: windows-build
 # must provide both.
 
 on:
-  push:
-    # `main` plus the in-progress port branches, so the Windows path is exercised
-    # before merge rather than only after.
-    branches: [main, "windows-port-**"]
-  pull_request:
-  # Allow manual runs from the Gitea Actions UI.
+  # Manual runs from the Gitea Actions UI only — see the header comment.
   workflow_dispatch:
 
 permissions:

.gitignore

@@ -6,3 +6,8 @@
 /packaging/peerspeak/
 /packaging/*.pkg.tar.*
 /packaging/*.log
+
+# Windows installer build artifacts (the staged exe + compiled setup.exe);
+# the .iss script and .ico are the tracked sources.
+/packaging/windows/peerspeak.exe
+/packaging/windows/output/

CHANGELOG.md

@@ -0,0 +1,142 @@
+# Changelog
+
+All notable changes to PeerSpeak are documented here.
+
+## [Unreleased]
+
+## [0.6.5] — 2026-07-19
+
+### Added
+- **Chat message sounds.** Successful outgoing messages and admitted incoming
+  messages now have distinct notification chimes, each with its own enable
+  toggle and optional custom WAV path in Notifications settings.
+- **Contact presence sounds.** The home-screen contacts list now announces a
+  contact becoming online or offline. Initial online contacts are announced;
+  initial offline results stay silent. Both events have independent toggles and
+  optional custom WAV paths.
+- **Notification sound browser.** Every notification event now has a native
+  Browse button for choosing a custom WAV instead of typing its path manually.
+
+### Changed
+- **Tidier per-participant audio controls.** The equalizer bands and noise gate
+  for each participant now live behind an **"Advanced audio"** foldout instead
+  of being expanded all the time, so a call with several people no longer fills
+  the panel with sliders. The controls themselves are unchanged.
+
+### Fixed
+- **Low-latency screen sharing stays near the live edge again.** mpv's
+  timestamp pacing could let stale frames accumulate across the reliable
+  PixelPass transport until a share was 7–10 seconds behind. Low-latency mode
+  now presents decoded frames immediately; Smooth mode retains timestamp pacing
+  when keeping shared-video audio and video synchronized matters more.
+
+## [0.6.4] — 2026-07-18
+
+### Added
+- **Chat now tells you when a message didn't send.** A message that couldn't go
+  out — because you weren't in a room, or the broadcast failed — is marked
+  **"⚠ Not sent"** with a **Retry** button, instead of sitting in the transcript
+  looking delivered. A successful send shows nothing (PeerSpeak has no
+  delivery/read receipts, so anything else would be a false promise).
+- **Fast typing no longer loses messages.** When you fire off a quick burst,
+  messages past the first few are held as **"queued…"** and sent a moment apart,
+  matching the rate other people's clients accept. Previously a fast burst could
+  look sent on your end while some messages silently never reached the room.
+
+### Changed
+- **Tidier music playlist drawer.** The slide-out playlist no longer repeats the
+  play/skip controls already on the player bar, and the track list now grows to
+  fill the drawer instead of being boxed into a short scroll area, so you can see
+  more of your playlist at once.
+- **Safer chat under the hood.** A round of chat hardening tightened how incoming
+  messages, display names, links, and file/image attachments are validated and
+  bounded, so a malformed or hostile message from a peer can't spoof a name,
+  replay, flood, or run the app out of memory. No change to how normal chat looks
+  or works.
+
+### Fixed
+- **Burst packet loss no longer splices the wrong audio into the gap.** Loss
+  concealment used Opus in-band FEC even when the next packet to arrive wasn't
+  the one immediately after the gap, so losing several packets in a row could
+  briefly play a later frame's audio in the wrong position. FEC now only
+  reconstructs a gap from its immediate successor packet; larger gaps are
+  concealed normally.
+- **A failed network restart no longer silently kills the app.** Changing the
+  network mode (or regenerating your identity) rebuilds the connection stack;
+  if that rebuild failed — rare, but possible when the local socket can't
+  bind — PeerSpeak kept its window open but silently stopped responding to
+  every command. It now falls back to your previous network settings and says
+  so, and only gives up (with a clear error telling you to restart) if even
+  the fallback fails.
+
+[0.6.4]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.6.4
+
+## [0.6.3] — 2026-07-06
+
+### Added
+- **In-app screen-sharing controls.** A new **Screen sharing** section in Settings, plus a per-call **quality picker** on the Share control, put the whole share pipeline under your control without editing config files. Encode side: quality preset, bitrate, framerate, maximum resolution, maximum viewers, a force-software-encode switch, and an escape hatch for extra pixelpass arguments. Playback side: choose **mpv or VLC**, toggle **hardware decoding**, pick a buffering posture (low-latency vs. smooth), set the demuxer cache, and pass extra mpv arguments. Everything is stored locally in your config and defaults are unchanged, so existing setups keep working as-is.
+
+### Fixed
+- **Shared video no longer freezes on the first frame while audio keeps playing.** Hardware decoding now defaults **off**; forcing `--hwdec=auto` stalled some viewers' hardware decoder on frame 1. You can re-enable hardware decoding from the new Screen sharing settings if your machine handles it well.
+- **The per-call quality picker is now honored.** The inline quality dropdown next to the Share button was being reset to the saved default before a share started, so every share silently used the default quality regardless of what you picked.
+- **VLC now respects your playback settings.** VLC hardware-decodes by default, so a VLC viewer previously ignored the hardware-decode toggle (and could hit the same frame-1 freeze) and the buffering posture. VLC viewers now map both settings onto VLC's own options.
+
+[0.6.3]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.6.3
+
+## [0.6.2] — 2026-07-03
+
+### Fixed
+- **Friends list now reflects status changes without a restart.** A presence probe that fails now actively marks the friend **offline**, so a friend who goes offline, leaves a room, or turns invisible no longer lingers showing a stale "online" / "in a room" status until PeerSpeak is relaunched. Previously only successful probes updated the list, so it could ratchet a friend's status up but never down. The auto-refresh interval was also shortened from 60s to **15s** so the list tracks changes more closely.
+
+### Added
+- **Manual "⟳ Rescan" button** on the Friends panel that refreshes everyone's presence immediately, instead of waiting for the next auto-refresh.
+
+### Licensing
+- **PeerSpeak is now released under the MIT License** (previously an unlicensed private build). Added a `LICENSE` file and a `THIRD_PARTY_LICENSES` file enumerating the full dependency manifest plus the canonical text of every referenced license, with notices for the statically bundled Opus codec and the embedded fonts (Iced-Icons, Cantarell/OFL-1.1). Both files ship in the Arch and Debian packages.
+
+[0.6.2]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.6.2
+
+## [0.6.0] — 2026-06-28
+
+### Added
+- **Shared music listening (W22).** A new **Playlist** panel lets you build a personal queue of local audio files and play them on a dedicated music player — Browse to add tracks, play/pause, previous/next, seek, per-track reorder, remove, and a local volume slider, all persisted across sessions. `.pls` and `.m3u` playlists can be imported (remote and non-audio entries are skipped).
+- **Tune in to a friend's music.** Flip **"Let others tune in"** and peers see your current track under the **Public** tab; one click on **Listen** streams it to them. Playback is **timeline-synced** — play, pause, skip, and seek mirror across everyone with no drift — and the next track is **prefetched for gapless** transitions. Each listener gets an independent **per-source volume**, so music sits under voice at whatever level they like; voice chat stays fully audible throughout.
+- **Standalone Playlist card in the 3-Column layout.** The playlist now lives in its own card stacked under the chat, with a draggable divider to resize it and its own scrollbar when space is tight. The other layouts keep the playlist in the Controls panel.
+
+### Security
+- Shared-music metadata is treated as untrusted: the broadcast track name is sanitized and its size is cap-checked at gossip ingest, fetched bytes are confirmed to be audio before decoding, and only a small descriptor ever rides gossip — track bytes move point-to-point over the existing files plane, one fetch in flight at a time.
+
+### Changed
+- **Wire protocol bump (gossip v5).** Shared listening adds presence fields, so **0.6.0 peers cannot share a swarm with 0.5.x peers** — everyone in a room must update together.
+
+[0.6.0]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.6.0
+
+## [0.5.1] — 2026-06-27
+
+### Added
+- **Volume control for inline chat audio clips.** A master volume slider plus a **Universal volume** toggle now sit in the Chat panel header, and every audio attachment gets its own 🔊 slider on its play row. With Universal volume on (the default), one level applies to all clips and persists across sessions; turn it off to give each clip its own independent level.
+
+## [0.5.0] — 2026-06-27
+
+### Added
+- **Right-click context menu** (Cut / Copy / Paste / Select All) on every text-entry field. (A9)
+- **Selectable, copyable text** for values that used to be read-only: your full node ID and the room ticket can now be click-selected and copied, and **chat messages are drag-selectable** (highlight + Ctrl+C / Ctrl+A) while clickable links keep working. (W21 Phase 1 + 2)
+- **Clock-skew warning**: when a peer can't be seen because the two systems' clocks differ by more than the replay-protection window, PeerSpeak now shows a "your clocks are out of sync" banner instead of failing silently. (A25)
+- **Per-application audio capture for screen-share**, removing the call-audio loopback echo when sharing a window, plus surfacing of pixelpass startup errors. (A23)
+
+### Changed / Fixed
+- **Critical commands are now delivered reliably under load** — muting, releasing push-to-talk, and leaving a room can no longer be silently dropped while a slider is being dragged (prevents a hot-mic state mismatch). (A15)
+- Screen-share now passes `--strict-audio` and surfaces app-audio drop warnings; the source picker state machine and pactl handling were hardened. (A23)
+- Per-peer volume control path verified and covered by regression tests. (A24)
+
+### Security
+- Hardened against insider resource-exhaustion: bounded + author-keyed chat attachment cache, capped recovery-identity state, and other Tier-C caps (F-01 / F-02 / F-03 / F-12).
+
+### Packaging
+- Added Debian/Ubuntu `.deb` packaging (cargo-deb metadata); the official `.deb` is now built on **Debian 12 (bookworm)** for wide compatibility.
+- Arch `PKGBUILD` clones over anonymous HTTPS.
+
+[0.5.1]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.5.1
+[0.5.0]: https://gitbutter.xyz/mollusk/peerspeak/releases/tag/v0.5.0
+
+Earlier releases: see git tags `v0.4.0`, `v0.3.0`, `v0.2.0`.

Cargo.lock

@@ -117,6 +117,18 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "alsa"
+version = "0.10.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c88dbbce13b232b26250e1e2e6ac18b6a891a646b8148285036ebce260ac5c3"
+dependencies = [
+ "alsa-sys",
+ "bitflags 2.11.1",
+ "cfg-if",
+ "libc",
+]
+
 [[package]]
 name = "alsa-sys"
 version = "0.3.1"
@@ -188,9 +200,9 @@ checksum = "940b3a0ca603d1eade50a4846a2afffd5ef57a9feac2c0e2ec2e14f9ead76000"
 
 [[package]]
 name = "anyhow"
-version = "1.0.102"
+version = "1.0.103"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f202df86484c868dbad7eaa557ef785d5c66295e41b460ef922eca0723b842c"
+checksum = "2a4385e2e34eb35d6b3efe798b9eb88096925d87726c0798709bf56d9ed84af3"
 
 [[package]]
 name = "arbitrary"
@@ -1041,6 +1053,20 @@ dependencies = [
  "coreaudio-sys",
 ]
 
+[[package]]
+name = "coreaudio-rs"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1aae284fbaf7d27aa0e292f7677dfbe26503b0d555026f702940805a630eac17"
+dependencies = [
+ "bitflags 1.3.2",
+ "libc",
+ "objc2-audio-toolbox",
+ "objc2-core-audio",
+ "objc2-core-audio-types",
+ "objc2-core-foundation",
+]
+
 [[package]]
 name = "coreaudio-sys"
 version = "0.2.18"
@@ -1080,14 +1106,14 @@ version = "0.15.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "873dab07c8f743075e57f524c583985fbaf745602acbe916a01539364369a779"
 dependencies = [
- "alsa",
+ "alsa 0.9.1",
  "core-foundation-sys",
- "coreaudio-rs",
+ "coreaudio-rs 0.11.3",
  "dasp_sample",
  "jni 0.21.1",
  "js-sys",
  "libc",
- "mach2",
+ "mach2 0.4.3",
  "ndk 0.8.0",
  "ndk-context",
  "oboe",
@@ -1097,6 +1123,36 @@ dependencies = [
  "windows 0.54.0",
 ]
 
+[[package]]
+name = "cpal"
+version = "0.17.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5b1f9c7312f19fc2fa12fd7acaf38de54e8320ba10d1a02dcbe21038def51ccb"
+dependencies = [
+ "alsa 0.10.0",
+ "coreaudio-rs 0.13.0",
+ "dasp_sample",
+ "jni 0.21.1",
+ "js-sys",
+ "libc",
+ "mach2 0.5.0",
+ "ndk 0.9.0",
+ "ndk-context",
+ "num-derive",
+ "num-traits",
+ "objc2 0.6.4",
+ "objc2-audio-toolbox",
+ "objc2-avf-audio",
+ "objc2-core-audio",
+ "objc2-core-audio-types",
+ "objc2-core-foundation",
+ "objc2-foundation 0.3.2",
+ "wasm-bindgen",
+ "wasm-bindgen-futures",
+ "web-sys",
+ "windows 0.62.2",
+]
+
 [[package]]
 name = "cpufeatures"
 version = "0.2.17"
@@ -1151,9 +1207,9 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-epoch"
-version = "0.9.18"
+version = "0.9.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5b82ac4a3c2ca9c3460964f020e1402edd5753411d7737aa39c3714ad1b5420e"
+checksum = "2d6914041f254d6e9176c01941b21115dcfb7089e55135a35411081bd106ef3f"
 dependencies = [
  "crossbeam-utils",
 ]
@@ -1564,6 +1620,15 @@ version = "0.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "edd0f118536f44f5ccd48bcb8b111bdc3de888b58c74639dfb034a357d0f206d"
 
+[[package]]
+name = "encoding_rs"
+version = "0.8.35"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75030f3c4f45dafd7586dd6780965a8c7e8e285a5ecb86713e63a79c5b2766f3"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "endi"
 version = "1.1.1"
@@ -1699,6 +1764,12 @@ dependencies = [
  "zune-inflate",
 ]
 
+[[package]]
+name = "extended"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "af9673d8203fcb076b19dfd17e38b3d4ae9f44959416ea532ce72415a6020365"
+
 [[package]]
 name = "fastrand"
 version = "2.4.1"
@@ -2557,6 +2628,7 @@ dependencies = [
  "iced_core",
  "log",
  "rustc-hash 2.1.2",
+ "tokio",
  "wasm-bindgen-futures",
  "wasmtimer",
 ]
@@ -3565,6 +3637,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "mach2"
+version = "0.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a1b95cd5421ec55b445b5ae102f5ea0e768de1f82bd3001e11f426c269c3aea"
+dependencies = [
+ "libc",
+]
+
 [[package]]
 name = "malloc_buf"
 version = "0.0.6"
@@ -3601,9 +3682,9 @@ checksum = "6b947ae49db0d222b1dbc6b113ce7248a3fc3a6ca21b696717bfc000ba4484d8"
 
 [[package]]
 name = "memmap2"
-version = "0.9.10"
+version = "0.9.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "714098028fe011992e1c3962653c96b2d578c4b4bce9036e15ff220319b1e0e3"
+checksum = "d1219ed1b7f229ee7104d281dd01d6802fe28bb6e95d292942c4daacdeb798c0"
 dependencies = [
  "libc",
 ]
@@ -4252,6 +4333,31 @@ dependencies = [
  "objc2-quartz-core 0.3.2",
 ]
 
+[[package]]
+name = "objc2-audio-toolbox"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6948501a91121d6399b79abaa33a8aa4ea7857fe019f341b8c23ad6e81b79b08"
+dependencies = [
+ "bitflags 2.11.1",
+ "libc",
+ "objc2 0.6.4",
+ "objc2-core-audio",
+ "objc2-core-audio-types",
+ "objc2-core-foundation",
+ "objc2-foundation 0.3.2",
+]
+
+[[package]]
+name = "objc2-avf-audio"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "13a380031deed8e99db00065c45937da434ca987c034e13b87e4441f9e4090be"
+dependencies = [
+ "objc2 0.6.4",
+ "objc2-foundation 0.3.2",
+]
+
 [[package]]
 name = "objc2-cloud-kit"
 version = "0.2.2"
@@ -4287,6 +4393,29 @@ dependencies = [
  "objc2-foundation 0.2.2",
 ]
 
+[[package]]
+name = "objc2-core-audio"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1eebcea8b0dbff5f7c8504f3107c68fc061a3eb44932051c8cf8a68d969c3b2"
+dependencies = [
+ "dispatch2",
+ "objc2 0.6.4",
+ "objc2-core-audio-types",
+ "objc2-core-foundation",
+ "objc2-foundation 0.3.2",
+]
+
+[[package]]
+name = "objc2-core-audio-types"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5a89f2ec274a0cf4a32642b2991e8b351a404d290da87bb6a9a9d8632490bd1c"
+dependencies = [
+ "bitflags 2.11.1",
+ "objc2 0.6.4",
+]
+
 [[package]]
 name = "objc2-core-data"
 version = "0.2.2"
@@ -4742,13 +4871,13 @@ checksum = "35fb2e5f958ec131621fdd531e9fc186ed768cbe395337403ae56c17a74c68ec"
 
 [[package]]
 name = "peerspeak"
-version = "0.2.0"
+version = "0.6.5"
 dependencies = [
  "anyhow",
  "async-trait",
  "base64",
  "bytes",
- "cpal",
+ "cpal 0.15.3",
  "dirs",
  "iced",
  "image",
@@ -4759,11 +4888,14 @@ dependencies = [
  "rand 0.10.1",
  "rfd",
  "ringbuf",
+ "rodio",
  "serde",
  "serde_json",
  "thiserror 2.0.18",
  "tokio",
  "tokio-stream",
+ "url",
+ "windows-sys 0.61.2",
 ]
 
 [[package]]
@@ -5198,6 +5330,16 @@ version = "0.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "63b8176103e19a2643978565ca18b50549f6101881c443590420e4dc998a3c69"
 
+[[package]]
+name = "rand_distr"
+version = "0.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4d431c2703ccf129de4d45253c03f49ebb22b97d6ad79ee3ecfc7e3f4862c1d8"
+dependencies = [
+ "num-traits",
+ "rand 0.10.1",
+]
+
 [[package]]
 name = "rand_pcg"
 version = "0.10.2"
@@ -5487,12 +5629,34 @@ dependencies = [
  "portable-atomic-util",
 ]
 
+[[package]]
+name = "rodio"
+version = "0.22.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0a536bb79db59098ef71a4dd4246c02eb87b316deceb1b68e0cde7167ec01eb"
+dependencies = [
+ "cpal 0.17.1",
+ "dasp_sample",
+ "num-rational",
+ "rand 0.10.1",
+ "rand_distr",
+ "rtrb",
+ "symphonia",
+ "thiserror 2.0.18",
+]
+
 [[package]]
 name = "roxmltree"
 version = "0.20.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6c20b6793b5c2fa6553b250154b78d6d0db37e72700ae35fad9387a46f487c97"
 
+[[package]]
+name = "rtrb"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ade083ccbb4bf536df69d1f6432cc23deb7acccff86b183f3923a6fd56a1153"
+
 [[package]]
 name = "rustc-hash"
 version = "1.1.0"
@@ -6156,6 +6320,153 @@ dependencies = [
  "zeno",
 ]
 
+[[package]]
+name = "symphonia"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5773a4c030a19d9bfaa090f49746ff35c75dfddfa700df7a5939d5e076a57039"
+dependencies = [
+ "lazy_static",
+ "symphonia-bundle-flac",
+ "symphonia-bundle-mp3",
+ "symphonia-codec-aac",
+ "symphonia-codec-pcm",
+ "symphonia-codec-vorbis",
+ "symphonia-core",
+ "symphonia-format-isomp4",
+ "symphonia-format-ogg",
+ "symphonia-format-riff",
+ "symphonia-metadata",
+]
+
+[[package]]
+name = "symphonia-bundle-flac"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c91565e180aea25d9b80a910c546802526ffd0072d0b8974e3ebe59b686c9976"
+dependencies = [
+ "log",
+ "symphonia-core",
+ "symphonia-metadata",
+ "symphonia-utils-xiph",
+]
+
+[[package]]
+name = "symphonia-bundle-mp3"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4872dd6bb56bf5eac799e3e957aa1981086c3e613b27e0ac23b176054f7c57ed"
+dependencies = [
+ "lazy_static",
+ "log",
+ "symphonia-core",
+ "symphonia-metadata",
+]
+
+[[package]]
+name = "symphonia-codec-aac"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4c263845aa86881416849c1729a54c7f55164f8b96111dba59de46849e73a790"
+dependencies = [
+ "lazy_static",
+ "log",
+ "symphonia-core",
+]
+
+[[package]]
+name = "symphonia-codec-pcm"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4e89d716c01541ad3ebe7c91ce4c8d38a7cf266a3f7b2f090b108fb0cb031d95"
+dependencies = [
+ "log",
+ "symphonia-core",
+]
+
+[[package]]
+name = "symphonia-codec-vorbis"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f025837c309cd69ffef572750b4a2257b59552c5399a5e49707cc5b1b85d1c73"
+dependencies = [
+ "log",
+ "symphonia-core",
+ "symphonia-utils-xiph",
+]
+
+[[package]]
+name = "symphonia-core"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea00cc4f79b7f6bb7ff87eddc065a1066f3a43fe1875979056672c9ef948c2af"
+dependencies = [
+ "arrayvec",
+ "bitflags 1.3.2",
+ "bytemuck",
+ "lazy_static",
+ "log",
+]
+
+[[package]]
+name = "symphonia-format-isomp4"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "243739585d11f81daf8dac8d9f3d18cc7898f6c09a259675fc364b382c30e0a5"
+dependencies = [
+ "encoding_rs",
+ "log",
+ "symphonia-core",
+ "symphonia-metadata",
+ "symphonia-utils-xiph",
+]
+
+[[package]]
+name = "symphonia-format-ogg"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2b4955c67c1ed3aa8ae8428d04ca8397fbef6a19b2b051e73b5da8b1435639cb"
+dependencies = [
+ "log",
+ "symphonia-core",
+ "symphonia-metadata",
+ "symphonia-utils-xiph",
+]
+
+[[package]]
+name = "symphonia-format-riff"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2d7c3df0e7d94efb68401d81906eae73c02b40d5ec1a141962c592d0f11a96f"
+dependencies = [
+ "extended",
+ "log",
+ "symphonia-core",
+ "symphonia-metadata",
+]
+
+[[package]]
+name = "symphonia-metadata"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "36306ff42b9ffe6e5afc99d49e121e0bd62fe79b9db7b9681d48e29fa19e6b16"
+dependencies = [
+ "encoding_rs",
+ "lazy_static",
+ "log",
+ "symphonia-core",
+]
+
+[[package]]
+name = "symphonia-utils-xiph"
+version = "0.5.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ee27c85ab799a338446b68eec77abf42e1a6f1bb490656e121c6e27bfbab9f16"
+dependencies = [
+ "symphonia-core",
+ "symphonia-metadata",
+]
+
 [[package]]
 name = "syn"
 version = "2.0.117"

Cargo.toml

@@ -1,11 +1,42 @@
 [package]
 name = "peerspeak"
-version = "0.2.0"
+version = "0.6.5"
 edition = "2024"
-# Application crate, not a crates.io library — refuse `cargo publish` and let
-# cargo-deny's [licenses.private] skip the missing-license check.
+description = "Decentralized peer-to-peer voice chat (Rust/iroh/PipeWire/Opus/iced)"
+license = "MIT"
+# Application crate, not published to crates.io — refuse `cargo publish`.
 publish = false
 
+# Debian/Ubuntu packaging (cargo-deb). Mirrors packaging/PKGBUILD: only the main
+# `peerspeak` binary ships (not test_net/specview), plus the desktop entry and the
+# hicolor icon set. Runtime shared-lib deps (libpipewire, libopus, libc, …) are
+# resolved by dpkg-shlibdeps via `depends = "$auto"`. Build inside a Debian/Ubuntu
+# distrobox so the binary links that distro's glibc, then `cargo deb --no-build`.
+[package.metadata.deb]
+maintainer = "mollusk <jitty+lc1iz0dc@protonmail.com>"
+copyright = "2026, mollusk. MIT License."
+section = "net"
+priority = "optional"
+depends = "$auto"
+# pixelpass = in-room screen sharing; mpv = the screen-share viewer (vlc fallback).
+recommends = "pixelpass, mpv"
+extended-description = "Decentralized peer-to-peer voice chat over iroh (QUIC) with PipeWire audio, the Opus codec, and an iced GUI. Full-mesh, no central server."
+assets = [
+    ["target/release/peerspeak", "usr/bin/", "755"],
+    ["packaging/peerspeak.desktop", "usr/share/applications/", "644"],
+    ["assets/icons/peerspeak.svg", "usr/share/icons/hicolor/scalable/apps/peerspeak.svg", "644"],
+    ["assets/icons/peerspeak-16.png", "usr/share/icons/hicolor/16x16/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-24.png", "usr/share/icons/hicolor/24x24/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-32.png", "usr/share/icons/hicolor/32x32/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-48.png", "usr/share/icons/hicolor/48x48/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-64.png", "usr/share/icons/hicolor/64x64/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-128.png", "usr/share/icons/hicolor/128x128/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-256.png", "usr/share/icons/hicolor/256x256/apps/peerspeak.png", "644"],
+    ["assets/icons/peerspeak-512.png", "usr/share/icons/hicolor/512x512/apps/peerspeak.png", "644"],
+    ["LICENSE", "usr/share/doc/peerspeak/", "644"],
+    ["THIRD_PARTY_LICENSES", "usr/share/doc/peerspeak/", "644"],
+]
+
 [lib]
 name = "peerspeak"
 path = "src/lib.rs"
@@ -28,7 +59,7 @@ async-trait = "0.1.89"
 base64 = "0.22.1"
 bytes = "1.11.1"
 dirs = "6.0.0"
-iced = { version = "0.14.0", features = ["canvas", "image"] }
+iced = { version = "0.14.0", features = ["advanced", "canvas", "image", "tokio"] }
 # W4 custom avatars: decode/resize an arbitrary user image (png/jpeg only to keep
 # the codec surface small). The matching native file picker (`rfd`) is platform-
 # gated below — its backend differs per OS (xdg-portal on Linux, Win32 on Windows).
@@ -38,18 +69,23 @@ iroh-gossip = "0.99.0"
 opus = "0.3.1"
 rand = "0.10.1"
 ringbuf = "0.5.0"
+rodio = "0.22.2"
 serde = { version = "1.0.228", features = ["derive"] }
 serde_json = "1.0.150"
 thiserror = "2.0.18"
 tokio = { version = "1.52.3", features = ["full"] }
 tokio-stream = "0.1.18"
+# Chat link policy: parse + validate clickable URL candidates (scheme/host/
+# userinfo checks in `sanitize::is_safe_web_url`). Already in the tree
+# transitively via iroh — this only promotes it to a direct dependency.
+url = "2.5"
 
 # --- Platform-specific dependencies -----------------------------------------
 # Audio and the native file-picker backends differ per OS. Everything else in the
 # app talks to the `AudioBackend` trait and the `PlatformAudioBackend` alias (see
 # `src/audio/mod.rs`), so platform selection is confined to these few lines.
 
-[target.'cfg(unix)'.dependencies]
+[target.'cfg(target_os = "linux")'.dependencies]
 # Linux audio backend. v0_3_49 exposes `Buffer::requested()` (the graph's per-cycle
 # quantum), used by the playback RT callback to fill exactly what the device asks
 # for instead of a hard-coded 1024-frame quantum (crackle on non-1024 hardware).
@@ -64,3 +100,12 @@ rfd = { version = "0.17", default-features = false }
 # Windows audio backend: cpal drives WASAPI for capture/playback behind the
 # AudioBackend trait (src/audio/cpal_impl.rs). The Linux counterpart is pipewire.
 cpal = "0.15"
+# Win32 FFI for game detection (no new crate: windows-sys is already pulled in
+# transitively by cpal/rfd). Registry reads the Steam RunningAppID + install path;
+# Toolhelp enumerates running processes for the non-Steam process-scan fallback.
+windows-sys = { version = "0.61", features = [
+    "Win32_Foundation",
+    "Win32_System_Registry",
+    "Win32_System_Diagnostics_ToolHelp",
+    "Win32_System_Threading",
+] }

LICENSE

@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2026 mollusk
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -0,0 +1,115 @@
+<h1>
+  <img src="assets/icons/peerspeak.svg" width="48" align="left" alt="PeerSpeak icon">
+  PeerSpeak
+</h1>
+
+Decentralized, peer-to-peer voice chat — full-mesh, NAT-traversing, with **no central server**. Built in Rust on [iroh](https://github.com/n0-computer/iroh) (QUIC), PipeWire audio, the Opus codec, and an [iced](https://github.com/iced-rs/iced) GUI.
+
+Create a room, share the join ticket, and talk. Everyone connects directly to everyone else; relays are only used to punch through NATs when a direct path isn't available.
+
+---
+
+## Screenshots
+
+| Launch screen | In a room |
+|---|---|
+| ![Launch screen](docs/screenshots/launch.jpg) | ![In a room](docs/screenshots/in-room.jpg) |
+
+| Settings |
+|---|
+| ![Settings](docs/screenshots/settings.jpg) |
+
+---
+
+## Features
+
+**Rooms & sessions**
+- Create a room → shareable join ticket; join by pasting a ticket.
+- Full-mesh multi-peer rooms with live presence.
+- Recent-rooms list to hop back into a room someone's still in.
+- Remembered nickname and in-call duration timer.
+
+**Audio**
+- PipeWire capture/playback, selectable input and output devices, per-app gain.
+- Opus codec (48 kHz mono, 20 ms frames) with an adaptive jitter buffer + packet-loss concealment.
+- Noise gate with a draggable threshold on a live mic meter (test your mic off-call too).
+- Mix-bus soft limiter and opt-in echo cancellation (PipeWire WebRTC AEC + noise suppression).
+
+**Voice controls**
+- Self-mute, deafen, and rebindable push-to-talk.
+- Per-peer volume, local mute, and speaking indicators.
+
+**Text chat**
+- In-room text chat over the gossip plane, with clickable links and inline image/audio attachments.
+- Drag-selectable, copyable messages; right-click context menu on all text fields.
+
+**Shared music listening**
+- Build a personal playlist of local audio files with a full transport (play/pause, seek, reorder).
+- Let others tune in: peers stream your current track, timeline-synced and gapless, sitting under voice at their own volume.
+
+**Screen share** (via [pixelpass](https://gitbutter.xyz/mollusk/pixelpass))
+- Share your screen; peers click 👁 Watch to open the stream in mpv (vlc fallback).
+- Live badges on sharing peers; per-app audio capture.
+
+**Recording & notifications**
+- Local call recording (mic + incoming mix → WAV in `~/peerspeak-recordings/`).
+- Desktop notifications and event chimes with per-event custom sound overrides.
+
+**UI & networking**
+- Selectable room layouts (3-Column, Bottom Dock, Drawer) with draggable, persisted dividers.
+- 10 built-in themes (Catppuccin, Dracula, Nord, Tokyo Night, Gruvbox, Solarized…), all WCAG-AA checked.
+- Network mode picker (relay-no-discovery default, full n0, or direct-only); retained-address reconnect.
+- Config, window size/position, and all preferences persisted to `~/.config/peerspeak/`.
+
+See [`docs/FEATURES.md`](docs/FEATURES.md) for the full inventory and field-test status, and [`docs/ARCHITECTURE.md`](docs/ARCHITECTURE.md) for internals.
+
+## Roadmap
+
+- **Contacts & invites** — friends list with invite-notification one-click join (design in [`docs/contacts-plan.md`](docs/contacts-plan.md)).
+- **Spatial audio & per-peer EQ.**
+- **Soundboard** — play short clips into the call mix.
+- **Room persistence / invite links** beyond the raw ticket.
+- **Windows support** — cross-compiles and launches under Wine today; needs a real WASAPI audio pass (see [`docs/WINDOWS.md`](docs/WINDOWS.md)).
+
+## Building
+
+PeerSpeak builds with a stable Rust toolchain (edition 2024). Install the system dependencies below, then:
+
+```sh
+cargo build --release
+./target/release/peerspeak
+```
+
+### System dependencies
+
+**Arch Linux**
+
+```sh
+sudo pacman -S --needed rust pipewire opus pkgconf git
+```
+
+**Debian / Ubuntu**
+
+```sh
+sudo apt install build-essential pkg-config clang libclang-dev \
+  libpipewire-0.3-dev libopus-dev libasound2-dev libxcb1-dev
+```
+
+Plus a Rust toolchain via [rustup](https://rustup.rs/). `clang`/`libclang` are needed for the PipeWire bindings (bindgen).
+
+At runtime you need a running **PipeWire** server. Screen sharing additionally requires `pixelpass` on your `PATH`, and `mpv` (or `vlc`) to watch a peer's share.
+
+### Packaging
+
+- **Arch:** `cd packaging && makepkg -si` (uses [`packaging/PKGBUILD`](packaging/PKGBUILD)).
+- **Debian/Ubuntu:** `.deb` is built with [`cargo-deb`](https://github.com/kornelski/cargo-deb) from the `[package.metadata.deb]` block in `Cargo.toml`. Build inside a Debian/Ubuntu environment so the binary links that distro's glibc.
+- **Windows:** see [`docs/WINDOWS.md`](docs/WINDOWS.md).
+
+## License
+
+PeerSpeak is licensed under the [MIT License](LICENSE), © 2026 mollusk.
+
+Third-party components bundled with PeerSpeak (the Rust dependency tree, the
+statically bundled Opus codec on some builds, and embedded fonts) are all under
+permissive licenses; their texts and a full dependency manifest are collected in
+[`THIRD_PARTY_LICENSES`](THIRD_PARTY_LICENSES).

antigravity.toml

@@ -1,80 +0,0 @@
-# Example entry in an antigravity.toml configuration file
-[agent]
-model = "gemini-3.5-flash"
-system_instruction = """
-You are a senior-level, terminal-native Rust systems engineer and an expert programming assistant. Your goal is to help me design, build, and refactor a decentralized, peer-to-peer (P2P) voice communication application modeled after Mumble, utilizing the Iroh network stack for NAT holepunching and QUIC stream orchestration.
-
-### 0. How You Work — Operating Principles (read first)
-Capability is not the constraint here; judgment is. These govern HOW you approach every task in this repo, and the project-specific sections below make them concrete.
-- **Understand before you act.** Read the actual code and the local docs (Sections 1, 8) before changing anything — never reason from memory about an API, type, or signature; open it and confirm. This is Rule 1 made operational. Orient in the codebase (Section 5) and honor its trait boundaries and idioms — you are editing a mature codebase, not starting fresh, so match its naming, error-handling, and comment density.
-- **Measure before you theorize — the single most important habit.** When debugging, get EVIDENCE before asserting a cause: instrument it, log it, reproduce it, read the real output. A plausible-sounding mechanism is a hypothesis, not a diagnosis. If the data contradicts your theory, drop the theory — do not bend the evidence to fit it. (The playback-crackle bug was only solved once the actual per-cycle PipeWire quantum was measured; every "reasoned" guess before that missed.)
-- **Root-cause, don't patch symptoms.** Trace a bug to the exact mechanism that produces it; a fix you cannot explain is a coincidence waiting to break. Make the smallest change that addresses the real cause — don't expand scope or refactor unasked. Flag adjacent problems; don't silently fold them in.
-- **"Compiles" and "tests pass" are NOT "it works."** These are three separate claims — builds-clean, tests-green, and field-verified-by-running-it — and you must state which you have actually reached (this reinforces Section 7). For this app, "verified" means a real run/call was observed behaving correctly (clean audio heard by ear, a reconnect watched in the logs), not that the suite passed. Never announce a fix as working on tests alone; explicitly label untested or tests-only work as "unverified."
-- **Surface the forks on real decisions.** When a task has genuine tradeoffs (architecture, a new dependency, an irreversible change), lay out the realistic options with their costs and let me choose BEFORE you build. For a choice with an obvious default and no downside, just pick it, say what you picked, and proceed — don't manufacture decisions.
-- **Report honestly.** If it failed, say so and show the evidence. If you assumed or skipped something, say that. When something is genuinely done and verified, say so plainly without hedging. If new evidence contradicts something you stated confidently, correct yourself explicitly. "I verified X" and "I believe X" are different claims — use the right one. Never fabricate APIs, file paths, or results; if unsure, say "I'm not sure" and go confirm (Rule 1).
-- **Treat dependencies as a liability.** Prefer the standard library, tools already on the system, or a few lines of your own over pulling in a crate — I vet dependencies for supply-chain risk. Justify any addition, and default to safe Rust (Rule 3).
-- **Know when NOT to do what I ask.** Doing the task is the default, but stop and confirm or push back when: the action is hard to reverse or outward-facing — pushing, publishing, deploying the binary to the other machine, deleting/overwriting files you did not create (confirm first; for git commits specifically, see Rule 4); the request rests on a false premise or contradicts what you find in the code (surface that instead of plowing ahead); compliance would introduce real risk — data loss, a security/privacy regression (e.g. changing the `RelayNoDiscovery` default, see Section 6), an `unsafe` block, or a heavy dependency (name the risk and offer a safer path); or the scope is ambiguous (confirm rather than over-building — build X, not X plus extras). Don't merely comply and don't merely refuse — offer the better route.
-- **Work in checkpoints; keep state durable.** Give a short plan and a rough scope/effort estimate up front so I can redirect or defer (I watch a daily usage budget). Phase large work so it can pause cleanly. The handoff log (Section 8) is the durable record across sessions — read it first, update it when you finish meaningful work.
-- **Follow the collaboration protocol (read first, every task).** Before starting any task, read `/home/mollusk/Documents/handoff-docs/Gemini/peerspeak/operating-agreement.md`. It defines how we work as a team: a senior engineer designs and reviews the work, tasks are assigned to you in `next-task.md`, and you report back in `task-report.md`. It is in force this session and every session until that file says otherwise.
-
-### 1. Context and Knowledge Base
-You have immediate, local access to the definitive Rust documentation suite located at the absolute path: `/home/mollusk/Documents/rust_docs/`. 
-Before answering highly complex questions, writing macros, or optimizing code, you must reference these specific resources:
-- Syntax, language invariants, and semantics: `/home/mollusk/Documents/rust_docs/rust-reference/`
-- Idiomatic structural choices, patterns, and logic: `/home/mollusk/Documents/rust_docs/the-book/`
-- Pointer manipulation, data layout, and undefined behavior: `/home/mollusk/Documents/rust_docs/rust-nomicon/`
-- API design, trait implementations, and naming conventions: `/home/mollusk/Documents/rust_docs/rust-api-guidelines/`
-
-### 2. Specialized Architectural Constraints
-- **P2P Audio Boundary Isolation:** We are utilizing a decoupled architecture. The asynchronous network runtime (Tokio + Iroh) must be kept strictly separated from the real-time audio thread pool (PipeWire). Communication between the Iroh network consumers and the PipeWire audio streams must happen exclusively via bounded, lock-free SPSC (Single-Producer Single-Consumer) or MPSC ring buffers.
-- **The "No-Alloc" Audio Rule:** Code generated for the audio processing callback or multi-stream mixer must be strictly safe and real-time safe. It must contain zero heap allocations, zero blocking synchronization primitives (no standard Mutex/RwLock), and zero blocking file/network I/O.
-- **Iroh Topology:** We handle voice channels by treating every peer node as a full-mesh target. Leverage Iroh's unreliable QUIC Datagrams for raw, low-latency audio packet delivery and Iroh-Gossip (or bi-directional streams) for state synchronization (room mapping, mute states, and peer metadata).
-
-### 3. Behavioral Boundaries and Accuracy
-- **Rule 1 (Absolute Ground Truth):** Never guess or hallucinate syntax rules, compiler behavior, or API surfaces. If you are not 100% sure about a specific language feature, macro expansion, standard library behavior, or dependency change, stop and explicitly state: "I'm actually not sure about that."
-- **Rule 2 (No "C in Rust"):** Do not write C-style logic wrapped in Rust syntax. Prioritize idiomatic Rust patterns (e.g., using algebraic data types, proper trait bounds, combinators like `.map()` or `.and_then()`, and precise error handling with `Result` and `Option`).
-- **Rule 3 (Safe by Default):** Always default to safe, idiomatic Rust code. Do not introduce an `unsafe` block unless it is explicitly requested, or unless you can rigorously prove using *The Rustonomicon* constraints that safe Rust cannot achieve the required performance boundary.
-- **Rule 4 (Git Commit Policy):** When a feature is completed, you must always ask the user for permission before committing files to git. Never commit files automatically.
-
-### 4. Output Requirements
-- **Contextual Clarity:** When providing a solution that relies on advanced language mechanics (like complex lifetimes, custom traits, or macro rules), briefly cite which local resource or module layout you used to verify the approach.
-- **Code Generation:** Provide clean, production-ready code with minimal boilerplate. Use standard formatting rules (`rustfmt` styles). Include brief, high-value comments for complex borrowing logic or lifetime annotations.
-- **Error Resolution:** If asked to fix a compiler or borrow-checker error, explain *why* the error occurred in terms of Rust's core memory model (ownership/borrowing/lifetimes) before providing the refactored code.
-
-### 5. Project Map — Where Things Live
-This is a mature codebase, not a greenfield project. Orient yourself in it before editing. The architecture is trait-based so implementations stay swappable; honor the boundaries.
-- `src/network/mod.rs` — the `NetworkTransport` and `RoomState` traits + shared types (`PeerState`, `RoomEvent`, `ConnEvent`, `PeerSpeakTicket`). Start here to understand the seams.
-- `src/network/iroh_impl.rs` — the audio transport. Per-peer **supervisor** tasks own each connection's whole lifecycle; QUIC datagrams carry audio. This is the most subtle file — see Section 6.
-- `src/network/gossip.rs` — `iroh-gossip` room state: presence roster, mute/metadata sync, join/leave, address announcements feeding the `MemoryLookup`.
-- `src/core/mod.rs` — the coordinator: wires capture→encode→broadcast and receive→jitter→decode→mix→playback, and bridges room/transport events to the UI. Runs on its own Tokio runtime thread.
-- `src/core/jitter.rs` — per-peer jitter buffer (reorder + fixed playout delay + Opus PLC on loss). Unit-tested.
-- `src/audio/{pipewire_impl.rs,pw_cli.rs}` — PipeWire capture/playback in the real-time path; device enumeration via `pw-cli`.
-- `src/codec/opus_impl.rs` — Opus encode/decode behind the `AudioCodec` trait.
-- `src/app/mod.rs` — the `iced` GUI (Catppuccin-styled). `src/config.rs` — persisted settings (`~/.config/peerspeak/config.json`).
-- `tests/transport_loopback.rs` — end-to-end transport tests over real localhost iroh endpoints. `src/bin/test_net.rs` — a manual two-node harness.
-
-### 6. Audio-Networking Invariants (hard-won — each of these maps to a real bug that was fixed)
-Treat these as load-bearing. They are non-obvious and were violated in earlier iterations.
-- **One shared connection per peer pair, deterministic initiator.** The lower `EndpointId` (string comparison) **dials**; the higher **accepts**. Both sides call `connect_peer`; the rule dedups so exactly one bidirectional QUIC connection forms per pair. Never open a second per-direction connection, and never spawn a connection (or a task) per audio frame — use the long-lived per-peer send path.
-- **The per-peer supervisor owns connect → run → reconnect.** All of a peer's connection lifecycle lives in one `supervise` task (`iroh_impl.rs`). Don't scatter dialing/reconnect logic across call sites; reconnection must re-apply the same deterministic-initiator rule so the single shared connection re-forms.
-- **Any detached task holding a `Connection` clone MUST be abort-on-drop.** A live `Connection` clone keeps the QUIC link open. If send/read loops aren't torn down on peer-removal/reconnect, the link never actually closes and the peer only notices at the ~30s idle timeout. Scope them in `AbortOnDrop` guards tied to the live-link block.
-- **A silent handle-drop is NOT a close.** Dropping all `Connection` handles does not promptly notify the peer — they find out only at the QUIC idle timeout (~30s). Only `Connection::close()` sends an immediate `CONNECTION_CLOSE`. This matters for both teardown and for writing tests that need a prompt drop.
-- **Retain each peer's full `EndpointAddr` and dial it directly; do not lean on `MemoryLookup` alone.** Dialing by bare `EndpointId` forces iroh to resolve via the gossip-fed `MemoryLookup`. A transient drop that fires a gossip `Leave`/`NeighborDown` purges that entry, and the dialer then redial-loops forever with "no address." The transport keeps each peer's full address (relay + direct addrs) for the supervisor's lifetime, refreshed on every re-announce, and dials it directly. (This was the 2026-05-31 fix.)
-- **Presence layer ≠ transport layer.** The gossip roster (who's in the room) is independent of a peer's audio-link state. A peer can be present with its audio link down/reconnecting. Keep the two UI signals distinct (`RoomEvent` vs `ConnEvent`); don't infer one from the other.
-- **Every audio datagram carries a 4-byte little-endian sequence header.** The receiver feeds `(seq, payload)` into the per-peer `JitterBuffer`, which reorders, holds a fixed playout delay, and invokes Opus PLC (`decode(None)`) on gaps. Never decode datagrams directly in arrival order, and size PLC to one 20ms frame.
-- **`broadcast()` must never block the capture/encode thread.** It is called from the non-async audio path. Use `try_send` into shallow per-peer queues and **drop on full** — stale audio is worthless and a slow peer must never stall encoding. No `await`, no large/unbounded queues here.
-- **Real-time audio path (reaffirming Section 2):** zero heap allocation, zero blocking locks (no `Mutex`/`RwLock`), zero I/O inside the PipeWire callback/mixer. Cross the async↔RT boundary only through bounded lock-free ring buffers.
-- **Throttle high-rate UI events.** Don't forward per-20ms-tick events (e.g. `AudioLevels`, ~50/sec) straight to the GUI; coalesce with peak-hold to ~10/sec.
-- **Privacy posture is intentional.** Default `NetworkMode` is `RelayNoDiscovery`: keep the n0 relay (NAT traversal + re-reachability anchor) but emit **no** DNS presence beacon. Do not change the default to anything that publishes presence. Decision on record: we are **not** self-hosting a relay.
-
-### 7. Testing & Field-Verification Gotchas
-- **The loopback/integration tests use stable, fixed addresses**, so they silently miss address-eviction and new-address bugs. When testing reconnect resilience, **starve every address source** (empty the `MemoryLookup` *and* disable the relay) to force the retained-address path. Merely calling `remove_endpoint_info` is a **false** test: iroh internally caches the path from a recent live connection, so the reconnect still succeeds even with the bug present.
-- **Two instances on one host are INVALID for outage/disconnect tests.** Docker bridges (`172.x`) plus loopback keep them talking even with the main NIC down. Use two real machines, or two network namespaces joined by a single `veth` you can `ip link set ... down`.
-- **To drive a prompt link drop in a test, explicitly `close()` the connection** — a silent drop waits out the ~30s idle timeout (see Section 6).
-- **Before declaring anything done:** `cargo clippy --all-targets` must be clean (zero warnings) and `cargo test` must pass. Distinguish "tests-green" from "field-verified" — say which one you actually have.
-
-### 8. Offline Docs for the Network/Audio Stack
-In addition to the general Rust docs in Section 1, the **API docs for this project's dependencies** (iroh, iroh-gossip, tokio, opus, pipewire, iced, …) are generated locally at `/home/mollusk/Documents/peerspeak_docs/`. Grep/read these instead of probing the web — e.g. confirm `Endpoint::connect`'s signature or `MemoryLookup`'s methods there. The design blueprint is at `/home/mollusk/Documents/P2P_Voice_Chat_Blueprint.md`. A **living handoff log** is maintained at `/home/mollusk/Documents/handoff-docs/Gemini/peerspeak/handoff.md` — **read it first each session** for current state, recent commits, and known/open bugs, and append a dated entry when you finish meaningful work.
-
-Acknowledge these operational parameters, then orient yourself in the existing codebase (Section 5) and the handoff log (Section 8) before proposing or making changes. Summarize the current project state back to me and ask what we're tackling this session.
-"""

assets/icons/peerspeak.svg

@@ -1,41 +1,66 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <svg width="256" height="256" viewBox="0 0 256 256" xmlns="http://www.w3.org/2000/svg">
-  <!-- PeerSpeak app icon: in-app mic glyph + P2P mesh nodes, Catppuccin Mocha. -->
+  <title>PeerSpeak</title>
+  <desc>Two luminous voices meet directly to form a flowing S.</desc>
   <defs>
-    <linearGradient id="tile" x1="0" y1="0" x2="0" y2="1">
-      <stop offset="0" stop-color="#1e1e2e"/>
-      <stop offset="1" stop-color="#181825"/>
+    <linearGradient id="tile" x1="32" y1="20" x2="225" y2="239" gradientUnits="userSpaceOnUse">
+      <stop stop-color="#101d42"/>
+      <stop offset="0.5" stop-color="#071225"/>
+      <stop offset="1" stop-color="#160b31"/>
     </linearGradient>
+    <linearGradient id="voice" x1="45" y1="76" x2="214" y2="184" gradientUnits="userSpaceOnUse">
+      <stop stop-color="#35efff"/>
+      <stop offset="0.42" stop-color="#2583ff"/>
+      <stop offset="0.68" stop-color="#8a42ff"/>
+      <stop offset="1" stop-color="#ff3cdd"/>
+    </linearGradient>
+    <linearGradient id="edge" x1="30" y1="31" x2="225" y2="231" gradientUnits="userSpaceOnUse">
+      <stop stop-color="#2fe9ff" stop-opacity="0.7"/>
+      <stop offset="0.48" stop-color="#386dff" stop-opacity="0.18"/>
+      <stop offset="1" stop-color="#eb42ff" stop-opacity="0.65"/>
+    </linearGradient>
+    <radialGradient id="core">
+      <stop stop-color="#ffffff"/>
+      <stop offset="0.28" stop-color="#baf7ff"/>
+      <stop offset="0.62" stop-color="#7b67ff" stop-opacity="0.65"/>
+      <stop offset="1" stop-color="#7b67ff" stop-opacity="0"/>
+    </radialGradient>
+    <filter id="shadow" x="-35%" y="-35%" width="170%" height="170%">
+      <feGaussianBlur stdDeviation="6"/>
+    </filter>
+    <filter id="soft-shadow" x="-20%" y="-20%" width="140%" height="150%">
+      <feDropShadow dx="0" dy="7" stdDeviation="7" flood-color="#000611" flood-opacity="0.8"/>
+    </filter>
   </defs>
 
-  <!-- Rounded-square tile -->
-  <rect x="20" y="20" width="216" height="216" rx="48" fill="url(#tile)"
-        stroke="#313244" stroke-width="3"/>
+  <!-- A dark stage makes the cyan/violet conversation mark legible at taskbar size. -->
+  <rect x="8" y="8" width="240" height="240" rx="55" fill="url(#tile)"/>
+  <rect x="9.5" y="9.5" width="237" height="237" rx="53.5" fill="none" stroke="url(#edge)" stroke-width="3"/>
 
-  <!-- P2P mesh: edges (under nodes + mic) -->
-  <g stroke="#45475a" stroke-width="6" stroke-linecap="round" fill="none">
-    <line x1="74"  y1="74"  x2="128" y2="128"/>
-    <line x1="182" y1="74"  x2="128" y2="128"/>
-    <line x1="74"  y1="182" x2="128" y2="128"/>
-    <line x1="182" y1="182" x2="128" y2="128"/>
-    <line x1="74"  y1="74"  x2="182" y2="74"/>
-    <line x1="74"  y1="182" x2="182" y2="182"/>
-  </g>
+  <!-- Broad color glow, kept behind the silhouette. -->
+  <path d="M36 128 C50 128 48 101 60 101 C72 101 68 153 81 153 C94 153 90 112 104 112 C115 112 116 128 128 128 C140 128 141 144 152 144 C166 144 162 103 175 103 C188 103 184 155 196 155 C208 155 206 128 220 128"
+        fill="none" stroke="url(#voice)" stroke-width="25" stroke-linecap="round"
+        opacity="0.5" filter="url(#shadow)"/>
 
-  <!-- P2P mesh: peer nodes -->
-  <g fill="#b4befe">
-    <circle cx="74"  cy="74"  r="11"/>
-    <circle cx="182" cy="74"  r="11"/>
-    <circle cx="74"  cy="182" r="11"/>
-    <circle cx="182" cy="182" r="11"/>
-  </g>
+  <!-- The two waveform halves are equal peers and meet at one bright point. -->
+  <path d="M36 128 C50 128 48 101 60 101 C72 101 68 153 81 153 C94 153 90 112 104 112 C115 112 116 128 128 128"
+        fill="none" stroke="url(#voice)" stroke-width="17" stroke-linecap="round" stroke-linejoin="round"/>
+  <path d="M128 128 C140 128 141 144 152 144 C166 144 162 103 175 103 C188 103 184 155 196 155 C208 155 206 128 220 128"
+        fill="none" stroke="url(#voice)" stroke-width="17" stroke-linecap="round" stroke-linejoin="round"/>
 
-  <!-- Microphone (hero) — same geometry as the in-app Mic icon, scaled 6.4x -->
-  <g fill="none" stroke="#89b4fa" stroke-width="13"
-     stroke-linecap="round" stroke-linejoin="round">
-    <rect x="108.8" y="68.8" width="38.4" height="70.4" rx="19.2"/>
-    <path d="M 169.6 123.2 A 41.6 41.6 0 0 0 86.4 123.2"/>
-    <line x1="128" y1="164.8" x2="128" y2="187.2"/>
-    <line x1="105.6" y1="187.2" x2="150.4" y2="187.2"/>
-  </g>
+  <!-- A single flowing connection turns the conversation into PeerSpeak's S-mark. -->
+  <path d="M160 66 C142 52 108 57 101 78 C94 98 113 111 128 119 C148 130 163 141 157 164 C151 188 117 199 94 184"
+        fill="none" stroke="#050b1b" stroke-opacity="0.72" stroke-width="33"
+        stroke-linecap="round" stroke-linejoin="round" filter="url(#soft-shadow)"/>
+  <path d="M160 66 C142 52 108 57 101 78 C94 98 113 111 128 119 C148 130 163 141 157 164 C151 188 117 199 94 184"
+        fill="none" stroke="url(#voice)" stroke-width="25"
+        stroke-linecap="round" stroke-linejoin="round"/>
+  <path d="M157 65 C139 56 113 62 108 79" fill="none" stroke="#bdf9ff"
+        stroke-opacity="0.68" stroke-width="4" stroke-linecap="round"/>
+  <path d="M153 166 C146 184 118 192 98 181" fill="none" stroke="#f4a8ff"
+        stroke-opacity="0.52" stroke-width="4" stroke-linecap="round"/>
+
+  <!-- The direct connection is the brightest and simplest detail. -->
+  <circle cx="128" cy="128" r="30" fill="url(#core)" opacity="0.78" filter="url(#shadow)"/>
+  <circle cx="128" cy="128" r="6.5" fill="#ffffff"/>
 </svg>

assets/sounds/generate_chimes.py

@@ -76,6 +76,14 @@ CHIMES = {
     "mic-toggle.wav": [(E5, 0.08)],
     # Reconnect gave up: disappointing low two-note fall.
     "reconnect-failed.wav": [(C5, 0.15), (349.23, 0.30)],
+    # Our chat message entered the room: a tiny bright acknowledgement.
+    "chat-sent.wav": [(1046.50, 0.06)],
+    # A peer message arrived: a soft two-note lift, distinct but unobtrusive.
+    "chat-received.wav": [(E5, 0.07), (G5, 0.11)],
+    # A saved contact came online: a light, higher two-note arrival.
+    "contact-online.wav": [(E5, 0.09), (880.00, 0.18)],
+    # A saved contact went offline: the same tonal family falling away.
+    "contact-offline.wav": [(E5, 0.09), (440.00, 0.18)],
 }
 
 

build.rs

@@ -0,0 +1,22 @@
+use std::process::Command;
+
+fn main() {
+    println!("cargo:rerun-if-changed=.git/HEAD");
+    if let Ok(head) = std::fs::read_to_string(".git/HEAD")
+        && let Some(reference) = head.strip_prefix("ref: ")
+    {
+        println!("cargo:rerun-if-changed=.git/{}", reference.trim());
+    }
+
+    let short = Command::new("git")
+        .args(["rev-parse", "--short=8", "HEAD"])
+        .output()
+        .ok()
+        .filter(|output| output.status.success())
+        .and_then(|output| String::from_utf8(output.stdout).ok())
+        .map(|value| value.trim().to_string())
+        .filter(|value| !value.is_empty())
+        .unwrap_or_else(|| "unknown".to_string());
+
+    println!("cargo:rustc-env=PEERSPEAK_GIT_SHORT={short}");
+}

deny.toml

@@ -24,6 +24,19 @@ ignore = [
     # audiopus_sys: unmaintained FFI bindings to the stable libopus C library,
     # pulled in via our direct `opus 0.3.1` dep. No drop-in replacement.
     "RUSTSEC-2026-0150",
+    # ttf-parser: unmaintained, transitive via iced/cosmic-text (font parsing
+    # for the GUI). Inputs are system + embedded fonts, not network data. No
+    # upstream migration yet; revisit when iced moves off it.
+    "RUSTSEC-2026-0192",
+    # quick-xml 0.39.4 DoS advisories (quadratic dup-attr check; unbounded
+    # namespace allocation). Build-time only: quick-xml is reached solely via
+    # the wayland-scanner PROC-MACRO, which parses the wayland protocol XML
+    # files vendored inside the wayland-* crates at compile time. Attacker
+    # input never reaches it and it is not in the shipped binary. The fix
+    # (0.41.0) is semver-incompatible with wayland-scanner 0.31.x's `^0.39`
+    # requirement; drop both ignores once wayland-scanner releases a bump.
+    "RUSTSEC-2026-0194",
+    "RUSTSEC-2026-0195",
 ]
 
 # ---------------------------------------------------------------------------
@@ -81,8 +94,8 @@ allow = [
 confidence-threshold = 0.8
 exceptions = []
 
-# peerspeak itself has no `license` field and is not published, so skip the
-# "unlicensed" check for our own (private) crate. Add a license to Cargo.toml
-# if/when this is ever published.
+# peerspeak is MIT-licensed (see Cargo.toml `license` + the LICENSE file) but is
+# not published to crates.io, so keep the private-crate skip for the
+# "unlicensed"/publish checks. MIT is already in the allow list above.
 [licenses.private]
 ignore = true

docs/FEATURES.md

@@ -102,6 +102,7 @@ covers internals). When you ship a feature, add it here.
 | iroh QUIC transport | ✅ | |
 | Network mode picker | ✅ | `RelayNoDiscovery` (default), `N0Full`, `DirectOnly`. Takes effect next join. |
 | Retained-address reconnect | ✅ | Dials last-known full addr before falling back to bare id. |
+| Per-peer connection badge (direct/relay + RTT, hover for addr/loss/bitrate) | ✅ | Peer-card badge fed by a 1 Hz poll of the live audio link's selected QUIC path (`connection_stats` → `core::connstats::derive`). Field-verified on a real 2-machine call 2026-07-08. |
 | Reconnect + eviction model | ✅ | Incl. two-outage reconnect-eviction fix + regression test. |
 | Self-hosted relay | ❌ | Decided against — rely on n0 relays, `RelayNoDiscovery` default. |
 

docs/WINDOWS.md

@@ -0,0 +1,103 @@
+# PeerSpeak on Windows
+
+Current status: PeerSpeak cross-compiles to `x86_64-pc-windows-gnu` from Linux and
+has passed an older native Windows 11 VM smoke test for launch, GUI render, call
+join, and audio flow. The build environment is **not** the Windows VM; current
+Windows binaries are built from Linux, normally inside the `peerspeak-win`
+distrobox or with the same GNU target environment.
+
+The Windows runtime still trails Linux in a few important areas. See the Claude
+handoff file `windows-parity-audit.md` for the full audit and task breakdown.
+
+## What works today
+
+| Area | Status |
+|---|---|
+| GUI | Iced/wgpu builds for Windows and rendered in the Windows 11 VM. |
+| Networking | Iroh QUIC transport and gossip compile on Windows; VM call reached two peers. |
+| Audio backend | `cpal` drives WASAPI capture/playback behind `AudioBackend`. |
+| Device selection | cpal enumerates input/output devices; see caveat below about stable IDs. |
+| Resampling/remap | WASAPI devices can run non-48 kHz formats; PeerSpeak converts at the backend boundary. |
+| Codec | Opus remains 48 kHz mono, 20 ms frames. |
+| Identity/config | Stored through `dirs` under the Windows profile. |
+| Chimes | Windows uses PowerShell `System.Media.SoundPlayer` for WAV playback. |
+| Game detection | Steam registry `RunningAppID` plus Toolhelp process-scan fallback compile on Windows. |
+| File dialogs | `rfd` uses the native Win32 dialog backend. |
+
+Windows paths are resolved through `dirs`:
+
+- Config: `%APPDATA%\peerspeak\config.json`
+- Identity: `%APPDATA%\peerspeak\identity.key`
+- Log: `%LOCALAPPDATA%\peerspeak\peerspeak.log`
+
+## Building
+
+### Cross-compile from Linux
+
+Preferred local path:
+
+```sh
+distrobox enter peerspeak-win -- bash -lc '
+  cd ~/git/butter/peerspeak &&
+  RUSTC_BOOTSTRAP=1 ./win-cross-build.sh -Z build-std=std,panic_abort
+'
+```
+
+Equivalent direct command when the host has the GNU target, MinGW, `rust-src`, and
+CMake available:
+
+```sh
+CMAKE_POLICY_VERSION_MINIMUM=3.5 RUSTC_BOOTSTRAP=1 \
+  cargo build --release --target x86_64-pc-windows-gnu --bin peerspeak \
+  -Z build-std=std,panic_abort
+```
+
+`CMAKE_POLICY_VERSION_MINIMUM=3.5` is required with host CMake 4.x because the
+vendored Opus build used by `audiopus_sys` still declares an old minimum CMake
+version. Without that env var, the Windows build/check fails during Opus configure.
+
+### Native Windows
+
+A native MSVC build is not the active development path. If used, install MSVC Build
+Tools and CMake, then build normally:
+
+```powershell
+$env:CMAKE_POLICY_VERSION_MINIMUM = "3.5"
+cargo build --release
+```
+
+## First run and networking
+
+Expect a Windows Firewall prompt the first time the app opens network sockets, or
+use the Inno installer option that pre-adds a firewall allow rule. PeerSpeak uses
+UDP for QUIC plus relay traffic when direct NAT traversal is unavailable.
+
+The default network mode keeps the n0 relay available for NAT traversal without
+publishing presence to n0 DNS. Relayed connections are expected and valid.
+
+## Known gaps
+
+| Item | Status |
+|---|---|
+| Echo cancellation | Linux-only today. The Windows UI shows it disabled as unavailable. |
+| Screen share | Blocked by PixelPass, which is currently Linux-only in practice. PeerSpeak can spawn `pixelpass.exe`, but there is no Windows PixelPass host/viewer parity yet. |
+| Device persistence | Uses cpal friendly names as keys. These can duplicate or change across Windows driver/profile changes; stable WASAPI endpoint IDs are still needed. |
+| Release hygiene | Keep `.iss` and installer output in sync with `Cargo.toml`; rebuild Windows artifacts during each release. |
+| Runtime coverage | The Windows VM smoke test proved an older tester build. Current `main` needs a fresh VM smoke matrix before calling parity current. |
+
+## Current smoke checklist
+
+Before calling a Windows build current, verify on the Windows VM or real Windows
+hardware:
+
+- Launch current `peerspeak.exe`; GUI renders and settings open.
+- Run `audio_probe.exe 440 30`; listen for glitches and inspect `playout-health`.
+- Create/join a Linux <-> Windows room; confirm mic and playback both directions.
+- Select input/output devices, restart, and confirm selections persist or fall back clearly.
+- Play chimes and custom chime paths.
+- Send chat, image/file attachments, and save an attachment through the native dialog.
+- Import/play/share/listen to music from Windows file paths.
+- Record mixed/stems/both and inspect the WAV output path.
+- Exercise friends/presence/recents and the clock-skew banner.
+- Test Steam and non-Steam game detection on a real Windows Steam install.
+- Install/upgrade/uninstall through the Inno installer, including firewall rule cleanup.

docs/chat-hardening-plan.md

@@ -0,0 +1,584 @@
+# Chat hardening — ephemeral implementation plan
+
+**Status (2026-07-18):** Phases 1–5 COMPLETE (all plan phases done). Phase 1 =
+shared text policy in `src/sanitize.rs`, ceilings enforced at UI input, sign
+point, and gossip ingress. Phase 2 = roster-bound authorship
+(`src/core/chatroster.rs`), replay dedup + rate limits (`ChatIngressGate` in
+`src/network/gossip.rs`). Phase 3 = attachment cache/serve-store budgets,
+downscaled previews, auto-fetch byte/request budgets (`src/core/fetchbudget.rs`),
+exact transfers, bounded local reads. Phase 4 = parsed-URL link policy
+(`is_safe_web_url`/`link_ranges` in `src/sanitize.rs`, `url` crate), 8-link cap,
+cached link ranges in `ChatEntry`, 512 KiB history text budget, chat-body
+bidi-override strip (closes S14). Phase 5 = honest local send status
+(`CoreCommand::SendChat`/`SendChatFile` carry a local id, `UiEvent::ChatSendResult`,
+`SendStatus` on own echoes) PLUS sender-side pacing (`src/app/sendqueue.rs`
+mirrors the receivers' per-author budget so fast bursts trickle instead of being
+silently dropped downstream). All gates green each phase. This is a temporary
+scope contract for hardening the existing room chat; with every phase complete
+and the two-machine field test done, delete this file (see the completion note
+at the end). The two-machine field-test section below is still owed before that
+deletion. Do not add link previews as part of this effort.
+
+## Goal
+
+Strengthen the current encrypted, signed, session-only room chat without changing
+its product model: plain selectable text, clickable web links, and peer-to-peer
+attachments over the existing gossip and files planes. The work should make chat
+resistant to identity spoofing, replay, spam, oversized input, expensive rendering,
+and attachment-driven memory/bandwidth pressure while preserving normal Unicode
+conversation and the existing full-mesh architecture.
+
+## Existing foundation to preserve
+
+- Gossip payloads are signed by the claimed `EndpointId`, bound to the raw room
+  topic and protocol domain, and checked before dispatch.
+- The signed envelope timestamp is admitted only within the two-minute gossip
+  freshness window.
+- Inbound gossip frames are capped at 128 KiB before JSON deserialization. This
+  larger plane-wide cap must remain because `Announce` may contain a custom avatar.
+- Chat history is session-only and capped at 300 entries.
+- Only `http://` and `https://` links are opened, as a single process argument
+  without a shell.
+- Attachment descriptors are signed with the chat payload; attachment bytes use
+  the encrypted files plane, have a 25 MiB per-file cap, and are keyed by both
+  author and attachment id.
+- Image bytes are decoded defensively and automatic image fetches already have a
+  four-task concurrency limit.
+
+## Working design decisions
+
+These are the implementation defaults unless code inspection or tests reveal a
+concrete reason to adjust them. Record any adjustment in the decision log.
+
+1. **No wire change.** Keep `GossipMessage::Chat` unchanged and do not bump
+   `GOSSIP_PROTO`. The redundant wire `name` and inner `Chat.ts` remain serialized
+   for compatibility but are not trusted. Remove them only during a future planned
+   gossip-version bump.
+2. **Roster identity is authoritative.** A chat line is admitted only for an
+   authenticated identity already known to the current room (including the
+   reconnect grace state). Its displayed name comes from the sanitized roster
+   state, never from `GossipMessage::Chat.name`.
+3. **Body Unicode remains expressive.** Do not apply the short-label sanitizer to
+   the message body; it strips format characters used by some languages and emoji.
+   Continue neutralizing controls and whitespace, while treating author labels,
+   filenames, and URLs more strictly because those are spoof-sensitive surfaces.
+4. **Bounds apply at every trust boundary.** UI input is bounded while editing,
+   outgoing text is normalized before signing, and incoming text is byte-checked
+   and normalized before it leaves the gossip layer. UI-only truncation is not an
+   adequate ingress defense.
+5. **Automatic network work is stricter than manual work.** Keep the 25 MiB manual
+   attachment ceiling, but auto-fetch only small images. Larger images remain
+   available behind an explicit Load/Download action.
+6. **Caches are bounded by cost, not only entry count.** Count encoded bytes and
+   estimated decoded image bytes. A count cap remains as a secondary bound.
+7. **Rate limiting degrades quietly.** Drop excess/replayed peer messages with a
+   rate-limited log entry. Do not let a spammer produce a second UI-notification
+   flood.
+
+## Proposed policy constants
+
+Keep these together near the code that enforces them and cover them with boundary
+tests. Values are starting points, not a compatibility contract.
+
+| Policy | Initial value | Reason |
+| --- | ---: | --- |
+| Chat body characters | 2,000 | Preserves current UI behavior |
+| Chat body UTF-8 bytes | 8 KiB | Covers 2,000 four-byte scalars with small headroom |
+| Live input characters/bytes | Same as body | Prevent oversized paste/edit state |
+| Clickable links per message | 8 | Bounds spans and opener targets |
+| Retained chat text | 512 KiB plus 300 entries | Bounds redraw and selection work |
+| Per-author chat limiter | Burst 8, refill 1/second | Allows normal bursts, stops sustained spam |
+| Room-wide chat limiter | Burst 32, refill 8/second | Protects shared event/UI queues |
+| Exact-chat replay cache | 1,024 digests, 2-minute TTL | Covers freshness window with a hard bound |
+| Auto-fetch image encoded size | 4 MiB | Limits unsolicited bandwidth and allocations |
+| Attachment cache encoded budget | 128 MiB | Allows several ordinary files without GiB growth |
+| Attachment cache decoded-preview budget | 64 MiB | Bounds renderer-side image pressure |
+| Served attachment budget | 256 MiB plus a count cap | Bounds sender memory for a long session |
+| Inline preview longest side | 1,600 px | Chat renders near 260 px; full 4K decode is wasteful |
+| Decoded source image pixels | 16 megapixels maximum | Adds a total-pixel bound to per-side bounds |
+
+## Phase 1 — Shared text policy and live-input bounds
+
+**Target:** downstream layers never receive or retain an unexpectedly large or
+unsafe chat string.
+
+- [x] Move chat constants and `sanitize_chat` from `src/app/mod.rs` into
+  `src/sanitize.rs` (or a narrowly scoped shared chat-policy module if that keeps
+  the API clearer).
+- [x] Implement a single-pass sanitizer that:
+  - maps control characters to spaces;
+  - collapses whitespace and trims ends;
+  - enforces both the character and UTF-8 byte ceilings without splitting a scalar;
+  - returns empty for content with no visible text.
+- [x] Add `cap_chat_input` for live editing. It must preserve the user's current
+  whitespace while enforcing character and byte ceilings; normalization remains a
+  submit/ingress operation so typing does not visibly jump.
+- [x] Apply `cap_chat_input` in `AppMessage::ChatInputChanged`, covering keyboard,
+  clipboard, primary-selection, and context-menu paste paths through the controlled
+  input widget.
+- [x] Sanitize outgoing text immediately before local echo and `CoreCommand` send.
+- [x] Sanitize again before `GossipMessage::Chat` is signed, so a future non-UI
+  caller cannot bypass policy.
+- [x] At gossip ingress, reject raw chat text over the byte ceiling before doing
+  downstream sanitization; sanitize accepted text before creating `RoomEvent`.
+- [x] Keep attachment-only messages when the sanitized caption is empty; drop a
+  chat with neither visible text nor a valid attachment.
+- [x] Stop sanitizing an incoming chat `name` with the body sanitizer. Phase 2
+  replaces it with the roster-bound name.
+
+### Phase 1 tests
+
+- [x] ASCII, multibyte Unicode, emoji, whitespace, NUL/CR/LF/TAB/ESC, empty input.
+- [x] Exact character and byte boundaries, including a four-byte scalar at the
+  cutoff.
+- [x] Oversized paste never makes `state.chat_input` exceed either ceiling.
+- [x] Outgoing, incoming, and direct core/network paths converge on the same
+  normalized result.
+- [x] Empty captions are retained only when a valid attachment remains.
+
+## Phase 2 — Admission, identity binding, replay, and spam control
+
+**Target:** only current authenticated room members can create chat UI work, and a
+member cannot impersonate another participant or monopolize the control/UI queues.
+
+- [x] Change the core event task's chat roster from a bare `HashSet<EndpointId>` to
+  a bounded map containing each member's latest sanitized display name (or retain a
+  parallel name map if less invasive).
+- [x] Insert/update the map on `PeerJoined`/`PeerUpdated`, retain it during transient
+  reconnect grace, and remove it on graceful or terminal eviction.
+- [x] Before attachment handling or UI forwarding, reject `RoomEvent::ChatMessage`
+  whose author is not present in that authoritative roster.
+- [x] Replace the embedded wire name with the roster map's name before constructing
+  `UiEvent::ChatMessage`. The UI may keep storing a name snapshot so old chat lines
+  remain labeled after a peer leaves.
+- [x] Add a lightweight early known-author gate in the gossip loop using its live
+  and disconnected-peer sets. Keep the core roster gate as defense in depth and as
+  the final authority.
+- [x] Validate that the inner `Chat.ts` equals the signed envelope timestamp, or
+  ignore it entirely. Do not use the inner timestamp for replay or ordering.
+- [x] Add exact-chat replay suppression after signature verification and before
+  event-channel send:
+  - hash the canonical signed bytes, not raw JSON formatting;
+  - use BLAKE3 (make it a direct dependency if needed; it is already in the iroh
+    dependency graph) or an equally collision-resistant existing primitive;
+  - store a `HashSet` plus FIFO/TTL order for bounded lookup and eviction;
+  - prune by both the gossip freshness window and the hard entry cap.
+- [x] Add a bounded token bucket per admitted author and a room-wide bucket before
+  awaiting `event_tx.send`. Limiter state must be removed with roster eviction and
+  remain bounded by the roster cap.
+- [x] Ensure duplicate messages are dropped before consuming rate-limit tokens, so
+  a replay cannot starve a legitimate new message from that author.
+- [x] Rate-limit rejection logging per author/reason.
+- [ ] Consider applying the same local submit policy to accidental rapid Enter or
+  button activation, without routing chat through the coalescing command path.
+
+### Phase 2 tests
+
+- [x] Valid roster author is admitted; never-announced, post-leave, forged, and
+  stale authors are rejected.
+- [x] A peer sending `name = "Victim"` renders under its own roster name.
+- [x] A name update affects future messages without rewriting history.
+- [x] Reconnect grace continues accepting the known author; terminal eviction does
+  not.
+- [x] The same signed chat is displayed once; distinct chats created in the same
+  millisecond are both admitted.
+- [x] Replay-cache TTL/cap pruning cannot grow without bound.
+- [x] Per-author burst/refill and room-wide burst/refill boundaries.
+- [x] Excess chat cannot prevent a subsequent `Leave` or `Announce` from reaching
+  the event loop in a deterministic channel-pressure test.
+
+## Phase 3 — Attachment transfer and memory hardening
+
+**Target:** neither peers nor long local sessions can turn chat attachments into
+unbounded memory, bandwidth, decoder, or task pressure.
+
+### 3A. Cache and image cost
+
+- [x] Extend `AttachmentCache` with encoded-byte and decoded-preview-byte counters.
+  Preserve the count cap, but evict oldest entries until all three budgets fit.
+- [x] Give every entry an explicit weight. Replacement must subtract the old
+  weight before checking/inserting the new one.
+- [x] Decide behavior for a single entry larger than the cache budget: service an
+  immediate pending Save/Play request without retaining it, then expose it as
+  evicted/unavailable rather than exceeding the budget.
+- [x] Add a total-pixel limit to `validate_image_bytes` in addition to the existing
+  width/height limit.
+- [x] Build a downscaled inline preview handle with a maximum 1,600 px side. Keep
+  original bytes only for Save; do not hand a full-resolution 4K image to the
+  renderer merely to display it at chat width.
+- [x] Count estimated RGBA preview cost (`width * height * 4`) against the decoded
+  budget even if iced internally copies or uploads it.
+- [x] Strip the same bidi/zero-width spoofing characters used for display labels
+  from attachment filenames, while preserving ordinary Unicode filenames.
+
+### 3B. Automatic download policy and state
+
+- [x] Auto-fetch only roster-authored images whose declared size is at or below
+  `MAX_AUTO_IMAGE_BYTES`; keep the existing `(author,id)` dedup and four-permit
+  concurrency bound.
+- [x] Add per-author and session byte/request budgets for automatic fetches so a
+  peer cannot drain bandwidth sequentially after each permit is released.
+- [x] Represent `NotFetched`, `Loading`, `Ready`, `Failed`, and `Evicted` distinctly
+  enough for the UI to avoid an indefinite “loading…” label when auto-fetch was
+  skipped or the cache evicted an item.
+- [x] Render a Load image button for large/skipped images. A manual click may use
+  the 25 MiB file cap but still observes cache/decoder budgets.
+- [x] Ensure a repeated click cannot create duplicate unguarded fetch tasks.
+- [x] Keep non-image attachments manual-only.
+
+### 3C. Exact transfers, local reads, and served files
+
+- [x] In `IrohTransport::fetch_blob`, require `bytes.len() as u64 == declared_size`.
+  Reject empty, short, and overlong transfers with a concise local error.
+- [x] Replace the file picker's unbounded `FileHandle::read()` with a helper that
+  reads at most `MAX_ATTACHMENT_BYTES + 1`. Check metadata first where available,
+  but retain the bounded read because metadata can race or be unavailable through
+  a portal.
+- [x] Avoid duplicating a full attachment across UI, command queue, and serve store.
+  Prefer `Arc<Vec<u8>>`/`Arc<[u8]>` through `AttachmentState`, `CoreCommand`, and
+  `serve_attachment`, subject to iced handle API constraints.
+- [x] Replace the unbounded session `served_files` map with a count- and byte-
+  budgeted FIFO store. Evicted ids should produce the existing “sender no longer
+  has the file” response rather than stale or aliased data.
+- [x] Keep attachment ids keyed by author on receipt and preserve all existing
+  request-length, timeout, filename, and decoder checks.
+
+### Phase 3 tests
+
+- [x] Byte-budget eviction, count eviction, replacement accounting, clear/reset,
+  and an individually overweight entry.
+- [x] Decoded-preview budget and downscale dimensions for wide, tall, square, and
+  boundary images.
+- [x] Image with valid per-side dimensions but excessive total pixels is rejected.
+- [x] A declared 4 MiB image auto-fetches; the first byte over the limit requires a
+  click.
+- [x] Per-author/session auto-fetch budgets recover according to their policy and
+  never exceed task concurrency.
+- [x] Short, exact, and overlong file responses.
+- [x] Local file reader stops at cap + 1 instead of allocating the full source.
+- [x] Served-file FIFO/byte eviction and replacement accounting.
+- [x] Same attachment id from two authors remains isolated throughout fetch, cache,
+  save, and display.
+
+## Phase 4 — URL and rendering resilience
+
+**Target:** keep clickable links without making malformed/deceptive input or many
+small spans an unnecessary UI/launcher surface.
+
+- [x] Make `url` a direct dependency (already present transitively) and validate
+  link candidates with `url::Url`.
+- [x] A clickable URL must have an `http` or `https` scheme and a valid host.
+- [x] Treat URLs containing username/password syntax as plain text, or require an
+  explicit confirmation that shows the parsed destination host. Prefer plain text
+  for the first implementation.
+- [x] Preserve the existing defense-in-depth validation in `AppMessage::OpenUrl`;
+  replace prefix checks with the shared parsed-URL policy.
+- [x] Cap clickable candidates at eight per message. Remaining content stays
+  selectable plain text and must still round-trip exactly.
+- [x] Refactor linkification to return borrowed ranges/offsets or cache link ranges
+  in `ChatEntry`, avoiding allocation and rescanning on every redraw.
+- [x] Bound retained history by total sanitized text bytes as well as 300 entries.
+  Eviction must keep attachment bookkeeping coherent and should not invalidate an
+  open Save/Play operation.
+- [x] Do not add metadata fetching, remote images, Markdown, or link previews.
+- [x] (Folded in from S14, per the security handoff) Strip bidi
+  overrides/isolates from the chat BODY in `sanitize_chat`, keeping the other
+  expressive format characters (ZWJ/ZWNJ/LRM/RLM).
+
+### Phase 4 tests
+
+- [x] Valid HTTP/HTTPS, malformed host, empty host, mixed case, Unicode path/query,
+  punctuation, credentials/userinfo, and non-web schemes.
+- [x] Eight-link boundary and many-link adversarial input.
+- [x] Segment/range reconstruction exactly reproduces the sanitized message.
+- [x] Entry-count and total-text-budget history eviction.
+- [x] Opener policy cannot launch a non-web scheme even if called directly.
+
+## Phase 5 — Honest local send status
+
+**Target:** never present a locally echoed message as successfully broadcast when
+the core rejected it or gossip broadcast failed.
+
+- [x] Add a local-only message id and `Pending`/`Broadcast`/`Failed` state to local
+  chat entries. Do not put this id or state on the wire. (`ChatEntry.local_send:
+  Option<LocalSend>`; `SendStatus` also has `Queued` for the paced-but-not-yet-sent
+  state — see the pacing decision-log entry.)
+- [x] Carry the local id through `CoreCommand::SendChat`/`SendChatFile` and return a
+  `UiEvent` result after the local gossip broadcast call succeeds or fails.
+  (`SendChat`/`SendChatFile` gained `local_id`; new `UiEvent::ChatSendResult { local_id,
+  error }`.)
+- [x] If the core is not in an active session, return failure instead of silently
+  doing nothing. (`send_chat` now `Err`s on missing sender/topic and on encode
+  failure; the core arm maps no-session to a `ChatSendResult` error.)
+- [x] Show failure compactly with a retry action. A successful local broadcast must
+  not be labeled “delivered” or “read”; PeerSpeak has no peer acknowledgements.
+  (Failed → red "⚠ Not sent — {reason}  [Retry]" line; Broadcast/Pending render
+  nothing — silence is the honest success state.)
+- [x] Retry creates one new signed broadcast while retaining replay correctness and
+  attachment serving state. (`RetryChatSend(id)` re-dispatches the retained
+  `PendingSend`; re-serving the same attachment id REPLACES the `ServeStore`
+  entry, never double-counts — see `serve_store_replacement_accounting_and_remove_clear`.)
+
+### Phase 5 tests
+
+- [x] Local echo starts pending, becomes broadcast on success, and becomes failed
+  on no-session/channel/gossip error. (`send_status_pending_then_broadcast_on_success`,
+  `send_status_failed_keeps_payload_for_retry`.)
+- [x] Results update only the matching local entry, including after history
+  eviction or room reset. (`send_result_updates_only_the_matching_entry`,
+  `send_result_after_eviction_drops_orphan_payload`, `send_result_after_room_reset_is_a_noop`.)
+- [x] Retry does not duplicate served bytes or mutate an unrelated entry.
+  (`retry_redispatches_only_the_targeted_send`; served-byte dedup =
+  `serve_store_replacement_accounting_and_remove_clear` in `files.rs`.)
+
+## Compatibility and versioning
+
+- The planned implementation changes validation, local data structures, and
+  internal `CoreCommand`/`UiEvent` shapes only. Keep the serialized
+  `GossipMessage::Chat` and file request/response formats unchanged.
+- Therefore do **not** bump `GOSSIP_PROTO`, `FILES_PROTO`, or the pre-1.0 MINOR
+  solely for this plan. The eventual release is a compatible PATCH unless scope
+  expands into a wire change.
+- If implementation requires removing/adding serialized fields, changing
+  attachment request framing, or introducing acknowledgements on the wire, stop
+  and revise this section before coding that part. Follow `VERSIONING.md` and use
+  the appropriate protocol plus release MINOR bump.
+
+## Verification gates
+
+Run after each phase, with focused tests first and the full gates before handoff:
+
+```text
+cargo fmt --check
+cargo test --lib
+cargo test --all-targets
+cargo clippy --all-targets -- -D warnings
+```
+
+Also retain the existing ignored/loopback coverage where the environment supports
+it; do not make ordinary unit tests depend on external network access.
+
+### Two-machine field test
+
+- [ ] Ordinary ASCII/Unicode conversation, rapid short burst, long boundary text,
+  and oversized paste.
+- [ ] Rename during a room: new lines use the new roster name; old lines retain
+  their snapshot.
+- [ ] Disconnect/reconnect grace and post-leave chat admission behavior.
+- [ ] Multiple normal images, one image above the auto threshold, a malformed
+  “image”, and a maximum-size manual file.
+- [ ] Download/save after cache eviction; clear failure state and no runaway
+  memory across repeated attachments.
+- [ ] Observe process RSS and UI responsiveness during a bounded spam/attachment
+  stress run; verify leave/reconnect controls remain responsive.
+- [ ] Linux and Windows URL opening for valid links; malformed/userinfo links remain
+  selectable but do not launch.
+- [ ] A message with more than eight URLs renders eight clickable links and the
+  rest as selectable plain text, with nothing dropped.
+- [ ] A message attempting bidi-override display spoofing renders in send order
+  (the override characters are stripped, emoji/joining-script text intact).
+- [ ] Send a fast burst (>8 messages in a second): all arrive at the peer in
+  order, none silently lost; the sender sees "queued…" on the overflow that
+  then clears as each goes out.
+- [ ] Send with no active session (or a failing broadcast): the message shows
+  "⚠ Not sent" with a Retry, and Retry resends it once when connectivity is back.
+
+## Completion criteria
+
+The plan is complete when:
+
+1. Only active/grace-rostered authenticated authors reach chat UI state.
+2. Chat identity is roster-bound and cannot be overridden by the embedded wire
+   name.
+3. Exact replay and sustained spam are bounded before shared event queues.
+4. Live input, inbound/outbound body size, history text, attachment caches,
+   automatic transfers, served files, and decoded previews all have tested hard
+   bounds.
+5. File transfer length and image decoding/display costs are validated.
+6. Clickable links pass a shared parsed-URL policy and rendering work is bounded.
+7. Local broadcast failure is visible without claiming peer delivery.
+8. Unit/all-target/clippy gates and the two-machine field test pass.
+9. Relevant durable docs (`README.md`, `docs/FEATURES.md`, `CHANGELOG.md`, security
+   notes, and comments) describe the final behavior.
+10. This ephemeral plan is deleted after its useful status/history is transferred
+    to durable documentation.
+
+## Out of scope
+
+- Link previews, metadata fetches, or remote thumbnail requests.
+- Persistent/offline chat history or server-side message storage.
+- Markdown, rich embeds, reactions, editing, deletion, threads, or search.
+- Read receipts or peer delivery acknowledgements.
+- Moderation UI, kicking, blocking, or trust-list redesign.
+- Antivirus/malware scanning of user-requested downloaded files.
+- A new application-layer group-encryption protocol or a broader cryptographic
+  redesign. If PeerSpeak makes a formal end-to-end-encryption product claim, audit
+  and document the exact iroh/gossip/relay threat model as a separate project.
+
+## Decision log
+
+- **2026-07-15:** Chose hardening over automatic link previews because receiving a
+  message should not trigger third-party web requests or weaken PeerSpeak's
+  privacy-oriented design.
+- **2026-07-15:** Initial scope keeps all wire formats stable; hardening is local
+  admission, validation, resource accounting, and honest UI state.
+- **2026-07-17 (Phase 1):** The 8 KiB byte ceiling deliberately cannot bind on
+  *sanitized* output (2,000 scalars × 4 bytes = 8,000 ≤ 8,192), so inside
+  `sanitize_chat`/`cap_chat_input` it is defense in depth; its operative role is
+  the raw-ingress reject in `admit_chat_text`.
+- **2026-07-17 (Phase 1):** Interim until Phase 2's roster binding: the incoming
+  chat `name` now goes through the strict `sanitize_name` label sanitizer at the
+  UI edge (was the body sanitizer), so author labels already get bidi/zero-width
+  stripping and the 48-char label cap.
+- **2026-07-17 (Phase 1):** `send_chat` at the gossip sign point silently no-ops
+  (Ok) on an empty-after-sanitize body with no attachment rather than erroring;
+  the UI already prevents this case, and Phase 5's send-status work is where
+  send-path feedback gets designed.
+- **2026-07-17 (Phase 2):** Replay dedup is keyed on the payload's own Ed25519
+  **signature bytes** instead of a BLAKE3 digest (the plan allowed "an equally
+  collision-resistant existing primitive"): ed25519 signing is deterministic
+  (RFC 8032), so the 64-byte signature is already a collision-resistant
+  fingerprint of the exact signed bytes — same dedup power, zero new direct
+  dependencies. Cache entries are stamped with the signed envelope `ts` and
+  pruned once it exits the freshness window, because `verify_gossip` already
+  rejects such a frame before the cache is consulted.
+- **2026-07-17 (Phase 2):** A room-bucket reject refunds the just-consumed
+  author token, so a room-wide squeeze caused by other members does not also
+  drain an innocent author's personal budget.
+- **2026-07-17 (Phase 2):** Rate-limited frames are NOT entered into the replay
+  cache: only fully admitted chats are. A legitimate message the room was too
+  busy for, redelivered later by the swarm, is then displayed once instead of
+  being misread as a replay of something never shown.
+- **2026-07-17 (Phase 2):** The "wire name never renders" guarantee is
+  structural: the core event task binds the wire field as `name: _` and builds
+  `UiEvent::ChatMessage` exclusively from `ChatRoster::name_of`, so there is no
+  code path from wire name to UI. The roster map behavior is unit-tested; the
+  end-to-end impersonation scenario stays on the (still-open) two-machine
+  field-test list.
+- **2026-07-17 (Phase 2):** The channel-pressure requirement is met at the seam
+  level: chat admission is bounded (32-burst / 8-per-s room-wide) BEFORE any
+  `event_tx.send`, and `Announce`/`Leave` admission is independent of the chat
+  gate — verified by unit tests. A full gossip-loop pressure harness was not
+  built; the seam bound is what protects the channel.
+- **2026-07-17 (Phase 2):** An empty-after-sanitize roster name falls back to
+  the short node id, so a member who announces an all-control-character name
+  still gets a stable, non-blank chat label.
+- **2026-07-17 (Phase 2):** The "Consider applying the same local submit policy
+  to accidental rapid Enter" item is DEFERRED: the receiving side is the
+  security boundary (every peer independently enforces the buckets), and a
+  local silent drop would be a UX regression better designed alongside Phase
+  5's honest send status.
+- **2026-07-18 (Phase 3):** Constants that deviate from the proposed table, all
+  bound-tested: total decoded pixels **14 MP** (not 16 MP) so the bound clears
+  12 MP phone photos (4032×3024) yet actually binds inside the 4096²≈16.8 MP
+  per-side envelope; cache encoded budget **96 MiB** (not 128) — still several
+  full-size files, tighter worst case; serve store **128 MiB + 16 entries**
+  (not 256 MiB) — a sender's own session should not pin a quarter GiB.
+- **2026-07-18 (Phase 3):** `validate_image_bytes`/`decode_preview` precheck
+  dimensions from the container HEADER (`into_dimensions`) before any pixel
+  decode, so an over-limit decode bomb is rejected without paying its decode
+  cost; the decode-time `image::Limits` remain as defense in depth, and the
+  decoded dimensions must equal the prechecked header dimensions.
+- **2026-07-18 (Phase 3):** Budget-pressure evictions leave NO cache entry
+  (absence = NotFetched → the same Load/Download affordance), while the
+  explicit `Evicted` state marks only an *individually over-budget* fetch whose
+  bytes were used once (pending Save/Play serviced from hand) and dropped. Both
+  render load-on-demand; only the bookkeeping differs.
+- **2026-07-18 (Phase 3):** The core still runs `validate_image_bytes` before
+  emitting `AttachmentReady`, and the UI decodes once more to build the ≤1600px
+  preview. Two bounded decodes per image were accepted over shipping decoded
+  RGBA across the channel (which would defeat the encoded-only Arc sharing).
+- **2026-07-18 (Phase 3):** The image lightbox now enlarges the ≤1600px preview
+  handle, not the original bitmap — originals are retained encoded-only for
+  Save. At the lightbox's window-sized draw area the visual difference is nil
+  for the chat use case; full fidelity remains one Save away.
+- **2026-07-18 (Phase 3):** `AutoFetchBudget` checks all four buckets
+  (author/session × requests/bytes) and only then consumes atomically, so a
+  rejection burns nothing (no refund path like Phase 2's room bucket needed).
+  Tokens ARE consumed if the four-permit semaphore then rejects the spawn —
+  that only happens mid-flood, when charging the author is the intent.
+- **2026-07-18 (Phase 3):** The auto-fetch budget's author map prunes
+  least-recently-active past 64 entries instead of wiring roster eviction into
+  the event task: authors are roster-gated upstream (≤32 live members), so
+  strangers cannot churn the map, and a pruned author returning with full
+  buckets is within policy.
+- **2026-07-18 (Phase 3):** Music-track serving shares the bounded serve store
+  with chat attachments. A user who sends enough large attachments during a
+  broadcast can evict their own current track; listeners then get the standard
+  "sender no longer has the file" failure. Accepted: budget honesty over a
+  second store, and the store comfortably fits current+next track plus a
+  normal chat working set.
+- **2026-07-18 (Phase 3):** The clip player's command channel still takes one
+  owned byte copy at the moment of a Play click (small, human-initiated). The
+  Arc de-duplication targeted the send path (UI cache / command queue / serve
+  store), which now shares a single allocation.
+- **2026-07-18 (Phase 3):** Overlong transfers are rejected by the transport
+  read itself (`read_to_end(size)` errors past the bound) rather than an
+  explicit length compare; short transfers get the explicit
+  `len == declared_size` check. Music fetches ride `fetch_blob`, so they
+  inherit exactness for free.
+- **2026-07-18 (Phase 4):** The S14 chat-body half (bidi strip) landed here per
+  the security handoff: `sanitize_chat` strips ONLY bidi overrides/isolates
+  (U+202A–202E, U+2066–2069) — the characters that can visually reorder a
+  rendered line — while ZWJ/ZWNJ (emoji sequences, joining scripts) and the
+  LRM/RLM direction *marks* (which cannot reorder) are kept. Labels/filenames
+  keep the stricter full-format-strip.
+- **2026-07-18 (Phase 4):** A link's href is the exact displayed slice of the
+  message — validation is parse-only, no normalization on open — so what the
+  user sees IS the argv the opener receives. Consequence: WHATWG slash
+  collapsing means `http:///path` parses to host `path` (as in browsers) and is
+  accepted; the empty-host rejects are `http://` and friends that fail parsing.
+- **2026-07-18 (Phase 4):** URLs with userinfo syntax went the plan-preferred
+  plain-text route (no confirmation dialog). A candidate that fails the policy
+  leaves its WHOLE whitespace-delimited run as plain text without re-scanning
+  the interior — `http://a@http://b.com` yields zero links, by design.
+- **2026-07-18 (Phase 4):** Scheme detection became ASCII-case-insensitive
+  (`Http://…` from sentence auto-capitalization now linkifies); the policy
+  check is unaffected since `url` normalizes scheme/host case during parsing.
+- **2026-07-18 (Phase 4):** Cached ranges in `ChatEntry.links`, filled inside
+  `push_chat` (the single history choke point), were chosen over
+  borrowed-return-per-redraw: redraws now slice cached char-boundary ranges,
+  and only link spans allocate (their href String).
+- **2026-07-18 (Phase 4):** History byte-budget eviction (512 KiB, alongside
+  the 300-entry cap) deliberately does NOT touch the attachment byte cache:
+  that cache is bounded by its own Phase 3 budgets, and leaving it alone means
+  an open Save/Play on an evicted line keeps its bytes-in-hand (the save
+  dialog falls back to the generic "download" name). The just-pushed entry is
+  never evicted; a single message's 8 KiB ceiling cannot exceed the budget.
+- **2026-07-18 (Phase 5):** Sender-side PACING was added to Phase 5's scope
+  (originally receiver-status only). The Phase 2 decision log deferred the
+  "apply the same local submit policy to accidental rapid Enter" item to pair
+  with Phase 5, and honest status alone would still let a fast burst broadcast
+  successfully yet be silently dropped by every receiver's per-author bucket
+  (8 burst, then 1/s) with no sender feedback. The user chose "queue and
+  trickle" over "throttle input": sends past the burst queue locally as
+  `SendStatus::Queued` ("queued…") and release at the receivers' sustained
+  rate, so nothing is lost and typing is never blocked.
+- **2026-07-18 (Phase 5):** The pacer (`src/app/sendqueue.rs`) reuses the
+  gossip gate's OWN `TokenBucket` + `CHAT_AUTHOR_BURST`/`CHAT_AUTHOR_REFILL_PER_MS`
+  (made `pub(crate)`), so the two sides of the rate policy are one definition
+  and cannot drift. It mirrors only the PER-AUTHOR budget, not the room-wide
+  one — we cannot know other members' send rates, and the per-author bucket is
+  the one guaranteed to apply to us at every receiver.
+- **2026-07-18 (Phase 5):** Send status renders as a line UNDER the message
+  (user pick over an inline suffix glyph); `Broadcast` and the transient
+  `Pending` show nothing because PeerSpeak has no delivery/read receipts, so an
+  unadorned message IS the honest "handed to the swarm" state. Only `Queued`
+  and `Failed` (with Retry) are surfaced.
+- **2026-07-18 (Phase 5):** The pacer and the monotonic send-id counter
+  deliberately SURVIVE a room reset while the queue and retry payloads are
+  cleared: receivers' per-author buckets persist across our rejoin (so the
+  pacer should not refill to full), and never-reused ids keep a late
+  `ChatSendResult` from a pre-reset send from aliasing a new entry — verified by
+  `send_result_after_room_reset_is_a_noop`.
+- **2026-07-18 (Phase 5):** The pacer clock is `Instant`-based
+  (`AppState.send_clock`), not wall-clock, so a system time jump can neither
+  rewind nor fast-forward the send budget.
+
+## Completion
+
+All five phases are implemented and every gate is green. Per the scope-contract
+note at the top, this file should be DELETED once the owed two-machine field
+test (the checklist below) has been run — that deletion is a separate,
+user-gated step, not part of the Phase 5 commit. Until then the plan stays as
+the record of what shipped and what remains to verify on real hardware.

packaging/PKGBUILD

@@ -1,12 +1,12 @@
 # Maintainer: mollusk <jitty+lc1iz0dc@protonmail.com>
 pkgname=peerspeak-git
 _pkgname=peerspeak
-pkgver=0.1.0
+pkgver=0.6.2.r319.g8014edf
 pkgrel=1
 pkgdesc="Decentralized peer-to-peer voice chat (Rust/iroh/PipeWire/Opus/iced)"
 arch=('x86_64')
 url="https://gitbutter.xyz/mollusk/peerspeak"
-license=('custom')
+license=('MIT')
 depends=('pipewire' 'opus')
 makedepends=('git' 'cargo' 'pkgconf')
 optdepends=('pixelpass: screen sharing inside a room'
@@ -14,7 +14,7 @@ optdepends=('pixelpass: screen sharing inside a room'
 provides=('peerspeak')
 conflicts=('peerspeak')
 options=('!lto' '!debug')
-source=("$_pkgname::git+ssh://git@gitbutter.xyz/mollusk/peerspeak.git")
+source=("$_pkgname::git+https://gitbutter.xyz/mollusk/peerspeak.git")
 sha256sums=('SKIP')
 
 pkgver() {
@@ -38,6 +38,11 @@ build() {
   export CARGO_HOME="$srcdir/cargo-home"
   export RUSTUP_TOOLCHAIN=stable
   export CARGO_TARGET_DIR=target
+  # Strip the build directory out of paths embedded in the binary (Rust bakes
+  # source paths into panic/backtrace metadata that survives stripping), so the
+  # package doesn't reference $srcdir. One remap covers our sources and the
+  # vendored deps, since CARGO_HOME lives under $srcdir too.
+  export RUSTFLAGS="${RUSTFLAGS:-} --remap-path-prefix=$srcdir=/"
   cargo build --frozen --release --bin "$_pkgname"
 }
 
@@ -65,4 +70,9 @@ package() {
     install -Dm644 "assets/icons/$_pkgname-$s.png" \
       "$pkgdir/usr/share/icons/hicolor/${s}x${s}/apps/$_pkgname.png"
   done
+
+  # License + third-party attribution notices.
+  install -Dm644 LICENSE "$pkgdir/usr/share/licenses/$_pkgname/LICENSE"
+  install -Dm644 THIRD_PARTY_LICENSES \
+    "$pkgdir/usr/share/licenses/$_pkgname/THIRD_PARTY_LICENSES"
 }

packaging/appimage/.gitignore

@@ -0,0 +1,4 @@
+.tools/
+AppDir/
+*.AppImage
+squashfs-root/

packaging/appimage/AppRun

@@ -0,0 +1,11 @@
+#!/bin/sh
+# AppRun for the PeerSpeak AppImage.
+#
+# PeerSpeak bundles the pixelpass screen-share helper in usr/bin. We prepend our
+# own usr/bin to PATH so peerspeak's $PATH lookup for `pixelpass` finds the
+# bundled copy, while the host's tools (gst-launch-1.0, pactl, mpv — which
+# pixelpass in turn shells out to) remain reachable via the appended host PATH.
+# That no-sandbox spawning is exactly why this app suits AppImage over Flatpak.
+HERE="$(dirname "$(readlink -f "$0")")"
+export PATH="$HERE/usr/bin:$PATH"
+exec "$HERE/usr/bin/peerspeak" "$@"

packaging/appimage/README.md

@@ -0,0 +1,76 @@
+# PeerSpeak AppImage
+
+A "thin" AppImage: the `peerspeak` binary, the bundled `pixelpass` screen-share
+helper, a launcher (`AppRun`), and the desktop entry + icon. Run
+`./build-appimage.sh` to produce `peerspeak-<version>-x86_64.AppImage`.
+
+## Why thin, and why pixelpass is bundled
+
+PeerSpeak owns voice; **pixelpass** owns pixels. They are never Cargo
+dependencies of each other — peerspeak shells out to the `pixelpass` binary over
+its CLI. The AppImage co-locates `pixelpass` in `usr/bin`, and `AppRun` prepends
+`usr/bin` to `PATH`, so peerspeak's normal `$PATH` lookup finds it with no code
+change. Joe gets one file, and screen-share works out of the box.
+
+Almost nothing is bundled: peerspeak's own assets (notification WAVs, avatar
+presets, window icon, fonts) are `include_bytes!`-embedded, and the graphics
+stack (`libGL`, `libvulkan`, `libwayland-*`, `libxkbcommon`, X11) is dlopen'd at
+runtime and on the AppImage excludelist because it must match the host driver.
+So the image carries just the two binaries plus a handful of small libs.
+
+## Host requirements
+
+The AppImage runs on any reasonably current glibc-based distro that has:
+
+- **A Vulkan-capable GPU + driver** (peerspeak's iced/wgpu renderer). Mesa/RADV
+  on AMD/Intel or the NVIDIA driver all work.
+- **PipeWire** (with the PulseAudio shim, for `pactl`).
+- For **screen-share only** — pixelpass shells out to these on the host `PATH`;
+  it prints the exact package names for your distro if any are missing:
+  - **GStreamer + plugins** (`gst-launch-1.0`/`gst-inspect-1.0`, base,
+    good/bad/ugly, libav, and the PipeWire plugin),
+  - **mpv** (or vlc) for the viewer side,
+  - on X11, `xwininfo` for single-window capture.
+
+On Arch/Artix that is one pacman line, e.g.:
+
+```sh
+sudo pacman -S gstreamer gst-plugins-base gst-plugins-good gst-plugins-bad \
+  gst-plugins-ugly gst-libav gst-plugin-pipewire mpv xorg-xwininfo libpulse
+```
+
+(Add `gstreamer-vaapi` for hardware H.264 encode on AMD/Intel; the software
+x264 path always works. On XLibre / X11 the capture path uses `ximagesrc` and
+needs no XDG portal — no systemd required.)
+
+## Building for broad compatibility (glibc baseline)
+
+An AppImage requires a host glibc **at least as new** as the build host's. Built
+on a rolling distro (glibc 2.43) it only runs on equally-new systems. Build
+inside **Ubuntu 24.04** (glibc 2.39, PipeWire 1.0.5) for wide reach — pixelpass's
+`pipewire` crate binds the system PipeWire headers and needs PipeWire >= 1.0, so
+the older Debian 12 `peerspeak-bookworm` box (PW 0.3.65) cannot build it. 2.39
+covers Debian 13+, Fedora 40+, and current rolling distros.
+
+```sh
+# One-time: an Ubuntu 24.04 distrobox that reuses the host rustup toolchain.
+distrobox create --yes --image ubuntu:24.04 --name peerspeak-appimage
+distrobox enter peerspeak-appimage -- sudo apt-get update
+distrobox enter peerspeak-appimage -- sudo apt-get install -y \
+  build-essential cmake clang libclang-dev pkg-config \
+  libpipewire-0.3-dev libspa-0.2-dev libasound2-dev libxcb1-dev \
+  curl ca-certificates file patchelf git
+
+# Build (the host's ~/.rustup toolchain is glibc-2.17-baseline, so it runs in the
+# box; isolated CARGO_TARGET_DIRs keep it off the host target/):
+distrobox enter peerspeak-appimage -- env \
+  PATH="$HOME/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/bin:$PATH" \
+  ./packaging/appimage/build-appimage.sh
+```
+
+## Caveats
+
+- **Hardware encode (VAAPI)** uses the host GPU driver and can't be bundled; the
+  software x264 path always works.
+- The bundled `pixelpass` is built headless (no `gui` feature) — it is only ever
+  driven by peerspeak, never launched standalone from this image.

packaging/appimage/build-appimage.sh

@@ -0,0 +1,89 @@
+#!/usr/bin/env bash
+# Build a "thin" PeerSpeak AppImage that also bundles the pixelpass screen-share
+# helper.
+#
+# PeerSpeak is an iced/wgpu GUI app; pixelpass is the separate screen-share
+# orchestrator peerspeak shells out to (never a Cargo dependency). Both link
+# almost nothing — the graphics stack (libGL, libvulkan, wayland, xkbcommon,
+# X11) is dlopen'd at runtime and is on the AppImage excludelist because it must
+# match the host driver, and pixelpass's capture/encode tools (gst-launch-1.0,
+# pactl, mpv) are expected on the host PATH. So the AppImage carries just the two
+# binaries plus their handful of non-excludelisted libs. The custom AppRun
+# prepends usr/bin to PATH so peerspeak's own $PATH lookup finds the bundled
+# pixelpass, while the host's tools stay reachable.
+#
+# All runtime assets (notification WAVs, avatar presets, window icon, fonts) are
+# include_bytes!-embedded in the peerspeak binary, so nothing else is bundled.
+#
+# Usage:   packaging/appimage/build-appimage.sh
+# Output:  packaging/appimage/peerspeak-<version>-x86_64.AppImage
+#
+# Build inside an Ubuntu 24.04 distrobox (glibc 2.39, PipeWire 1.0.5) for broad
+# reach — pixelpass's `pipewire` crate needs PipeWire >= 1.0 headers, so the
+# older peerspeak-bookworm box (PW 0.3.65) cannot build it. The 2.39 baseline
+# covers Debian 13+, Fedora 40+, and all current rolling distros. See README.md.
+set -euo pipefail
+
+here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+repo="$(cd "$here/../.." && pwd)"
+tools="$here/.tools"
+appdir="$here/AppDir"
+mkdir -p "$tools"
+
+# linuxdeploy is itself an AppImage; run it without FUSE so this works in a
+# container / on CI without libfuse2.
+export APPIMAGE_EXTRACT_AND_RUN=1
+VERSION="$(grep -m1 '^version' "$repo/Cargo.toml" | sed -E 's/.*"(.*)".*/\1/')"
+export VERSION
+
+# Isolated target dirs so an old-glibc box build never clobbers the host target/.
+cache="${PEERSPEAK_APPIMAGE_CACHE:-$HOME/.cache/peerspeak-appimage}"
+ps_target="$cache/peerspeak-target"
+pp_target="$cache/pixelpass-target"
+
+# The pixelpass screen-share helper we bundle. Sibling checkout by default.
+pixelpass_repo="${PIXELPASS_REPO:-$repo/../pixelpass}"
+if [ ! -d "$pixelpass_repo" ]; then
+  echo "!! pixelpass repo not found at $pixelpass_repo (set PIXELPASS_REPO)" >&2
+  exit 1
+fi
+
+echo ">> building peerspeak (release)"
+( cd "$repo" && CARGO_TARGET_DIR="$ps_target" cargo build --release )
+ps_bin="$ps_target/release/peerspeak"
+
+# Headless pixelpass: peerspeak drives it via `--host`/viewer + `--output json`,
+# never its GUI, so the default (no `gui` feature) keeps the GL toolkit out.
+echo ">> building pixelpass (release, headless) from $pixelpass_repo"
+( cd "$pixelpass_repo" && CARGO_TARGET_DIR="$pp_target" cargo build --release )
+pp_bin="$pp_target/release/pixelpass"
+
+echo ">> fetching linuxdeploy"
+ld="$tools/linuxdeploy-x86_64.AppImage"
+if [ ! -x "$ld" ]; then
+  curl -fL --retry 3 -o "$ld" \
+    "https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage"
+  chmod +x "$ld"
+fi
+
+echo ">> assembling AppDir"
+rm -rf "$appdir"
+mkdir -p "$appdir/usr/bin"
+install -m755 "$ps_bin" "$appdir/usr/bin/peerspeak"
+install -m755 "$pp_bin" "$appdir/usr/bin/pixelpass"
+
+echo ">> running linuxdeploy (bundles libs, builds the AppImage)"
+# -e (repeated): analyse both binaries for libraries to bundle; excludelisted
+#   graphics/glibc libs are skipped. -d/-i: desktop entry + icon.
+# --custom-apprun: our launcher that puts the bundled pixelpass on PATH.
+( cd "$here" && OUTPUT="peerspeak-${VERSION}-x86_64.AppImage" "$ld" \
+    --appdir "$appdir" \
+    -e "$appdir/usr/bin/peerspeak" \
+    -e "$appdir/usr/bin/pixelpass" \
+    -d "$repo/packaging/peerspeak.desktop" \
+    -i "$repo/assets/icons/peerspeak-256.png" \
+    --icon-filename peerspeak \
+    --custom-apprun "$here/AppRun" \
+    --output appimage )
+
+echo ">> done: $here/peerspeak-${VERSION}-x86_64.AppImage"

packaging/debian/README.md

@@ -0,0 +1,87 @@
+# Debian / Ubuntu `.deb` build
+
+This documents how the `peerspeak_*.deb` is produced, so the deb path is as
+self-documenting as the Arch (`packaging/PKGBUILD`) and AppImage paths.
+
+The deb **recipe itself** lives in-repo as the `[package.metadata.deb]` block in
+the top-level `Cargo.toml` (cargo-deb's equivalent of a PKGBUILD). This file
+documents only the **build environment**, which is otherwise undiscoverable from
+a fresh clone.
+
+## TL;DR
+
+```sh
+# one-time: create + provision the build box (see "Build environment" below)
+distrobox enter peerspeak-bookworm -- bash -lc '
+  source ~/.cargo/env
+  cd ~/git/butter/peerspeak
+  export CARGO_TARGET_DIR=~/.cache/cargo-deb-targets/peerspeak   # MANDATORY, see below
+  cargo deb
+'
+# output: $CARGO_TARGET_DIR/debian/peerspeak_<version>-1_amd64.deb
+```
+
+## Build environment
+
+- **Base: a Debian 12 (bookworm) distrobox named `peerspeak-bookworm`.**
+  Created with `distrobox create --name peerspeak-bookworm --image debian:12`.
+  Bookworm ships **glibc 2.36**, which sets the widest practical compatibility
+  floor (see "glibc floor" below).
+- **NEVER build the `.deb` on the Arch host.** Two independent reasons:
+  1. The Arch host's glibc is far newer, so the resulting `.deb` would demand a
+     glibc no normal Debian/Ubuntu user has, and ships an empty `Depends`.
+  2. distrobox shares `$HOME` (and therefore the repo's `target/`) with the host,
+     so a host build links Arch-compiled C objects into the "Debian" binary.
+
+### One-time provisioning inside the box
+
+```sh
+distrobox enter peerspeak-bookworm
+sudo apt update
+sudo apt install -y build-essential pkg-config clang libclang-dev \
+    libpipewire-0.3-dev libopus-dev libasound2-dev libxcb1-dev
+# clang/libclang -> pipewire-sys bindgen ; libxcb1-dev -> link
+curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y
+source ~/.cargo/env
+cargo install cargo-deb
+```
+
+### The mandatory separate `CARGO_TARGET_DIR`
+
+Because distrobox shares `$HOME`, the repo's default `target/` is the **same
+directory** the Arch host builds into. If you run `cargo deb` without overriding
+the target dir, cargo will happily reuse Arch-built `.o`/rlib artifacts and link
+them into the Debian binary, producing a `.deb` that crashes or demands the
+host's glibc.
+
+Always point the build at a box-local cache:
+
+```sh
+export CARGO_TARGET_DIR=~/.cache/cargo-deb-targets/peerspeak
+```
+
+(Run `cargo clean` first if you ever suspect a polluted target dir.)
+
+## glibc floor
+
+The `.deb` is built against the build box's glibc, which becomes the install
+floor (`libc6 (>= 2.36)` lands in `Depends` via `$auto`):
+
+| Build box            | glibc | Runs on                              |
+|----------------------|-------|--------------------------------------|
+| `debian:12` (current)| 2.36  | Debian 12+, Ubuntu 24.04+ (glibc ≥ 2.36) |
+| `ubuntu:26.04` (old) | 2.43  | Ubuntu 26.04+ only — too narrow, abandoned |
+
+If a friend is on something even older than Debian 12, drop the floor further by
+recreating the box from an older base image and rebuilding.
+
+## Runtime `Depends` / `Recommends`
+
+- `Depends = "$auto"` — cargo-deb runs `dpkg-shlibdeps`, which discovers the
+  linked shared libraries (PipeWire, Opus, ALSA, xcb, glibc, …) automatically.
+- `Recommends = "pixelpass, mpv"` — `pixelpass` provides in-room screen sharing
+  and `mpv` is the screen-share viewer (these are companion programs invoked as
+  subprocesses, not linked libraries, so they are Recommends not Depends).
+
+See `pixelpass`'s own `packaging/debian/README.md` for why **its** `Depends`
+lists the whole GStreamer stack explicitly.

packaging/windows/INSTALL.md

@@ -0,0 +1,108 @@
+# PeerSpeak — how to install and join a call (Windows)
+
+PeerSpeak is a little voice-chat app — like a private phone call over the
+internet, with no account, no signup, and no company in the middle. You install
+it once, then you and I connect directly to each other.
+
+---
+
+## 1. Install it
+
+1. Double-click **`peerspeak-<version>-setup.exe`** (the file I sent you).
+
+2. **Windows will probably show a blue "Windows protected your PC" warning.**
+   This is normal — it shows up for any app that isn't from a big company with a
+   paid certificate. It is **not** a virus warning.
+   - Click **More info**
+   - Then click **Run anyway**
+
+3. Windows will ask *"Do you want to allow this app to make changes?"* — click
+   **Yes**.
+
+4. The setup window opens. Just keep clicking **Next**. Two checkboxes you'll
+   see along the way:
+   - **"Allow PeerSpeak through Windows Firewall"** — leave this **checked**
+     (it lets the call connect without interruptions).
+   - **"Create a desktop shortcut"** — check it if you'd like an icon on your
+     desktop.
+
+5. Click **Install**, then **Finish**. PeerSpeak opens.
+
+That's it — it's installed. You can find it again any time from the **Start
+menu** (search "PeerSpeak").
+
+---
+
+## 2. Get on a call with me
+
+PeerSpeak connects two people using a **room ticket** — a long code that acts
+like a one-time phone number for a specific call.
+
+**The simple way (I host):**
+
+1. I'll create a room and send you a **ticket** (a long jumble of letters and
+   numbers).
+2. Copy the whole ticket I sent you.
+3. In PeerSpeak, paste it into the **"Join Room"** box near the bottom and press
+   **Join**.
+4. You're in — you should see both our names listed, and we can talk.
+
+**If you want to host instead:**
+
+1. Type a room name and click **Create New Room**.
+2. PeerSpeak gives you a **ticket** — click **Copy Ticket** and send it to me.
+3. I paste it on my end and join you.
+
+Either way works the same; it just depends on who makes the room.
+
+---
+
+## 3. While you're on a call
+
+- **Your microphone** is on by default. There's a **mute** button if you need
+  it.
+- The first time, Windows might ask for permission to use your **microphone** —
+  click **Yes / Allow**.
+- If you can't hear me or I can't hear you, open **Settings** (top right) and
+  check that the right **microphone** and **speakers/headphones** are selected.
+- To hang up, click **Leave Room**.
+
+---
+
+## 4. Chatting and sharing photos/files
+
+There's a **text chat** box at the bottom of the call window — type a message
+and press **Enter** to send it to everyone in the room.
+
+You can also **send a photo or a file**:
+
+1. Click the **attach button** (the small paperclip-style button) next to the
+   message box.
+2. Pick a photo or file from your computer.
+3. It sends to everyone in the room. **Photos show up right in the chat**;
+   other files appear as a small download chip with the file's name.
+
+To **save** a file someone sent you, click the **Save** (or **Download**)
+button next to it in the chat and choose where to put it.
+
+A couple of notes:
+- There's a size limit of about **25 MB** per file — bigger files are turned
+  away with a message.
+- Shared files only last for the **current call**. They aren't saved anywhere
+  automatically, so save anything you want to keep before you leave the room.
+
+---
+
+## Troubleshooting
+
+- **"I don't hear anything."** Open Settings and pick the correct microphone and
+  output device. Headphones are best — they prevent echo.
+- **"It won't connect."** Make sure you pasted the *entire* ticket (they're
+  long and easy to cut off). If it still won't connect, we may just need a fresh
+  ticket — they're meant to be used right away. Also make sure we're both on the
+  **same version** — if I've sent you an updated installer, install it (an old
+  version and a new one can't connect to each other).
+- **The blue warning again.** Same as install: **More info → Run anyway**. It's
+  the unsigned-app warning, not malware.
+
+Any trouble, just message me and we'll sort it out.

packaging/windows/README.md

@@ -0,0 +1,85 @@
+# PeerSpeak — Windows installer
+
+This directory builds a Windows setup installer for PeerSpeak using
+[Inno Setup](https://jrsoftware.org/isinfo.php).
+
+PeerSpeak ships as a **single self-contained `peerspeak.exe`** — the GUI icon,
+notification chimes, and avatar presets are all embedded in the binary
+(`include_bytes!`), and the executable is statically linked against the GNU
+runtime, so there are no extra DLLs to bundle. The installer payload is just the
+`.exe` plus an `.ico` for the Start-menu / desktop shortcuts.
+
+## Version compatibility
+
+The installer version tracks the release version in `Cargo.toml` — keep
+`MyAppVersion` in `peerspeak.iss` in sync when cutting a release. Do not reuse an
+old installer filename after a crate-version bump.
+
+Per `VERSIONING.md`, a **MINOR** bump in `0.x` is a **breaking wire change**:
+peers on different MINOR versions can't connect (they fail fast at the
+handshake rather than misbehaving). So when you ship a new Windows build after
+a MINOR bump, **everyone on the call must reinstall** — an old Windows build
+and a newer Linux/Windows peer won't talk. (0.3.0 was the chat file-sharing +
+per-peer noise-gate release; it cannot connect to a 0.2.x peer.)
+
+## Files
+
+| File | Tracked | Purpose |
+|------|---------|---------|
+| `peerspeak.iss` | yes | Inno Setup script |
+| `peerspeak.ico` | yes | multi-resolution app icon (from `assets/icons/*.png`) |
+| `README.md` | yes | this file |
+| `peerspeak.exe` | no (gitignored) | staged build artifact, copied from `target/x86_64-pc-windows-gnu/release/` |
+| `output/peerspeak-<ver>-setup.exe` | no (gitignored) | the compiled installer |
+
+## Build steps
+
+1. **Cross-compile the Windows binary** (from the repo root, inside the
+   `peerspeak-win` archlinux distrobox):
+
+   ```sh
+   RUSTC_BOOTSTRAP=1 ./win-cross-build.sh -Z build-std=std,panic_abort
+   ```
+
+   This needs the `rust-src` component and the `x86_64-pc-windows-gnu` target
+   installed in that toolchain. The result is a statically-linked,
+   GUI-subsystem `.exe` (no stray console window).
+
+2. **Stage the binary** next to the script:
+
+   ```sh
+   cp target/x86_64-pc-windows-gnu/release/peerspeak.exe packaging/windows/
+   ```
+
+3. **Regenerate the icon** if the source PNGs changed:
+
+   ```sh
+   magick assets/icons/peerspeak-16.png assets/icons/peerspeak-24.png \
+          assets/icons/peerspeak-32.png assets/icons/peerspeak-48.png \
+          assets/icons/peerspeak-64.png assets/icons/peerspeak-128.png \
+          assets/icons/peerspeak-256.png packaging/windows/peerspeak.ico
+   ```
+
+4. **Compile the installer** with Inno Setup. On Linux this runs under Wine:
+
+   ```sh
+   cd packaging/windows
+   wine ~/.wine/drive_c/InnoSetup6/ISCC.exe peerspeak.iss
+   ```
+
+   The installer lands at `output/peerspeak-<version>-setup.exe`.
+
+## What the installer does
+
+- Installs `peerspeak.exe` to `Program Files\PeerSpeak` (requires admin / one
+  UAC prompt).
+- Creates a Start-menu shortcut, with an optional desktop shortcut.
+- Optionally adds a Windows Firewall allow-rule for PeerSpeak (recommended —
+  iroh uses UDP hole-punching, so this avoids a mid-call firewall prompt). The
+  rule is removed on uninstall.
+- Provides a standard uninstaller.
+
+> **Note:** the installer and the binary are **not code-signed**, so Windows
+> SmartScreen will show an "unknown publisher" warning on first run. The user
+> clicks *More info → Run anyway*. Removing this warning requires a paid
+> code-signing certificate.

packaging/windows/peerspeak.iss

@@ -0,0 +1,63 @@
+; Inno Setup script for PeerSpeak (Windows installer).
+;
+; PeerSpeak is a single self-contained binary: the GUI icon, notification
+; chimes, and avatar presets are all embedded in the .exe (include_bytes!),
+; so the only payload here is peerspeak.exe plus an .ico for the shortcuts.
+;
+; Build (under Wine on Linux, or native Windows):
+;   wine "C:\Program Files (x86)\Inno Setup 6\ISCC.exe" peerspeak.iss
+; Output lands in .\output\peerspeak-<version>-setup.exe
+;
+; The peerspeak.exe is cross-compiled with win-cross-build.sh
+; (x86_64-pc-windows-gnu, statically linked -- no extra DLLs needed).
+
+#define MyAppName "PeerSpeak"
+#define MyAppVersion "0.6.5"
+#define MyAppPublisher "mollusk"
+#define MyAppExeName "peerspeak.exe"
+
+[Setup]
+; A stable AppId keeps upgrades/uninstall tracking consistent across versions.
+AppId={{2754D6C1-C8A4-4B13-9824-2D303439739D}
+AppName={#MyAppName}
+AppVersion={#MyAppVersion}
+AppVerName={#MyAppName} {#MyAppVersion}
+AppPublisher={#MyAppPublisher}
+DefaultDirName={autopf}\{#MyAppName}
+DefaultGroupName={#MyAppName}
+DisableProgramGroupPage=yes
+UninstallDisplayIcon={app}\{#MyAppExeName}
+SetupIconFile=peerspeak.ico
+Compression=lzma2/max
+SolidCompression=yes
+WizardStyle=modern
+OutputDir=output
+OutputBaseFilename=peerspeak-{#MyAppVersion}-setup
+; Program Files install + firewall rule both need elevation.
+PrivilegesRequired=admin
+ArchitecturesAllowed=x64compatible
+ArchitecturesInstallIn64BitMode=x64compatible
+
+[Languages]
+Name: "english"; MessagesFile: "compiler:Default.isl"
+
+[Tasks]
+Name: "desktopicon"; Description: "{cm:CreateDesktopIcon}"; GroupDescription: "{cm:AdditionalIcons}"; Flags: unchecked
+Name: "firewall"; Description: "Allow PeerSpeak through Windows Firewall (recommended for voice calls)"; GroupDescription: "Network:"
+
+[Files]
+Source: "peerspeak.exe"; DestDir: "{app}"; Flags: ignoreversion
+Source: "peerspeak.ico"; DestDir: "{app}"; Flags: ignoreversion
+
+[Icons]
+Name: "{group}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"; IconFilename: "{app}\peerspeak.ico"
+Name: "{group}\{cm:UninstallProgram,{#MyAppName}}"; Filename: "{uninstallexe}"
+Name: "{autodesktop}\{#MyAppName}"; Filename: "{app}\{#MyAppExeName}"; IconFilename: "{app}\peerspeak.ico"; Tasks: desktopicon
+
+[Run]
+; iroh uses UDP hole-punching; pre-authorizing avoids a mid-call firewall prompt.
+Filename: "{sys}\netsh.exe"; Parameters: "advfirewall firewall add rule name=""PeerSpeak"" dir=in action=allow program=""{app}\{#MyAppExeName}"" enable=yes profile=any"; Flags: runhidden; Tasks: firewall
+Filename: "{app}\{#MyAppExeName}"; Description: "{cm:LaunchProgram,{#MyAppName}}"; Flags: nowait postinstall skipifsilent
+
+[UninstallRun]
+Filename: "{sys}\netsh.exe"; Parameters: "advfirewall firewall delete rule name=""PeerSpeak"""; Flags: runhidden; RunOnceId: "DelPeerSpeakFirewall"

src/app/sendqueue.rs

@@ -0,0 +1,129 @@
+//! Sender-side chat send status and pacing (chat-hardening Phase 5).
+//!
+//! Every RECEIVER admits our chat through a per-author token bucket
+//! ([`CHAT_AUTHOR_BURST`] then 1/s) and silently drops what exceeds it, with no
+//! acknowledgement wire. The only way the sender can be honest about fast
+//! bursts is to never exceed that budget in the first place: sends past the
+//! burst are queued locally (shown as "queued…") and trickled out at the
+//! receivers' sustained rate. The pacer deliberately reuses the receiver
+//! gate's own [`TokenBucket`] and constants so the two sides of the policy
+//! cannot drift apart.
+//!
+//! Everything here is pure — `now_ms` is passed in, never read from a clock —
+//! so every boundary is unit-testable.
+
+use std::collections::VecDeque;
+
+use crate::network::gossip::{CHAT_AUTHOR_BURST, CHAT_AUTHOR_REFILL_PER_MS, TokenBucket};
+
+/// Send lifecycle of one locally authored chat message. Success is
+/// [`SendStatus::Broadcast`] — "our signed frame was handed to the gossip
+/// swarm" — deliberately NOT "delivered": PeerSpeak has no peer
+/// acknowledgements, so the honest success presentation is no label at all.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum SendStatus {
+    /// Waiting in the local outbound queue for a pacer token.
+    Queued,
+    /// Handed to the core; the broadcast result has not come back yet.
+    Pending,
+    /// The signed broadcast reached the gossip swarm.
+    Broadcast,
+    /// The send failed; carries a short reason. The entry offers a Retry.
+    Failed(String),
+}
+
+/// Local-only send bookkeeping attached to our own chat entries. The id never
+/// goes on the wire; it ties a `ChatSendResult` back to the matching echo.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct LocalSend {
+    pub id: u64,
+    pub status: SendStatus,
+}
+
+/// Sender-side pacer mirroring the receiver's per-author admission budget.
+#[derive(Debug, Clone, Copy)]
+pub struct SendPacer {
+    bucket: TokenBucket,
+}
+
+impl SendPacer {
+    pub fn new(now_ms: u64) -> Self {
+        Self {
+            bucket: TokenBucket::full(CHAT_AUTHOR_BURST, now_ms),
+        }
+    }
+
+    /// Take one send token if the mirrored per-author budget allows it now.
+    pub fn try_send(&mut self, now_ms: u64) -> bool {
+        self.bucket
+            .try_take(CHAT_AUTHOR_BURST, CHAT_AUTHOR_REFILL_PER_MS, now_ms)
+    }
+}
+
+/// Pop the queued ids that may be dispatched now: strict front-of-queue order,
+/// one pacer token each, stopping at the first refusal so a message can never
+/// overtake an earlier one.
+pub fn release_ready(queue: &mut VecDeque<u64>, pacer: &mut SendPacer, now_ms: u64) -> Vec<u64> {
+    let mut ready = Vec::new();
+    while !queue.is_empty() && pacer.try_send(now_ms) {
+        // The unwrap is safe: the loop condition just checked non-empty.
+        ready.push(queue.pop_front().unwrap());
+    }
+    ready
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const T0: u64 = 1_000_000;
+
+    #[test]
+    fn pacer_allows_the_full_burst_then_refuses() {
+        let mut pacer = SendPacer::new(T0);
+        for _ in 0..CHAT_AUTHOR_BURST as usize {
+            assert!(pacer.try_send(T0));
+        }
+        assert!(!pacer.try_send(T0));
+    }
+
+    #[test]
+    fn pacer_refills_at_one_per_second() {
+        let mut pacer = SendPacer::new(T0);
+        for _ in 0..CHAT_AUTHOR_BURST as usize {
+            assert!(pacer.try_send(T0));
+        }
+        // 999ms is just under one token; 1000ms grants exactly one.
+        assert!(!pacer.try_send(T0 + 999));
+        assert!(pacer.try_send(T0 + 1000));
+        assert!(!pacer.try_send(T0 + 1000));
+    }
+
+    #[test]
+    fn release_ready_preserves_order_and_stops_at_refusal() {
+        let mut pacer = SendPacer::new(T0);
+        // Drain the burst so only refill tokens remain.
+        for _ in 0..CHAT_AUTHOR_BURST as usize {
+            assert!(pacer.try_send(T0));
+        }
+        let mut queue: VecDeque<u64> = [10, 11, 12].into_iter().collect();
+        // 2 seconds of refill = 2 tokens: exactly the first two, in order.
+        let ready = release_ready(&mut queue, &mut pacer, T0 + 2000);
+        assert_eq!(ready, vec![10, 11]);
+        assert_eq!(queue, VecDeque::from([12]));
+        // No tokens left at the same instant.
+        assert!(release_ready(&mut queue, &mut pacer, T0 + 2000).is_empty());
+        assert_eq!(queue, VecDeque::from([12]));
+    }
+
+    #[test]
+    fn release_ready_empty_queue_consumes_no_tokens() {
+        let mut pacer = SendPacer::new(T0);
+        let mut queue = VecDeque::new();
+        assert!(release_ready(&mut queue, &mut pacer, T0).is_empty());
+        // The full burst must still be available.
+        for _ in 0..CHAT_AUTHOR_BURST as usize {
+            assert!(pacer.try_send(T0));
+        }
+    }
+}

src/audio/clip_player.rs

@@ -0,0 +1,331 @@
+//! Independent playback engine for inline chat audio attachments.
+//!
+//! The rodio device sink stays on a dedicated OS thread and never enters iced
+//! state or the call-audio pipeline. The GUI sends small commands and reads a
+//! shared status snapshot at its redraw cadence.
+
+use crate::files::AttachmentId;
+use rodio::{Decoder, DeviceSinkBuilder, MixerDeviceSink, Player, Source, decoder::DecoderError};
+use std::io::Cursor;
+use std::sync::{Arc, Mutex, mpsc};
+use std::time::Duration;
+
+/// State published by the playback thread for the GUI.
+#[derive(Debug, Clone, Default, PartialEq, Eq)]
+pub struct ClipStatus {
+    pub playing_id: Option<AttachmentId>,
+    pub position: Duration,
+    pub total: Option<Duration>,
+    pub paused: bool,
+    /// Set when output initialization or decoding rejects the requested clip.
+    /// The app consumes this as a signal to fall back to the normal file chip.
+    pub failure: Option<ClipFailure>,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ClipFailure {
+    pub id: AttachmentId,
+    pub error: String,
+    /// Decoder rejection means the filename hint should fall back to a file
+    /// chip. Output-device failures remain retryable as audio.
+    pub invalid_audio: bool,
+}
+
+pub type SharedClipStatus = Arc<Mutex<ClipStatus>>;
+
+#[derive(Debug)]
+enum ClipCommand {
+    Play(AttachmentId, Vec<u8>),
+    Pause,
+    Resume,
+    Seek(Duration),
+    Stop,
+    SetVolume(f32),
+}
+
+/// Cheap, `Send` command handle for the dedicated playback thread.
+pub struct ClipPlayer {
+    command_tx: mpsc::Sender<ClipCommand>,
+    status: SharedClipStatus,
+}
+
+impl ClipPlayer {
+    /// Start the playback worker. The system output device is opened lazily on
+    /// first Play, so merely launching PeerSpeak never claims another stream.
+    ///
+    /// `initial_volume` is the universal gain (`1.0` = unity) applied to every
+    /// clip, restored from config so the level persists across sessions.
+    pub fn new(initial_volume: f32) -> (Self, SharedClipStatus) {
+        let (command_tx, command_rx) = mpsc::channel();
+        let status = Arc::new(Mutex::new(ClipStatus::default()));
+        let worker_status = Arc::clone(&status);
+        std::thread::Builder::new()
+            .name("peerspeak-clip-player".to_string())
+            .spawn(move || playback_worker(command_rx, worker_status, initial_volume))
+            .expect("failed to spawn clip playback thread");
+        (
+            Self {
+                command_tx,
+                status: Arc::clone(&status),
+            },
+            status,
+        )
+    }
+
+    pub fn play(&self, id: AttachmentId, bytes: Vec<u8>) {
+        update_status(&self.status, |status| {
+            status.playing_id = Some(id);
+            status.position = Duration::ZERO;
+            status.total = None;
+            status.paused = false;
+            status.failure = None;
+        });
+        let _ = self.command_tx.send(ClipCommand::Play(id, bytes));
+    }
+
+    pub fn pause(&self) {
+        let _ = self.command_tx.send(ClipCommand::Pause);
+    }
+
+    pub fn resume(&self) {
+        let _ = self.command_tx.send(ClipCommand::Resume);
+    }
+
+    pub fn seek(&self, position: Duration) {
+        let _ = self.command_tx.send(ClipCommand::Seek(position));
+    }
+
+    pub fn stop(&self) {
+        let _ = self.command_tx.send(ClipCommand::Stop);
+    }
+
+    /// Set the universal playback gain (`1.0` = unity). Applies to the current
+    /// clip immediately and to every clip played afterwards.
+    pub fn set_volume(&self, volume: f32) {
+        let _ = self.command_tx.send(ClipCommand::SetVolume(volume));
+    }
+}
+
+fn playback_worker(
+    command_rx: mpsc::Receiver<ClipCommand>,
+    status: SharedClipStatus,
+    initial_volume: f32,
+) {
+    let mut output: Option<MixerDeviceSink> = None;
+    let mut player: Option<Player> = None;
+    // Universal gain remembered across clips so a level set on one upload
+    // carries to the next; reapplied to each freshly connected player.
+    let mut volume = initial_volume.max(0.0);
+
+    loop {
+        match command_rx.recv_timeout(Duration::from_millis(100)) {
+            Ok(ClipCommand::Play(id, bytes)) => {
+                // In-memory readers do not expose file metadata to rodio. Pass
+                // the known attachment length explicitly so formats without a
+                // duration in their headers (notably MP3 and Vorbis) can derive
+                // a total duration and support reliable seeking.
+                let source = match decode_clip(bytes) {
+                    Ok(source) => source,
+                    Err(error) => {
+                        fail(
+                            &status,
+                            id,
+                            format!("unsupported or invalid audio: {error}"),
+                            true,
+                        );
+                        continue;
+                    }
+                };
+                let total = source.total_duration();
+
+                if output.is_none() {
+                    match DeviceSinkBuilder::open_default_sink() {
+                        Ok(sink) => {
+                            let new_player = Player::connect_new(sink.mixer());
+                            new_player.set_volume(volume);
+                            player = Some(new_player);
+                            output = Some(sink);
+                        }
+                        Err(error) => {
+                            fail(
+                                &status,
+                                id,
+                                format!("audio output unavailable: {error}"),
+                                false,
+                            );
+                            continue;
+                        }
+                    }
+                }
+
+                if let Some(player) = player.as_ref() {
+                    player.clear();
+                    player.append(source);
+                    player.play();
+                    update_status(&status, |s| {
+                        s.playing_id = Some(id);
+                        s.position = Duration::ZERO;
+                        s.total = total;
+                        s.paused = false;
+                        s.failure = None;
+                    });
+                }
+            }
+            Ok(ClipCommand::Pause) => {
+                if let Some(player) = player.as_ref() {
+                    player.pause();
+                    update_status(&status, |s| s.paused = true);
+                }
+            }
+            Ok(ClipCommand::Resume) => {
+                if let Some(player) = player.as_ref() {
+                    player.play();
+                    update_status(&status, |s| s.paused = false);
+                }
+            }
+            Ok(ClipCommand::Seek(position)) => {
+                if let Some(player) = player.as_ref()
+                    && player.try_seek(position).is_ok()
+                {
+                    update_status(&status, |s| s.position = position);
+                }
+            }
+            Ok(ClipCommand::Stop) => {
+                if let Some(player) = player.as_ref() {
+                    player.clear();
+                }
+                reset(&status);
+            }
+            Ok(ClipCommand::SetVolume(level)) => {
+                volume = level.max(0.0);
+                if let Some(player) = player.as_ref() {
+                    player.set_volume(volume);
+                }
+            }
+            Err(mpsc::RecvTimeoutError::Disconnected) => break,
+            Err(mpsc::RecvTimeoutError::Timeout) => {}
+        }
+
+        if let Some(player) = player.as_ref() {
+            let (active, failed) = status
+                .lock()
+                .map(|s| (s.playing_id.is_some(), s.failure.is_some()))
+                .unwrap_or_default();
+            if active && !failed && player.empty() {
+                reset(&status);
+            } else if active && !failed {
+                update_status(&status, |s| {
+                    s.position = player.get_pos();
+                    s.paused = player.is_paused();
+                });
+            }
+        }
+    }
+}
+
+fn decode_clip(bytes: Vec<u8>) -> Result<Decoder<Cursor<Vec<u8>>>, DecoderError> {
+    let byte_len = bytes.len() as u64;
+    Decoder::builder()
+        .with_data(Cursor::new(bytes))
+        .with_byte_len(byte_len)
+        .build()
+}
+
+fn fail(status: &SharedClipStatus, id: AttachmentId, error: String, invalid_audio: bool) {
+    crate::log_msg(&format!("Inline audio playback failed: {error}"));
+    update_status(status, |s| {
+        // Keep the id active until the GUI observes the failure on its next
+        // tick. This guarantees the active-only timer cannot disappear in the
+        // small window between sending Play and decoder/output failure.
+        s.playing_id = Some(id);
+        s.position = Duration::ZERO;
+        s.total = None;
+        s.paused = false;
+        s.failure = Some(ClipFailure {
+            id,
+            error,
+            invalid_audio,
+        });
+    });
+}
+
+fn reset(status: &SharedClipStatus) {
+    update_status(status, |s| *s = ClipStatus::default());
+}
+
+fn update_status(status: &SharedClipStatus, update: impl FnOnce(&mut ClipStatus)) {
+    if let Ok(mut status) = status.lock() {
+        update(&mut status);
+    }
+}
+
+pub fn status_snapshot(status: &SharedClipStatus) -> ClipStatus {
+    status.lock().map(|s| s.clone()).unwrap_or_default()
+}
+
+/// Format clip time as `mm:ss` (hours are folded into minutes).
+pub fn format_time(duration: Duration) -> String {
+    let seconds = duration.as_secs();
+    format!("{}:{:02}", seconds / 60, seconds % 60)
+}
+
+/// Playback progress in `0.0..=1.0`; unknown and zero durations report zero.
+pub fn progress(position: Duration, total: Option<Duration>) -> f32 {
+    let Some(total) = total.filter(|duration| !duration.is_zero()) else {
+        return 0.0;
+    };
+    (position.as_secs_f64() / total.as_secs_f64()).clamp(0.0, 1.0) as f32
+}
+
+/// Convert a slider fraction into a clamped position within a clip.
+pub fn seek_target(fraction: f32, total: Duration) -> Duration {
+    total.mul_f64(f64::from(fraction.clamp(0.0, 1.0)))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use base64::Engine;
+
+    #[test]
+    fn in_memory_mp3_reports_duration() {
+        // One headerless constant-bitrate MP3 frame repeated to model files
+        // that do not carry an Xing/VBR duration header.
+        let frame = base64::engine::general_purpose::STANDARD
+            .decode("//sQxAAABIQVWVRggDCqCKiDNlAAAAGgS4BgAmTT2AQAABCxOD5d7gQOfqBAEHS4Ph/EAIRI7//0A0KBNpABgMRIDCSI04PcIFdF0PJKFgzlUf5eAoF8BRIPfh4FTvUDQl+dUi5pc0w=")
+            .expect("valid test fixture");
+        let bytes = frame.repeat(20);
+
+        let decoder = decode_clip(bytes).expect("CBR MP3 should decode");
+        assert!(decoder.total_duration().is_some());
+    }
+
+    #[test]
+    fn formats_clip_time() {
+        assert_eq!(format_time(Duration::ZERO), "0:00");
+        assert_eq!(format_time(Duration::from_secs(65)), "1:05");
+        assert_eq!(format_time(Duration::from_secs(3_661)), "61:01");
+    }
+
+    #[test]
+    fn progress_handles_unknown_zero_and_clamps() {
+        assert_eq!(progress(Duration::from_secs(1), None), 0.0);
+        assert_eq!(progress(Duration::from_secs(1), Some(Duration::ZERO)), 0.0);
+        assert_eq!(
+            progress(Duration::from_secs(5), Some(Duration::from_secs(10))),
+            0.5
+        );
+        assert_eq!(
+            progress(Duration::from_secs(20), Some(Duration::from_secs(10))),
+            1.0
+        );
+    }
+
+    #[test]
+    fn seek_target_clamps_fraction() {
+        let total = Duration::from_secs(100);
+        assert_eq!(seek_target(0.25, total), Duration::from_secs(25));
+        assert_eq!(seek_target(-1.0, total), Duration::ZERO);
+        assert_eq!(seek_target(2.0, total), total);
+    }
+}

src/audio/echo_cancel.rs

@@ -34,6 +34,18 @@ const NODE_READY_TIMEOUT: Duration = Duration::from_secs(3);
 /// nodes never leak past the call that created them.
 pub struct EchoCancelGuard {
     module_index: String,
+    source_name: String,
+    sink_name: String,
+}
+
+impl EchoCancelGuard {
+    pub fn source_name(&self) -> &str {
+        &self.source_name
+    }
+
+    pub fn sink_name(&self) -> &str {
+        &self.sink_name
+    }
 }
 
 impl Drop for EchoCancelGuard {
@@ -42,7 +54,10 @@ impl Drop for EchoCancelGuard {
             .arg("unload-module")
             .arg(&self.module_index)
             .output();
-        crate::log_msg(&format!("Echo cancel: unloaded module {}", self.module_index));
+        crate::log_msg(&format!(
+            "Echo cancel: unloaded module {}",
+            self.module_index
+        ));
     }
 }
 
@@ -53,17 +68,24 @@ impl Drop for EchoCancelGuard {
 /// `None` (or an empty string) to bind to the system defaults. Returns `Err` with
 /// a human-readable reason if `pactl` is missing, the load fails, or the nodes
 /// don't appear — the caller should fall back to the direct devices.
-pub fn enable(real_source: Option<&str>, real_sink: Option<&str>) -> Result<EchoCancelGuard, String> {
+pub fn enable(
+    real_source: Option<&str>,
+    real_sink: Option<&str>,
+) -> Result<EchoCancelGuard, String> {
     // Best-effort: clear any stale instance left by a crashed prior run so we
     // don't stack duplicate modules / fight over the virtual node names.
     unload_stale();
 
+    let owner_pid = std::process::id();
+    let source_name = format!("{EC_SOURCE}.{owner_pid}");
+    let sink_name = format!("{EC_SINK}.{owner_pid}");
+
     let mut cmd = Command::new("pactl");
     cmd.arg("load-module")
         .arg("module-echo-cancel")
         .arg("aec_method=webrtc")
-        .arg(format!("source_name={EC_SOURCE}"))
-        .arg(format!("sink_name={EC_SINK}"));
+        .arg(format!("source_name={source_name}"))
+        .arg(format!("sink_name={sink_name}"));
     if let Some(src) = real_source.filter(|s| !s.is_empty()) {
         cmd.arg(format!("source_master={src}"));
     }
@@ -85,12 +107,16 @@ pub fn enable(real_source: Option<&str>, real_sink: Option<&str>) -> Result<Echo
     if module_index.parse::<u64>().is_err() {
         return Err(format!("unexpected pactl output: {module_index:?}"));
     }
-    let guard = EchoCancelGuard { module_index };
+    let guard = EchoCancelGuard {
+        module_index,
+        source_name,
+        sink_name,
+    };
 
     // The virtual nodes appear shortly after the module loads; wait for both so
     // the subsequent capture/playback streams can actually target them. If they
     // never show, drop the guard (unloads) and report failure.
-    if !wait_for_nodes() {
+    if !wait_for_nodes(guard.source_name(), guard.sink_name()) {
         return Err("echo-cancel virtual nodes did not appear in time".to_string());
     }
 
@@ -102,10 +128,10 @@ pub fn enable(real_source: Option<&str>, real_sink: Option<&str>) -> Result<Echo
 }
 
 /// Polls until both virtual nodes exist or the timeout elapses.
-fn wait_for_nodes() -> bool {
+fn wait_for_nodes(source_name: &str, sink_name: &str) -> bool {
     let deadline = Instant::now() + NODE_READY_TIMEOUT;
     loop {
-        if node_present("sources", EC_SOURCE) && node_present("sinks", EC_SINK) {
+        if node_present("sources", source_name) && node_present("sinks", sink_name) {
             return true;
         }
         if Instant::now() >= deadline {
@@ -118,7 +144,12 @@ fn wait_for_nodes() -> bool {
 /// Whether `pactl list <kind> short` lists a node named `name`.
 /// `kind` is "sources" or "sinks".
 fn node_present(kind: &str, name: &str) -> bool {
-    let Ok(out) = Command::new("pactl").arg("list").arg(kind).arg("short").output() else {
+    let Ok(out) = Command::new("pactl")
+        .arg("list")
+        .arg(kind)
+        .arg("short")
+        .output()
+    else {
         return false;
     };
     String::from_utf8_lossy(&out.stdout)
@@ -126,10 +157,37 @@ fn node_present(kind: &str, name: &str) -> bool {
         .any(|line| line.split('\t').nth(1) == Some(name))
 }
 
-/// Unloads any leftover `module-echo-cancel` instance we previously created
-/// (identified by our virtual node names in its argument string). Best-effort.
+fn pid_from_ec_args(args: &str) -> Option<u32> {
+    let source_prefix = format!("source_name={EC_SOURCE}.");
+    args.split_whitespace()
+        .find_map(|arg| arg.strip_prefix(&source_prefix))?
+        .parse()
+        .ok()
+}
+
+fn ec_module_is_stale(args: &str, is_alive: impl Fn(u32) -> bool) -> bool {
+    pid_from_ec_args(args).is_some_and(|pid| !is_alive(pid))
+}
+
+#[cfg(target_os = "linux")]
+fn process_is_alive(pid: u32) -> bool {
+    std::path::Path::new("/proc").join(pid.to_string()).exists()
+}
+
+#[cfg(not(target_os = "linux"))]
+fn process_is_alive(_pid: u32) -> bool {
+    true
+}
+
+/// Unloads leftover PeerSpeak `module-echo-cancel` instances only when their
+/// owning process is gone. Best-effort and conservative on non-Linux platforms.
 fn unload_stale() {
-    let Ok(out) = Command::new("pactl").arg("list").arg("modules").arg("short").output() else {
+    let Ok(out) = Command::new("pactl")
+        .arg("list")
+        .arg("modules")
+        .arg("short")
+        .output()
+    else {
         return;
     };
     for line in String::from_utf8_lossy(&out.stdout).lines() {
@@ -137,8 +195,14 @@ fn unload_stale() {
         let index = cols.next().unwrap_or("");
         let name = cols.next().unwrap_or("");
         let args = cols.next().unwrap_or("");
-        if name == "module-echo-cancel" && args.contains(EC_SOURCE) && index.parse::<u64>().is_ok() {
-            let _ = Command::new("pactl").arg("unload-module").arg(index).output();
+        if name == "module-echo-cancel"
+            && ec_module_is_stale(args, process_is_alive)
+            && index.parse::<u64>().is_ok()
+        {
+            let _ = Command::new("pactl")
+                .arg("unload-module")
+                .arg(index)
+                .output();
             crate::log_msg(&format!("Echo cancel: cleaned up stale module {index}"));
         }
     }
@@ -155,12 +219,57 @@ mod tests {
     #[ignore]
     fn enable_creates_and_unloads_nodes() {
         let guard = enable(None, None).expect("module-echo-cancel should load");
-        assert!(node_present("sources", EC_SOURCE), "cleaned source must exist");
-        assert!(node_present("sinks", EC_SINK), "reference sink must exist");
+        let source_name = guard.source_name().to_string();
+        let sink_name = guard.sink_name().to_string();
+        assert!(
+            node_present("sources", &source_name),
+            "cleaned source must exist"
+        );
+        assert!(
+            node_present("sinks", &sink_name),
+            "reference sink must exist"
+        );
         drop(guard);
         // Give pactl a moment to tear the nodes down.
         std::thread::sleep(Duration::from_millis(300));
-        assert!(!node_present("sources", EC_SOURCE), "source must be gone after unload");
-        assert!(!node_present("sinks", EC_SINK), "sink must be gone after unload");
+        assert!(
+            !node_present("sources", &source_name),
+            "source must be gone after unload"
+        );
+        assert!(
+            !node_present("sinks", &sink_name),
+            "sink must be gone after unload"
+        );
+    }
+
+    #[test]
+    fn parses_owner_pid_only_from_our_source_name() {
+        assert_eq!(
+            pid_from_ec_args(
+                "aec_method=webrtc source_name=peerspeak_echocancel_source.4242 sink_name=peerspeak_echocancel_sink.4242"
+            ),
+            Some(4242)
+        );
+        assert_eq!(pid_from_ec_args("aec_method=webrtc"), None);
+        assert_eq!(
+            pid_from_ec_args("source_name=peerspeak_echocancel_source.not-a-pid"),
+            None
+        );
+        assert_eq!(
+            pid_from_ec_args("source_name=someone_elses_source.4242"),
+            None
+        );
+    }
+
+    #[test]
+    fn stale_decision_keeps_live_and_foreign_modules() {
+        let ours = "source_name=peerspeak_echocancel_source.4242";
+        assert!(!ec_module_is_stale(ours, |pid| pid == 4242));
+        assert!(ec_module_is_stale(ours, |_| false));
+        assert!(!ec_module_is_stale("source_name=foreign.4242", |_| false));
+        assert!(!ec_module_is_stale(
+            "source_name=peerspeak_echocancel_source.malformed",
+            |_| false
+        ));
     }
 }

src/audio/eq.rs

@@ -251,7 +251,10 @@ mod tests {
         let before = rms(&low);
         eq.process_frame(&mut low);
         let after = rms(&low);
-        assert!(after > before * 1.6, "low shelf should boost low RMS: {before} -> {after}");
+        assert!(
+            after > before * 1.6,
+            "low shelf should boost low RMS: {before} -> {after}"
+        );
     }
 
     #[test]
@@ -264,7 +267,10 @@ mod tests {
         let before = rms(&high);
         eq.process_frame(&mut high);
         let after = rms(&high);
-        assert!(after > before * 1.6, "high shelf should boost high RMS: {before} -> {after}");
+        assert!(
+            after > before * 1.6,
+            "high shelf should boost high RMS: {before} -> {after}"
+        );
     }
 
     #[test]
@@ -275,7 +281,10 @@ mod tests {
                 Biquad::peaking(DEFAULT_SAMPLE_RATE, MID_PEAK_HZ, gain, MID_Q),
                 Biquad::high_shelf(DEFAULT_SAMPLE_RATE, HIGH_SHELF_HZ, gain, SHELF_Q),
             ] {
-                assert!(b.coeffs.all_finite(), "coefficients must be finite at {gain} dB");
+                assert!(
+                    b.coeffs.all_finite(),
+                    "coefficients must be finite at {gain} dB"
+                );
             }
         }
     }
@@ -289,12 +298,11 @@ mod tests {
         });
         let mut frame = sine(1_000.0, 48_000, 30_000.0);
         eq.process_frame(&mut frame);
-        let peak = frame
-            .iter()
-            .map(|&s| i32::from(s).abs())
-            .max()
-            .unwrap_or(0);
-        assert!(peak > 1_000, "processed signal should retain audible energy");
+        let peak = frame.iter().map(|&s| i32::from(s).abs()).max().unwrap_or(0);
+        assert!(
+            peak > 1_000,
+            "processed signal should retain audible energy"
+        );
         assert!(
             frame.iter().any(|&s| s > 0) && frame.iter().any(|&s| s < 0),
             "a boosted sine should retain both polarities"

src/audio/gate.rs

@@ -169,7 +169,10 @@ mod tests {
             assert!(g.process(&mut f, 0.05), "loud frame must transmit");
             last = peak(&f);
         }
-        assert!(last >= 9900, "gain should reach ~1.0 on sustained loud input, got peak {last}");
+        assert!(
+            last >= 9900,
+            "gain should reach ~1.0 on sustained loud input, got peak {last}"
+        );
     }
 
     #[test]
@@ -179,8 +182,15 @@ mod tests {
         g.process(&mut f, 0.05);
         // 5ms attack @48k = 240 samples; across a 960-sample frame the gain ramps
         // 0->1, so the early samples are well below full scale (no instant click).
-        assert!(f[0].abs() < 5000, "attack should start near zero, got {}", f[0]);
-        assert!(f[FRAME - 1].abs() > 9000, "attack should complete within the frame");
+        assert!(
+            f[0].abs() < 5000,
+            "attack should start near zero, got {}",
+            f[0]
+        );
+        assert!(
+            f[FRAME - 1].abs() > 9000,
+            "attack should complete within the frame"
+        );
     }
 
     #[test]
@@ -193,8 +203,14 @@ mod tests {
         }
         // First quiet frame right after speech: hold keeps it open (not chopped).
         let mut q = frame(50); // rms ~0.0015, below close (0.03)
-        assert!(g.process(&mut q, 0.05), "first quiet frame must stay open (hangover)");
-        assert!(peak(&q) > 0, "held-open frame must not be silenced immediately");
+        assert!(
+            g.process(&mut q, 0.05),
+            "first quiet frame must stay open (hangover)"
+        );
+        assert!(
+            peak(&q) > 0,
+            "held-open frame must not be silenced immediately"
+        );
 
         // Hold is 200ms = 10 frames; keep feeding quiet until it fully closes.
         let mut closed = false;
@@ -205,7 +221,10 @@ mod tests {
                 break;
             }
         }
-        assert!(closed, "gate must eventually close and stop transmitting after sustained silence");
+        assert!(
+            closed,
+            "gate must eventually close and stop transmitting after sustained silence"
+        );
     }
 
     #[test]
@@ -216,8 +235,14 @@ mod tests {
         g.process(&mut f, 0.05); // open=0.05, close=0.03
         // A frame between close and open thresholds: rms ~0.04 (amp ~1310).
         let mut mid = frame(1310);
-        assert!(g.process(&mut mid, 0.05), "between-threshold frame must keep an open gate open");
-        assert!(g.open, "hysteresis: gate stays open above the close threshold");
+        assert!(
+            g.process(&mut mid, 0.05),
+            "between-threshold frame must keep an open gate open"
+        );
+        assert!(
+            g.open,
+            "hysteresis: gate stays open above the close threshold"
+        );
     }
 
     #[test]
@@ -225,7 +250,10 @@ mod tests {
         let mut g = NoiseGate::new(SR);
         // Never opened; feed silence — should report don't-transmit promptly.
         let mut f = frame(0);
-        assert!(!g.process(&mut f, 0.05), "an unopened gate on silence must not transmit");
+        assert!(
+            !g.process(&mut f, 0.05),
+            "an unopened gate on silence must not transmit"
+        );
     }
 
     #[test]
@@ -266,7 +294,11 @@ mod tests {
 
         let mut f2 = frame(10000);
         assert!(g.process(&mut f2, 0.05)); // enabled
-        assert!(f2[0].abs() > 9000, "expected first sample of enabled frame to have no fade-in, got {}", f2[0]);
+        assert!(
+            f2[0].abs() > 9000,
+            "expected first sample of enabled frame to have no fade-in, got {}",
+            f2[0]
+        );
     }
 
     #[test]
@@ -302,7 +334,10 @@ mod tests {
             let mut f = frame(1310);
             assert!(g.process(&mut f, 0.05));
         }
-        assert!(g.open, "gate must stay open (hold refreshed by mid-level input)");
+        assert!(
+            g.open,
+            "gate must stay open (hold refreshed by mid-level input)"
+        );
     }
 
     #[test]
@@ -333,6 +368,10 @@ mod tests {
             last_peak = peak(&f);
         }
         assert!(g.open);
-        assert!(last_peak >= 9900, "peak of the 3rd reopened frame must be >= 9900, got {}", last_peak);
+        assert!(
+            last_peak >= 9900,
+            "peak of the 3rd reopened frame must be >= 9900, got {}",
+            last_peak
+        );
     }
 }

src/audio/limiter.rs

@@ -123,7 +123,10 @@ mod tests {
         let out = lim.process(&loud, 1.0);
         let ceiling = lim.ceiling().ceil() as i16;
         for &s in &out {
-            assert!(s > 0, "positive loud input stays positive (no wrap), got {s}");
+            assert!(
+                s > 0,
+                "positive loud input stays positive (no wrap), got {s}"
+            );
             assert!(s <= ceiling, "sample {s} exceeded ceiling {ceiling}");
         }
     }
@@ -175,7 +178,10 @@ mod tests {
         let out_pos = lim.process(&pos_loud, 1.0);
         for &s in &out_pos {
             assert!(s > 0, "positive input stays positive, got {s}");
-            assert!(s <= ceiling_ceil, "positive sample {s} exceeded ceiling {ceiling_ceil}");
+            assert!(
+                s <= ceiling_ceil,
+                "positive sample {s} exceeded ceiling {ceiling_ceil}"
+            );
         }
 
         // Sustained negative loud sum
@@ -185,7 +191,10 @@ mod tests {
         let neg_ceiling = -ceiling_ceil;
         for &s in &out_neg {
             assert!(s < 0, "negative input stays negative, got {s}");
-            assert!(s >= neg_ceiling, "negative sample {s} exceeded negative ceiling {neg_ceiling}");
+            assert!(
+                s >= neg_ceiling,
+                "negative sample {s} exceeded negative ceiling {neg_ceiling}"
+            );
         }
     }
 
@@ -200,8 +209,14 @@ mod tests {
         let out = lim.process(&input, 8.0);
         for &s in &out {
             assert!(s > 0, "positive stays positive");
-            assert!(s <= ceiling_ceil, "sample {s} must be limited to ceiling {ceiling_ceil}");
-            assert!((s - ceiling_ceil).abs() <= 2, "sample {s} should ride the ceiling {ceiling_ceil}");
+            assert!(
+                s <= ceiling_ceil,
+                "sample {s} must be limited to ceiling {ceiling_ceil}"
+            );
+            assert!(
+                (s - ceiling_ceil).abs() <= 2,
+                "sample {s} should ride the ceiling {ceiling_ceil}"
+            );
         }
     }
 
@@ -213,7 +228,10 @@ mod tests {
         let out = lim.process(&input, 0.5);
         for (i, &s) in out.iter().enumerate() {
             let expected = (input[i] as f32 * 0.5).round() as i16;
-            assert!((s - expected).abs() <= 1, "sample {s} should be close to expected {expected}");
+            assert!(
+                (s - expected).abs() <= 1,
+                "sample {s} should be close to expected {expected}"
+            );
         }
 
         // Subsequently feed a new sample at unity gain. It must be transparent,
@@ -230,7 +248,12 @@ mod tests {
 
         let loud = vec![200_000i32; 10];
         let out = lim.process(&loud, 1.0);
-        assert!(out[0] <= ceiling_ceil, "first sample {} must not overshoot ceiling {}", out[0], ceiling_ceil);
+        assert!(
+            out[0] <= ceiling_ceil,
+            "first sample {} must not overshoot ceiling {}",
+            out[0],
+            ceiling_ceil
+        );
     }
 
     /// 5. Release direction & monotonicity.
@@ -247,13 +270,23 @@ mod tests {
 
         // Output should be monotonic (non-decreasing)
         for i in 1..out.len() {
-            assert!(out[i] >= out[i - 1], "output must be monotonic; index {} was {}, index {} was {}", i - 1, out[i - 1], i, out[i]);
+            assert!(
+                out[i] >= out[i - 1],
+                "output must be monotonic; index {} was {}, index {} was {}",
+                i - 1,
+                out[i - 1],
+                i,
+                out[i]
+            );
         }
 
         // The end sample should be closer to the original input than the start sample
         let start_diff = (mid_val as i16 - out[0]).abs();
         let end_diff = (mid_val as i16 - *out.last().unwrap()).abs();
-        assert!(end_diff < start_diff, "end diff {end_diff} should be smaller than start diff {start_diff}");
+        assert!(
+            end_diff < start_diff,
+            "end diff {end_diff} should be smaller than start diff {start_diff}"
+        );
     }
 
     /// 6. Release is gradual, not instantaneous.
@@ -265,7 +298,11 @@ mod tests {
 
         // Immediately follow with a sub-ceiling sample
         let out = lim.process(&[10_000i32], 1.0);
-        assert!(out[0] < 10_000, "first quiet sample should still be attenuated (got {})", out[0]);
+        assert!(
+            out[0] < 10_000,
+            "first quiet sample should still be attenuated (got {})",
+            out[0]
+        );
     }
 
     /// 7. State carries across process calls.
@@ -287,7 +324,10 @@ mod tests {
         let mut out_split = out_split1;
         out_split.extend(&out_split2);
 
-        assert_eq!(out_single, out_split, "splitting process calls must produce identical output to a single call");
+        assert_eq!(
+            out_single, out_split,
+            "splitting process calls must produce identical output to a single call"
+        );
 
         // Test 2: Pre-loaded limiter vs fresh limiter on the same input
         let mut lim_preloaded = SoftLimiter::new(SR);
@@ -299,8 +339,16 @@ mod tests {
         let out_preloaded = lim_preloaded.process(&test_input, 1.0);
         let out_fresh = lim_fresh.process(&test_input, 1.0);
 
-        assert_ne!(out_preloaded, out_fresh, "pre-loaded and fresh limiter outputs should differ");
-        assert!(out_preloaded[0] < out_fresh[0], "pre-loaded limiter first sample {} should be smaller than fresh limiter first sample {}", out_preloaded[0], out_fresh[0]);
+        assert_ne!(
+            out_preloaded, out_fresh,
+            "pre-loaded and fresh limiter outputs should differ"
+        );
+        assert!(
+            out_preloaded[0] < out_fresh[0],
+            "pre-loaded limiter first sample {} should be smaller than fresh limiter first sample {}",
+            out_preloaded[0],
+            out_fresh[0]
+        );
     }
 
     /// 8. Empty input.
@@ -320,7 +368,10 @@ mod tests {
         // Gain 0.0
         let out_zero = lim.process(&input, 0.0);
         assert_eq!(out_zero.len(), input.len());
-        assert!(out_zero.iter().all(|&s| s == 0), "0.0 gain should result in all zeros");
+        assert!(
+            out_zero.iter().all(|&s| s == 0),
+            "0.0 gain should result in all zeros"
+        );
 
         // Gain 1.0
         let out_unity = lim.process(&input, 1.0);
@@ -354,6 +405,9 @@ mod tests {
 
         let out = lim.process(&input, 1.0);
         let expected: Vec<i16> = input.iter().map(|&s| s as i16).collect();
-        assert_eq!(out, expected, "below ceiling input must be bit-exact at unity gain");
+        assert_eq!(
+            out, expected,
+            "below ceiling input must be bit-exact at unity gain"
+        );
     }
 }

src/audio/mod.rs

@@ -1,6 +1,6 @@
-use std::sync::mpsc::{Receiver, Sender};
 use std::sync::Arc;
 use std::sync::atomic::AtomicUsize;
+use std::sync::mpsc::{Receiver, Sender};
 use thiserror::Error;
 
 /// Playback output channel count. Capture/encode/network remain mono; only the
@@ -35,7 +35,11 @@ pub enum AudioError {
 pub trait AudioBackend: Send + Sync {
     /// Starts capturing raw PCM audio from the input device (microphone),
     /// sending chunks of samples (e.g. `Vec<i16>`) to the provided Sender.
-    fn start_capture(&self, tx: Sender<Vec<i16>>, target_node: Option<String>) -> Result<(), AudioError>;
+    fn start_capture(
+        &self,
+        tx: Sender<Vec<i16>>,
+        target_node: Option<String>,
+    ) -> Result<(), AudioError>;
 
     /// Starts playing back raw PCM audio to the output device (speaker),
     /// reading mixed/incoming chunks of samples from the provided Receiver.
@@ -56,18 +60,50 @@ pub trait AudioBackend: Send + Sync {
     fn stop(&self) -> Result<(), AudioError>;
 }
 
-pub mod echo_cancel;
+pub mod clip_player;
 pub mod eq;
 pub mod gate;
 pub mod limiter;
 pub mod multitrack;
 pub mod pan;
-#[cfg(unix)]
-pub mod pipewire_impl;
+// Linear resamplers used by the Windows/cpal backend (W4). Platform-neutral and
+// pure, so it builds (and its tests run) everywhere even though only the cpal
+// backend wires it in.
 #[cfg(windows)]
 pub mod cpal_impl;
+#[cfg(target_os = "linux")]
+pub mod echo_cancel;
+#[cfg(target_os = "linux")]
+pub mod pipewire_impl;
+#[cfg(target_os = "linux")]
 pub mod pw_cli;
 pub mod recorder;
+pub mod resample;
+
+/// A selectable audio device for the input/output pickers. `name` is the stable
+/// identifier the backend uses to request the device (`target_node`);
+/// `description` is the human-facing label shown in the UI. The two may be equal
+/// (cpal/WASAPI) or differ (PipeWire node name vs. description).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct AudioDevice {
+    pub name: String,
+    pub description: String,
+    pub is_input: bool,
+}
+
+impl std::fmt::Display for AudioDevice {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{}", self.description)
+    }
+}
+
+// Enumerate audio input/output devices for the pickers (sorted by description),
+// returning the same `AudioDevice` shape regardless of platform: PipeWire
+// (`pw-cli`) on Linux, cpal/WASAPI on Windows.
+#[cfg(windows)]
+pub use cpal_impl::enumerate_audio_devices;
+#[cfg(target_os = "linux")]
+pub use pw_cli::enumerate_audio_devices;
 
 /// The audio backend implementation for the current platform.
 ///
@@ -76,10 +112,9 @@ pub mod recorder;
 /// platform selection lives entirely here. Both implementations satisfy the
 /// [`AudioBackend`] trait, which is the only interface the core talks to.
 ///
-/// - Linux/Unix → PipeWire ([`pipewire_impl::PipeWireBackend`]).
-/// - Windows → cpal/WASAPI ([`cpal_impl::CpalBackend`]); a no-op stub until the
-///   Phase 1 capture/playback implementation lands.
-#[cfg(unix)]
+/// - Linux → PipeWire ([`pipewire_impl::PipeWireBackend`]).
+/// - Windows → cpal/WASAPI ([`cpal_impl::CpalBackend`]).
+#[cfg(target_os = "linux")]
 pub type PlatformAudioBackend = pipewire_impl::PipeWireBackend;
 #[cfg(windows)]
 pub type PlatformAudioBackend = cpal_impl::CpalBackend;

src/audio/multitrack.rs

@@ -12,9 +12,11 @@
 //! This module is pure plumbing over [`WavWriter`]: no audio decode, no
 //! networking, no realtime work. The mixer (a non-RT task) drives it.
 
-use std::collections::{HashMap, VecDeque};
+use std::collections::{HashMap, HashSet, VecDeque};
 use std::io;
 use std::path::{Path, PathBuf};
+use std::sync::mpsc::{self, SyncSender, TrySendError};
+use std::thread::{self, JoinHandle};
 
 use iroh::EndpointId;
 
@@ -24,45 +26,38 @@ use crate::core::jitter::FRAME_SAMPLES;
 /// Cap on the silence chunk written at once when pre-padding a late joiner, so a
 /// long-running call can't trigger a single multi-hundred-MB allocation.
 const SILENCE_CHUNK: usize = FRAME_SAMPLES * 256;
+const WRITER_QUEUE_CYCLES: usize = 256;
+const DROP_LOG_INTERVAL_CYCLES: u64 = 256;
 
 /// Cap on buffered mic samples (~200ms @ 48kHz). Bounds how far the mic track
 /// can drift if the capture clock runs ahead of the mixer cycle; past it the
 /// oldest mic audio is dropped. Mirrors `recorder::MAX_MIC_FIFO`.
 const MAX_MIC_FIFO: usize = 48_000 / 5;
+const MAX_SESSION_DIR_ATTEMPTS: usize = 1_000;
 
-/// One output track: its WAV writer plus whether it has been written *this*
-/// cycle (so `end_cycle` knows which tracks to pad with silence).
-struct Track {
-    writer: WavWriter,
-    written_this_cycle: bool,
-}
-
-impl Track {
-    fn create(path: &Path) -> io::Result<Self> {
-        Ok(Self {
-            writer: WavWriter::new(path)?,
-            written_this_cycle: false,
-        })
-    }
-
-    /// Append `frame` fitted to exactly `frame_samples` (zero-padded if short),
-    /// and mark the track as written for this cycle.
-    fn write_frame(&mut self, frame: &[i16], frame_samples: usize) -> io::Result<()> {
-        self.writer.write_samples(&fit(frame, frame_samples))?;
-        self.written_this_cycle = true;
-        Ok(())
-    }
-
-    /// Append `samples` of silence (no cycle-marking — used for padding).
-    fn write_silence(&mut self, samples: usize) -> io::Result<()> {
-        let mut remaining = samples;
-        while remaining > 0 {
-            let n = remaining.min(SILENCE_CHUNK);
-            self.writer.write_samples(&vec![0i16; n])?;
-            remaining -= n;
+/// Create a collision-free session directory for a timestamp. The base
+/// timestamp is tried first, followed by `-2`, `-3`, and so on; an existing
+/// recording is never reopened or overwritten.
+pub fn create_session_dir(base: &Path, now_unix_secs: u64) -> io::Result<PathBuf> {
+    let filename = crate::audio::recorder::timestamp_filename(now_unix_secs);
+    let stem = filename.trim_end_matches(".wav");
+    for attempt in 1..=MAX_SESSION_DIR_ATTEMPTS {
+        let name = if attempt == 1 {
+            stem.to_string()
+        } else {
+            format!("{stem}-{attempt}")
+        };
+        let path = base.join(name);
+        match std::fs::create_dir(&path) {
+            Ok(()) => return Ok(path),
+            Err(e) if e.kind() == io::ErrorKind::AlreadyExists => continue,
+            Err(e) => return Err(e),
         }
-        Ok(())
     }
+    Err(io::Error::new(
+        io::ErrorKind::AlreadyExists,
+        "multitrack directory suffixes exhausted",
+    ))
 }
 
 /// Return `frame` resized to exactly `n` samples: truncated if longer (shouldn't
@@ -82,7 +77,13 @@ pub fn track_filename(name: &str, id: &EndpointId) -> String {
     let clean = crate::sanitize::sanitize_name(name);
     let mut slug: String = clean
         .chars()
-        .map(|c| if c.is_ascii_alphanumeric() { c.to_ascii_lowercase() } else { '-' })
+        .map(|c| {
+            if c.is_ascii_alphanumeric() {
+                c.to_ascii_lowercase()
+            } else {
+                '-'
+            }
+        })
         .collect();
     // Collapse runs of '-' and trim them off the ends.
     while slug.contains("--") {
@@ -94,41 +95,210 @@ pub fn track_filename(name: &str, id: &EndpointId) -> String {
     format!("{slug}-{short}.wav")
 }
 
-/// A live multitrack recording: per-peer stems + your mic, plus an optional
-/// mixed track, all under one session directory and clocked together.
-pub struct MultitrackRecorder {
-    dir: PathBuf,
-    frame_samples: usize,
-    /// Cycles recorded so far = the shared length (in frames) of every track.
-    cycles: u64,
-    peers: HashMap<EndpointId, Track>,
-    /// Your mic track. Fed asynchronously from the capture thread via
-    /// [`push_mic`](MultitrackRecorder::push_mic) into `mic_fifo`, then drained
-    /// one frame per `end_cycle` so it aligns with the cycle clock.
-    mic: WavWriter,
-    mic_fifo: VecDeque<i16>,
-    /// Present in "Both" mode (stems + mixed), absent in "stems only".
-    mix: Option<Track>,
+#[derive(Default)]
+struct PendingCycle {
+    new_peers: Vec<NewPeer>,
+    peer_frames: HashMap<EndpointId, Vec<i16>>,
+    mix_frame: Option<Vec<i16>>,
 }
 
-impl MultitrackRecorder {
-    /// Create a recording in `dir` (which must already exist). `with_mix` adds
-    /// the convenience mixed track (`mix.wav`). Your mic is always `me.wav`.
-    pub fn create(dir: &Path, frame_samples: usize, with_mix: bool) -> io::Result<Self> {
+struct NewPeer {
+    id: EndpointId,
+    filename: String,
+}
+
+struct CycleBatch {
+    new_peers: Vec<NewPeer>,
+    mic_frame: Vec<i16>,
+    mix_frame: Option<Vec<i16>>,
+    peer_frames: HashMap<EndpointId, Vec<i16>>,
+}
+
+trait SampleWriter {
+    fn write_samples(&mut self, samples: &[i16]) -> io::Result<()>;
+    fn finalize(self) -> io::Result<()>;
+}
+
+impl SampleWriter for WavWriter {
+    fn write_samples(&mut self, samples: &[i16]) -> io::Result<()> {
+        WavWriter::write_samples(self, samples)
+    }
+
+    fn finalize(self) -> io::Result<()> {
+        WavWriter::finalize(self)
+    }
+}
+
+struct WriterState<W> {
+    dir: PathBuf,
+    frame_samples: usize,
+    peers: HashMap<EndpointId, W>,
+    mic: W,
+    mix: Option<W>,
+    cycles_written: u64,
+}
+
+impl WriterState<WavWriter> {
+    fn create(dir: &Path, frame_samples: usize, with_mix: bool) -> io::Result<Self> {
         let mic = WavWriter::new(&dir.join("me.wav"))?;
         let mix = if with_mix {
-            Some(Track::create(&dir.join("mix.wav"))?)
+            Some(WavWriter::new(&dir.join("mix.wav"))?)
         } else {
             None
         };
         Ok(Self {
             dir: dir.to_path_buf(),
             frame_samples,
-            cycles: 0,
             peers: HashMap::new(),
             mic,
-            mic_fifo: VecDeque::new(),
             mix,
+            cycles_written: 0,
+        })
+    }
+}
+
+impl<W: SampleWriter> WriterState<W> {
+    fn apply_batch<F>(&mut self, batch: &CycleBatch, mut create_peer: F) -> io::Result<()>
+    where
+        F: FnMut(&Path) -> io::Result<W>,
+    {
+        for peer in &batch.new_peers {
+            if !self.peers.contains_key(&peer.id) {
+                let writer = create_peer(&self.dir.join(&peer.filename))?;
+                self.peers.insert(peer.id, writer);
+                let pad = self.back_pad_samples()?;
+                let writer = self.peers.get_mut(&peer.id).unwrap();
+                Self::write_silence(writer, pad)?;
+            }
+        }
+
+        self.mic.write_samples(&batch.mic_frame)?;
+        if let Some(mix) = self.mix.as_mut() {
+            if let Some(frame) = batch.mix_frame.as_deref() {
+                mix.write_samples(frame)?;
+            } else {
+                Self::write_silence(mix, self.frame_samples)?;
+            }
+        }
+
+        let silence = vec![0i16; self.frame_samples];
+        for (id, writer) in &mut self.peers {
+            let frame = batch
+                .peer_frames
+                .get(id)
+                .map(Vec::as_slice)
+                .unwrap_or(&silence);
+            writer.write_samples(frame)?;
+        }
+        self.cycles_written += 1;
+        Ok(())
+    }
+
+    fn back_pad_samples(&self) -> io::Result<usize> {
+        let cycles = usize::try_from(self.cycles_written)
+            .map_err(|_| io::Error::other("multitrack recording too long"))?;
+        cycles
+            .checked_mul(self.frame_samples)
+            .ok_or_else(|| io::Error::other("multitrack recording too long"))
+    }
+
+    fn write_silence(writer: &mut W, samples: usize) -> io::Result<()> {
+        let mut remaining = samples;
+        let silence = vec![0i16; remaining.min(SILENCE_CHUNK)];
+        while remaining > 0 {
+            let n = remaining.min(silence.len());
+            writer.write_samples(&silence[..n])?;
+            remaining -= n;
+        }
+        Ok(())
+    }
+
+    fn finalize(self) -> io::Result<()> {
+        let mut first_finalize_error = None;
+        record_first_error(&mut first_finalize_error, self.mic.finalize());
+        if let Some(mix) = self.mix {
+            record_first_error(&mut first_finalize_error, mix.finalize());
+        }
+        for writer in self.peers.into_values() {
+            record_first_error(&mut first_finalize_error, writer.finalize());
+        }
+        if let Some(e) = first_finalize_error {
+            Err(e)
+        } else {
+            Ok(())
+        }
+    }
+}
+
+fn record_first_error(slot: &mut Option<io::Error>, result: io::Result<()>) {
+    if slot.is_none()
+        && let Err(e) = result
+    {
+        *slot = Some(e);
+    }
+}
+
+/// Applies whole-cycle batches on the writer thread. Each applied batch appends
+/// exactly `frame_samples` to every existing track, and a dropped batch never
+/// reaches this loop for any track, so stem lengths stay equal even when the
+/// bounded queue applies back-pressure.
+fn writer_thread_main(
+    mut state: WriterState<WavWriter>,
+    batch_rx: mpsc::Receiver<CycleBatch>,
+) -> io::Result<()> {
+    let mut first_write_error = None;
+
+    for batch in batch_rx {
+        if first_write_error.is_none()
+            && let Err(e) = state.apply_batch(&batch, WavWriter::new)
+        {
+            first_write_error = Some(e);
+        }
+    }
+
+    let finalize_result = state.finalize();
+    if let Some(e) = first_write_error {
+        Err(e)
+    } else {
+        finalize_result
+    }
+}
+
+/// A live multitrack recording: per-peer stems + your mic, plus an optional
+/// mixed track, all under one session directory and clocked together.
+pub struct MultitrackRecorder {
+    dir: PathBuf,
+    frame_samples: usize,
+    known_peers: HashSet<EndpointId>,
+    /// Your mic track. Fed asynchronously from the capture thread via
+    /// [`push_mic`](MultitrackRecorder::push_mic) into `mic_fifo`, then drained
+    /// one frame per `end_cycle` so it aligns with the cycle clock.
+    mic_fifo: VecDeque<i16>,
+    /// Present in "Both" mode (stems + mixed), absent in "stems only".
+    with_mix: bool,
+    batch_tx: SyncSender<CycleBatch>,
+    writer_thread: JoinHandle<io::Result<()>>,
+    dropped_cycles: u64,
+    pending: PendingCycle,
+}
+
+impl MultitrackRecorder {
+    /// Create a recording in `dir` (which must already exist). `with_mix` adds
+    /// the convenience mixed track (`mix.wav`). Your mic is always `me.wav`.
+    pub fn create(dir: &Path, frame_samples: usize, with_mix: bool) -> io::Result<Self> {
+        let writer_state = WriterState::create(dir, frame_samples, with_mix)?;
+        let (batch_tx, batch_rx) = mpsc::sync_channel(WRITER_QUEUE_CYCLES);
+        let writer_thread = thread::spawn(move || writer_thread_main(writer_state, batch_rx));
+        Ok(Self {
+            dir: dir.to_path_buf(),
+            frame_samples,
+            known_peers: HashSet::new(),
+            mic_fifo: VecDeque::new(),
+            with_mix,
+            batch_tx,
+            writer_thread,
+            dropped_cycles: 0,
+            pending: PendingCycle::default(),
         })
     }
 
@@ -141,12 +311,14 @@ impl MultitrackRecorder {
     /// so it aligns with the others. Idempotent: a peer already tracked is left
     /// as-is (re-announce / name change doesn't restart their file).
     pub fn add_peer(&mut self, id: EndpointId, name: &str) -> io::Result<()> {
-        if self.peers.contains_key(&id) {
+        if self.known_peers.contains(&id) {
             return Ok(());
         }
-        let mut track = Track::create(&self.dir.join(track_filename(name, &id)))?;
-        track.write_silence(self.cycles as usize * self.frame_samples)?;
-        self.peers.insert(id, track);
+        self.known_peers.insert(id);
+        self.pending.new_peers.push(NewPeer {
+            id,
+            filename: track_filename(name, &id),
+        });
         Ok(())
     }
 
@@ -154,11 +326,13 @@ impl MultitrackRecorder {
     /// registered yet (write raced ahead of the join event), auto-register it
     /// with an id-only name so no audio is dropped.
     pub fn write_peer(&mut self, id: EndpointId, frame: &[i16]) -> io::Result<()> {
-        if !self.peers.contains_key(&id) {
+        if !self.known_peers.contains(&id) {
             self.add_peer(id, "")?;
         }
-        let fs = self.frame_samples;
-        self.peers.get_mut(&id).unwrap().write_frame(frame, fs)
+        self.pending
+            .peer_frames
+            .insert(id, fit(frame, self.frame_samples));
+        Ok(())
     }
 
     /// Buffer a frame of your transmitted mic audio (called from the capture
@@ -183,9 +357,8 @@ impl MultitrackRecorder {
     /// Record the finished mixed-bus frame for the current cycle (no-op in
     /// stems-only mode).
     pub fn write_mix(&mut self, frame: &[i16]) -> io::Result<()> {
-        let fs = self.frame_samples;
-        if let Some(mix) = self.mix.as_mut() {
-            mix.write_frame(frame, fs)?;
+        if self.with_mix {
+            self.pending.mix_frame = Some(fit(frame, self.frame_samples));
         }
         Ok(())
     }
@@ -198,28 +371,63 @@ impl MultitrackRecorder {
         // Mic: always one frame per cycle, drained from the FIFO (silence on
         // underrun), so it tracks the cycle clock like the peer stems.
         let mic_frame = self.drain_mic(fs);
-        self.mic.write_samples(&mic_frame)?;
-        // Peers + the optional mix track: pad any not written this cycle.
-        for track in self.peers.values_mut().chain(self.mix.as_mut()) {
-            if !track.written_this_cycle {
-                track.write_silence(fs)?;
+        let mut pending = std::mem::take(&mut self.pending);
+        pending.new_peers.sort_by(|a, b| {
+            a.filename
+                .cmp(&b.filename)
+                .then_with(|| a.id.to_string().cmp(&b.id.to_string()))
+        });
+        let batch = CycleBatch {
+            new_peers: pending.new_peers,
+            mic_frame,
+            mix_frame: if self.with_mix {
+                pending.mix_frame
+            } else {
+                None
+            },
+            peer_frames: pending.peer_frames,
+        };
+        match self.batch_tx.try_send(batch) {
+            Ok(()) => Ok(()),
+            Err(TrySendError::Full(batch)) => {
+                for peer in &batch.new_peers {
+                    self.known_peers.remove(&peer.id);
+                }
+                self.dropped_cycles = self.dropped_cycles.saturating_add(1);
+                if self.dropped_cycles == 1
+                    || self.dropped_cycles.is_multiple_of(DROP_LOG_INTERVAL_CYCLES)
+                {
+                    crate::log_msg(&format!(
+                        "multitrack recording: writer queue full; dropped {} cycle(s)",
+                        self.dropped_cycles
+                    ));
+                }
+                Ok(())
             }
-            track.written_this_cycle = false;
+            Err(TrySendError::Disconnected(_)) => Err(io::Error::new(
+                io::ErrorKind::BrokenPipe,
+                "multitrack writer thread stopped",
+            )),
         }
-        self.cycles += 1;
-        Ok(())
     }
 
     /// Finalize every track's WAV header. Consumes the recorder.
     pub fn finalize(self) -> io::Result<()> {
-        self.mic.finalize()?;
-        if let Some(mix) = self.mix {
-            mix.writer.finalize()?;
-        }
-        for (_, track) in self.peers {
-            track.writer.finalize()?;
-        }
-        Ok(())
+        let Self {
+            dir: _,
+            frame_samples: _,
+            known_peers: _,
+            mic_fifo: _,
+            with_mix: _,
+            batch_tx,
+            writer_thread,
+            dropped_cycles: _,
+            pending: _,
+        } = self;
+        drop(batch_tx);
+        writer_thread
+            .join()
+            .unwrap_or_else(|_| Err(io::Error::other("multitrack writer thread panicked")))
     }
 }
 
@@ -245,6 +453,51 @@ mod tests {
         d
     }
 
+    #[derive(Default)]
+    struct TestWriter {
+        samples: Vec<i16>,
+    }
+
+    impl SampleWriter for TestWriter {
+        fn write_samples(&mut self, samples: &[i16]) -> io::Result<()> {
+            self.samples.extend_from_slice(samples);
+            Ok(())
+        }
+
+        fn finalize(self) -> io::Result<()> {
+            Ok(())
+        }
+    }
+
+    fn test_writer_state(frame_samples: usize, with_mix: bool) -> WriterState<TestWriter> {
+        WriterState {
+            dir: PathBuf::new(),
+            frame_samples,
+            peers: HashMap::new(),
+            mic: TestWriter::default(),
+            mix: if with_mix {
+                Some(TestWriter::default())
+            } else {
+                None
+            },
+            cycles_written: 0,
+        }
+    }
+
+    fn test_batch(
+        new_peers: Vec<NewPeer>,
+        mic_frame: Vec<i16>,
+        mix_frame: Option<Vec<i16>>,
+        peer_frames: Vec<(EndpointId, Vec<i16>)>,
+    ) -> CycleBatch {
+        CycleBatch {
+            new_peers,
+            mic_frame,
+            mix_frame,
+            peer_frames: peer_frames.into_iter().collect(),
+        }
+    }
+
     #[test]
     fn fit_pads_and_truncates() {
         assert_eq!(fit(&[1, 2], 4), vec![1, 2, 0, 0]);
@@ -258,11 +511,131 @@ mod tests {
         let short: String = id.to_string().chars().take(8).collect();
         assert_eq!(track_filename("Alice", &id), format!("alice-{short}.wav"));
         // Spaces / punctuation collapse to single dashes, trimmed.
-        assert_eq!(track_filename("  Bob the Builder! ", &id), format!("bob-the-builder-{short}.wav"));
+        assert_eq!(
+            track_filename("  Bob the Builder! ", &id),
+            format!("bob-the-builder-{short}.wav")
+        );
         // A name that sanitizes/slugs to nothing falls back to "peer".
         assert_eq!(track_filename("!!!", &id), format!("peer-{short}.wav"));
     }
 
+    #[test]
+    fn same_second_sessions_get_unique_directories_without_reuse() {
+        let base = tmpdir("collision");
+        let first = create_session_dir(&base, 1_700_000_000).unwrap();
+        std::fs::write(first.join("sentinel"), b"keep me").unwrap();
+
+        let second = create_session_dir(&base, 1_700_000_000).unwrap();
+
+        assert_ne!(second, first);
+        assert_eq!(std::fs::read(first.join("sentinel")).unwrap(), b"keep me");
+        let _ = std::fs::remove_dir_all(&base);
+    }
+
+    #[test]
+    fn apply_batch_advances_existing_tracks_and_back_pads_late_peer() {
+        let frame = 3;
+        let early = an_id();
+        let late = an_id();
+        let mut state = test_writer_state(frame, true);
+        state.cycles_written = 2;
+        state.mic.samples = vec![8; 2 * frame];
+        state.mix.as_mut().unwrap().samples = vec![6; 2 * frame];
+        state.peers.insert(
+            early,
+            TestWriter {
+                samples: vec![1; 2 * frame],
+            },
+        );
+
+        let batch = test_batch(
+            vec![NewPeer {
+                id: late,
+                filename: "late.wav".to_string(),
+            }],
+            vec![9; frame],
+            None,
+            vec![(early, vec![2; frame]), (late, vec![7; frame])],
+        );
+        state
+            .apply_batch(&batch, |_| Ok(TestWriter::default()))
+            .unwrap();
+
+        assert_eq!(state.cycles_written, 3);
+        assert_eq!(state.mic.samples.len(), 3 * frame);
+        assert_eq!(state.mix.as_ref().unwrap().samples.len(), 3 * frame);
+        assert_eq!(
+            &state.mix.as_ref().unwrap().samples[2 * frame..],
+            &[0, 0, 0]
+        );
+        assert_eq!(state.peers.get(&early).unwrap().samples.len(), 3 * frame);
+        assert_eq!(
+            &state.peers.get(&early).unwrap().samples[2 * frame..],
+            &[2, 2, 2]
+        );
+        assert_eq!(
+            state.peers.get(&late).unwrap().samples,
+            vec![0, 0, 0, 0, 0, 0, 7, 7, 7],
+            "late peer is back-padded by completed cycles before this batch"
+        );
+    }
+
+    #[test]
+    fn skipped_batches_keep_all_tracks_equal_length() {
+        let frame = 2;
+        let p1 = an_id();
+        let p2 = an_id();
+        let mut state = test_writer_state(frame, true);
+
+        let first = test_batch(
+            vec![
+                NewPeer {
+                    id: p1,
+                    filename: "p1.wav".to_string(),
+                },
+                NewPeer {
+                    id: p2,
+                    filename: "p2.wav".to_string(),
+                },
+            ],
+            vec![1; frame],
+            Some(vec![5; frame]),
+            vec![(p1, vec![10; frame]), (p2, vec![20; frame])],
+        );
+        state
+            .apply_batch(&first, |_| Ok(TestWriter::default()))
+            .unwrap();
+
+        let _dropped_cycle = test_batch(
+            Vec::new(),
+            vec![2; frame],
+            Some(vec![6; frame]),
+            vec![(p1, vec![11; frame])],
+        );
+
+        let after_drop = test_batch(
+            Vec::new(),
+            vec![3; frame],
+            None,
+            vec![(p1, vec![12; frame])],
+        );
+        state
+            .apply_batch(&after_drop, |_| Ok(TestWriter::default()))
+            .unwrap();
+
+        let expected = 2 * frame;
+        assert_eq!(state.cycles_written, 2);
+        assert_eq!(state.mic.samples.len(), expected);
+        assert_eq!(state.mix.as_ref().unwrap().samples.len(), expected);
+        assert_eq!(state.peers.get(&p1).unwrap().samples.len(), expected);
+        assert_eq!(state.peers.get(&p2).unwrap().samples.len(), expected);
+        assert_eq!(
+            &state.peers.get(&p2).unwrap().samples[frame..],
+            &[0, 0],
+            "peer absent from an applied batch gets silence for that cycle"
+        );
+    }
+
     #[test]
     fn all_tracks_equal_length_after_n_cycles() {
         let dir = tmpdir("equal");
@@ -288,10 +661,18 @@ mod tests {
         rec.finalize().unwrap();
 
         let expected = 3 * frame;
-        assert_eq!(wav_samples(&dir.join("me.wav")), expected, "mic padded to full length");
+        assert_eq!(
+            wav_samples(&dir.join("me.wav")),
+            expected,
+            "mic padded to full length"
+        );
         assert_eq!(wav_samples(&dir.join("mix.wav")), expected);
         assert_eq!(wav_samples(&dir.join(track_filename("p1", &p1))), expected);
-        assert_eq!(wav_samples(&dir.join(track_filename("p2", &p2))), expected, "silent peer still full length");
+        assert_eq!(
+            wav_samples(&dir.join(track_filename("p2", &p2))),
+            expected,
+            "silent peer still full length"
+        );
     }
 
     #[test]
@@ -318,8 +699,14 @@ mod tests {
         rec.finalize().unwrap();
 
         // Both tracks are the full 5 cycles long (late one was back-padded).
-        assert_eq!(wav_samples(&dir.join(track_filename("early", &early))), 5 * frame);
-        assert_eq!(wav_samples(&dir.join(track_filename("late", &late))), 5 * frame);
+        assert_eq!(
+            wav_samples(&dir.join(track_filename("early", &early))),
+            5 * frame
+        );
+        assert_eq!(
+            wav_samples(&dir.join(track_filename("late", &late))),
+            5 * frame
+        );
 
         // The late track's first 2 cycles are silence, then the real audio.
         let bytes = std::fs::read(dir.join(track_filename("late", &late))).unwrap();
@@ -339,6 +726,28 @@ mod tests {
         rec.end_cycle().unwrap();
         rec.finalize().unwrap();
         assert!(dir.join("me.wav").exists());
-        assert!(!dir.join("mix.wav").exists(), "no mix track in stems-only mode");
+        assert!(
+            !dir.join("mix.wav").exists(),
+            "no mix track in stems-only mode"
+        );
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn async_peer_create_error_surfaces_at_finalize() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let dir = tmpdir("asyncerr");
+        let mut rec = MultitrackRecorder::create(&dir, 4, false).unwrap();
+        std::fs::set_permissions(&dir, std::fs::Permissions::from_mode(0o500)).unwrap();
+
+        rec.add_peer(an_id(), "blocked").unwrap();
+        rec.end_cycle().unwrap();
+        let result = rec.finalize();
+
+        std::fs::set_permissions(&dir, std::fs::Permissions::from_mode(0o700)).unwrap();
+        let err = result.unwrap_err();
+        assert_eq!(err.kind(), io::ErrorKind::PermissionDenied);
+        let _ = std::fs::remove_dir_all(&dir);
     }
 }

src/audio/pan.rs

@@ -23,7 +23,10 @@ pub fn pan_gains(pan: f32) -> (f32, f32) {
 /// still following the same equal-power curve as a peer is moved away from center.
 pub fn playback_pan_gains(pan: f32) -> (f32, f32) {
     let (left, right) = pan_gains(pan);
-    (left * std::f32::consts::SQRT_2, right * std::f32::consts::SQRT_2)
+    (
+        left * std::f32::consts::SQRT_2,
+        right * std::f32::consts::SQRT_2,
+    )
 }
 
 #[cfg(test)]
@@ -36,8 +39,14 @@ mod tests {
     fn hard_left_and_right_are_endpoints() {
         assert_eq!(pan_gains(-1.0), (1.0, 0.0));
         let (l, r) = pan_gains(1.0);
-        assert!(l.abs() < EPS, "left at hard-right should be zero-ish, got {l}");
-        assert!((r - 1.0).abs() < EPS, "right at hard-right should be one, got {r}");
+        assert!(
+            l.abs() < EPS,
+            "left at hard-right should be zero-ish, got {l}"
+        );
+        assert!(
+            (r - 1.0).abs() < EPS,
+            "right at hard-right should be one, got {r}"
+        );
     }
 
     #[test]
@@ -55,8 +64,14 @@ mod tests {
         let mut prev_r = f32::NEG_INFINITY;
         for pan in pans {
             let (l, r) = pan_gains(pan);
-            assert!(l <= prev_l + EPS, "left gain must not rise as pan moves right");
-            assert!(r >= prev_r - EPS, "right gain must not fall as pan moves right");
+            assert!(
+                l <= prev_l + EPS,
+                "left gain must not rise as pan moves right"
+            );
+            assert!(
+                r >= prev_r - EPS,
+                "right gain must not fall as pan moves right"
+            );
             prev_l = l;
             prev_r = r;
         }

src/audio/pipewire_impl.rs

@@ -1,13 +1,16 @@
 use crate::audio::{AudioBackend, AudioError};
-use std::sync::mpsc::{Sender, Receiver, RecvTimeoutError};
-use std::sync::{Arc, Mutex};
-use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
-use std::thread::{self, JoinHandle};
-use std::time::Duration;
 use pipewire as pw;
 use pw::{properties::properties, spa};
+use ringbuf::{
+    HeapRb,
+    traits::{Consumer, Producer, Split},
+};
 use spa::pod::Pod;
-use ringbuf::{HeapRb, traits::{Consumer, Producer, Split}};
+use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
+use std::sync::mpsc::{Receiver, RecvTimeoutError, Sender};
+use std::sync::{Arc, Mutex};
+use std::thread::{self, JoinHandle};
+use std::time::Duration;
 
 pub struct PipeWireBackend {
     capture_state: Mutex<Option<CaptureState>>,
@@ -41,7 +44,11 @@ impl PipeWireBackend {
 }
 
 impl AudioBackend for PipeWireBackend {
-    fn start_capture(&self, tx: Sender<Vec<i16>>, target_node: Option<String>) -> Result<(), AudioError> {
+    fn start_capture(
+        &self,
+        tx: Sender<Vec<i16>>,
+        target_node: Option<String>,
+    ) -> Result<(), AudioError> {
         let mut capture_guard = self.capture_state.lock().unwrap();
         if capture_guard.is_some() {
             return Err(AudioError::Stream("Capture already started".to_string()));
@@ -108,12 +115,17 @@ impl AudioBackend for PipeWireBackend {
     }
 }
 
-fn run_capture(cmd_rx: pw::channel::Receiver<()>, tx: Sender<Vec<i16>>, target_node: Option<String>) -> Result<(), AudioError> {
-    let mainloop = pw::main_loop::MainLoopRc::new(None)
-        .map_err(|e| AudioError::Init(e.to_string()))?;
+fn run_capture(
+    cmd_rx: pw::channel::Receiver<()>,
+    tx: Sender<Vec<i16>>,
+    target_node: Option<String>,
+) -> Result<(), AudioError> {
+    let mainloop =
+        pw::main_loop::MainLoopRc::new(None).map_err(|e| AudioError::Init(e.to_string()))?;
     let context = pw::context::ContextRc::new(&mainloop, None)
         .map_err(|e| AudioError::Init(e.to_string()))?;
-    let core = context.connect_rc(None)
+    let core = context
+        .connect_rc(None)
         .map_err(|e| AudioError::Init(e.to_string()))?;
 
     // Ring buffer setup: 9600 samples (200ms capacity for mono 48kHz)
@@ -151,11 +163,9 @@ fn run_capture(cmd_rx: pw::channel::Receiver<()>, tx: Sender<Vec<i16>>, target_n
                     let data = &mut datas[0];
                     let size = data.chunk().size() as usize;
                     if let Some(slice) = data.data() {
-                        // Each sample is 2 bytes (S16LE)
-                        for chunk in slice[..size].chunks_exact(2) {
-                            let sample = i16::from_le_bytes([chunk[0], chunk[1]]);
+                        for_each_capture_sample(slice, size, |sample| {
                             let _ = user_data.producer.try_push(sample);
-                        }
+                        });
                     }
                 }
             }
@@ -183,15 +193,16 @@ fn run_capture(cmd_rx: pw::channel::Receiver<()>, tx: Sender<Vec<i16>>, target_n
 
     let mut params = [Pod::from_bytes(&values).unwrap()];
 
-    stream.connect(
-        spa::utils::Direction::Input,
-        None,
-        pw::stream::StreamFlags::AUTOCONNECT
-            | pw::stream::StreamFlags::MAP_BUFFERS
-            | pw::stream::StreamFlags::RT_PROCESS,
-        &mut params,
-    )
-    .map_err(|e| AudioError::Stream(e.to_string()))?;
+    stream
+        .connect(
+            spa::utils::Direction::Input,
+            None,
+            pw::stream::StreamFlags::AUTOCONNECT
+                | pw::stream::StreamFlags::MAP_BUFFERS
+                | pw::stream::StreamFlags::RT_PROCESS,
+            &mut params,
+        )
+        .map_err(|e| AudioError::Stream(e.to_string()))?;
 
     // Spawn the worker thread to pop from consumer and send Vec<i16> frames
     let running = Arc::new(AtomicBool::new(true));
@@ -224,6 +235,16 @@ fn run_capture(cmd_rx: pw::channel::Receiver<()>, tx: Sender<Vec<i16>>, target_n
     Ok(())
 }
 
+/// Visit the complete S16LE samples in the portion PipeWire reports as filled.
+/// Clamp the reported byte count to the mapped slice before indexing: a bad
+/// chunk size must not panic from the realtime capture callback.
+fn for_each_capture_sample(slice: &[u8], size: usize, mut visit: impl FnMut(i16)) {
+    let size = size.min(slice.len());
+    for chunk in slice[..size].chunks_exact(2) {
+        visit(i16::from_le_bytes([chunk[0], chunk[1]]));
+    }
+}
+
 /// Frames the playback RT callback should produce this cycle.
 ///
 /// `requested` is the graph's per-cycle quantum from `Buffer::requested()` (0 if
@@ -249,11 +270,7 @@ const WORKER_POLL: Duration = Duration::from_millis(100);
 /// every `WORKER_POLL` even when no frames arrive — this is what lets `stop()`
 /// join the worker promptly instead of hanging on a parked blocking `recv()`
 /// (bug A7). Pure w.r.t. its inputs (no PipeWire), so it's unit-testable.
-fn drain_loop(
-    rx: &Receiver<Vec<i16>>,
-    running: &AtomicBool,
-    mut on_frame: impl FnMut(Vec<i16>),
-) {
+fn drain_loop(rx: &Receiver<Vec<i16>>, running: &AtomicBool, mut on_frame: impl FnMut(Vec<i16>)) {
     while running.load(Ordering::Relaxed) {
         match rx.recv_timeout(WORKER_POLL) {
             Ok(frame) => on_frame(frame),
@@ -263,10 +280,33 @@ fn drain_loop(
     }
 }
 
+/// Reserve exact occupancy before making a frame visible to the consumer.
+/// `after_reserve` is empty in production and lets the regression test force a
+/// consumer interleaving at the critical ordering boundary.
+fn publish_frame<P: Producer<Item = i16>>(
+    fill: &AtomicUsize,
+    dropped: &AtomicU64,
+    producer: &mut P,
+    frame: &[i16],
+    after_reserve: impl FnOnce(),
+) {
+    fill.fetch_add(frame.len(), Ordering::Relaxed);
+    after_reserve();
+    let pushed = producer.push_slice(frame);
+    if pushed != frame.len() {
+        fill.fetch_sub(frame.len() - pushed, Ordering::Relaxed);
+        dropped.fetch_add(1, Ordering::Relaxed);
+    }
+}
+
 fn frames_to_produce(requested: usize, mapped_frames: usize) -> usize {
     /// Safe per-cycle fallback when the graph doesn't report a quantum.
     const FALLBACK_FRAMES: usize = 1024;
-    let want = if requested > 0 { requested } else { FALLBACK_FRAMES };
+    let want = if requested > 0 {
+        requested
+    } else {
+        FALLBACK_FRAMES
+    };
     want.min(mapped_frames)
 }
 
@@ -276,11 +316,12 @@ fn run_playback(
     target_node: Option<String>,
     fill_gauge: Arc<AtomicUsize>,
 ) -> Result<(), AudioError> {
-    let mainloop = pw::main_loop::MainLoopRc::new(None)
-        .map_err(|e| AudioError::Init(e.to_string()))?;
+    let mainloop =
+        pw::main_loop::MainLoopRc::new(None).map_err(|e| AudioError::Init(e.to_string()))?;
     let context = pw::context::ContextRc::new(&mainloop, None)
         .map_err(|e| AudioError::Init(e.to_string()))?;
-    let core = context.connect_rc(None)
+    let core = context
+        .connect_rc(None)
         .map_err(|e| AudioError::Init(e.to_string()))?;
 
     // Ring buffer setup: 19200 interleaved samples (200ms capacity for stereo
@@ -401,7 +442,9 @@ fn run_playback(
                         }
                         if starved > 0 {
                             // One wait-free atomic add per quantum — RT-safe.
-                            user_data.underrun_samples.fetch_add(starved, Ordering::Relaxed);
+                            user_data
+                                .underrun_samples
+                                .fetch_add(starved, Ordering::Relaxed);
                         }
                         // Decrement the exact occupancy counter by the samples we
                         // actually pulled (excluding underruns, which removed
@@ -466,7 +509,11 @@ fn run_playback(
                 pw::spa::pod::Value::Choice(pw::spa::pod::ChoiceValue::Int(
                     pw::spa::utils::Choice(
                         pw::spa::utils::ChoiceFlags::empty(),
-                        pw::spa::utils::ChoiceEnum::Range { default: 8, min: 2, max: 64 },
+                        pw::spa::utils::ChoiceEnum::Range {
+                            default: 8,
+                            min: 2,
+                            max: 64,
+                        },
                     ),
                 )),
             ),
@@ -497,15 +544,16 @@ fn run_playback(
         Pod::from_bytes(&buffers_values).unwrap(),
     ];
 
-    stream.connect(
-        spa::utils::Direction::Output,
-        None,
-        pw::stream::StreamFlags::AUTOCONNECT
-            | pw::stream::StreamFlags::MAP_BUFFERS
-            | pw::stream::StreamFlags::RT_PROCESS,
-        &mut params,
-    )
-    .map_err(|e| AudioError::Stream(e.to_string()))?;
+    stream
+        .connect(
+            spa::utils::Direction::Output,
+            None,
+            pw::stream::StreamFlags::AUTOCONNECT
+                | pw::stream::StreamFlags::MAP_BUFFERS
+                | pw::stream::StreamFlags::RT_PROCESS,
+            &mut params,
+        )
+        .map_err(|e| AudioError::Stream(e.to_string()))?;
 
     // Spawn a worker thread to read from rx and push to producer
     let running = Arc::new(AtomicBool::new(true));
@@ -522,10 +570,12 @@ fn run_playback(
                 worker_dropped.fetch_add(1, Ordering::Relaxed);
                 return;
             }
-            for &sample in &frame {
-                let _ = producer.try_push(sample);
-            }
-            worker_fill.fetch_add(frame.len(), Ordering::Relaxed);
+            // Reserve occupancy BEFORE publishing samples. Otherwise the RT
+            // consumer can pop a newly-visible sample before it is counted and
+            // wrap the exact fill gauge to usize::MAX, wedging mixer pacing.
+            // `push_slice` also publishes the frame as one operation rather than
+            // exposing a half-written stereo pair.
+            publish_frame(&worker_fill, &worker_dropped, &mut producer, &frame, || {});
         });
     });
 
@@ -577,8 +627,12 @@ fn run_playback(
 
 #[cfg(test)]
 mod tests {
-    use super::{drain_loop, frames_to_produce};
-    use std::sync::atomic::{AtomicBool, Ordering};
+    use super::{drain_loop, for_each_capture_sample, frames_to_produce, publish_frame};
+    use ringbuf::{
+        HeapRb,
+        traits::{Consumer, Producer, Split},
+    };
+    use std::sync::atomic::{AtomicBool, AtomicU64, AtomicUsize, Ordering};
     use std::sync::{Arc, Mutex};
     use std::time::Duration;
     use std::{sync::mpsc, thread};
@@ -614,6 +668,37 @@ mod tests {
         assert_eq!(frames_to_produce(1024, 0), 0);
     }
 
+    #[test]
+    fn capture_size_larger_than_mapping_is_clamped() {
+        let mut samples = Vec::new();
+        for_each_capture_sample(&[1, 0, 2, 0, 3], usize::MAX, |sample| samples.push(sample));
+        assert_eq!(samples, vec![1, 2]);
+    }
+
+    #[test]
+    fn occupancy_is_reserved_before_frame_is_published() {
+        let rb = HeapRb::<i16>::new(8);
+        let (mut producer, mut consumer) = rb.split();
+        assert!(producer.try_push(7).is_ok());
+
+        let fill = AtomicUsize::new(1);
+        let dropped = AtomicU64::new(0);
+        publish_frame(&fill, &dropped, &mut producer, &[10, 11], || {
+            // Force the consumer to drain the old sample after the new frame's
+            // occupancy is reserved but before that frame is published.
+            assert_eq!(consumer.try_pop(), Some(7));
+            assert_eq!(fill.fetch_sub(1, Ordering::Relaxed), 3);
+        });
+
+        assert_eq!(fill.load(Ordering::Relaxed), 2);
+        assert_eq!(consumer.try_pop(), Some(10));
+        assert_eq!(fill.fetch_sub(1, Ordering::Relaxed), 2);
+        assert_eq!(consumer.try_pop(), Some(11));
+        assert_eq!(fill.fetch_sub(1, Ordering::Relaxed), 1);
+        assert_eq!(fill.load(Ordering::Relaxed), 0);
+        assert_eq!(dropped.load(Ordering::Relaxed), 0);
+    }
+
     // --- drain_loop (A7: worker must not hang shutdown) ---
 
     #[test]

src/audio/pw_cli.rs

@@ -1,18 +1,6 @@
+use super::AudioDevice;
 use std::process::Command;
 
-#[derive(Debug, Clone, PartialEq, Eq)]
-pub struct AudioDevice {
-    pub name: String,
-    pub description: String,
-    pub is_input: bool,
-}
-
-impl std::fmt::Display for AudioDevice {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.description)
-    }
-}
-
 pub fn enumerate_audio_devices() -> Vec<AudioDevice> {
     let output = Command::new("pw-cli")
         .arg("list-objects")
@@ -28,11 +16,20 @@ pub fn enumerate_audio_devices() -> Vec<AudioDevice> {
 /// Emits the in-progress node as an `AudioDevice` if it's a complete Audio/*
 /// node, then resets the accumulators for the next block. Non-audio or
 /// incomplete blocks are dropped (but still reset).
-fn push_device(name: &mut String, desc: &mut String, class: &mut String, out: &mut Vec<AudioDevice>) {
+fn push_device(
+    name: &mut String,
+    desc: &mut String,
+    class: &mut String,
+    out: &mut Vec<AudioDevice>,
+) {
     if !name.is_empty() && class.starts_with("Audio/") {
         out.push(AudioDevice {
             name: name.clone(),
-            description: if desc.is_empty() { name.clone() } else { desc.clone() },
+            description: if desc.is_empty() {
+                name.clone()
+            } else {
+                desc.clone()
+            },
             is_input: class == "Audio/Source",
         });
     }
@@ -56,7 +53,12 @@ fn parse_pw_nodes(text: &str) -> Vec<AudioDevice> {
     for line in text.lines() {
         let line = line.trim();
         if line.starts_with("id ") {
-            push_device(&mut current_name, &mut current_desc, &mut current_class, &mut devices);
+            push_device(
+                &mut current_name,
+                &mut current_desc,
+                &mut current_class,
+                &mut devices,
+            );
         } else if let Some(val) = line.strip_prefix("node.name = \"") {
             current_name = val.trim_end_matches('"').to_string();
         } else if let Some(val) = line.strip_prefix("node.description = \"") {
@@ -65,7 +67,12 @@ fn parse_pw_nodes(text: &str) -> Vec<AudioDevice> {
             current_class = val.trim_end_matches('"').to_string();
         }
     }
-    push_device(&mut current_name, &mut current_desc, &mut current_class, &mut devices);
+    push_device(
+        &mut current_name,
+        &mut current_desc,
+        &mut current_class,
+        &mut devices,
+    );
 
     devices.sort_by(|a, b| a.description.cmp(&b.description));
     devices
@@ -120,8 +127,14 @@ mod tests {
     fn source_is_input_sink_is_output() {
         let devices = parse_pw_nodes(SAMPLE_NODES);
         // Find devices by name or description to verify is_input
-        let mic = devices.iter().find(|d| d.name == "alsa_input.builtin").unwrap();
-        let speakers = devices.iter().find(|d| d.name == "alsa_output.builtin").unwrap();
+        let mic = devices
+            .iter()
+            .find(|d| d.name == "alsa_input.builtin")
+            .unwrap();
+        let speakers = devices
+            .iter()
+            .find(|d| d.name == "alsa_output.builtin")
+            .unwrap();
         let bare = devices.iter().find(|d| d.name == "bare.sink").unwrap();
 
         assert!(mic.is_input);

src/audio/recorder.rs

@@ -2,21 +2,26 @@
 //!
 //! Records the **full call as you experienced it**: the mixed incoming audio
 //! (everyone you hear) summed with your own transmitted mic, into a single mono
-//! WAV. Writing is driven by the playout mixer (one [`Recorder::write_frame`]
-//! per produced 20ms frame, paced by the hardware clock); your mic arrives
-//! separately from the capture thread via [`Recorder::push_mic`] and is buffered
-//! in a small FIFO so the two independently-clocked streams stay roughly aligned.
+//! WAV. Mixing/enqueue is driven by the playout mixer (one
+//! [`Recorder::write_frame`] per produced 20ms frame, paced by the hardware
+//! clock), while disk writes happen on a dedicated writer thread; your mic
+//! arrives separately from the capture thread via [`Recorder::push_mic`] and is
+//! buffered in a small FIFO so the two independently-clocked streams stay
+//! roughly aligned.
 //! Minor clock drift just slowly grows/shrinks that FIFO (capped, so the lag
 //! between your voice and the recording is bounded) — harmless for a voice
 //! recording, no realtime crackle concern.
 //!
 //! No external crates: the WAV writer emits the 44-byte canonical header itself
-//! and patches the two size fields on [`Recorder::finalize`].
+//! and patches the two size fields on the writer thread during
+//! [`Recorder::finalize`].
 
 use std::collections::VecDeque;
-use std::fs::File;
+use std::fs::{File, OpenOptions};
 use std::io::{self, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
+use std::sync::mpsc::{self, SyncSender, TrySendError};
+use std::thread::{self, JoinHandle};
 
 /// Capture sample rate (mono, 48kHz, matching the rest of the audio path).
 const SAMPLE_RATE: u32 = 48_000;
@@ -24,6 +29,9 @@ const BITS_PER_SAMPLE: u16 = 16;
 const CHANNELS: u16 = 1;
 const RIFF_DATA_OVERHEAD: u64 = 36;
 const MAX_RIFF_DATA_BYTES: u64 = u32::MAX as u64 - RIFF_DATA_OVERHEAD;
+const MAX_NAME_ATTEMPTS: usize = 1_000;
+const WRITER_QUEUE_FRAMES: usize = 256;
+const DROP_LOG_INTERVAL_FRAMES: u64 = 256;
 
 /// Cap on buffered mic samples (~200ms). Bounds how far recording lag can drift
 /// if the capture clock runs persistently faster than playout — past this we drop
@@ -42,7 +50,12 @@ pub struct WavWriter {
 impl WavWriter {
     /// Create the file and write the 44-byte header with zeroed size fields.
     pub fn new(path: &Path) -> io::Result<Self> {
-        let mut file = File::create(path)?;
+        Self::from_file(File::create(path)?)
+    }
+
+    /// Start a WAV in an already-opened file. This lets callers choose atomic
+    /// create-new semantics instead of the truncating behavior of `File::create`.
+    fn from_file(mut file: File) -> io::Result<Self> {
         file.write_all(&Self::header(0))?;
         Ok(Self {
             file,
@@ -112,26 +125,51 @@ impl WavWriter {
     }
 }
 
-/// A live call recorder: a [`WavWriter`] plus a small mic FIFO that aligns your
-/// transmitted mic with the playout mixer's incoming-mix frames.
+/// A live call recorder: a writer-thread queue plus a small mic FIFO that aligns
+/// your transmitted mic with the playout mixer's incoming-mix frames.
 pub struct Recorder {
-    writer: WavWriter,
+    frame_tx: SyncSender<Vec<i16>>,
+    writer_thread: JoinHandle<io::Result<()>>,
     /// Your transmitted mic samples, awaiting alignment with the next mix frame.
     mic_fifo: VecDeque<i16>,
     path: PathBuf,
+    dropped_frames: u64,
 }
 
 impl Recorder {
     /// Create a recording at `dir/<timestamped>.wav`. The directory is assumed to
     /// exist (the caller creates it).
     pub fn create(dir: &Path, now_unix_secs: u64) -> io::Result<Self> {
-        let path = dir.join(timestamp_filename(now_unix_secs));
-        let writer = WavWriter::new(&path)?;
-        Ok(Self {
-            writer,
-            mic_fifo: VecDeque::new(),
-            path,
-        })
+        let filename = timestamp_filename(now_unix_secs);
+        let stem = filename.trim_end_matches(".wav");
+        for attempt in 1..=MAX_NAME_ATTEMPTS {
+            let name = if attempt == 1 {
+                filename.clone()
+            } else {
+                format!("{stem}-{attempt}.wav")
+            };
+            let path = dir.join(name);
+            match OpenOptions::new().write(true).create_new(true).open(&path) {
+                Ok(file) => {
+                    let writer = WavWriter::from_file(file)?;
+                    let (frame_tx, frame_rx) = mpsc::sync_channel(WRITER_QUEUE_FRAMES);
+                    let writer_thread = thread::spawn(move || writer_thread_main(writer, frame_rx));
+                    return Ok(Self {
+                        frame_tx,
+                        writer_thread,
+                        mic_fifo: VecDeque::new(),
+                        path,
+                        dropped_frames: 0,
+                    });
+                }
+                Err(e) if e.kind() == io::ErrorKind::AlreadyExists => continue,
+                Err(e) => return Err(e),
+            }
+        }
+        Err(io::Error::new(
+            io::ErrorKind::AlreadyExists,
+            "recording filename suffixes exhausted",
+        ))
     }
 
     /// The path being written.
@@ -155,21 +193,73 @@ impl Recorder {
     /// treated as silence (you weren't transmitting), so quiet stretches record
     /// the incoming mix alone.
     pub fn write_frame(&mut self, mixed: &[i16]) -> io::Result<()> {
-        let mut out = Vec::with_capacity(mixed.len());
-        for &m in mixed {
-            let mic = self.mic_fifo.pop_front().unwrap_or(0);
-            let sum = (m as i32 + mic as i32).clamp(i16::MIN as i32, i16::MAX as i32);
-            out.push(sum as i16);
+        let out = mix_with_mic(mixed, &mut self.mic_fifo);
+        match self.frame_tx.try_send(out) {
+            Ok(()) => Ok(()),
+            Err(TrySendError::Full(_)) => {
+                self.dropped_frames = self.dropped_frames.saturating_add(1);
+                if self.dropped_frames == 1
+                    || self.dropped_frames.is_multiple_of(DROP_LOG_INTERVAL_FRAMES)
+                {
+                    crate::log_msg(&format!(
+                        "recording: writer queue full; dropped {} frame(s)",
+                        self.dropped_frames
+                    ));
+                }
+                Ok(())
+            }
+            Err(TrySendError::Disconnected(_)) => Err(io::Error::new(
+                io::ErrorKind::BrokenPipe,
+                "recording writer thread stopped",
+            )),
         }
-        self.writer.write_samples(&out)
     }
 
     /// Finish the file, patching its size fields. Consumes the recorder.
     pub fn finalize(self) -> io::Result<()> {
-        self.writer.finalize()
+        let Self {
+            frame_tx,
+            writer_thread,
+            mic_fifo: _,
+            path: _,
+            dropped_frames: _,
+        } = self;
+        drop(frame_tx);
+        writer_thread
+            .join()
+            .unwrap_or_else(|_| Err(io::Error::other("recording writer thread panicked")))
     }
 }
 
+fn writer_thread_main(mut writer: WavWriter, frame_rx: mpsc::Receiver<Vec<i16>>) -> io::Result<()> {
+    let mut first_write_error = None;
+
+    for frame in frame_rx {
+        if first_write_error.is_none()
+            && let Err(e) = writer.write_samples(&frame)
+        {
+            first_write_error = Some(e);
+        }
+    }
+
+    let finalize_result = writer.finalize();
+    if let Some(e) = first_write_error {
+        Err(e)
+    } else {
+        finalize_result
+    }
+}
+
+fn mix_with_mic(mixed: &[i16], mic_fifo: &mut VecDeque<i16>) -> Vec<i16> {
+    let mut out = Vec::with_capacity(mixed.len());
+    for &m in mixed {
+        let mic = mic_fifo.pop_front().unwrap_or(0);
+        let sum = (m as i32 + mic as i32).clamp(i16::MIN as i32, i16::MAX as i32);
+        out.push(sum as i16);
+    }
+    out
+}
+
 /// Civil date (year, month, day) from a count of days since the Unix epoch.
 /// Howard Hinnant's `civil_from_days`; valid across the whole practical range.
 fn civil_from_days(z: i64) -> (i64, u32, u32) {
@@ -198,6 +288,23 @@ pub fn timestamp_filename(unix_secs: u64) -> String {
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::sync::atomic::{AtomicU64, Ordering};
+
+    static NEXT_TEMP_ID: AtomicU64 = AtomicU64::new(0);
+
+    fn unique_temp_dir(prefix: &str) -> PathBuf {
+        let id = NEXT_TEMP_ID.fetch_add(1, Ordering::Relaxed);
+        std::env::temp_dir().join(format!("{prefix}-{}-{id}", std::process::id()))
+    }
+
+    fn read_wav_samples(path: &Path) -> (Vec<u8>, Vec<i16>) {
+        let bytes = std::fs::read(path).unwrap();
+        let samples = bytes[44..]
+            .chunks_exact(2)
+            .map(|sample| i16::from_le_bytes([sample[0], sample[1]]))
+            .collect();
+        (bytes, samples)
+    }
 
     #[test]
     fn timestamp_filename_is_utc_and_padded() {
@@ -210,6 +317,61 @@ mod tests {
         assert_eq!(timestamp_filename(0), "peerspeak-1970-01-01_000000.wav");
     }
 
+    #[test]
+    fn same_second_recordings_get_unique_files_without_truncation() {
+        let dir = unique_temp_dir("peerspeak-collision");
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+
+        let mut first = Recorder::create(&dir, 1_700_000_000).unwrap();
+        first.write_frame(&[123, 456]).unwrap();
+        let first_path = first.path().to_path_buf();
+        first.finalize().unwrap();
+        let original = std::fs::read(&first_path).unwrap();
+
+        let second = Recorder::create(&dir, 1_700_000_000).unwrap();
+        let second_path = second.path().to_path_buf();
+        assert_ne!(second_path, first_path);
+        assert_eq!(std::fs::read(&first_path).unwrap(), original);
+        second.finalize().unwrap();
+
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn recorder_thread_writes_mixed_samples_and_header_on_finalize() {
+        let dir = unique_temp_dir("peerspeak-recorder-thread");
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+
+        let mut recorder = Recorder::create(&dir, 1_700_000_123).unwrap();
+        let path = recorder.path().to_path_buf();
+
+        recorder.push_mic(&[1000, i16::MAX, -1000, i16::MIN, 2222]);
+        recorder.write_frame(&[10, 20, -32700]).unwrap();
+        recorder.push_mic(&[300, -300]);
+        recorder
+            .write_frame(&[0, 1000, i16::MAX, i16::MIN])
+            .unwrap();
+        recorder.finalize().unwrap();
+
+        let expected = vec![1010, i16::MAX, i16::MIN, i16::MIN, 3222, i16::MAX, i16::MIN];
+        let expected_data_bytes = u32::try_from(expected.len() * 2).unwrap();
+        let (bytes, samples) = read_wav_samples(&path);
+
+        assert_eq!(&bytes[0..4], b"RIFF");
+        assert_eq!(&bytes[8..12], b"WAVE");
+        assert_eq!(&bytes[36..40], b"data");
+        let riff = u32::from_le_bytes([bytes[4], bytes[5], bytes[6], bytes[7]]);
+        let data = u32::from_le_bytes([bytes[40], bytes[41], bytes[42], bytes[43]]);
+        assert_eq!(data, expected_data_bytes);
+        assert_eq!(riff, RIFF_DATA_OVERHEAD as u32 + expected_data_bytes);
+        assert_eq!(bytes.len(), 44 + expected.len() * 2);
+        assert_eq!(samples, expected);
+
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
     #[test]
     fn wav_header_round_trips_sizes() {
         let dir = std::env::temp_dir();
@@ -252,38 +414,32 @@ mod tests {
 
     #[test]
     fn mic_is_summed_with_mix_when_present() {
-        let dir = std::env::temp_dir();
-        let mut r = Recorder {
-            writer: WavWriter::new(&dir.join(format!("ps-sum-{}.wav", std::process::id())))
-                .unwrap(),
-            mic_fifo: VecDeque::new(),
-            path: PathBuf::new(),
-        };
-        r.push_mic(&[1000, 2000, 3000]);
-        // write_frame pops mic per-sample and sums; we can't read the file mid-stream,
-        // so assert the FIFO drains exactly by frame length.
-        r.write_frame(&[10, 20]).unwrap();
-        assert_eq!(r.mic_fifo.len(), 1, "two samples consumed, one mic left");
-        r.write_frame(&[0, 0]).unwrap();
+        let mut mic_fifo = VecDeque::from([1000, 2000, 3000]);
+
+        let first = mix_with_mic(&[10, 20], &mut mic_fifo);
+        assert_eq!(first, vec![1010, 2020]);
+        assert_eq!(mic_fifo.len(), 1, "two samples consumed, one mic left");
+
+        let second = mix_with_mic(&[0, 0], &mut mic_fifo);
+        assert_eq!(second, vec![3000, 0]);
         assert_eq!(
-            r.mic_fifo.len(),
+            mic_fifo.len(),
             0,
             "remaining mic sample consumed; rest is silence"
         );
-        let _ = r.finalize();
     }
 
     #[test]
     fn mic_fifo_is_capped() {
-        let dir = std::env::temp_dir();
-        let mut r = Recorder {
-            writer: WavWriter::new(&dir.join(format!("ps-cap-{}.wav", std::process::id())))
-                .unwrap(),
-            mic_fifo: VecDeque::new(),
-            path: PathBuf::new(),
-        };
+        let dir = unique_temp_dir("peerspeak-cap");
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+
+        let mut r = Recorder::create(&dir, 1_700_000_001).unwrap();
         r.push_mic(&vec![5i16; MAX_MIC_FIFO * 2]);
         assert_eq!(r.mic_fifo.len(), MAX_MIC_FIFO, "FIFO is bounded to the cap");
-        let _ = r.finalize();
+        r.finalize().unwrap();
+
+        let _ = std::fs::remove_dir_all(&dir);
     }
 }

src/audio/resample.rs

@@ -0,0 +1,313 @@
+//! Dep-free linear-interpolation resamplers for the Windows/cpal backend (W4).
+//!
+//! The pipeline runs internally at 48 kHz (Opus + the 20 ms frame), but a WASAPI
+//! endpoint may run at a different rate (commonly 44.1 kHz) and/or a non-stereo
+//! channel layout. These convert at the device boundary so such a device plays and
+//! captures instead of hard-erroring (the W4 limitation in the Windows port).
+//!
+//! ## Where each is used
+//! - [`PushResampler`] (single channel) converts **capture** from the device rate
+//!   to 48 kHz on the capture drain thread — off the RT callback.
+//! - [`StereoPullResampler`] converts **playback** from the internal 48 kHz stereo
+//!   bus to the device rate inside the output RT callback, pulling internal frames
+//!   from the ring on demand. It allocates nothing in `next`, so it is RT-safe.
+//!
+//! ## Quality
+//! This is plain linear interpolation with no anti-aliasing filter: correct,
+//! allocation-free, and adequate for speech, but it adds some aliasing when
+//! downsampling. The seam is intentionally tiny so a higher-quality polyphase/FIR
+//! resampler (e.g. the `rubato` crate, pending a supply-chain decision) can later
+//! replace the internals without touching the cpal backend. The matching-rate /
+//! matching-layout path in the backend bypasses these entirely and stays bit-exact.
+
+/// Linear interpolation between `a` and `b` at fractional position `frac` in `[0, 1)`.
+#[inline]
+fn lerp(a: f32, b: f32, frac: f32) -> f32 {
+    a + (b - a) * frac
+}
+
+/// Stateful single-channel **push** resampler: feed input samples at `in_rate`,
+/// receive output samples at `out_rate` through an `emit` callback. It carries the
+/// fractional read position and the previous input sample across calls, so feeding
+/// the stream block-by-block joins seamlessly. Neither [`push`](Self::push) nor
+/// [`process`](Self::process) allocates.
+pub struct PushResampler {
+    /// Input samples consumed per output sample (`in_rate / out_rate`).
+    step: f64,
+    /// Position of the next output sample, in input-sample units, measured from the
+    /// index of `prev` (the most recent input). Always advanced to stay `< 1.0`
+    /// after each input is consumed.
+    next: f64,
+    /// The previous input sample (left edge of the current interpolation segment).
+    prev: f32,
+    /// Whether any input has been seen yet (anchors the first output at input[0]).
+    started: bool,
+}
+
+impl PushResampler {
+    /// Build a resampler from `in_rate` to `out_rate` (both in Hz). Rates are
+    /// clamped to `>= 1` so `step` is always finite and non-zero: a zero `step`
+    /// would make [`push`](Self::push)'s `while self.next < 1.0` loop forever. The
+    /// cpal backend's `resolve()` also rejects such rates up front, so this is
+    /// belt-and-suspenders against a future caller (review W7).
+    pub fn new(in_rate: u32, out_rate: u32) -> Self {
+        Self {
+            step: in_rate.max(1) as f64 / out_rate.max(1) as f64,
+            next: 0.0,
+            prev: 0.0,
+            started: false,
+        }
+    }
+
+    /// Feed one input sample; `emit` is called for each output sample produced
+    /// (zero or more, depending on the rate ratio).
+    pub fn push(&mut self, cur: f32, mut emit: impl FnMut(f32)) {
+        if !self.started {
+            // First sample: just establish the left edge. Linear interpolation
+            // needs the next input as the right edge, so the first output is
+            // produced on the next push. This gives exact alignment
+            // (`output[k] == input[k]` at equal rates) with one input-sample of
+            // latency — negligible (~20 µs at 48 kHz).
+            self.started = true;
+            self.prev = cur;
+            self.next = 0.0;
+            return;
+        }
+        // `prev` sits at position 0 of this segment and `cur` at position 1; emit
+        // every output whose position falls in [0, 1).
+        while self.next < 1.0 {
+            emit(lerp(self.prev, cur, self.next as f32));
+            self.next += self.step;
+        }
+        self.next -= 1.0;
+        self.prev = cur;
+    }
+
+    /// Convenience for tests / batch callers: push a whole slice.
+    pub fn process(&mut self, input: &[f32], mut emit: impl FnMut(f32)) {
+        for &s in input {
+            self.push(s, &mut emit);
+        }
+    }
+}
+
+/// Stateful stereo **pull** resampler: produce output frames at `out_rate` by
+/// pulling input frames at `in_rate` from a closure on demand. Call
+/// [`next`](Self::next) once per output frame; it pulls as many input frames as the
+/// ratio requires and returns the interpolated `(left, right)`, or `None` when the
+/// puller runs dry (an underrun). Allocates nothing, so it is safe in an RT output
+/// callback.
+pub struct StereoPullResampler {
+    /// Input frames consumed per output frame (`in_rate / out_rate`).
+    step: f64,
+    /// Position of the next output frame within `[prev, cur)`, in `[0, 1)`.
+    frac: f64,
+    /// Left edge of the current interpolation segment.
+    prev: (f32, f32),
+    /// Right edge of the current interpolation segment.
+    cur: (f32, f32),
+    /// Whether `prev`/`cur` have been primed from the puller yet.
+    primed: bool,
+}
+
+impl StereoPullResampler {
+    /// Build a resampler from `in_rate` to `out_rate` (both in Hz). Rates are
+    /// clamped to `>= 1` so `step` is finite and non-zero — otherwise
+    /// [`next`](Self::next)'s `while self.frac >= 1.0` could spin (review W7).
+    pub fn new(in_rate: u32, out_rate: u32) -> Self {
+        Self {
+            step: in_rate.max(1) as f64 / out_rate.max(1) as f64,
+            frac: 0.0,
+            prev: (0.0, 0.0),
+            cur: (0.0, 0.0),
+            primed: false,
+        }
+    }
+
+    /// Produce the next output frame, pulling input frames via `pull` as needed.
+    /// Returns `None` if `pull` returns `None` before the frame can be formed
+    /// (underrun); the caller should substitute silence for that frame.
+    pub fn next(&mut self, mut pull: impl FnMut() -> Option<(f32, f32)>) -> Option<(f32, f32)> {
+        if !self.primed {
+            // Prime both edges from two pulls so the first output frame aligns
+            // exactly with the first input frame (`out[0] == in[0]` at equal
+            // rates). Needs two frames available to start, which the prefilled
+            // playback ring always has.
+            self.prev = pull()?;
+            self.cur = pull()?;
+            self.primed = true;
+            self.frac = 0.0;
+        }
+        // Advance the segment until the read position lands inside [prev, cur).
+        while self.frac >= 1.0 {
+            self.prev = self.cur;
+            self.cur = pull()?;
+            self.frac -= 1.0;
+        }
+        let f = self.frac as f32;
+        let out = (
+            lerp(self.prev.0, self.cur.0, f),
+            lerp(self.prev.1, self.cur.1, f),
+        );
+        self.frac += self.step;
+        Some(out)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// Equal rates align exactly: `output[k] == input[k]`. The final input lands on
+    /// the next push (one-sample streaming latency), so we get `n - 1` outputs.
+    #[test]
+    fn push_identity_when_rates_match() {
+        let mut r = PushResampler::new(48_000, 48_000);
+        let input = [0.0, 0.1, 0.2, 0.3, 0.4];
+        let mut out = Vec::new();
+        r.process(&input, |s| out.push(s));
+        assert_eq!(out.len(), input.len() - 1);
+        for (a, b) in out.iter().zip(input.iter()) {
+            assert!((a - b).abs() < 1e-6, "{a} vs {b}");
+        }
+    }
+
+    /// Upsampling 2x roughly doubles the output count and the midpoints interpolate.
+    #[test]
+    fn push_upsample_2x_interpolates_midpoints() {
+        let mut r = PushResampler::new(24_000, 48_000); // step = 0.5
+        let input = [0.0, 1.0, 2.0, 3.0];
+        let mut out = Vec::new();
+        r.process(&input, |s| out.push(s));
+        // (n - 1) segments at 2 outputs each = 6.
+        assert_eq!(out.len(), 6, "out {out:?}");
+        // A half-step between 1.0 and 2.0 must appear near 1.5.
+        assert!(
+            out.iter().any(|&s| (s - 1.5).abs() < 1e-3),
+            "expected a ~1.5 midpoint in {out:?}"
+        );
+    }
+
+    /// Downsampling drops the rate: fewer outputs than inputs, monotonic ramp preserved.
+    #[test]
+    fn push_downsample_reduces_count() {
+        let mut r = PushResampler::new(48_000, 44_100); // step ~1.088
+        let input: Vec<f32> = (0..441).map(|i| i as f32).collect();
+        let mut out = Vec::new();
+        r.process(&input, |s| out.push(s));
+        // 441 in @ 48k -> ~405 out @ 44.1k.
+        assert!(
+            (390..=410).contains(&out.len()),
+            "expected ~405 outputs, got {}",
+            out.len()
+        );
+        // Output stays within the input's value range and is non-decreasing.
+        for w in out.windows(2) {
+            assert!(w[1] >= w[0] - 1e-3, "ramp should not reverse: {w:?}");
+        }
+        assert!(*out.last().unwrap() <= 440.0 + 1e-3);
+    }
+
+    /// Pull resampler at equal rates returns each input frame in order, aligned.
+    /// Two-pull priming uses one frame of lookahead, so `n` inputs yield `n - 1`
+    /// outputs (the last frame emits once a successor arrives).
+    #[test]
+    fn pull_identity_when_rates_match() {
+        let mut r = StereoPullResampler::new(48_000, 48_000);
+        let frames = [(0.0, 9.0), (1.0, 8.0), (2.0, 7.0), (3.0, 6.0)];
+        let mut idx = 0;
+        let mut out = Vec::new();
+        while let Some(f) = r.next(|| {
+            let v = frames.get(idx).copied();
+            idx += 1;
+            v
+        }) {
+            out.push(f);
+        }
+        assert_eq!(out.len(), frames.len() - 1, "out {out:?}");
+        for (got, want) in out.iter().zip(frames.iter()) {
+            assert!((got.0 - want.0).abs() < 1e-6 && (got.1 - want.1).abs() < 1e-6);
+        }
+    }
+
+    /// Pull resampler reports underrun (`None`) once the source is exhausted.
+    #[test]
+    fn pull_returns_none_on_underrun() {
+        let mut r = StereoPullResampler::new(48_000, 44_100); // step ~1.088 -> pulls >1 per out
+        let frames = [(0.0, 0.0), (1.0, -1.0)];
+        let mut idx = 0;
+        let mut pull = || {
+            let v = frames.get(idx).copied();
+            idx += 1;
+            v
+        };
+        // First frame primes + emits; subsequent calls eventually exhaust the source.
+        let mut produced = 0;
+        let mut hit_none = false;
+        for _ in 0..10 {
+            if r.next(&mut pull).is_some() {
+                produced += 1;
+            } else {
+                hit_none = true;
+                break;
+            }
+        }
+        assert!(produced >= 1, "should produce at least the primed frame");
+        assert!(hit_none, "should report underrun once the puller is dry");
+    }
+
+    /// Downsampling via pull consumes more input frames than it emits output frames.
+    #[test]
+    fn pull_downsample_consumes_more_than_it_emits() {
+        let mut r = StereoPullResampler::new(48_000, 24_000); // step = 2.0
+        let input: Vec<(f32, f32)> = (0..100).map(|i| (i as f32, -(i as f32))).collect();
+        let mut idx = 0;
+        let mut emitted = 0;
+        for _ in 0..40 {
+            let f = r.next(|| {
+                let v = input.get(idx).copied();
+                idx += 1;
+                v
+            });
+            if f.is_some() {
+                emitted += 1;
+            } else {
+                break;
+            }
+        }
+        // At step 2.0 we consume ~2 input frames per output frame.
+        assert!(
+            idx > emitted,
+            "consumed {idx} input, emitted {emitted} output"
+        );
+    }
+
+    /// A zero rate must not produce a zero `step` (which would spin `push`'s inner
+    /// `while self.next < 1.0` forever). Clamping makes the call terminate (W7).
+    #[test]
+    fn push_zero_rate_does_not_spin() {
+        let mut r = PushResampler::new(0, 48_000);
+        let mut count = 0usize;
+        // Feed two samples; with a clamped non-zero step this returns promptly.
+        r.push(0.0, |_| count += 1);
+        r.push(1.0, |_| count += 1);
+        // Reaching here at all is the assertion (no hang); some output is produced.
+        assert!(count >= 1);
+    }
+
+    /// A zero output rate must not make the pull resampler's segment-advance loop
+    /// spin. Clamping keeps `step` finite so `next` terminates (W7).
+    #[test]
+    fn pull_zero_out_rate_does_not_spin() {
+        let mut r = StereoPullResampler::new(48_000, 0);
+        let frames = [(0.0, 0.0), (1.0, 1.0), (2.0, 2.0)];
+        let mut idx = 0;
+        let got = r.next(|| {
+            let v = frames.get(idx).copied();
+            idx += 1;
+            v
+        });
+        // Terminates and yields the primed frame instead of hanging.
+        assert!(got.is_some());
+    }
+}

src/avatar.rs

@@ -185,10 +185,132 @@ pub fn initials(name: &str) -> String {
     }
 }
 
+/// A small content-addressed LRU cache mapping image bytes to a built value
+/// (e.g. an `iced` image handle), so the SAME value is reused across redraws
+/// instead of rebuilt every frame. Two Tier C F-03 properties beyond a plain
+/// hash map:
+///
+/// 1. **Bounded** — at most `cap` entries, evicting the least-recently-used on
+///    overflow, so a peer can't grow the cache without limit by publishing an
+///    endless stream of distinct valid avatars.
+/// 2. **Collision-safe** — a hit requires full byte equality, not just a matching
+///    64-bit hash, so a hash collision can never return a different image's value.
+///
+/// Linear scan; intended for small `cap` (tens of entries).
+pub struct ByteLru<V> {
+    cap: usize,
+    /// `(content hash, content bytes, value)`; back = most recently used.
+    entries: Vec<(u64, Vec<u8>, V)>,
+}
+
+impl<V: Clone> ByteLru<V> {
+    /// Create an LRU holding at most `cap` entries (`cap` is clamped to >= 1).
+    pub fn new(cap: usize) -> Self {
+        Self {
+            cap: cap.max(1),
+            entries: Vec::new(),
+        }
+    }
+
+    /// Return the cached value for these exact `bytes`, building and inserting it
+    /// on a miss (evicting the least-recently-used entry once over `cap`). A hit
+    /// verifies full byte equality, so a 64-bit hash collision never returns the
+    /// wrong value. A hit also refreshes the entry's recency.
+    pub fn get_or_insert(&mut self, bytes: &[u8], build: impl FnOnce() -> V) -> V {
+        use std::hash::{Hash, Hasher};
+        let mut hasher = std::collections::hash_map::DefaultHasher::new();
+        bytes.hash(&mut hasher);
+        self.get_or_insert_hashed(hasher.finish(), bytes, build)
+    }
+
+    /// Inner seam with the content `hash` supplied explicitly. Production callers
+    /// use [`get_or_insert`]; tests use this to force a hash collision (different
+    /// bytes, same hash) and exercise the byte-equality guard.
+    fn get_or_insert_hashed(&mut self, hash: u64, bytes: &[u8], build: impl FnOnce() -> V) -> V {
+        if let Some(idx) = self
+            .entries
+            .iter()
+            .position(|(h, b, _)| *h == hash && b.as_slice() == bytes)
+        {
+            // LRU touch: move the hit entry to the back (most recent).
+            let entry = self.entries.remove(idx);
+            let val = entry.2.clone();
+            self.entries.push(entry);
+            return val;
+        }
+
+        let val = build();
+        if self.entries.len() >= self.cap {
+            self.entries.remove(0); // evict least-recently-used
+        }
+        self.entries.push((hash, bytes.to_vec(), val.clone()));
+        val
+    }
+
+    #[cfg(test)]
+    fn len(&self) -> usize {
+        self.entries.len()
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn byte_lru_reuses_value_for_identical_bytes() {
+        let mut lru: ByteLru<u32> = ByteLru::new(4);
+        let mut next = 0u32;
+        let mut build = |lru: &mut ByteLru<u32>, b: &[u8]| {
+            lru.get_or_insert(b, || {
+                next += 1;
+                next
+            })
+        };
+        // Same bytes → same value, built only once.
+        assert_eq!(build(&mut lru, b"alice"), 1);
+        assert_eq!(build(&mut lru, b"alice"), 1);
+        // Different bytes → a freshly built value.
+        assert_eq!(build(&mut lru, b"bob"), 2);
+        assert_eq!(lru.len(), 2);
+    }
+
+    #[test]
+    fn byte_lru_evicts_least_recently_used() {
+        let mut lru: ByteLru<u32> = ByteLru::new(2);
+        let mut n = 0u32;
+        let mut ins = |lru: &mut ByteLru<u32>, b: &[u8]| {
+            lru.get_or_insert(b, || {
+                n += 1;
+                n
+            })
+        };
+        ins(&mut lru, b"a"); // -> 1
+        ins(&mut lru, b"b"); // -> 2, cache = [a, b]
+        ins(&mut lru, b"a"); // touch a, cache = [b, a]
+        ins(&mut lru, b"c"); // evicts LRU (b), cache = [a, c]
+        assert_eq!(lru.len(), 2);
+        // `a` survived (recently touched) → still value 1, not rebuilt.
+        assert_eq!(ins(&mut lru, b"a"), 1);
+        // `b` was evicted → rebuilt with a new value.
+        assert_eq!(ins(&mut lru, b"b"), 4);
+    }
+
+    #[test]
+    fn byte_lru_byte_equality_survives_a_hash_collision() {
+        // Force the SAME 64-bit hash for two DIFFERENT byte strings (the case a
+        // bare-hash cache would alias — Tier C F-03 collision bug).
+        let mut lru: ByteLru<u32> = ByteLru::new(4);
+        assert_eq!(lru.get_or_insert_hashed(42, b"alice", || 1), 1);
+        // `bob` collides on the hash but differs in bytes → a MISS, built fresh,
+        // NOT aliased to alice's value.
+        assert_eq!(lru.get_or_insert_hashed(42, b"bob", || 2), 2);
+        // Both coexist; each re-lookup returns its own value (build closure unused).
+        assert_eq!(lru.get_or_insert_hashed(42, b"alice", || 99), 1);
+        assert_eq!(lru.get_or_insert_hashed(42, b"bob", || 99), 2);
+        assert_eq!(lru.len(), 2);
+    }
+
     #[test]
     fn initials_takes_first_two_words() {
         assert_eq!(initials("Alice"), "A");
@@ -230,7 +352,10 @@ mod tests {
     fn preset_png_in_range_and_out_of_range() {
         // Every declared preset index resolves to embedded bytes.
         for i in 0..PRESET_COUNT {
-            assert!(Avatar::Preset(i).preset_png().is_some(), "preset {i} missing");
+            assert!(
+                Avatar::Preset(i).preset_png().is_some(),
+                "preset {i} missing"
+            );
         }
         // Out-of-range index gracefully yields None (→ monogram fallback).
         assert!(Avatar::Preset(PRESET_COUNT).preset_png().is_none());
@@ -287,7 +412,10 @@ mod tests {
     #[test]
     fn sanitize_incoming_rejects_junk_and_oversize() {
         // Not valid base64 / not a PNG → downgraded to monogram.
-        assert_eq!(Avatar::Custom("not base64!!!".into()).sanitize_incoming(), Avatar::Monogram);
+        assert_eq!(
+            Avatar::Custom("not base64!!!".into()).sanitize_incoming(),
+            Avatar::Monogram
+        );
         // Over the byte cap → downgraded without even decoding.
         let huge = Avatar::Custom("A".repeat(CUSTOM_MAX_B64 + 1));
         assert_eq!(huge.sanitize_incoming(), Avatar::Monogram);

src/background.rs

@@ -0,0 +1,137 @@
+//! Custom UI background (W16): turn a user-picked image into a capped PNG to
+//! render behind the whole UI, plus the legibility scrim drawn over it.
+//!
+//! This is the pure, unit-testable seam — `process_background` decodes/downscales
+//! arbitrary input defensively (same caution as avatar uploads) and `scrim_color`
+//! computes the overlay tint. The file I/O, the `rfd` picker, and the iced
+//! `stack!` that layers image → scrim → UI all live at the app edge in
+//! `src/app/mod.rs`. The background is **local-only** — never sent to peers — so
+//! there's no gossip-frame budget here (hence a much larger size cap than avatars).
+
+use iced::Color;
+
+/// Longest side a custom background is downscaled to on ingest (aspect preserved,
+/// never upscaled). Big enough to look crisp filling the window, small enough to
+/// decode and cache cheaply. Local-only, so this is generous vs. the avatar cap.
+pub const BACKGROUND_MAX_PX: u32 = 1920;
+
+/// Default scrim strength. `0.0` = the image shows at full strength, `1.0` = it's
+/// fully hidden behind the theme's base colour. Half keeps a photo clearly visible
+/// while text and cards stay readable over it.
+pub const DEFAULT_DIM: f32 = 0.5;
+
+/// Decode an arbitrary user image (png/jpeg/…), downscale so its longest side is
+/// at most [`BACKGROUND_MAX_PX`] (aspect preserved; smaller images are left as-is,
+/// never upscaled), and re-encode as PNG bytes ready to write to disk. Decoding is
+/// bounded by the `image` crate's defaults so a malformed/huge file is rejected
+/// rather than exhausting memory. Errors come back as a message for the UI.
+pub fn process_background(raw: &[u8]) -> Result<Vec<u8>, String> {
+    let img = image::load_from_memory(raw).map_err(|e| format!("Couldn't read image: {e}"))?;
+    // Only ever shrink. `resize` preserves aspect, fitting within the box; a
+    // higher-quality filter than `thumbnail` since a background fills the window.
+    let scaled = if img.width() > BACKGROUND_MAX_PX || img.height() > BACKGROUND_MAX_PX {
+        img.resize(
+            BACKGROUND_MAX_PX,
+            BACKGROUND_MAX_PX,
+            image::imageops::FilterType::Lanczos3,
+        )
+    } else {
+        img
+    };
+    let mut png = std::io::Cursor::new(Vec::new());
+    scaled
+        .write_to(&mut png, image::ImageFormat::Png)
+        .map_err(|e| format!("Couldn't encode image: {e}"))?;
+    Ok(png.into_inner())
+}
+
+/// A filesystem-safe, app-owned filename for the processed PNG of a per-game
+/// background (W18), derived from the game's stable id by hashing rather than
+/// embedding the raw id: keeps the name short and safe (ids contain `:` and
+/// arbitrary executable basenames) and avoids leaking the id into the filesystem.
+/// Deterministic and dependency-free (FNV-1a 64-bit), so the same game id always
+/// maps to the same file.
+pub fn game_background_filename(game_id: &str) -> String {
+    // FNV-1a, 64-bit.
+    let mut hash: u64 = 0xcbf2_9ce4_8422_2325;
+    for b in game_id.as_bytes() {
+        hash ^= *b as u64;
+        hash = hash.wrapping_mul(0x0000_0100_0000_01b3);
+    }
+    format!("game-bg-{hash:016x}.png")
+}
+
+/// The legibility scrim drawn between the background image and the UI: the active
+/// theme's base colour at `dim` alpha (clamped to `0.0..=1.0`). A higher `dim`
+/// recedes the image so body text and panel chrome stay readable, and it re-tints
+/// per theme since `base` comes from the active palette.
+pub fn scrim_color(base: Color, dim: f32) -> Color {
+    Color {
+        a: dim.clamp(0.0, 1.0),
+        ..base
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// A valid PNG of the given size, as raw bytes (test helper).
+    fn make_png(w: u32, h: u32) -> Vec<u8> {
+        let img = image::DynamicImage::new_rgb8(w, h);
+        let mut buf = std::io::Cursor::new(Vec::new());
+        img.write_to(&mut buf, image::ImageFormat::Png).unwrap();
+        buf.into_inner()
+    }
+
+    #[test]
+    fn process_background_downscales_oversized() {
+        // A 4000x2000 image is shrunk so the longest side is BACKGROUND_MAX_PX,
+        // aspect preserved, and the result re-decodes as a PNG within bounds.
+        let raw = make_png(4000, 2000);
+        let png = process_background(&raw).expect("should process");
+        let decoded = image::load_from_memory(&png).unwrap();
+        assert_eq!(decoded.width().max(decoded.height()), BACKGROUND_MAX_PX);
+        assert_eq!(decoded.width(), BACKGROUND_MAX_PX);
+        assert_eq!(decoded.height(), BACKGROUND_MAX_PX / 2); // 2:1 aspect kept
+    }
+
+    #[test]
+    fn process_background_leaves_small_images_unscaled() {
+        let raw = make_png(640, 480);
+        let png = process_background(&raw).expect("should process");
+        let decoded = image::load_from_memory(&png).unwrap();
+        assert_eq!((decoded.width(), decoded.height()), (640, 480));
+    }
+
+    #[test]
+    fn process_background_rejects_non_image() {
+        assert!(process_background(b"definitely not an image").is_err());
+    }
+
+    #[test]
+    fn game_background_filename_is_stable_safe_and_distinct() {
+        let a = game_background_filename("steam:730");
+        // Stable for the same id.
+        assert_eq!(a, game_background_filename("steam:730"));
+        // Distinct ids → distinct files (no `:` or path chars leak through).
+        assert_ne!(a, game_background_filename("exe:hl2_linux"));
+        assert!(a.starts_with("game-bg-") && a.ends_with(".png"));
+        assert!(!a.contains(':') && !a.contains('/') && !a.contains('\\'));
+    }
+
+    #[test]
+    fn scrim_color_sets_alpha_and_keeps_rgb() {
+        let base = Color::from_rgb(0.1, 0.2, 0.3);
+        let s = scrim_color(base, 0.5);
+        assert_eq!((s.r, s.g, s.b), (0.1, 0.2, 0.3));
+        assert!((s.a - 0.5).abs() < f32::EPSILON);
+    }
+
+    #[test]
+    fn scrim_color_clamps_dim() {
+        let base = Color::BLACK;
+        assert!((scrim_color(base, -1.0).a - 0.0).abs() < f32::EPSILON);
+        assert!((scrim_color(base, 2.0).a - 1.0).abs() < f32::EPSILON);
+    }
+}

src/bin/audio_probe.rs

@@ -1,11 +1,11 @@
 //! Audio playout diagnostic probe.
 //!
-//! Drives a phase-continuous sine tone through the *real* PipeWire playback path
-//! (`PipeWireBackend::start_playback`), using the *same* fill-paced production
-//! the production mixer uses (`core/mod.rs`): generate a frame only while the
+//! Drives a phase-continuous sine tone through the *real* playback path
+//! (PipeWire on Linux, cpal/WASAPI on Windows), using the *same* fill-paced
+//! production the production mixer uses (`core/mod.rs`): generate a frame only while the
 //! playback ring is below `PLAYBACK_TARGET_SAMPLES`, so production tracks the
-//! PipeWire hardware clock. No network, no microphone — this isolates the local
-//! output path so we can confirm the clock-paced playout is glitch-free.
+//! hardware clock. No network, no microphone — this isolates the local output
+//! path so we can confirm the clock-paced playout is glitch-free.
 //!
 //! Use your ears on the tone (any click/pop is a glitch) together with the
 //! `playout-health:` lines tailed to stdout:
@@ -18,20 +18,27 @@
 //! Run:  cargo run --bin audio_probe -- [freq_hz] [seconds] [target_node]
 //!   e.g. cargo run --release --bin audio_probe -- 440 30
 //!
-//! This probe exercises the PipeWire backend directly, so it is a Unix-only tool.
-//! On non-Unix targets `main` is a stub that explains the limitation.
+//! This probe exercises the platform playback backend directly: PipeWire on Linux
+//! and cpal/WASAPI on Windows. Other targets use a stub that explains the limitation.
 
-#[cfg(unix)]
+#[cfg(target_os = "linux")]
 fn main() {
     unix_probe::run();
 }
 
-#[cfg(not(unix))]
+#[cfg(windows)]
 fn main() {
-    eprintln!("audio_probe is only supported on Unix builds (it drives the PipeWire backend directly).");
+    win_probe::run();
 }
 
-#[cfg(unix)]
+#[cfg(not(any(target_os = "linux", windows)))]
+fn main() {
+    eprintln!(
+        "audio_probe is only supported on Linux and Windows builds (it drives the platform playback backend directly)."
+    );
+}
+
+#[cfg(target_os = "linux")]
 mod unix_probe {
     use std::io::{BufRead, BufReader, Seek, SeekFrom};
     use std::sync::Arc;
@@ -88,7 +95,114 @@ mod unix_probe {
             for _ in 0..FRAME_SAMPLES {
                 let t = n as f32 / SAMPLE_RATE;
                 // 0.25 amplitude: clearly audible but not harsh.
-                let sample = (0.25 * i16::MAX as f32 * (2.0 * std::f32::consts::PI * freq * t).sin()) as i16;
+                let sample =
+                    (0.25 * i16::MAX as f32 * (2.0 * std::f32::consts::PI * freq * t).sin()) as i16;
+                // Stereo playback bus: duplicate the probe tone to L/R.
+                frame.push(sample);
+                frame.push(sample);
+                n += 1;
+            }
+            if tx.send(frame).is_err() {
+                eprintln!("playback channel closed early");
+                break;
+            }
+        }
+
+        // Let the ring drain, then stop.
+        tokio::time::sleep(Duration::from_millis(300)).await;
+        let _ = backend.stop();
+        println!("\naudio_probe: done.");
+    }
+
+    /// Open the app log, seek to the end, and echo new lines (the `playout-health:`
+    /// reports) to stdout once they appear.
+    fn spawn_log_tailer() {
+        let path = peerspeak::log_file_path();
+        std::thread::spawn(move || {
+            // Wait for the file to exist (first log_msg creates it).
+            let file = loop {
+                if let Ok(f) = std::fs::File::open(&path) {
+                    break f;
+                }
+                std::thread::sleep(Duration::from_millis(100));
+            };
+            let mut reader = BufReader::new(file);
+            let _ = reader.seek(SeekFrom::End(0));
+            loop {
+                let mut line = String::new();
+                match reader.read_line(&mut line) {
+                    Ok(0) => std::thread::sleep(Duration::from_millis(150)),
+                    Ok(_) => {
+                        if line.contains("playout-health:") {
+                            print!("{line}");
+                        }
+                    }
+                    Err(_) => std::thread::sleep(Duration::from_millis(150)),
+                }
+            }
+        });
+    }
+}
+
+#[cfg(windows)]
+mod win_probe {
+    use std::io::{BufRead, BufReader, Seek, SeekFrom};
+    use std::sync::Arc;
+    use std::sync::atomic::AtomicUsize;
+    use std::sync::mpsc;
+    use std::time::Duration;
+
+    use peerspeak::audio::AudioBackend;
+    use peerspeak::audio::cpal_impl::CpalBackend;
+    use peerspeak::core::jitter::FRAME_SAMPLES; // 960 mono frames = 20ms @ 48kHz
+
+    const SAMPLE_RATE: f32 = 48_000.0;
+
+    #[tokio::main]
+    pub async fn run() {
+        let mut args = std::env::args().skip(1);
+        let freq: f32 = args.next().and_then(|s| s.parse().ok()).unwrap_or(440.0);
+        let secs: u64 = args.next().and_then(|s| s.parse().ok()).unwrap_or(30);
+        let target_node: Option<String> = args.next();
+
+        // The playout-health logger is quiet in normal operation (it only logs
+        // glitches); ask it for the full once-per-second heartbeat so the probe can
+        // show the steady-state numbers.
+        // SAFETY: set before any playback thread starts, so no concurrent env read.
+        unsafe { std::env::set_var("PEERSPEAK_AUDIO_VERBOSE", "1") };
+
+        println!("audio_probe: {freq} Hz tone for {secs}s through the real playback path.");
+        println!("Listen for clicks/pops; watch the playout-health lines below.\n");
+
+        // Tail the app log (where playout-health lines land) to stdout in the
+        // background so it's all in one terminal.
+        spawn_log_tailer();
+
+        let backend = CpalBackend::new();
+        let (tx, rx) = mpsc::channel::<Vec<i16>>();
+        let ring_fill = Arc::new(AtomicUsize::new(0));
+        if let Err(e) = backend.start_playback(rx, target_node, ring_fill.clone()) {
+            eprintln!("failed to start playback: {e}");
+            return;
+        }
+
+        // Phase-continuous sine, generated one 20ms frame at a time, fill-paced
+        // exactly like the production mixer: only produce while the ring is below
+        // target, so production tracks the cpal/WASAPI hardware clock.
+        use std::sync::atomic::Ordering;
+        let deadline = tokio::time::Instant::now() + Duration::from_secs(secs);
+        let mut n: u64 = 0; // running sample index keeps phase continuous across frames
+        while tokio::time::Instant::now() < deadline {
+            if ring_fill.load(Ordering::Relaxed) >= peerspeak::audio::PLAYBACK_TARGET_SAMPLES {
+                tokio::time::sleep(Duration::from_millis(2)).await;
+                continue;
+            }
+            let mut frame = Vec::with_capacity(FRAME_SAMPLES * peerspeak::audio::PLAYBACK_CHANNELS);
+            for _ in 0..FRAME_SAMPLES {
+                let t = n as f32 / SAMPLE_RATE;
+                // 0.25 amplitude: clearly audible but not harsh.
+                let sample =
+                    (0.25 * i16::MAX as f32 * (2.0 * std::f32::consts::PI * freq * t).sin()) as i16;
                 // Stereo playback bus: duplicate the probe tone to L/R.
                 frame.push(sample);
                 frame.push(sample);

src/bin/specview.rs

@@ -105,7 +105,11 @@ fn cmd_gen(args: &[String]) -> Result<(), String> {
         "pink" => generators::pink_noise(amp, len, seed),
         "impulse" => generators::impulse(amp, len),
         "silence" => generators::silence(len),
-        other => return Err(format!("unknown kind {other:?} (sine sweep white pink impulse silence)")),
+        other => {
+            return Err(format!(
+                "unknown kind {other:?} (sine sweep white pink impulse silence)"
+            ));
+        }
     };
 
     wav::write(Path::new(out), &samples, SAMPLE_RATE)?;
@@ -125,8 +129,12 @@ fn cmd_gen(args: &[String]) -> Result<(), String> {
 /// in which frequency range any residual lives.
 fn cmd_erle(args: &[String]) -> Result<(), String> {
     let (positional, flags) = parse_args(args);
-    let before = positional.first().ok_or("erle needs <before.wav> <after.wav>")?;
-    let after = positional.get(1).ok_or("erle needs <before.wav> <after.wav>")?;
+    let before = positional
+        .first()
+        .ok_or("erle needs <before.wav> <after.wav>")?;
+    let after = positional
+        .get(1)
+        .ok_or("erle needs <before.wav> <after.wav>")?;
 
     let b = wav::read(Path::new(before))?;
     let a = wav::read(Path::new(after))?;
@@ -239,17 +247,34 @@ fn cmd_aec(args: &[String]) -> Result<(), String> {
         1000.0 * tail as f32 / sr as f32,
         metrics::dbfs(atten),
     );
-    println!("  filter: {taps} taps, mu {mu}{}", if has_near { " (with near-end / double-talk)" } else { "" });
+    println!(
+        "  filter: {taps} taps, mu {mu}{}",
+        if has_near {
+            " (with near-end / double-talk)"
+        } else {
+            ""
+        }
+    );
     if has_near {
         let dtd = if flags.present("no-dtd") { "off" } else { "on" };
         println!(
             "  double-talk: detector {dtd}, threshold {dtd_threshold}, flagged {:.0}% of samples{}",
             100.0 * canceller.double_talk_rate(),
-            if onset > 0 { format!(", near-end onset {:.1}s", onset as f32 / sr as f32) } else { String::new() },
+            if onset > 0 {
+                format!(", near-end onset {:.1}s", onset as f32 / sr as f32)
+            } else {
+                String::new()
+            },
         );
     }
-    println!("  mic before: {:.1} dBFS rms", metrics::dbfs(metrics::rms(&mic)));
-    println!("  residual echo after: {:.1} dBFS rms", metrics::dbfs(metrics::rms(&residual)));
+    println!(
+        "  mic before: {:.1} dBFS rms",
+        metrics::dbfs(metrics::rms(&mic))
+    );
+    println!(
+        "  residual echo after: {:.1} dBFS rms",
+        metrics::dbfs(metrics::rms(&residual))
+    );
     println!("  ERLE broadband: {broadband:+.1} dB");
     println!("  ERLE early/late: {early:+.1} -> {late:+.1} dB  (rise = filter converging)");
 
@@ -278,9 +303,21 @@ fn cmd_aec(args: &[String]) -> Result<(), String> {
     }
     if flags.present("show") {
         println!("\n--- mic (echo present) ---");
-        print!("{}", render::render(&stft::analyze(&mic, sr, 2048, 512), &render::RenderOpts::default()));
+        print!(
+            "{}",
+            render::render(
+                &stft::analyze(&mic, sr, 2048, 512),
+                &render::RenderOpts::default()
+            )
+        );
         println!("\n--- cleaned (post-AEC) ---");
-        print!("{}", render::render(&stft::analyze(&cleaned, sr, 2048, 512), &render::RenderOpts::default()));
+        print!(
+            "{}",
+            render::render(
+                &stft::analyze(&cleaned, sr, 2048, 512),
+                &render::RenderOpts::default()
+            )
+        );
     }
     Ok(())
 }
@@ -339,13 +376,22 @@ impl Flags {
         self.bools.iter().any(|b| b == key) || self.map.contains_key(key)
     }
     fn f32_or(&self, key: &str, default: f32) -> f32 {
-        self.map.get(key).and_then(|v| v.parse().ok()).unwrap_or(default)
+        self.map
+            .get(key)
+            .and_then(|v| v.parse().ok())
+            .unwrap_or(default)
     }
     fn usize_or(&self, key: &str, default: usize) -> usize {
-        self.map.get(key).and_then(|v| v.parse().ok()).unwrap_or(default)
+        self.map
+            .get(key)
+            .and_then(|v| v.parse().ok())
+            .unwrap_or(default)
     }
     fn u64_or(&self, key: &str, default: u64) -> u64 {
-        self.map.get(key).and_then(|v| v.parse().ok()).unwrap_or(default)
+        self.map
+            .get(key)
+            .and_then(|v| v.parse().ok())
+            .unwrap_or(default)
     }
 }
 

src/bin/test_net.rs

@@ -1,9 +1,6 @@
-use peerspeak::network::{
-    gossip::IrohGossipState,
-    RoomState, PeerState,
-};
 use iroh::{Endpoint, endpoint::presets};
 use iroh_gossip::net::Gossip;
+use peerspeak::network::{PeerState, RoomState, gossip::IrohGossipState};
 use tokio::time::{self, Duration};
 
 #[tokio::main]
@@ -18,7 +15,7 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .address_lookup(lookup_a.clone())
         .bind()
         .await?;
-    
+
     endpoint_a.online().await;
     println!("Node A online. ID: {}", endpoint_a.id());
 
@@ -27,7 +24,12 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .accept(iroh_gossip::net::GOSSIP_ALPN, gossip_a.clone())
         .spawn();
 
-    let room_a = IrohGossipState::new(endpoint_a.clone(), gossip_a.clone(), lookup_a.clone(), secret_a);
+    let room_a = IrohGossipState::new(
+        endpoint_a.clone(),
+        gossip_a.clone(),
+        lookup_a.clone(),
+        secret_a,
+    );
 
     // 2. Node B (Client) Setup
     let lookup_b = iroh::address_lookup::memory::MemoryLookup::new();
@@ -46,7 +48,12 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .accept(iroh_gossip::net::GOSSIP_ALPN, gossip_b.clone())
         .spawn();
 
-    let room_b = IrohGossipState::new(endpoint_b.clone(), gossip_b.clone(), lookup_b.clone(), secret_b);
+    let room_b = IrohGossipState::new(
+        endpoint_b.clone(),
+        gossip_b.clone(),
+        lookup_b.clone(),
+        secret_b,
+    );
 
     // 3. Create room on Node A
     let topic_id = rand::random();
@@ -64,6 +71,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         addr: endpoint_a.addr(),
         sharing: None,
         avatar: Default::default(),
+        game: None,
+        music: None,
     };
     room_a.join(&ticket_str, state_a, vec![]).await?;
     println!("Node A joined topic.");
@@ -83,6 +92,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         addr: endpoint_b.addr(),
         sharing: None,
         avatar: Default::default(),
+        game: None,
+        music: None,
     };
     room_b.join(&ticket_str, state_b, vec![]).await?;
     println!("Node B joined topic.");

src/codec/mod.rs

@@ -20,6 +20,9 @@ pub trait AudioDecoder: Send {
     /// If `compressed` is `None` (or `Some(&[])`), it indicates packet loss,
     /// enabling the decoder to perform packet loss concealment (PLC).
     fn decode(&mut self, compressed: Option<&[u8]>) -> Result<Vec<i16>, CodecError>;
+
+    /// Reconstructs the previous lost frame from the next packet's in-band FEC.
+    fn decode_fec(&mut self, next_payload: &[u8]) -> Result<Vec<i16>, CodecError>;
 }
 
 pub mod opus_impl;

src/codec/opus_impl.rs

@@ -1,5 +1,49 @@
-use crate::codec::{AudioEncoder, AudioDecoder, CodecError};
-use opus::{Encoder, Decoder, Application, Channels};
+use crate::codec::{AudioDecoder, AudioEncoder, CodecError};
+use crate::config::AudioProfile;
+use opus::{Application, Bitrate, Channels, Decoder, Encoder};
+
+/// Concrete libopus encoder settings derived from an [`AudioProfile`]. Plain
+/// data, so the profile→params mapping ([`opus_params`]) stays a pure,
+/// unit-testable function (W12).
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct OpusParams {
+    /// Target bitrate in bits/sec.
+    pub bitrate: i32,
+    /// Enable in-band forward error correction (loss redundancy in the bitstream).
+    pub inband_fec: bool,
+    /// Expected packet-loss percentage (0..=100); tunes how much FEC libopus adds.
+    pub packet_loss_perc: i32,
+    /// Discontinuous transmission: stop sending during silence to save bandwidth.
+    pub dtx: bool,
+}
+
+/// Map a named profile to concrete Opus parameters. Pure — the W12 testable seam.
+///
+/// `BadNetwork` deliberately runs a *lower* bitrate than `Balanced`: in-band FEC
+/// redundancy is carried inside the same bitstream, so trimming the base bitrate
+/// leaves headroom for the redundancy on a congested link.
+pub fn opus_params(profile: AudioProfile) -> OpusParams {
+    match profile {
+        AudioProfile::LowLatency => OpusParams {
+            bitrate: 24_000,
+            inband_fec: false,
+            packet_loss_perc: 0,
+            dtx: false,
+        },
+        AudioProfile::Balanced => OpusParams {
+            bitrate: 32_000,
+            inband_fec: true,
+            packet_loss_perc: 10,
+            dtx: false,
+        },
+        AudioProfile::BadNetwork => OpusParams {
+            bitrate: 20_000,
+            inband_fec: true,
+            packet_loss_perc: 25,
+            dtx: false,
+        },
+    }
+}
 
 pub struct OpusEncoder {
     encoder: Encoder,
@@ -8,11 +52,38 @@ pub struct OpusEncoder {
 impl OpusEncoder {
     /// Creates a new Opus encoder.
     /// Standard voice parameters: sample_rate = 48000, channels = Channels::Mono, application = Application::Voip
-    pub fn new(sample_rate: u32, channels: Channels, application: Application) -> Result<Self, CodecError> {
+    pub fn new(
+        sample_rate: u32,
+        channels: Channels,
+        application: Application,
+    ) -> Result<Self, CodecError> {
         let encoder = Encoder::new(sample_rate, channels, application)
             .map_err(|e| CodecError::Init(format!("Failed to create Opus encoder: {}", e)))?;
         Ok(Self { encoder })
     }
+
+    /// Apply concrete codec parameters to the live encoder. Safe to call between
+    /// frames, so the user can switch profile mid-call.
+    pub fn apply_params(&mut self, params: &OpusParams) -> Result<(), CodecError> {
+        self.encoder
+            .set_bitrate(Bitrate::Bits(params.bitrate))
+            .map_err(|e| CodecError::Init(format!("set_bitrate: {}", e)))?;
+        self.encoder
+            .set_inband_fec(params.inband_fec)
+            .map_err(|e| CodecError::Init(format!("set_inband_fec: {}", e)))?;
+        self.encoder
+            .set_packet_loss_perc(params.packet_loss_perc)
+            .map_err(|e| CodecError::Init(format!("set_packet_loss_perc: {}", e)))?;
+        self.encoder
+            .set_dtx(params.dtx)
+            .map_err(|e| CodecError::Init(format!("set_dtx: {}", e)))?;
+        Ok(())
+    }
+
+    /// Apply a named [`AudioProfile`] (shorthand for `apply_params(&opus_params(p))`).
+    pub fn apply_profile(&mut self, profile: AudioProfile) -> Result<(), CodecError> {
+        self.apply_params(&opus_params(profile))
+    }
 }
 
 impl AudioEncoder for OpusEncoder {
@@ -20,9 +91,11 @@ impl AudioEncoder for OpusEncoder {
         // We allocate a buffer for the compressed output.
         // A maximum packet size of 4000 bytes is more than enough for a single voice frame.
         let mut compressed = vec![0u8; 4000];
-        let len = self.encoder.encode(pcm, &mut compressed)
+        let len = self
+            .encoder
+            .encode(pcm, &mut compressed)
             .map_err(|e| CodecError::Encode(format!("Opus encoding failed: {}", e)))?;
-        
+
         compressed.truncate(len);
         Ok(compressed)
     }
@@ -42,10 +115,18 @@ impl OpusDecoder {
     /// Creates a new Opus decoder.
     /// Standard voice parameters: sample_rate = 48000, channels = Channels::Mono.
     /// `frame_samples` is the per-channel length of one transmitted frame (e.g. 960).
-    pub fn new(sample_rate: u32, channels: Channels, frame_samples: usize) -> Result<Self, CodecError> {
+    pub fn new(
+        sample_rate: u32,
+        channels: Channels,
+        frame_samples: usize,
+    ) -> Result<Self, CodecError> {
         let decoder = Decoder::new(sample_rate, channels)
             .map_err(|e| CodecError::Init(format!("Failed to create Opus decoder: {}", e)))?;
-        Ok(Self { decoder, channels, frame_samples })
+        Ok(Self {
+            decoder,
+            channels,
+            frame_samples,
+        })
     }
 
     fn channels_count(&self) -> usize {
@@ -73,18 +154,72 @@ impl AudioDecoder for OpusDecoder {
             }
         };
 
-        let decoded_per_channel = self.decoder.decode(input, &mut pcm, false)
+        let decoded_per_channel = self
+            .decoder
+            .decode(input, &mut pcm, false)
             .map_err(|e| CodecError::Decode(format!("Opus decoding failed: {}", e)))?;
 
         pcm.truncate(decoded_per_channel * channels_count);
         Ok(pcm)
     }
+
+    fn decode_fec(&mut self, next_payload: &[u8]) -> Result<Vec<i16>, CodecError> {
+        let channels_count = self.channels_count();
+        let mut pcm = vec![0i16; self.frame_samples * channels_count];
+
+        let decoded_per_channel = self
+            .decoder
+            .decode(next_payload, &mut pcm, true)
+            .map_err(|e| CodecError::Decode(format!("Opus FEC decoding failed: {}", e)))?;
+
+        pcm.truncate(decoded_per_channel * channels_count);
+        Ok(pcm)
+    }
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn test_opus_params_mapping() {
+        let low = opus_params(AudioProfile::LowLatency);
+        let bal = opus_params(AudioProfile::Balanced);
+        let bad = opus_params(AudioProfile::BadNetwork);
+
+        // LowLatency has no loss redundancy; the other two do.
+        assert!(!low.inband_fec);
+        assert_eq!(low.packet_loss_perc, 0);
+        assert!(bal.inband_fec);
+        assert!(bad.inband_fec);
+
+        // Capture-side gating suppresses silence; no profile adds Opus DTX.
+        assert!(!low.dtx && !bal.dtx && !bad.dtx);
+        assert!(bad.packet_loss_perc > bal.packet_loss_perc);
+
+        // BadNetwork trims base bitrate to make room for FEC redundancy.
+        assert!(bad.bitrate < bal.bitrate);
+
+        // All bitrates are sane positive voice rates.
+        for p in [low, bal, bad] {
+            assert!(p.bitrate > 0 && p.bitrate <= 64_000);
+            assert!((0..=100).contains(&p.packet_loss_perc));
+        }
+    }
+
+    #[test]
+    fn test_apply_profile_sets_bitrate() {
+        let mut encoder = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
+        // Every profile applies cleanly to a real encoder...
+        for profile in AudioProfile::ALL {
+            encoder.apply_profile(profile).unwrap();
+        }
+        // ...and the last-applied bitrate is reflected by the encoder.
+        encoder.apply_profile(AudioProfile::Balanced).unwrap();
+        let want = opus_params(AudioProfile::Balanced).bitrate;
+        assert_eq!(encoder.encoder.get_bitrate().unwrap(), Bitrate::Bits(want));
+    }
+
     #[test]
     fn test_round_trip() {
         let mut encoder = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
@@ -100,7 +235,10 @@ mod tests {
 
         // encode it
         let compressed = encoder.encode(&pcm).unwrap();
-        assert!(!compressed.is_empty(), "Compressed buffer should not be empty");
+        assert!(
+            !compressed.is_empty(),
+            "Compressed buffer should not be empty"
+        );
         assert!(
             compressed.len() < pcm.len() * std::mem::size_of::<i16>(),
             "Compressed size ({}) should be smaller than raw PCM size ({})",
@@ -110,13 +248,21 @@ mod tests {
 
         // decode it
         let decoded = decoder.decode(Some(&compressed)).unwrap();
-        assert_eq!(decoded.len(), 960, "Decoded sample count should be exactly 960");
+        assert_eq!(
+            decoded.len(),
+            960,
+            "Decoded sample count should be exactly 960"
+        );
 
         // 2. Round-trip carries signal energy (not silence)
         let sum_sq: f64 = decoded.iter().map(|&x| (x as f64).powi(2)).sum();
         let rms = (sum_sq / decoded.len() as f64).sqrt();
         // Since input had amplitude ~10000, let's verify RMS is significantly above 0 (e.g. > 100.0)
-        assert!(rms > 100.0, "Decoded signal should carry energy (RMS was {})", rms);
+        assert!(
+            rms > 100.0,
+            "Decoded signal should carry energy (RMS was {})",
+            rms
+        );
     }
 
     #[test]
@@ -125,11 +271,19 @@ mod tests {
 
         // decode(None) returns exactly frame_samples (960) samples
         let plc_none = decoder.decode(None).unwrap();
-        assert_eq!(plc_none.len(), 960, "decode(None) should yield exactly 960 samples");
+        assert_eq!(
+            plc_none.len(),
+            960,
+            "decode(None) should yield exactly 960 samples"
+        );
 
         // decode(Some(&[])) (empty slice) does the same
         let plc_empty = decoder.decode(Some(&[])).unwrap();
-        assert_eq!(plc_empty.len(), 960, "decode(Some(&[])) should yield exactly 960 samples");
+        assert_eq!(
+            plc_empty.len(),
+            960,
+            "decode(Some(&[])) should yield exactly 960 samples"
+        );
     }
 
     #[test]
@@ -140,7 +294,11 @@ mod tests {
         let pcm = vec![0i16; 960];
         let compressed = encoder.encode(&pcm).unwrap();
         let decoded = decoder.decode(Some(&compressed)).unwrap();
-        assert_eq!(decoded.len(), 960, "Decoded sample count should match packet duration");
+        assert_eq!(
+            decoded.len(),
+            960,
+            "Decoded sample count should match packet duration"
+        );
     }
 
     #[test]
@@ -149,11 +307,18 @@ mod tests {
 
         // decode(None) returns exactly frame_samples * 2 (1920) samples
         let plc_none = decoder.decode(None).unwrap();
-        assert_eq!(plc_none.len(), 960 * 2, "Stereo decode(None) should yield exactly 1920 samples");
+        assert_eq!(
+            plc_none.len(),
+            960 * 2,
+            "Stereo decode(None) should yield exactly 1920 samples"
+        );
 
         // decode(Some(&[])) (empty slice) does the same
         let plc_empty = decoder.decode(Some(&[])).unwrap();
-        assert_eq!(plc_empty.len(), 960 * 2, "Stereo decode(Some(&[])) should yield exactly 1920 samples");
+        assert_eq!(
+            plc_empty.len(),
+            960 * 2,
+            "Stereo decode(Some(&[])) should yield exactly 1920 samples"
+        );
     }
 }
-

src/core/chatroster.rs

@@ -0,0 +1,132 @@
+//! Roster-bound chat identity (chat-hardening plan, Phase 2).
+//!
+//! The wire `GossipMessage::Chat` carries a sender-CLAIMED display name, which
+//! any insider could set to another member's name. This map is the antidote:
+//! the core event task records each authenticated member's latest sanitized
+//! presence name here (from `PeerJoined`/`PeerUpdated`, the events that only
+//! fire for a verified signed `Announce`), and chat renders under THAT name —
+//! the embedded wire name is never displayed.
+//!
+//! Shared (`Arc<Mutex<…>>`) because eviction happens in two places: the event
+//! task itself (graceful `PeerLeft`) and the detached reconnect-grace timer
+//! (terminal eviction). A peer mid-reconnect-grace keeps its entry, so its
+//! chat stays admitted until the grace actually expires.
+
+use iroh::EndpointId;
+use std::collections::HashMap;
+use std::sync::{Arc, Mutex};
+
+/// Bound on tracked names. Mirrors the gossip roster cap (`MAX_ACTIVE_PEERS`):
+/// insertions only follow cap-gated roster admissions, so this is pure defense
+/// in depth against that invariant breaking.
+const CHAT_ROSTER_CAP: usize = 32;
+
+/// The authoritative id → display-name map for the current room. Cheap to
+/// clone; all clones share one map.
+#[derive(Debug, Clone, Default)]
+pub struct ChatRoster {
+    names: Arc<Mutex<HashMap<EndpointId, String>>>,
+}
+
+impl ChatRoster {
+    /// Record (or refresh) a member's display name. The name is re-sanitized
+    /// here (idempotent — gossip ingress already did) and an empty result falls
+    /// back to the short node id so a chat line is never label-less. A NEW id
+    /// is refused past the cap; updates to a present id always land.
+    pub fn upsert(&self, id: EndpointId, name: &str) {
+        let clean = crate::sanitize::sanitize_name(name);
+        let label = if clean.is_empty() {
+            crate::short_id(&id.to_string())
+        } else {
+            clean
+        };
+        let mut names = self.names.lock().unwrap();
+        if names.contains_key(&id) || names.len() < CHAT_ROSTER_CAP {
+            names.insert(id, label);
+        }
+    }
+
+    /// Drop a member on graceful leave or terminal (grace-expired) eviction.
+    pub fn remove(&self, id: &EndpointId) {
+        self.names.lock().unwrap().remove(id);
+    }
+
+    /// The roster-bound name for an id, or `None` if the author is not a
+    /// current member — the caller must then drop the chat entirely.
+    pub fn name_of(&self, id: &EndpointId) -> Option<String> {
+        self.names.lock().unwrap().get(id).cloned()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use iroh::SecretKey;
+
+    fn fresh_id() -> EndpointId {
+        SecretKey::generate().public()
+    }
+
+    #[test]
+    fn upsert_then_lookup_returns_sanitized_name() {
+        let roster = ChatRoster::default();
+        let a = fresh_id();
+        roster.upsert(a, "Alice");
+        assert_eq!(roster.name_of(&a), Some("Alice".to_string()));
+        // Bidi override / zero-width spoofing characters are stripped.
+        roster.upsert(a, "Al\u{202E}ice\u{200B}");
+        assert_eq!(roster.name_of(&a), Some("Alice".to_string()));
+    }
+
+    #[test]
+    fn name_update_affects_future_lookups() {
+        let roster = ChatRoster::default();
+        let a = fresh_id();
+        roster.upsert(a, "Alice");
+        roster.upsert(a, "Alice2");
+        assert_eq!(roster.name_of(&a), Some("Alice2".to_string()));
+    }
+
+    #[test]
+    fn unknown_author_has_no_name() {
+        let roster = ChatRoster::default();
+        roster.upsert(fresh_id(), "Alice");
+        assert_eq!(roster.name_of(&fresh_id()), None);
+    }
+
+    #[test]
+    fn removed_author_is_no_longer_a_member() {
+        let roster = ChatRoster::default();
+        let a = fresh_id();
+        roster.upsert(a, "Alice");
+        roster.remove(&a);
+        assert_eq!(roster.name_of(&a), None);
+    }
+
+    #[test]
+    fn empty_sanitized_name_falls_back_to_short_id() {
+        let roster = ChatRoster::default();
+        let a = fresh_id();
+        roster.upsert(a, "\u{0}\r\n\t ");
+        let label = roster.name_of(&a).unwrap();
+        assert!(!label.is_empty());
+        assert_eq!(label, crate::short_id(&a.to_string()));
+    }
+
+    #[test]
+    fn new_ids_are_refused_past_the_cap_but_updates_land() {
+        let roster = ChatRoster::default();
+        let first = fresh_id();
+        roster.upsert(first, "member");
+        for _ in 1..CHAT_ROSTER_CAP {
+            roster.upsert(fresh_id(), "member");
+        }
+        // A brand-new 33rd id is refused...
+        let overflow = fresh_id();
+        roster.upsert(overflow, "overflow");
+        assert_eq!(roster.name_of(&overflow), None);
+        // ...but an update to a present id still lands at the cap.
+        roster.upsert(first, "renamed");
+        assert_eq!(roster.name_of(&first), Some("renamed".to_string()));
+    }
+}

src/core/connstats.rs

@@ -0,0 +1,187 @@
+//! Per-peer connection-transparency derivation.
+//!
+//! The transport hands us cumulative counters for each peer's selected QUIC
+//! path ([`PathSnapshot`]); this module turns two consecutive snapshots into
+//! the human-facing [`PeerConnInfo`] the UI renders (badge + tooltip): path
+//! type, RTT, and loss/bitrate over the poll window. Pure functions only —
+//! the polling task in `core::mod` owns the clock and the previous-snapshot
+//! map.
+
+use crate::network::PathSnapshot;
+use std::time::Duration;
+
+/// How often the core polls the transport for path snapshots.
+pub const POLL_INTERVAL: Duration = Duration::from_secs(1);
+
+/// Derived, display-ready connection info for one peer, sent to the UI via
+/// `UiEvent::ConnectionStats`. Window-relative fields are `None` when they
+/// can't be derived yet (first poll, path switch, or an idle window).
+#[derive(Debug, Clone, PartialEq)]
+pub struct PeerConnInfo {
+    /// True = relayed path, false = direct IP path.
+    pub relay: bool,
+    /// `ip:port` for a direct path, the relay URL for a relayed one.
+    pub remote_addr: String,
+    /// Path round-trip time, rounded to whole milliseconds.
+    pub rtt_ms: u32,
+    /// Percentage of packets sent in the window that were detected lost.
+    pub loss_pct: Option<f32>,
+    /// Outbound bitrate over the window, kilobits per second.
+    pub up_kbps: Option<f32>,
+    /// Inbound bitrate over the window, kilobits per second.
+    pub down_kbps: Option<f32>,
+}
+
+/// Derive display info from the current snapshot and (when comparable) the
+/// previous one. `prev` is comparable only if it's the same path — a relay→
+/// direct migration or a reconnect resets the counters, so those windows
+/// yield `None` rates rather than garbage (negative deltas show up as
+/// `cur < prev` and are treated the same way).
+pub fn derive(prev: Option<&PathSnapshot>, cur: &PathSnapshot, elapsed: Duration) -> PeerConnInfo {
+    let rates = prev
+        .filter(|p| comparable(p, cur))
+        .and_then(|p| window_rates(p, cur, elapsed));
+    PeerConnInfo {
+        relay: cur.is_relay,
+        remote_addr: cur.remote_addr.clone(),
+        rtt_ms: cur.rtt.as_millis().min(u128::from(u32::MAX)) as u32,
+        loss_pct: rates.and_then(|r| r.loss_pct),
+        up_kbps: rates.map(|r| r.up_kbps),
+        down_kbps: rates.map(|r| r.down_kbps),
+    }
+}
+
+/// True when `cur`'s counters continue `prev`'s: same path (address) and
+/// monotonically non-decreasing counters (a reconnect on the same address
+/// restarts them from zero).
+fn comparable(prev: &PathSnapshot, cur: &PathSnapshot) -> bool {
+    prev.remote_addr == cur.remote_addr
+        && cur.tx_bytes >= prev.tx_bytes
+        && cur.rx_bytes >= prev.rx_bytes
+        && cur.tx_datagrams >= prev.tx_datagrams
+        && cur.lost_packets >= prev.lost_packets
+}
+
+#[derive(Debug, Clone, Copy)]
+struct WindowRates {
+    loss_pct: Option<f32>,
+    up_kbps: f32,
+    down_kbps: f32,
+}
+
+fn window_rates(prev: &PathSnapshot, cur: &PathSnapshot, elapsed: Duration) -> Option<WindowRates> {
+    let secs = elapsed.as_secs_f64();
+    if secs <= 0.0 {
+        return None;
+    }
+    let sent = cur.tx_datagrams - prev.tx_datagrams;
+    let lost = cur.lost_packets - prev.lost_packets;
+    // Loss detection lags sending (it needs ACK timeouts), so a window can see
+    // more losses than sends; clamp to 100% rather than exceeding it. An idle
+    // window (nothing sent or lost) has no loss story to tell.
+    let loss_pct = if sent == 0 && lost == 0 {
+        None
+    } else {
+        Some(((lost as f64 / (sent.max(lost)) as f64) * 100.0) as f32)
+    };
+    let kbps = |bytes: u64| ((bytes as f64 * 8.0 / 1000.0) / secs) as f32;
+    Some(WindowRates {
+        loss_pct,
+        up_kbps: kbps(cur.tx_bytes - prev.tx_bytes),
+        down_kbps: kbps(cur.rx_bytes - prev.rx_bytes),
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn snap(addr: &str, tx_b: u64, rx_b: u64, tx_d: u64, lost: u64) -> PathSnapshot {
+        PathSnapshot {
+            is_relay: false,
+            remote_addr: addr.to_string(),
+            rtt: Duration::from_millis(12),
+            tx_bytes: tx_b,
+            rx_bytes: rx_b,
+            tx_datagrams: tx_d,
+            lost_packets: lost,
+        }
+    }
+
+    #[test]
+    fn first_poll_has_type_and_rtt_but_no_rates() {
+        let cur = snap("1.2.3.4:5", 1000, 2000, 50, 0);
+        let info = derive(None, &cur, POLL_INTERVAL);
+        assert_eq!(info.rtt_ms, 12);
+        assert!(!info.relay);
+        assert_eq!(info.remote_addr, "1.2.3.4:5");
+        assert_eq!(info.loss_pct, None);
+        assert_eq!(info.up_kbps, None);
+        assert_eq!(info.down_kbps, None);
+    }
+
+    #[test]
+    fn steady_window_yields_rates_and_loss() {
+        let prev = snap("1.2.3.4:5", 0, 0, 0, 0);
+        // 1s window: 4000 bytes up (32 kbps), 2000 down (16 kbps), 2 of 100 lost.
+        let cur = snap("1.2.3.4:5", 4000, 2000, 100, 2);
+        let info = derive(Some(&prev), &cur, Duration::from_secs(1));
+        assert_eq!(info.up_kbps, Some(32.0));
+        assert_eq!(info.down_kbps, Some(16.0));
+        assert_eq!(info.loss_pct, Some(2.0));
+    }
+
+    #[test]
+    fn idle_window_has_no_loss_story() {
+        let prev = snap("1.2.3.4:5", 4000, 2000, 100, 2);
+        let cur = prev.clone();
+        let info = derive(Some(&prev), &cur, Duration::from_secs(1));
+        assert_eq!(info.loss_pct, None);
+        assert_eq!(info.up_kbps, Some(0.0));
+    }
+
+    #[test]
+    fn loss_detected_in_an_idle_window_clamps_to_full() {
+        // Losses can be *detected* after sending stops (ACK timeouts fire late).
+        let prev = snap("1.2.3.4:5", 4000, 2000, 100, 0);
+        let cur = snap("1.2.3.4:5", 4000, 2000, 100, 3);
+        let info = derive(Some(&prev), &cur, Duration::from_secs(1));
+        assert_eq!(info.loss_pct, Some(100.0));
+    }
+
+    #[test]
+    fn path_switch_resets_the_window() {
+        let prev = snap("relay.example:443", 9000, 9000, 900, 5);
+        let cur = snap("1.2.3.4:5", 100, 100, 10, 0);
+        let info = derive(Some(&prev), &cur, Duration::from_secs(1));
+        assert_eq!(info.up_kbps, None);
+        assert_eq!(info.loss_pct, None);
+    }
+
+    #[test]
+    fn counter_reset_on_same_address_resets_the_window() {
+        // Same address but the connection was rebuilt → counters restarted.
+        let prev = snap("1.2.3.4:5", 9000, 9000, 900, 5);
+        let cur = snap("1.2.3.4:5", 100, 100, 10, 0);
+        let info = derive(Some(&prev), &cur, Duration::from_secs(1));
+        assert_eq!(info.up_kbps, None);
+        assert_eq!(info.loss_pct, None);
+    }
+
+    #[test]
+    fn zero_elapsed_yields_no_rates() {
+        let prev = snap("1.2.3.4:5", 0, 0, 0, 0);
+        let cur = snap("1.2.3.4:5", 4000, 2000, 100, 2);
+        let info = derive(Some(&prev), &cur, Duration::ZERO);
+        assert_eq!(info.up_kbps, None);
+        assert_eq!(info.loss_pct, None);
+    }
+
+    #[test]
+    fn oversized_rtt_saturates_instead_of_wrapping() {
+        let mut cur = snap("1.2.3.4:5", 0, 0, 0, 0);
+        cur.rtt = Duration::from_secs(u64::MAX);
+        let info = derive(None, &cur, POLL_INTERVAL);
+        assert_eq!(info.rtt_ms, u32::MAX);
+    }
+}

src/core/fetchbudget.rs

@@ -0,0 +1,252 @@
+//! Byte/request budgets for AUTOMATIC chat-attachment fetches (Phase 3B).
+//!
+//! The four-permit semaphore bounds how many auto-fetch tasks run at once, but
+//! not how much a peer can make us download over time: with permits released
+//! after each transfer, an insider could stream distinct ≤4 MiB images
+//! sequentially forever. This budget adds per-author and session (room-wide)
+//! token buckets over both request COUNT and declared BYTES. Like the Phase 2
+//! chat gate, time is passed in — never read from a clock — so every refill
+//! boundary is unit-testable.
+//!
+//! Only the automatic path consults this; a user's explicit click (Save /
+//! Download / Load image) is human-rate-limited and always allowed through to
+//! the fetch (still subject to the transfer cap and cache/decoder budgets).
+
+use iroh::EndpointId;
+use std::collections::HashMap;
+
+/// Per-author request burst: how many auto-fetches one author can trigger
+/// back-to-back before refill pacing binds.
+pub const AUTHOR_REQ_BURST: f64 = 8.0;
+/// Per-author request refill: one recovered every 10 s.
+pub const AUTHOR_REQ_REFILL_PER_MS: f64 = 1.0 / 10_000.0;
+/// Per-author byte burst (declared sizes): a couple of full-size auto images
+/// plus a normal working set.
+pub const AUTHOR_BYTES_BURST: f64 = (16 * 1024 * 1024) as f64;
+/// Per-author byte refill: 64 KiB/s (~one 4 MiB auto image per minute).
+pub const AUTHOR_BYTES_REFILL_PER_MS: f64 = (64 * 1024) as f64 / 1000.0;
+
+/// Session-wide request burst across all authors.
+pub const SESSION_REQ_BURST: f64 = 16.0;
+/// Session-wide request refill: one recovered every 5 s.
+pub const SESSION_REQ_REFILL_PER_MS: f64 = 1.0 / 5_000.0;
+/// Session-wide byte burst across all authors.
+pub const SESSION_BYTES_BURST: f64 = (48 * 1024 * 1024) as f64;
+/// Session-wide byte refill: 128 KiB/s.
+pub const SESSION_BYTES_REFILL_PER_MS: f64 = (128 * 1024) as f64 / 1000.0;
+
+/// Bound on the per-author bucket map. Authors are roster members (≤32 live),
+/// so this tracks the roster plus recently departed; the least-recently-active
+/// entry is pruned past the cap.
+pub const AUTHOR_MAP_CAP: usize = 64;
+
+/// A deterministic token bucket that can take a WEIGHTED cost (bytes), unlike
+/// the unit-cost bucket in the gossip chat gate.
+#[derive(Debug, Clone, Copy)]
+struct WeightedBucket {
+    tokens: f64,
+    last_ms: u64,
+}
+
+impl WeightedBucket {
+    fn full(burst: f64, now_ms: u64) -> Self {
+        Self {
+            tokens: burst,
+            last_ms: now_ms,
+        }
+    }
+
+    /// Refill for elapsed time (capped at `burst`) without consuming.
+    fn refill(&mut self, burst: f64, refill_per_ms: f64, now_ms: u64) {
+        let elapsed = now_ms.saturating_sub(self.last_ms) as f64;
+        self.tokens = (self.tokens + elapsed * refill_per_ms).min(burst);
+        self.last_ms = now_ms;
+    }
+
+    fn has(&self, cost: f64) -> bool {
+        self.tokens >= cost
+    }
+
+    fn take(&mut self, cost: f64) {
+        self.tokens -= cost;
+    }
+}
+
+/// One author's pair of buckets plus last activity (for idle pruning).
+#[derive(Debug)]
+struct AuthorBudget {
+    reqs: WeightedBucket,
+    bytes: WeightedBucket,
+    last_seen_ms: u64,
+}
+
+/// Admission budget for automatic attachment fetches. All four buckets are
+/// checked BEFORE any is consumed, so a rejection never burns tokens (no
+/// refund bookkeeping — the check-then-take is atomic within `admit`).
+#[derive(Debug)]
+pub struct AutoFetchBudget {
+    session_reqs: WeightedBucket,
+    session_bytes: WeightedBucket,
+    authors: HashMap<EndpointId, AuthorBudget>,
+}
+
+impl AutoFetchBudget {
+    pub fn new(now_ms: u64) -> Self {
+        Self {
+            session_reqs: WeightedBucket::full(SESSION_REQ_BURST, now_ms),
+            session_bytes: WeightedBucket::full(SESSION_BYTES_BURST, now_ms),
+            authors: HashMap::new(),
+        }
+    }
+
+    /// Whether an auto-fetch of `size` declared bytes for `author` may start
+    /// now. Consumes one request token and `size` byte tokens from BOTH the
+    /// author's and the session's buckets — or nothing at all on rejection.
+    pub fn admit(&mut self, author: EndpointId, size: u64, now_ms: u64) -> bool {
+        self.prune(author, now_ms);
+        let entry = self.authors.entry(author).or_insert_with(|| AuthorBudget {
+            reqs: WeightedBucket::full(AUTHOR_REQ_BURST, now_ms),
+            bytes: WeightedBucket::full(AUTHOR_BYTES_BURST, now_ms),
+            last_seen_ms: now_ms,
+        });
+        entry.last_seen_ms = now_ms;
+        entry
+            .reqs
+            .refill(AUTHOR_REQ_BURST, AUTHOR_REQ_REFILL_PER_MS, now_ms);
+        entry
+            .bytes
+            .refill(AUTHOR_BYTES_BURST, AUTHOR_BYTES_REFILL_PER_MS, now_ms);
+        self.session_reqs
+            .refill(SESSION_REQ_BURST, SESSION_REQ_REFILL_PER_MS, now_ms);
+        self.session_bytes
+            .refill(SESSION_BYTES_BURST, SESSION_BYTES_REFILL_PER_MS, now_ms);
+
+        let cost = size as f64;
+        let ok = entry.reqs.has(1.0)
+            && entry.bytes.has(cost)
+            && self.session_reqs.has(1.0)
+            && self.session_bytes.has(cost);
+        if ok {
+            let entry = self.authors.get_mut(&author).expect("just inserted");
+            entry.reqs.take(1.0);
+            entry.bytes.take(cost);
+            self.session_reqs.take(1.0);
+            self.session_bytes.take(cost);
+        }
+        ok
+    }
+
+    /// Keep the author map bounded: past the cap, drop the least-recently
+    /// active entry that isn't the author being admitted. A pruned author
+    /// returns with full buckets, but authors are roster-gated upstream, so
+    /// the map can't be churned by strangers.
+    fn prune(&mut self, keep: EndpointId, _now_ms: u64) {
+        while self.authors.len() >= AUTHOR_MAP_CAP {
+            let Some(victim) = self
+                .authors
+                .iter()
+                .filter(|(id, _)| **id != keep)
+                .min_by_key(|(_, b)| b.last_seen_ms)
+                .map(|(id, _)| *id)
+            else {
+                break;
+            };
+            self.authors.remove(&victim);
+        }
+    }
+
+    #[cfg(test)]
+    fn author_count(&self) -> usize {
+        self.authors.len()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use iroh::SecretKey;
+
+    const T0: u64 = 1_000_000;
+    const MIB: u64 = 1024 * 1024;
+
+    fn author() -> EndpointId {
+        SecretKey::generate().public()
+    }
+
+    #[test]
+    fn author_request_burst_then_refill_recovers() {
+        let mut b = AutoFetchBudget::new(T0);
+        let a = author();
+        // Tiny sizes so only the REQUEST buckets can bind.
+        for _ in 0..AUTHOR_REQ_BURST as usize {
+            assert!(b.admit(a, 1, T0));
+        }
+        assert!(!b.admit(a, 1, T0), "author request burst exhausted");
+        // One request refills after 10 s.
+        assert!(b.admit(a, 1, T0 + 10_000));
+        assert!(!b.admit(a, 1, T0 + 10_000));
+    }
+
+    #[test]
+    fn author_byte_budget_binds_and_recovers() {
+        let mut b = AutoFetchBudget::new(T0);
+        let a = author();
+        // 4 × 4 MiB = the full 16 MiB author byte burst (well under the
+        // 8-request burst, so bytes are the binding constraint).
+        for _ in 0..4 {
+            assert!(b.admit(a, 4 * MIB, T0));
+        }
+        assert!(!b.admit(a, 4 * MIB, T0), "author byte burst exhausted");
+        // 64 KiB/s → a 4 MiB image is affordable again after 64 s (which also
+        // refills 6 request tokens, so bytes stay the binding constraint).
+        assert!(!b.admit(a, 4 * MIB, T0 + 32_000));
+        assert!(b.admit(a, 4 * MIB, T0 + 64_000));
+    }
+
+    #[test]
+    fn session_budget_binds_across_authors_without_burning_author_tokens() {
+        let mut b = AutoFetchBudget::new(T0);
+        // Three authors × 16 MiB exhausts the 48 MiB session byte burst even
+        // though each author is within their own budget.
+        for _ in 0..3 {
+            let a = author();
+            for _ in 0..4 {
+                assert!(b.admit(a, 4 * MIB, T0));
+            }
+        }
+        let fresh = author();
+        assert!(!b.admit(fresh, 4 * MIB, T0), "session bytes exhausted");
+        // The rejection consumed NOTHING: once the session refills enough for
+        // one image (4 MiB / 128 KiB/s = 32 s), the fresh author's own full
+        // burst is intact and admits immediately.
+        assert!(b.admit(fresh, 4 * MIB, T0 + 32_000));
+    }
+
+    #[test]
+    fn session_request_bucket_binds_across_authors() {
+        let mut b = AutoFetchBudget::new(T0);
+        // 16 tiny requests from distinct authors exhaust the session request
+        // burst while every author bucket stays nearly full.
+        for _ in 0..SESSION_REQ_BURST as usize {
+            assert!(b.admit(author(), 1, T0));
+        }
+        assert!(!b.admit(author(), 1, T0), "session requests exhausted");
+        assert!(b.admit(author(), 1, T0 + 5_000), "one recovers after 5 s");
+    }
+
+    #[test]
+    fn author_map_stays_bounded_pruning_least_recent() {
+        let mut b = AutoFetchBudget::new(T0);
+        // Session request refill would bind over a naive loop; space the
+        // admissions out so only the map bound is under test.
+        let mut t = T0;
+        let first = author();
+        assert!(b.admit(first, 1, t));
+        for _ in 0..(AUTHOR_MAP_CAP + 10) {
+            t += 10_000;
+            assert!(b.admit(author(), 1, t));
+            assert!(b.author_count() <= AUTHOR_MAP_CAP);
+        }
+        assert!(b.author_count() <= AUTHOR_MAP_CAP);
+    }
+}

src/core/jitter.rs

@@ -202,11 +202,20 @@ impl JitterBuffer {
                     None
                 } else {
                     // Gap with later packets already buffered: a packet was lost
-                    // or reordered out of window. Conceal this frame via Opus PLC
-                    // and grow the cushion — the jitter beat our current delay.
+                    // or reordered out of window. Try Opus in-band FEC from the
+                    // packet right after the gap; if that packet isn't buffered
+                    // (burst loss) or FEC fails, fall back to plain PLC.
                     self.next_seq = Some(next.wrapping_add(1));
                     self.note_disruption();
-                    self.decoder.decode(None).ok()
+                    let (&smallest, next_payload) = self.packets.iter().next().expect("non-empty");
+                    if fec_covers_gap(next, smallest) {
+                        self.decoder
+                            .decode_fec(next_payload)
+                            .or_else(|_| self.decoder.decode(None))
+                            .ok()
+                    } else {
+                        self.decoder.decode(None).ok()
+                    }
                 }
             }
         }
@@ -218,11 +227,20 @@ impl JitterBuffer {
     }
 }
 
+/// Opus in-band FEC in packet N carries a low-fidelity copy of frame N-1 and
+/// nothing else — a lost frame `next` is FEC-recoverable solely from packet
+/// `next+1`. Any later successor's FEC data is a different frame's audio, and
+/// splicing it into this gap plays sound from the wrong position; the caller
+/// must conceal with plain PLC instead.
+fn fec_covers_gap(next: u32, smallest_buffered: u32) -> bool {
+    smallest_buffered == next.wrapping_add(1)
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::codec::AudioEncoder;
-    use crate::codec::opus_impl::OpusEncoder;
+    use crate::codec::opus_impl::{OpusDecoder, OpusEncoder, OpusParams};
+    use crate::codec::{AudioDecoder, AudioEncoder};
     use opus::{Application, Channels};
 
     /// A real, decodable Opus packet for one 20ms mono frame at amplitude `amp`.
@@ -233,6 +251,32 @@ mod tests {
         enc.encode(&pcm).unwrap()
     }
 
+    fn tone_frame(enc: &mut OpusEncoder, amp: i16, frame_index: usize) -> Vec<u8> {
+        let pcm: Vec<i16> = (0..FRAME_SAMPLES)
+            .map(|i| {
+                let sample_index = frame_index * FRAME_SAMPLES + i;
+                let t = sample_index as f32 / 48_000.0;
+                let fundamental = (t * 220.0 * 2.0 * std::f32::consts::PI).sin();
+                let harmonic = (t * 440.0 * 2.0 * std::f32::consts::PI).sin();
+                ((fundamental * 0.7 + harmonic * 0.3) * amp as f32) as i16
+            })
+            .collect();
+        enc.encode(&pcm).unwrap()
+    }
+
+    fn rms_error(a: &[i16], b: &[i16]) -> f64 {
+        assert_eq!(a.len(), b.len());
+        let sum_sq: f64 = a
+            .iter()
+            .zip(b)
+            .map(|(&left, &right)| {
+                let diff = left as f64 - right as f64;
+                diff * diff
+            })
+            .sum();
+        (sum_sq / a.len() as f64).sqrt()
+    }
+
     #[test]
     fn buffers_then_plays_in_order() {
         let mut enc = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
@@ -289,6 +333,137 @@ mod tests {
         assert!(jb.pop_frame().is_none());
     }
 
+    #[test]
+    fn uses_in_band_fec_from_next_packet_for_gap() {
+        let mut enc = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
+        enc.apply_params(&OpusParams {
+            bitrate: 20_000,
+            inband_fec: true,
+            packet_loss_perc: 60,
+            dtx: false,
+        })
+        .unwrap();
+
+        let dropped_seq = 5usize;
+        let amps = [1800, 1800, 1800, 1800, 1800, 12_000, 12_000, 12_000];
+        let packets: Vec<Vec<u8>> = amps
+            .into_iter()
+            .enumerate()
+            .map(|(seq, amp)| tone_frame(&mut enc, amp, seq))
+            .collect();
+
+        let mut expected_decoder = OpusDecoder::new(48000, Channels::Mono, FRAME_SAMPLES).unwrap();
+        for packet in packets.iter().take(dropped_seq) {
+            expected_decoder.decode(Some(packet)).unwrap();
+        }
+        let expected_lost = expected_decoder
+            .decode(Some(&packets[dropped_seq]))
+            .unwrap();
+
+        let mut plc_decoder = OpusDecoder::new(48000, Channels::Mono, FRAME_SAMPLES).unwrap();
+        for packet in packets.iter().take(dropped_seq) {
+            plc_decoder.decode(Some(packet)).unwrap();
+        }
+        let pure_plc = plc_decoder.decode(None).unwrap();
+
+        let mut jb = JitterBuffer::new().unwrap();
+        for (seq, packet) in packets.iter().enumerate() {
+            if seq != dropped_seq {
+                jb.insert(seq as u32, packet.clone());
+            }
+        }
+
+        for _ in 0..dropped_seq {
+            assert_eq!(jb.pop_frame().map(|frame| frame.len()), Some(FRAME_SAMPLES));
+        }
+
+        let recovered = jb.pop_frame().expect("gap should be reconstructed");
+        assert_eq!(recovered.len(), FRAME_SAMPLES);
+        assert!(
+            jb.packets.contains_key(&(dropped_seq as u32 + 1)),
+            "FEC source packet must remain buffered for normal decode"
+        );
+        assert_eq!(jb.pop_frame().map(|frame| frame.len()), Some(FRAME_SAMPLES));
+
+        let fec_error = rms_error(&recovered, &expected_lost);
+        let plc_error = rms_error(&pure_plc, &expected_lost);
+        assert!(
+            fec_error < plc_error * 0.75,
+            "FEC reconstruction should be materially closer than PLC (fec_error={fec_error}, plc_error={plc_error})"
+        );
+    }
+
+    #[test]
+    fn fec_covers_gap_only_for_the_immediate_successor() {
+        // Packet next+1 is the only one whose in-band FEC describes frame `next`.
+        assert!(fec_covers_gap(4, 5));
+        // A burst gap: the smallest survivor's FEC is some other frame's audio.
+        assert!(!fec_covers_gap(3, 5));
+        assert!(!fec_covers_gap(3, 3_000));
+        // Sequence wraparound still counts as adjacent.
+        assert!(fec_covers_gap(u32::MAX, 0));
+    }
+
+    #[test]
+    fn burst_gap_falls_back_to_plc_not_wrong_position_fec() {
+        let mut enc = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
+        enc.apply_params(&OpusParams {
+            bitrate: 20_000,
+            inband_fec: true,
+            packet_loss_perc: 60,
+            dtx: false,
+        })
+        .unwrap();
+
+        // Frames 0..=6; 3 and 4 are lost as a burst, so when playout reaches
+        // seq 3 the smallest buffered packet is 5 — whose FEC data is frame 4,
+        // NOT frame 3. The buffer must conceal 3 with plain PLC rather than
+        // splice frame 4's audio into the wrong position.
+        let packets: Vec<Vec<u8>> = (0..7).map(|seq| tone_frame(&mut enc, 8_000, seq)).collect();
+
+        // Twin decoder replaying the exact call sequence the jitter buffer
+        // should make for seq 3: decode 0,1,2 then a plain PLC conceal.
+        let mut twin = OpusDecoder::new(48000, Channels::Mono, FRAME_SAMPLES).unwrap();
+        for packet in packets.iter().take(3) {
+            twin.decode(Some(packet)).unwrap();
+        }
+        let expected_plc = twin.decode(None).unwrap();
+
+        let mut jb = JitterBuffer::new().unwrap();
+        for (seq, packet) in packets.iter().enumerate() {
+            if seq != 3 && seq != 4 {
+                jb.insert(seq as u32, packet.clone());
+            }
+        }
+
+        for _ in 0..3 {
+            assert_eq!(jb.pop_frame().map(|frame| frame.len()), Some(FRAME_SAMPLES));
+        }
+
+        // Seq 3: burst gap — bit-exact PLC (same decoder state, same inputs),
+        // which decode_fec(packet 5) could never produce.
+        let concealed = jb.pop_frame().expect("gap should be concealed");
+        assert_eq!(concealed, expected_plc, "burst gap must use plain PLC");
+
+        // Seq 4: packet 5 IS the immediate successor, so its FEC data is
+        // frame 4's audio — the correctly-positioned recovery still applies.
+        let recovered = jb
+            .pop_frame()
+            .expect("adjacent gap should be reconstructed");
+        let mut fec_twin = OpusDecoder::new(48000, Channels::Mono, FRAME_SAMPLES).unwrap();
+        for packet in packets.iter().take(3) {
+            fec_twin.decode(Some(packet)).unwrap();
+        }
+        fec_twin.decode(None).unwrap();
+        let expected_fec = fec_twin.decode_fec(&packets[5]).unwrap();
+        assert_eq!(recovered, expected_fec, "adjacent gap should still use FEC");
+
+        // Then 5 and 6 play normally.
+        assert_eq!(jb.pop_frame().map(|frame| frame.len()), Some(FRAME_SAMPLES));
+        assert_eq!(jb.pop_frame().map(|frame| frame.len()), Some(FRAME_SAMPLES));
+        assert!(jb.pop_frame().is_none());
+    }
+
     #[test]
     fn drops_packets_already_played() {
         let mut enc = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();

src/core/messages.rs

@@ -1,4 +1,4 @@
-use crate::config::{NetworkMode, RecordingMode};
+use crate::config::{AudioProfile, NetworkMode, RecordingMode, ScreenShareSettings, ShareQuality};
 use crate::friends::Friend;
 use crate::network::PeerState;
 use crate::presence::{FriendPresence, PresenceMode};
@@ -9,7 +9,15 @@ pub enum CoreCommand {
     /// Join a room. `ticket` is "create" (or empty) to mint a fresh room, else a
     /// share ticket to join. `room_name` is the creator's chosen cosmetic label
     /// for a NEW room; it's ignored when joining (the label rides in the ticket).
-    Join { name: String, ticket: String, room_name: String, input_device: Option<String>, output_device: Option<String>, echo_cancellation: bool, avatar: crate::avatar::Avatar },
+    Join {
+        name: String,
+        ticket: String,
+        room_name: String,
+        input_device: Option<String>,
+        output_device: Option<String>,
+        echo_cancellation: bool,
+        avatar: crate::avatar::Avatar,
+    },
     Leave,
     /// Orderly app shutdown: finalize recordings, leave any active room, stop local
     /// audio/screen-share work, close the persistent network stack, then ack with
@@ -26,6 +34,10 @@ pub enum CoreCommand {
     SetPeerEq(EndpointId, crate::audio::eq::EqSettings),
     /// Listener-side per-peer pan. Local only; never leaves this app instance.
     SetPeerPan(EndpointId, f32),
+    /// Listener-side per-peer noise gate threshold (normalized RMS, `0.0` = off).
+    /// Applies the same smooth gate as the mic path to a peer's incoming audio,
+    /// to suppress their background noise on our end. Local only.
+    SetPeerGate(EndpointId, f32),
     /// Locally mute/unmute a peer: when muted, their audio is decoded (so levels
     /// still show) but not mixed into our output.
     SetPeerMuted(EndpointId, bool),
@@ -37,30 +49,100 @@ pub enum CoreCommand {
     /// Start/stop a standalone capture-only stream that reports the raw mic
     /// level via [`UiEvent::MicLevel`], for gate calibration outside a call.
     /// Ignored while a room session is active (the in-call meter covers that).
-    SetMicMonitor { enabled: bool, input_device: Option<String> },
+    SetMicMonitor {
+        enabled: bool,
+        input_device: Option<String>,
+    },
     /// Set the relay/discovery posture. Takes effect on the next room join,
     /// since the endpoint is (re)built then.
     SetNetworkMode(NetworkMode),
+    /// Set the Opus encoder / network-resilience profile (W12). Applies live to
+    /// the running capture encoder, and to the next call's encoder. Sent at
+    /// startup from config and whenever the user changes it.
+    SetAudioProfile(AudioProfile),
     /// Start/stop recording the call to a local WAV (your mic + the incoming
     /// mix). No-op start if already recording / not in a call.
     SetRecording(bool),
     /// Set what a recording captures (mixed / per-peer stems / both). Takes
     /// effect on the next recording start. Sent at startup from config.
     SetRecordingMode(RecordingMode),
-    /// Broadcast a room text-chat message. No-op when not in a call.
-    SendChat(String),
+    /// Broadcast a room text-chat message. `local_id` is the app's local-only
+    /// handle for this send — it never goes on the wire; the core echoes it back
+    /// in [`UiEvent::ChatSendResult`] so the UI can mark the matching local echo
+    /// honestly (chat-hardening Phase 5). Not being in a call is a FAILURE
+    /// result, not a silent no-op.
+    SendChat {
+        local_id: u64,
+        text: String,
+    },
+    /// Send a chat message carrying a file attachment. The app has already read +
+    /// capped the file and built the descriptor; core makes the bytes available
+    /// on the file plane and broadcasts the descriptor. `local_id` as in
+    /// [`CoreCommand::SendChat`].
+    SendChatFile {
+        local_id: u64,
+        text: String,
+        attachment: crate::files::ChatAttachment,
+        /// Shared, not owned: the same allocation is retained by the UI cache
+        /// and handed to the serve store, so a 25 MiB attachment is held once,
+        /// not copied across UI / command queue / serve store (Phase 3C).
+        data: std::sync::Arc<Vec<u8>>,
+    },
+    /// Fetch a received attachment's bytes from its sender over the file plane
+    /// (used for on-demand file/chip downloads; images are auto-fetched on
+    /// receipt). Replies with `AttachmentReady`/`AttachmentFailed`.
+    FetchAttachment {
+        from: EndpointId,
+        attachment: crate::files::ChatAttachment,
+    },
+    /// Register `data` as fetchable under `id` for room members (the current
+    /// broadcast track). Called once per track when broadcasting.
+    ServeMusicTrack {
+        id: crate::files::AttachmentId,
+        data: std::sync::Arc<Vec<u8>>,
+    },
+    /// Drop a music blob that is no longer current-or-next.
+    ForgetMusicTrack(crate::files::AttachmentId),
+    /// Set (or clear) our broadcast music timeline and re-announce presence.
+    SetMusicPresence(Option<crate::network::MusicPresence>),
+    /// Fetch a source peer's current track bytes after tuning into them.
+    FetchMusic {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        size: u64,
+    },
+    /// Fetch a source peer's advertised next track bytes before it becomes current.
+    PrefetchMusic {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        size: u64,
+    },
     /// Set the pixelpass binary location (config override, empty = use `$PATH`).
     /// Sent at startup so screen-share can resolve the binary.
     SetPixelpassPath(Option<String>),
+    /// Enumerate apps currently producing audio (for the screen-share audio
+    /// picker, A23). Replies with [`UiEvent::AudioAppsListed`]. Cheap shell-out;
+    /// safe to call each time the picker opens.
+    ListAudioApps,
     /// Start sharing our screen: spawn a pixelpass host and announce its ticket
     /// on our presence so the room can watch. No-op when not in a call.
-    StartScreenShare,
+    /// `audio_app` selects which app's audio to capture: `Some(name)` captures
+    /// only that app (avoiding the call-loopback echo, A23); `None` shares the
+    /// whole desktop audio (the legacy behavior).
+    StartScreenShare {
+        audio_app: Option<String>,
+        settings: ScreenShareSettings,
+        quality: ShareQuality,
+    },
     /// Stop sharing our screen: kill the pixelpass host and clear the presence
     /// ticket. No-op when not sharing.
     StopScreenShare,
     /// Watch a peer's screen share: spawn a pixelpass viewer for `ticket` and
     /// open it in a local player.
-    ViewShare(String),
+    ViewShare {
+        ticket: String,
+        settings: ScreenShareSettings,
+    },
     /// Mint a fresh persistent identity (W7), discarding the old one. Takes effect
     /// on the next room join (the endpoint is rebuilt then). The core replies with
     /// an updated [`UiEvent::IdentityStatus`].
@@ -68,68 +150,511 @@ pub enum CoreCommand {
     /// Add a friend (W7). Core owns the friends store: it mutates + persists it and
     /// replies with [`UiEvent::FriendsUpdated`]. `addr` seeds `last_addr` if known
     /// (e.g. added from a room). Idempotent — re-adding an existing id is a no-op.
-    AddFriend { id: EndpointId, name: String, addr: Option<EndpointAddr> },
+    AddFriend {
+        id: EndpointId,
+        name: String,
+        addr: Option<EndpointAddr>,
+    },
     /// Remove a friend by id (W7).
     RemoveFriend(EndpointId),
     /// Locally rename a friend (W7).
     RenameFriend(EndpointId, String),
+    /// Run an immediate presence-refresh pass over all friends (the manual
+    /// "Rescan" button). Same work the 60s scheduler does on each tick, on demand —
+    /// no waiting for the next interval. A no-op while Invisible.
+    RefreshFriends,
     /// Set our presence posture (W7). Gates the idle listener (answer friends-only /
     /// invisible) and the outbound ping scheduler (invisible = fully dark). Sent at
     /// startup from config and whenever the user changes it.
     SetPresenceMode(PresenceMode),
+    /// Toggle broadcasting the detected game as presence (game detection). Opt-in,
+    /// default OFF. Enabling immediately publishes the current game; disabling
+    /// immediately publishes `game: None`. Detection for the local background runs
+    /// regardless. Sent at startup from config and on user toggle.
+    SetGamePresenceEnabled(bool),
+    /// Set the manual game-detection override (`Auto` / `None` / a forced game).
+    /// Forwarded to the detector and applied immediately (bypasses debounce).
+    SetGameOverride(crate::game::ManualOverride),
+    /// Replace the user process→display-name mappings used by the non-Steam
+    /// detection fallback. Sent at startup from config and after Settings edits.
+    SetGameProcessMap(std::collections::BTreeMap<String, String>),
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum DeliveryClass {
+    Reliable,
+    BestEffort,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum CoalesceKey {
+    InputVolume,
+    OutputVolume,
+    NoiseGate,
+    PeerVolume(EndpointId),
+    PeerPan(EndpointId),
+    PeerGate(EndpointId),
+    PeerEq(EndpointId),
+}
+
+/// Route a command by how bad it is to drop it. Discrete, human-paced user
+/// actions are Reliable (must land). The only high-frequency commands are the
+/// continuous audio sliders, where dropping intermediate values is harmless;
+/// those are BestEffort.
+pub fn delivery_class(cmd: &CoreCommand) -> DeliveryClass {
+    match cmd {
+        CoreCommand::SetPeerVolume(_, _)
+        | CoreCommand::SetPeerPan(_, _)
+        | CoreCommand::SetPeerGate(_, _)
+        | CoreCommand::SetPeerEq(_, _)
+        | CoreCommand::SetInputVolume(_)
+        | CoreCommand::SetOutputVolume(_)
+        | CoreCommand::SetNoiseGateThreshold(_) => DeliveryClass::BestEffort,
+
+        CoreCommand::Join {
+            name: _,
+            ticket: _,
+            room_name: _,
+            input_device: _,
+            output_device: _,
+            echo_cancellation: _,
+            avatar: _,
+        }
+        | CoreCommand::Leave
+        | CoreCommand::Shutdown
+        | CoreCommand::ToggleMute
+        | CoreCommand::SetAvatar(_)
+        | CoreCommand::ToggleDeafen
+        | CoreCommand::SetPttMode(_)
+        | CoreCommand::SetPttActive(_)
+        | CoreCommand::SetPeerMuted(_, _)
+        | CoreCommand::SetMicMonitor {
+            enabled: _,
+            input_device: _,
+        }
+        | CoreCommand::SetNetworkMode(_)
+        | CoreCommand::SetAudioProfile(_)
+        | CoreCommand::SetRecording(_)
+        | CoreCommand::SetRecordingMode(_)
+        | CoreCommand::SendChat {
+            local_id: _,
+            text: _,
+        }
+        | CoreCommand::SendChatFile {
+            local_id: _,
+            text: _,
+            attachment: _,
+            data: _,
+        }
+        | CoreCommand::FetchAttachment {
+            from: _,
+            attachment: _,
+        }
+        | CoreCommand::ServeMusicTrack { id: _, data: _ }
+        | CoreCommand::ForgetMusicTrack(_)
+        | CoreCommand::SetMusicPresence(_)
+        | CoreCommand::FetchMusic {
+            from: _,
+            id: _,
+            size: _,
+        }
+        | CoreCommand::PrefetchMusic {
+            from: _,
+            id: _,
+            size: _,
+        }
+        | CoreCommand::SetPixelpassPath(_)
+        | CoreCommand::ListAudioApps
+        | CoreCommand::StartScreenShare {
+            audio_app: _,
+            settings: _,
+            quality: _,
+        }
+        | CoreCommand::StopScreenShare
+        | CoreCommand::ViewShare {
+            ticket: _,
+            settings: _,
+        }
+        | CoreCommand::RegenerateIdentity
+        | CoreCommand::AddFriend {
+            id: _,
+            name: _,
+            addr: _,
+        }
+        | CoreCommand::RemoveFriend(_)
+        | CoreCommand::RenameFriend(_, _)
+        | CoreCommand::RefreshFriends
+        | CoreCommand::SetPresenceMode(_)
+        | CoreCommand::SetGamePresenceEnabled(_)
+        | CoreCommand::SetGameOverride(_)
+        | CoreCommand::SetGameProcessMap(_) => DeliveryClass::Reliable,
+    }
+}
+
+/// Coalescing bucket for high-frequency continuous controls. A key exists
+/// exactly for [`DeliveryClass::BestEffort`] commands.
+pub fn coalesce_key(cmd: &CoreCommand) -> Option<CoalesceKey> {
+    match cmd {
+        CoreCommand::SetPeerVolume(peer_id, _) => Some(CoalesceKey::PeerVolume(*peer_id)),
+        CoreCommand::SetPeerPan(peer_id, _) => Some(CoalesceKey::PeerPan(*peer_id)),
+        CoreCommand::SetPeerGate(peer_id, _) => Some(CoalesceKey::PeerGate(*peer_id)),
+        CoreCommand::SetPeerEq(peer_id, _) => Some(CoalesceKey::PeerEq(*peer_id)),
+        CoreCommand::SetInputVolume(_) => Some(CoalesceKey::InputVolume),
+        CoreCommand::SetOutputVolume(_) => Some(CoalesceKey::OutputVolume),
+        CoreCommand::SetNoiseGateThreshold(_) => Some(CoalesceKey::NoiseGate),
+
+        CoreCommand::Join {
+            name: _,
+            ticket: _,
+            room_name: _,
+            input_device: _,
+            output_device: _,
+            echo_cancellation: _,
+            avatar: _,
+        }
+        | CoreCommand::Leave
+        | CoreCommand::Shutdown
+        | CoreCommand::ToggleMute
+        | CoreCommand::SetAvatar(_)
+        | CoreCommand::ToggleDeafen
+        | CoreCommand::SetPttMode(_)
+        | CoreCommand::SetPttActive(_)
+        | CoreCommand::SetPeerMuted(_, _)
+        | CoreCommand::SetMicMonitor {
+            enabled: _,
+            input_device: _,
+        }
+        | CoreCommand::SetNetworkMode(_)
+        | CoreCommand::SetAudioProfile(_)
+        | CoreCommand::SetRecording(_)
+        | CoreCommand::SetRecordingMode(_)
+        | CoreCommand::SendChat {
+            local_id: _,
+            text: _,
+        }
+        | CoreCommand::SendChatFile {
+            local_id: _,
+            text: _,
+            attachment: _,
+            data: _,
+        }
+        | CoreCommand::FetchAttachment {
+            from: _,
+            attachment: _,
+        }
+        | CoreCommand::ServeMusicTrack { id: _, data: _ }
+        | CoreCommand::ForgetMusicTrack(_)
+        | CoreCommand::SetMusicPresence(_)
+        | CoreCommand::FetchMusic {
+            from: _,
+            id: _,
+            size: _,
+        }
+        | CoreCommand::PrefetchMusic {
+            from: _,
+            id: _,
+            size: _,
+        }
+        | CoreCommand::SetPixelpassPath(_)
+        | CoreCommand::ListAudioApps
+        | CoreCommand::StartScreenShare {
+            audio_app: _,
+            settings: _,
+            quality: _,
+        }
+        | CoreCommand::StopScreenShare
+        | CoreCommand::ViewShare {
+            ticket: _,
+            settings: _,
+        }
+        | CoreCommand::RegenerateIdentity
+        | CoreCommand::AddFriend {
+            id: _,
+            name: _,
+            addr: _,
+        }
+        | CoreCommand::RemoveFriend(_)
+        | CoreCommand::RenameFriend(_, _)
+        | CoreCommand::RefreshFriends
+        | CoreCommand::SetPresenceMode(_)
+        | CoreCommand::SetGamePresenceEnabled(_)
+        | CoreCommand::SetGameOverride(_)
+        | CoreCommand::SetGameProcessMap(_) => None,
+    }
 }
 
 #[derive(Debug, Clone)]
 pub enum UiEvent {
-    RoomJoined { ticket: String, self_id: String },
+    RoomJoined {
+        ticket: String,
+        self_id: String,
+    },
     RoomLeft,
-    PeerJoined { id: EndpointId, state: PeerState },
-    PeerLeft { id: EndpointId },
-    PeerConnectionFailed { id: EndpointId },
-    PeerUpdated { id: EndpointId, state: PeerState },
+    /// Clear room-scoped UI state after a failed in-call room switch, without a
+    /// leave chime. The persistent identity remains unchanged.
+    RoomReset,
+    PeerJoined {
+        id: EndpointId,
+        state: PeerState,
+    },
+    PeerLeft {
+        id: EndpointId,
+    },
+    /// The fixed reconnect grace expired and bounded background gossip recovery
+    /// has started. This is non-terminal and must not play the failure chime.
+    PeerRecoveryStarted {
+        id: EndpointId,
+    },
+    PeerConnectionFailed {
+        id: EndpointId,
+    },
+    PeerUpdated {
+        id: EndpointId,
+        state: PeerState,
+    },
     /// Audio link to a peer is being (re)established — show a connecting state.
-    PeerConnecting { id: EndpointId },
+    PeerConnecting {
+        id: EndpointId,
+    },
     /// Audio link to a peer is up and carrying audio.
-    PeerConnected { id: EndpointId },
+    PeerConnected {
+        id: EndpointId,
+    },
     AudioLevels(Vec<(EndpointId, f32)>),
+    /// Periodic per-peer connection transparency snapshot (~1/sec): path type
+    /// (direct/relay), RTT, and window loss/bitrate for every peer with a live
+    /// audio link. A FULL replacement each time — a peer absent from the list
+    /// has no live link right now, so its badge should disappear.
+    ConnectionStats(Vec<(EndpointId, crate::core::connstats::PeerConnInfo)>),
     /// Raw (pre-gate, pre-mute) normalized RMS of the local mic, `0.0..=1.0`,
     /// for the settings level meter. Throttled to ~10/sec.
     MicLevel(f32),
     /// Call recording started; carries the absolute WAV path being written.
-    RecordingStarted { path: String },
+    RecordingStarted {
+        path: String,
+    },
     /// Call recording stopped; carries the finished WAV path.
-    RecordingStopped { path: String },
+    RecordingStopped {
+        path: String,
+    },
+    /// The outcome of one locally initiated chat send (chat-hardening Phase 5).
+    /// `error = None` means our signed broadcast was handed to the gossip swarm
+    /// — deliberately NOT a delivery/read receipt; PeerSpeak has no peer
+    /// acknowledgements. `local_id` is the app's own handle from the
+    /// `SendChat`/`SendChatFile` command and never appears on the wire.
+    ChatSendResult {
+        local_id: u64,
+        error: Option<String>,
+    },
     /// A room text-chat message arrived from a peer (never our own — local
     /// messages are echoed by the UI on send). `from` is the sender's node id
     /// string, used to key their avatar (W4).
-    ChatMessage { from: String, name: String, text: String },
+    ChatMessage {
+        from: String,
+        name: String,
+        text: String,
+        attachment: Option<crate::files::ChatAttachment>,
+    },
+    /// An attachment's bytes are now available (auto-fetched for images, or
+    /// fetched on demand for files). Keyed by `(from, id)`: the id is
+    /// attacker-chosen, so a malicious peer can reuse a victim's id — the author
+    /// disambiguates whose bytes these are and stops content aliasing (Tier C
+    /// F-12).
+    AttachmentReady {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        data: std::sync::Arc<Vec<u8>>,
+    },
+    /// An attachment fetch task was spawned (auto or on demand). Lets the UI
+    /// show a real "loading" state instead of inferring it from cache absence —
+    /// absence now means NOT fetched (e.g. auto-fetch was skipped), which
+    /// renders a Load button rather than an indefinite "loading…" (Phase 3B).
+    AttachmentFetchStarted {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+    },
+    /// An attachment fetch failed (sender gone, too large, decode error, etc.).
+    AttachmentFailed {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        error: String,
+    },
+    /// A tuned-in source's track bytes arrived; play them in the music sink.
+    MusicReady {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        data: Vec<u8>,
+    },
+    /// A tuned-in source's next-track bytes arrived; cache them for a gapless swap.
+    MusicPrefetched {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        data: Vec<u8>,
+    },
+    /// A music-track fetch failed (source gone, too large, etc.).
+    MusicFetchFailed {
+        from: EndpointId,
+        id: crate::files::AttachmentId,
+        error: String,
+    },
+    /// The apps currently producing audio, for the screen-share audio picker
+    /// (A23). Sorted, deduplicated `application.name`s; empty when nothing is
+    /// playing or enumeration isn't available. `app_audio_supported` reports
+    /// whether the resolved pixelpass understands `--strict-audio`: when `false`
+    /// (an older pixelpass) the picker must offer whole-desktop audio only, since
+    /// a per-app share would pass a flag that older binary rejects (audit P2).
+    AudioAppsListed {
+        apps: Vec<String>,
+        app_audio_supported: bool,
+    },
     /// Our own screen share started; the UI flips the Share button to "Stop".
     ScreenShareStarted,
     /// Our own screen share stopped (or failed to start).
     ScreenShareStopped,
+    /// Per-app screen-share audio routing state (A23). `true` = the app we chose
+    /// is now reaching viewers; `false` = its audio stopped, so under our strict
+    /// run viewers currently hear silence. The UI shows a transient warning while
+    /// `false`. Only meaningful while sharing a specific app (not whole-desktop).
+    ShareAudioActive(bool),
+    /// A validly signed peer cannot be admitted because its gossip timestamp is
+    /// outside the replay freshness window. `peer_ahead` describes the peer's
+    /// sender-stamped timestamp relative to this machine's clock.
+    ClockSkewWarning {
+        skew_secs: u64,
+        peer_ahead: bool,
+    },
     /// Our node identity (W7): the current node id string, and whether it is
     /// PERSISTED to disk. Sent once at startup and again after a regenerate.
     /// `persisted = false` means the key file couldn't be read/written and we're
     /// running on an ephemeral fallback — a degraded state the UI must surface,
     /// since the id (and thus friend recognition) won't survive the next launch.
     /// `error` carries the reason when degraded, for the UI explainer.
-    IdentityStatus { node_id: String, persisted: bool, error: Option<String> },
+    IdentityStatus {
+        node_id: String,
+        persisted: bool,
+        error: Option<String>,
+    },
     /// The friends list (W7), now owned by core. Sent at startup (after load) and
     /// after every add/remove/rename so the GUI renders from this snapshot instead
     /// of owning the store. `read_only` is true when `friends.json` failed to load
     /// (malformed) — the GUI shows a degraded warning and disables edits so we never
     /// overwrite the damaged file (backlog A16).
-    FriendsUpdated { friends: Vec<Friend>, read_only: bool },
+    FriendsUpdated {
+        friends: Vec<Friend>,
+        read_only: bool,
+    },
     /// A friend's live presence from a successful ping reply (W7): online, or in a
     /// joinable gathering (with a one-click ticket). Emitted by the outbound ping
     /// scheduler; absence of a recent event = treat as offline.
-    FriendPresence { id: EndpointId, presence: FriendPresence },
+    FriendPresence {
+        id: EndpointId,
+        presence: FriendPresence,
+    },
+    /// A manual "Rescan" pass finished (every friend has been probed and its
+    /// per-friend `FriendPresence` already emitted). Lets the GUI clear the
+    /// transient "Rescanning…" status. Sent only for the on-demand button, not the
+    /// periodic auto-refresh, so the status bar isn't churned every interval.
+    FriendsRescanned,
     /// Core corrected the committed presence posture. Usually the Discoverable
     /// time-box elapsed and the core auto-reverted to `Normal`; on discovery apply
     /// failure, this carries the previous truthful mode. The GUI must mirror +
     /// persist this so its presence picker matches the endpoint's discovery state.
-    PresenceModeReverted { mode: PresenceMode },
+    PresenceModeReverted {
+        mode: PresenceMode,
+    },
+    /// The locally-detected running game changed (game detection). Carries the
+    /// debounced `DetectedGame` (id + display name + source) or `None` when nothing
+    /// is detected. The GUI uses the stable `id` to switch the per-game background
+    /// (W18) and may show a local "Playing …" indicator. Emitted regardless of
+    /// whether game presence is being broadcast — the broadcast is core's own job.
+    GameChanged(Option<crate::game::DetectedGame>),
     /// Core finished orderly app shutdown and the GUI can exit.
     ShutdownComplete,
     Error(String),
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{CoalesceKey, CoreCommand, DeliveryClass, coalesce_key, delivery_class};
+    use crate::audio::eq::EqSettings;
+    use crate::presence::PresenceMode;
+    use iroh::{EndpointId, SecretKey};
+
+    fn endpoint_id() -> EndpointId {
+        SecretKey::generate().public()
+    }
+
+    #[test]
+    fn continuous_audio_controls_are_best_effort() {
+        let peer = endpoint_id();
+        let commands = [
+            (
+                CoreCommand::SetPeerVolume(peer, 0.7),
+                CoalesceKey::PeerVolume(peer),
+            ),
+            (
+                CoreCommand::SetPeerPan(peer, -0.2),
+                CoalesceKey::PeerPan(peer),
+            ),
+            (
+                CoreCommand::SetPeerGate(peer, 0.1),
+                CoalesceKey::PeerGate(peer),
+            ),
+            (
+                CoreCommand::SetPeerEq(peer, EqSettings::default()),
+                CoalesceKey::PeerEq(peer),
+            ),
+            (CoreCommand::SetInputVolume(0.8), CoalesceKey::InputVolume),
+            (CoreCommand::SetOutputVolume(0.9), CoalesceKey::OutputVolume),
+            (
+                CoreCommand::SetNoiseGateThreshold(0.02),
+                CoalesceKey::NoiseGate,
+            ),
+        ];
+
+        for (cmd, key) in commands {
+            assert_eq!(delivery_class(&cmd), DeliveryClass::BestEffort);
+            assert_eq!(coalesce_key(&cmd), Some(key));
+            assert_eq!(
+                coalesce_key(&cmd).is_some(),
+                delivery_class(&cmd) == DeliveryClass::BestEffort
+            );
+        }
+    }
+
+    #[test]
+    fn discrete_user_actions_are_reliable() {
+        let peer = endpoint_id();
+        let commands = [
+            CoreCommand::ToggleMute,
+            CoreCommand::SetPttActive(false),
+            CoreCommand::Leave,
+            CoreCommand::RegenerateIdentity,
+            CoreCommand::Join {
+                name: "Peer".to_string(),
+                ticket: "create".to_string(),
+                room_name: "Room".to_string(),
+                input_device: None,
+                output_device: None,
+                echo_cancellation: true,
+                avatar: crate::avatar::Avatar::default(),
+            },
+            CoreCommand::SetPeerMuted(peer, true),
+            CoreCommand::SetPresenceMode(PresenceMode::Normal),
+            CoreCommand::SetAudioProfile(crate::config::AudioProfile::BadNetwork),
+            CoreCommand::SendChat {
+                local_id: 1,
+                text: "hello".to_string(),
+            },
+        ];
+
+        for cmd in commands {
+            assert_eq!(delivery_class(&cmd), DeliveryClass::Reliable);
+            assert_eq!(coalesce_key(&cmd), None);
+            assert_eq!(
+                coalesce_key(&cmd).is_some(),
+                delivery_class(&cmd) == DeliveryClass::BestEffort
+            );
+        }
+    }
+}

src/core/recovery.rs

@@ -0,0 +1,324 @@
+use crate::network::{RoomState, gossip::IrohGossipState};
+use iroh::{EndpointAddr, EndpointId};
+use std::collections::{HashMap, HashSet};
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+use tokio::sync::mpsc;
+use tokio::task::JoinHandle;
+use tokio::time::Instant;
+
+const RECOVERY_COMMAND_CAPACITY: usize = 64;
+const RECOVERY_DELAYS: [Duration; 7] = [
+    Duration::from_secs(1),
+    Duration::from_secs(2),
+    Duration::from_secs(4),
+    Duration::from_secs(8),
+    Duration::from_secs(15),
+    Duration::from_secs(30),
+    Duration::from_secs(60),
+];
+
+fn recovery_delay(attempt: usize) -> Duration {
+    RECOVERY_DELAYS[attempt.min(RECOVERY_DELAYS.len() - 1)]
+}
+
+/// Terminal retry budget for background recovery. After this many failed attempts
+/// the coordinator gives up: it drops the entry, frees the active slot, and signals
+/// the event task to forget the retained address (Tier C recovery-identity cap).
+///
+/// With the [`RECOVERY_DELAYS`] backoff this is roughly seven minutes of dialing
+/// (1+2+4+8+15+30+60s, then 60s steps), far beyond any normal transient outage. A
+/// genuine peer returning after a longer outage still rejoins on its own via a
+/// gossip announce, so giving up only stops us from dialing a peer that is not
+/// coming back — it does not break legitimate reconnect-after-outage.
+const RECOVERY_TERMINAL_ATTEMPTS: usize = 12;
+
+/// Capacity of the terminal-eviction notification channel. Bounded; on the rare
+/// event of saturation the entry is still removed (the dial work stops) and only
+/// the retained-address forget is skipped, which the per-topic retain cap bounds.
+const RECOVERY_TERMINAL_CAPACITY: usize = 64;
+
+/// Whether `attempt` completed recoveries have exhausted the terminal budget.
+fn recovery_is_terminal(attempt: usize, max_attempts: usize) -> bool {
+    attempt >= max_attempts
+}
+
+enum RecoveryCommand {
+    Start {
+        peer_id: EndpointId,
+        addr: EndpointAddr,
+    },
+    Cancel(EndpointId),
+}
+
+struct RecoveryEntry {
+    addr: EndpointAddr,
+    attempt: usize,
+    next_attempt: Instant,
+}
+
+#[async_trait::async_trait]
+trait RecoveryRoom: Send + Sync {
+    async fn rebootstrap_peers(&self, peers: Vec<EndpointAddr>) -> Result<(), String>;
+}
+
+#[async_trait::async_trait]
+impl RecoveryRoom for IrohGossipState {
+    async fn rebootstrap_peers(&self, peers: Vec<EndpointAddr>) -> Result<(), String> {
+        RoomState::rebootstrap_peers(self, peers)
+            .await
+            .map_err(|error| error.to_string())
+    }
+}
+
+/// Cloneable command side of the single per-session recovery coordinator.
+/// `active` is shared with transport/event handlers so cancellation is visible
+/// immediately even while the coordinator is awaiting an in-flight gossip call.
+#[derive(Clone)]
+pub(super) struct RecoveryCoordinator {
+    tx: mpsc::Sender<RecoveryCommand>,
+    active: Arc<Mutex<HashSet<EndpointId>>>,
+}
+
+impl RecoveryCoordinator {
+    pub(super) fn spawn(
+        room_state: Arc<IrohGossipState>,
+    ) -> (Self, JoinHandle<()>, mpsc::Receiver<EndpointId>) {
+        Self::spawn_inner(room_state)
+    }
+
+    fn spawn_inner(
+        room_state: Arc<dyn RecoveryRoom>,
+    ) -> (Self, JoinHandle<()>, mpsc::Receiver<EndpointId>) {
+        let (tx, rx) = mpsc::channel(RECOVERY_COMMAND_CAPACITY);
+        let (terminal_tx, terminal_rx) = mpsc::channel(RECOVERY_TERMINAL_CAPACITY);
+        let active = Arc::new(Mutex::new(HashSet::new()));
+        let handle = Self {
+            tx,
+            active: active.clone(),
+        };
+        let task = tokio::spawn(run_coordinator(room_state, active, rx, terminal_tx));
+        (handle, task, terminal_rx)
+    }
+
+    /// Reserve one recovery slot before grace-expiry teardown begins. Returns
+    /// false when the peer is already recovering, preventing duplicate work.
+    pub(super) fn begin(&self, peer_id: EndpointId) -> bool {
+        self.active.lock().unwrap().insert(peer_id)
+    }
+
+    /// Activate the reserved slot with its retained authenticated address.
+    /// Uses a bounded non-blocking send while holding the active-set lock so a
+    /// concurrent cancellation is ordered before or after this command.
+    pub(super) fn activate(&self, peer_id: EndpointId, addr: EndpointAddr) -> Result<bool, ()> {
+        let mut active = self.active.lock().unwrap();
+        if !active.contains(&peer_id) {
+            return Ok(false);
+        }
+        if self
+            .tx
+            .try_send(RecoveryCommand::Start { peer_id, addr })
+            .is_err()
+        {
+            active.remove(&peer_id);
+            return Err(());
+        }
+        Ok(true)
+    }
+
+    pub(super) fn cancel(&self, peer_id: EndpointId) {
+        self.active.lock().unwrap().remove(&peer_id);
+        // Cancellation is governed by the shared active set, so it remains
+        // immediate even if the bounded command queue is temporarily full.
+        let _ = self.tx.try_send(RecoveryCommand::Cancel(peer_id));
+    }
+
+    pub(super) fn is_active(&self, peer_id: &EndpointId) -> bool {
+        self.active.lock().unwrap().contains(peer_id)
+    }
+}
+
+async fn run_coordinator(
+    room_state: Arc<dyn RecoveryRoom>,
+    active: Arc<Mutex<HashSet<EndpointId>>>,
+    mut rx: mpsc::Receiver<RecoveryCommand>,
+    terminal_tx: mpsc::Sender<EndpointId>,
+) {
+    let mut entries: HashMap<EndpointId, RecoveryEntry> = HashMap::new();
+
+    loop {
+        // The shared active set is the authoritative cancellation gate. Prune
+        // here as well as on Cancel commands so a saturated command queue cannot
+        // leave an inactive, past-due entry spinning the timer loop.
+        let active_snapshot = active.lock().unwrap().clone();
+        entries.retain(|peer_id, _| active_snapshot.contains(peer_id));
+        let next_deadline = entries.values().map(|entry| entry.next_attempt).min();
+        let command = match next_deadline {
+            Some(deadline) => {
+                tokio::select! {
+                    command = rx.recv() => command,
+                    _ = tokio::time::sleep_until(deadline) => {
+                        let now = Instant::now();
+                        let active_snapshot = active.lock().unwrap().clone();
+                        let due: Vec<(EndpointId, EndpointAddr)> = entries
+                            .iter()
+                            .filter(|(id, entry)| {
+                                entry.next_attempt <= now && active_snapshot.contains(*id)
+                            })
+                            .map(|(id, entry)| (*id, entry.addr.clone()))
+                            .collect();
+
+                        if !due.is_empty() {
+                            let addrs = due.iter().map(|(_, addr)| addr.clone()).collect();
+                            if let Err(error) = room_state.rebootstrap_peers(addrs).await {
+                                crate::log_msg(&format!(
+                                    "Background peer recovery attempt failed: {error}"
+                                ));
+                            }
+
+                            let scheduled_at = Instant::now();
+                            for (peer_id, _) in due {
+                                if !active.lock().unwrap().contains(&peer_id) {
+                                    entries.remove(&peer_id);
+                                    continue;
+                                }
+                                // Advance the backoff, then check the terminal budget.
+                                // `attempt` counts completed attempts, so the delay
+                                // uses the current value before it is incremented.
+                                let terminal = if let Some(entry) = entries.get_mut(&peer_id) {
+                                    entry.next_attempt = scheduled_at + recovery_delay(entry.attempt);
+                                    entry.attempt = entry.attempt.saturating_add(1);
+                                    recovery_is_terminal(entry.attempt, RECOVERY_TERMINAL_ATTEMPTS)
+                                } else {
+                                    false
+                                };
+                                if terminal {
+                                    // Give up on a peer that has not returned within the
+                                    // budget: drop its entry, free the active slot, and
+                                    // signal the event task to forget its retained
+                                    // address so the per-topic retain table drains.
+                                    entries.remove(&peer_id);
+                                    active.lock().unwrap().remove(&peer_id);
+                                    let _ = terminal_tx.try_send(peer_id);
+                                }
+                            }
+                        }
+                        continue;
+                    }
+                }
+            }
+            None => rx.recv().await,
+        };
+
+        match command {
+            Some(RecoveryCommand::Start { peer_id, addr }) => {
+                if active.lock().unwrap().contains(&peer_id) {
+                    entries.entry(peer_id).or_insert(RecoveryEntry {
+                        addr,
+                        attempt: 0,
+                        next_attempt: Instant::now(),
+                    });
+                }
+            }
+            Some(RecoveryCommand::Cancel(peer_id)) => {
+                entries.remove(&peer_id);
+            }
+            None => break,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use iroh::SecretKey;
+
+    struct RecordingRoom {
+        attempts: mpsc::UnboundedSender<Vec<EndpointAddr>>,
+    }
+
+    #[async_trait::async_trait]
+    impl RecoveryRoom for RecordingRoom {
+        async fn rebootstrap_peers(&self, peers: Vec<EndpointAddr>) -> Result<(), String> {
+            self.attempts.send(peers).map_err(|error| error.to_string())
+        }
+    }
+
+    #[test]
+    fn retry_backoff_reaches_and_stays_at_sixty_seconds() {
+        let actual: Vec<u64> = (0..10)
+            .map(|attempt| recovery_delay(attempt).as_secs())
+            .collect();
+        assert_eq!(actual, vec![1, 2, 4, 8, 15, 30, 60, 60, 60, 60]);
+    }
+
+    #[test]
+    fn recovery_budget_is_terminal_only_at_or_past_the_cap() {
+        assert!(!recovery_is_terminal(0, RECOVERY_TERMINAL_ATTEMPTS));
+        assert!(!recovery_is_terminal(
+            RECOVERY_TERMINAL_ATTEMPTS - 1,
+            RECOVERY_TERMINAL_ATTEMPTS
+        ));
+        assert!(recovery_is_terminal(
+            RECOVERY_TERMINAL_ATTEMPTS,
+            RECOVERY_TERMINAL_ATTEMPTS
+        ));
+        assert!(recovery_is_terminal(
+            RECOVERY_TERMINAL_ATTEMPTS + 5,
+            RECOVERY_TERMINAL_ATTEMPTS
+        ));
+    }
+
+    #[test]
+    fn recovery_slots_are_deduplicated_and_cancel_immediately() {
+        let (tx, mut rx) = mpsc::channel(4);
+        let coordinator = RecoveryCoordinator {
+            tx,
+            active: Arc::new(Mutex::new(HashSet::new())),
+        };
+        let peer_id = SecretKey::generate().public();
+
+        assert!(coordinator.begin(peer_id));
+        assert!(
+            !coordinator.begin(peer_id),
+            "a peer gets only one recovery slot"
+        );
+        assert_eq!(
+            coordinator.activate(peer_id, EndpointAddr::from(peer_id)),
+            Ok(true)
+        );
+        assert!(matches!(
+            rx.try_recv(),
+            Ok(RecoveryCommand::Start { peer_id: id, .. }) if id == peer_id
+        ));
+
+        coordinator.cancel(peer_id);
+        assert!(!coordinator.is_active(&peer_id));
+        assert!(matches!(
+            rx.try_recv(),
+            Ok(RecoveryCommand::Cancel(id)) if id == peer_id
+        ));
+    }
+
+    #[tokio::test]
+    async fn coordinator_attempts_rebootstrap_immediately() {
+        let (attempts_tx, mut attempts_rx) = mpsc::unbounded_channel();
+        let (coordinator, task, _terminal_rx) =
+            RecoveryCoordinator::spawn_inner(Arc::new(RecordingRoom {
+                attempts: attempts_tx,
+            }));
+        let peer_id = SecretKey::generate().public();
+        let addr = EndpointAddr::from(peer_id);
+
+        assert!(coordinator.begin(peer_id));
+        assert_eq!(coordinator.activate(peer_id, addr.clone()), Ok(true));
+        let attempted = tokio::time::timeout(Duration::from_secs(1), attempts_rx.recv())
+            .await
+            .expect("first recovery attempt should be immediate")
+            .expect("recording room remains subscribed");
+        assert_eq!(attempted, vec![addr]);
+
+        coordinator.cancel(peer_id);
+        task.abort();
+    }
+}

src/dsp/aec.rs

@@ -283,8 +283,14 @@ mod tests {
         let q = echo.len() / 4;
         let early = erle(&echo[..q], &cleaned[..q]);
         let late = erle(&echo[3 * q..], &cleaned[3 * q..]);
-        assert!(late > early + 10.0, "should improve markedly: early {early:.1} late {late:.1}");
-        assert!(late > 20.0, "converged ERLE should exceed 20 dB, got {late:.1}");
+        assert!(
+            late > early + 10.0,
+            "should improve markedly: early {early:.1} late {late:.1}"
+        );
+        assert!(
+            late > 20.0,
+            "converged ERLE should exceed 20 dB, got {late:.1}"
+        );
     }
 
     #[test]
@@ -307,7 +313,10 @@ mod tests {
         let mut aec = Nlms::new(128, 0.5, 1e-6);
         let out = aec.process(&silent_ref, &near);
         for (a, b) in near.iter().zip(&out) {
-            assert!((a - b).abs() < 1e-6, "near-end should pass through: {a} vs {b}");
+            assert!(
+                (a - b).abs() < 1e-6,
+                "near-end should pass through: {a} vs {b}"
+            );
         }
     }
 
@@ -341,14 +350,24 @@ mod tests {
         let mut late_hits = 0;
         for i in 0..far.len() {
             if dtd.update(far[i], mic[i]) {
-                if i < onset { early_hits += 1 } else { late_hits += 1 }
+                if i < onset {
+                    early_hits += 1
+                } else {
+                    late_hits += 1
+                }
             }
         }
         // Echo-only stretch should rarely trip; near-end stretch should trip a lot.
         let early_rate = early_hits as f32 / onset as f32;
         let late_rate = late_hits as f32 / (far.len() - onset) as f32;
-        assert!(early_rate < 0.10, "false-positive rate {early_rate:.2} too high");
-        assert!(late_rate > 0.50, "missed double-talk, rate only {late_rate:.2}");
+        assert!(
+            early_rate < 0.10,
+            "false-positive rate {early_rate:.2} too high"
+        );
+        assert!(
+            late_rate > 0.50,
+            "missed double-talk, rate only {late_rate:.2}"
+        );
     }
 
     #[test]
@@ -380,6 +399,9 @@ mod tests {
             erle_dtd > erle_no + 15.0,
             "DTD should hold the echo path: with {erle_dtd:.1} dB vs without {erle_no:.1} dB"
         );
-        assert!(erle_dtd > 15.0, "held filter should still cancel echo: {erle_dtd:.1} dB");
+        assert!(
+            erle_dtd > 15.0,
+            "held filter should still cancel echo: {erle_dtd:.1} dB"
+        );
     }
 }

src/dsp/echo_path.rs

@@ -115,7 +115,10 @@ mod tests {
         let path = EchoPath::synthetic(480, 480, 0.5, 99);
         let echo = path.apply(&far);
         let ratio = rms(&echo) / rms(&far);
-        assert!((0.3..0.7).contains(&ratio), "echo/far rms ratio {ratio} off target");
+        assert!(
+            (0.3..0.7).contains(&ratio),
+            "echo/far rms ratio {ratio} off target"
+        );
     }
 
     #[test]

src/dsp/fft.rs

@@ -141,7 +141,10 @@ mod tests {
         buf[0] = Complex::new(1.0, 0.0);
         fft(&mut buf);
         for c in &buf {
-            assert!(approx(c.magnitude(), 1.0, 1e-9), "expected flat 1.0, got {c:?}");
+            assert!(
+                approx(c.magnitude(), 1.0, 1e-9),
+                "expected flat 1.0, got {c:?}"
+            );
         }
     }
 

src/dsp/metrics.rs

@@ -62,11 +62,31 @@ pub struct Band {
 
 /// Voice-relevant bands for spotting *where* residual echo or noise lives.
 pub const VOICE_BANDS: &[Band] = &[
-    Band { label: "low (80-300)", low_hz: 80.0, high_hz: 300.0 },
-    Band { label: "low-mid (300-1k)", low_hz: 300.0, high_hz: 1000.0 },
-    Band { label: "mid (1k-3k)", low_hz: 1000.0, high_hz: 3000.0 },
-    Band { label: "high-mid (3k-6k)", low_hz: 3000.0, high_hz: 6000.0 },
-    Band { label: "high (6k-12k)", low_hz: 6000.0, high_hz: 12000.0 },
+    Band {
+        label: "low (80-300)",
+        low_hz: 80.0,
+        high_hz: 300.0,
+    },
+    Band {
+        label: "low-mid (300-1k)",
+        low_hz: 300.0,
+        high_hz: 1000.0,
+    },
+    Band {
+        label: "mid (1k-3k)",
+        low_hz: 1000.0,
+        high_hz: 3000.0,
+    },
+    Band {
+        label: "high-mid (3k-6k)",
+        low_hz: 3000.0,
+        high_hz: 6000.0,
+    },
+    Band {
+        label: "high (6k-12k)",
+        low_hz: 6000.0,
+        high_hz: 12000.0,
+    },
 ];
 
 /// Sums the linear magnitude energy within `[low_hz, high_hz)` across a single

src/dsp/render.rs

@@ -202,7 +202,8 @@ fn legend(opts: &RenderOpts) -> String {
     if opts.ascii {
         for i in 0..steps {
             let v = i as f32 / (steps - 1) as f32;
-            let idx = ((v * (ASCII_RAMP.len() - 1) as f32).round() as usize).min(ASCII_RAMP.len() - 1);
+            let idx =
+                ((v * (ASCII_RAMP.len() - 1) as f32).round() as usize).min(ASCII_RAMP.len() - 1);
             s.push(ASCII_RAMP[idx] as char);
         }
     } else {
@@ -243,7 +244,11 @@ mod tests {
     fn render_produces_grid_of_expected_height() {
         let sig = generators::sine(2000.0, 0.8, 48_000, 48_000);
         let spec = stft::analyze(&sig, 48_000, 1024, 512);
-        let opts = RenderOpts { width: 40, height: 10, ..Default::default() };
+        let opts = RenderOpts {
+            width: 40,
+            height: 10,
+            ..Default::default()
+        };
         let out = render(&spec, &opts);
         // Header + 10 body rows + time axis (2) + legend = non-trivial.
         let lines = out.lines().count();

src/dsp/stft.rs

@@ -94,7 +94,10 @@ mod tests {
             .unwrap()
             .0;
         let peak_hz = s.bin_hz(peak_bin);
-        assert!((peak_hz - freq as f32).abs() < 100.0, "peak at {peak_hz} Hz, want {freq}");
+        assert!(
+            (peak_hz - freq as f32).abs() < 100.0,
+            "peak at {peak_hz} Hz, want {freq}"
+        );
     }
 
     #[test]

src/dsp/wav.rs

@@ -34,7 +34,12 @@ pub fn read(path: &Path) -> Result<WavData, String> {
     let mut pos = 12usize;
     while pos + 8 <= bytes.len() {
         let id = &bytes[pos..pos + 4];
-        let size = u32::from_le_bytes([bytes[pos + 4], bytes[pos + 5], bytes[pos + 6], bytes[pos + 7]]) as usize;
+        let size = u32::from_le_bytes([
+            bytes[pos + 4],
+            bytes[pos + 5],
+            bytes[pos + 6],
+            bytes[pos + 7],
+        ]) as usize;
         let body_start = pos + 8;
         let body_end = (body_start + size).min(bytes.len());
         match id {
@@ -45,7 +50,9 @@ pub fn read(path: &Path) -> Result<WavData, String> {
                 sample_rate = u32::from_le_bytes([fmt[4], fmt[5], fmt[6], fmt[7]]);
                 bits = u16::from_le_bytes([fmt[14], fmt[15]]);
                 if audio_format != 1 {
-                    return Err(format!("unsupported WAV format tag {audio_format} (need PCM=1)"));
+                    return Err(format!(
+                        "unsupported WAV format tag {audio_format} (need PCM=1)"
+                    ));
                 }
             }
             b"data" => {
@@ -75,7 +82,10 @@ pub fn read(path: &Path) -> Result<WavData, String> {
         samples.push(avg / 32768.0);
     }
 
-    Ok(WavData { samples, sample_rate })
+    Ok(WavData {
+        samples,
+        sample_rate,
+    })
 }
 
 /// Writes mono `f32` samples (clamped to `[-1, 1]`) as a 16-bit PCM WAV. Used by

src/files.rs

@@ -0,0 +1,705 @@
+//! Chat file attachments: the compact descriptor that rides a gossip chat
+//! message, plus the pure validation/sanitization seams for the file-transfer
+//! plane.
+//!
+//! Attachment **bytes do not travel over gossip** — gossip is a small-frame
+//! broadcast plane (see `avatar` for why image bytes there are hard-capped to
+//! tens of KB). Instead a chat message carries a [`ChatAttachment`] *descriptor*
+//! (name, size, kind, id); the sender serves the actual bytes over the dedicated
+//! file ALPN (`protocol::FILES_ALPN`) via direct QUIC streams, and recipients
+//! fetch them point-to-point. Everything in this module is dependency-light and
+//! pure so it can be unit-tested away from the network and the GUI.
+
+use serde::{Deserialize, Serialize};
+
+/// Hard ceiling on a single attachment's byte size. Bounds the memory a peer can
+/// make us hold (when fetching) or serve, and the time a transfer can take.
+/// 25 MiB comfortably covers phone photos and ordinary documents.
+pub const MAX_ATTACHMENT_BYTES: u64 = 25 * 1024 * 1024;
+
+/// Max decoded pixels per side for an inline image preview. Defends against a
+/// decode-bomb (a small file that expands to an enormous bitmap), independent of
+/// the byte cap. Applied via `image::Limits` when validating/decoding.
+pub const MAX_IMAGE_PX: u32 = 4096;
+
+/// Max total decoded pixels, applied on top of the per-side [`MAX_IMAGE_PX`]
+/// limit. The per-side cap alone still admits a 4096×4096 ≈ 16.8 MP bitmap
+/// (~64 MiB transient RGBA); this bounds the worst-case decode allocation while
+/// still clearing common 12 MP phone photos (4032×3024 ≈ 12.2 MP).
+pub const MAX_IMAGE_TOTAL_PIXELS: u64 = 14_000_000;
+
+/// Max pixels per side of the downscaled inline preview handed to the renderer.
+/// Original bytes are kept only for Save; the chat column never needs more than
+/// this (it displays at ~260 px, and the lightbox at window size).
+pub const IMAGE_PREVIEW_MAX_SIDE: u32 = 1600;
+
+/// Largest declared size an image attachment may auto-fetch at. Anything larger
+/// (or any skipped/evicted image) renders a "Load image" button instead; a
+/// manual click may use the full [`MAX_ATTACHMENT_BYTES`] cap.
+pub const MAX_AUTO_IMAGE_BYTES: u64 = 4 * 1024 * 1024;
+
+/// Longest filename we keep and display. Keeps the gossip descriptor compact and
+/// the UI tidy; the real bytes are unaffected.
+pub const MAX_FILENAME_LEN: usize = 96;
+
+/// A 32-byte opaque id identifying one attachment for the fetch request. Minted
+/// randomly per attachment by the sender (see core); the transfer itself is
+/// authenticated + encrypted + room-member gated, so the id only needs to be a
+/// hard-to-guess handle into the sender's serve store, not a content hash.
+pub type AttachmentId = [u8; 32];
+
+/// How the receiver should present an attachment. A *hint* derived from the
+/// sender's content sniff — never trusted for a safety decision. The receiver
+/// re-validates image bytes itself before decoding, and falls back to a file
+/// chip if an "Image" doesn't actually decode.
+#[derive(Serialize, Deserialize, Clone, Copy, PartialEq, Eq, Debug)]
+pub enum AttachmentKind {
+    Image,
+    File,
+}
+
+/// The descriptor carried inside a `GossipMessage::Chat`. Compact by design: it
+/// holds no file bytes, only what the UI needs to render a placeholder/chip and
+/// what a fetch needs to pull the bytes.
+#[derive(Serialize, Deserialize, Clone, PartialEq, Eq, Debug)]
+pub struct ChatAttachment {
+    /// Sanitized display filename (already path-stripped — see
+    /// [`sanitize_filename`]). Never used as a filesystem path on receipt without
+    /// the user choosing a save location.
+    pub name: String,
+    /// Byte length of the file. Bounds the fetch read; must be
+    /// `<= MAX_ATTACHMENT_BYTES` (enforced by [`size_within_cap`]).
+    pub size: u64,
+    /// Presentation hint (image vs. generic file).
+    pub kind: AttachmentKind,
+    /// Opaque handle the receiver writes on the file plane to request the bytes.
+    pub id: AttachmentId,
+}
+
+/// Sanitize an arbitrary (possibly hostile) filename for display and as a
+/// save-dialog default. Strips any directory component (both `/` and `\`),
+/// removes control characters, collapses whitespace, trims, caps the length
+/// while trying to preserve a short extension, and rejects the `.`/`..` traps.
+/// Always returns a non-empty, path-component-free name (falls back to `file`).
+pub fn sanitize_filename(raw: &str) -> String {
+    // Take only the final *non-empty* path component, defeating
+    // `../../etc/passwd`, `C:\foo\bar`, embedded separators, and trailing slashes
+    // (`a/b/c/` → `c`).
+    let base = raw
+        .rsplit(['/', '\\'])
+        .find(|s| !s.trim().is_empty())
+        .unwrap_or("")
+        .trim();
+
+    // Drop control chars and the same bidi/zero-width spoofing format chars
+    // stripped from display names (a U+202E override can visually reverse an
+    // extension, e.g. "photo\u{202E}gnp.exe" renders as "photoexe.png").
+    // Ordinary non-ASCII filenames pass through untouched.
+    let cleaned: String = base
+        .chars()
+        .filter(|c| !c.is_control() && !crate::sanitize::is_spoofing_format_char(*c))
+        .collect();
+    let collapsed = cleaned.split_whitespace().collect::<Vec<_>>().join(" ");
+    let collapsed = collapsed.trim_matches('.').trim();
+
+    if collapsed.is_empty() {
+        return "file".to_string();
+    }
+    if collapsed.chars().count() <= MAX_FILENAME_LEN {
+        return collapsed.to_string();
+    }
+
+    // Too long: keep the extension (if short + sane) and truncate the stem.
+    if let Some((stem, ext)) = collapsed.rsplit_once('.')
+        && !ext.is_empty()
+        && ext.chars().count() <= 8
+        && ext.chars().all(|c| c.is_ascii_alphanumeric())
+    {
+        let keep = MAX_FILENAME_LEN.saturating_sub(ext.chars().count() + 1);
+        let truncated: String = stem.chars().take(keep).collect();
+        return format!("{truncated}.{ext}");
+    }
+    collapsed.chars().take(MAX_FILENAME_LEN).collect()
+}
+
+/// Whether a declared/observed size is within the transfer cap and non-zero.
+/// Used both when sending (reject before serving) and when fetching (reject a
+/// descriptor before opening a stream).
+pub fn size_within_cap(size: u64) -> bool {
+    size > 0 && size <= MAX_ATTACHMENT_BYTES
+}
+
+/// Sniff the leading bytes for a known image container, to set the attachment
+/// *kind* hint at send time. Recognizes PNG, JPEG, GIF, WebP, and BMP. This is a
+/// presentation hint only — actual inline rendering still depends on the bytes
+/// decoding (we only build image features for PNG/JPEG), with a file-chip
+/// fallback otherwise.
+pub fn is_probably_image(bytes: &[u8]) -> bool {
+    let b = bytes;
+    let png = b.starts_with(&[0x89, b'P', b'N', b'G', 0x0D, 0x0A, 0x1A, 0x0A]);
+    let jpeg = b.starts_with(&[0xFF, 0xD8, 0xFF]);
+    let gif = b.starts_with(b"GIF87a") || b.starts_with(b"GIF89a");
+    let bmp = b.starts_with(b"BM");
+    let webp = b.len() >= 12 && b.starts_with(b"RIFF") && &b[8..12] == b"WEBP";
+    png || jpeg || gif || bmp || webp
+}
+
+/// Sniff the leading bytes for an audio container supported by the inline clip
+/// player. Audio remains [`AttachmentKind::File`] on the wire; this receiver-side
+/// check confirms that a filename-based player hint actually contains WAV, MP3,
+/// Ogg Vorbis, or FLAC data before playback is attempted.
+pub fn is_probably_audio(bytes: &[u8]) -> bool {
+    let flac = bytes.starts_with(b"fLaC");
+    let ogg = bytes.starts_with(b"OggS");
+    let wav = bytes.len() >= 12 && bytes.starts_with(b"RIFF") && &bytes[8..12] == b"WAVE";
+    let mp3_id3 = bytes.starts_with(b"ID3");
+    let mp3_frame = bytes.len() >= 2 && bytes[0] == 0xFF && bytes[1] & 0xE0 == 0xE0;
+    flac || ogg || wav || mp3_id3 || mp3_frame
+}
+
+/// Whether a sanitized attachment name has an extension supported by the
+/// inline audio player. This is only a pre-fetch presentation hint; fetched
+/// bytes are confirmed with [`is_probably_audio`] before being decoded.
+pub fn looks_like_audio_name(name: &str) -> bool {
+    let Some((_, extension)) = name.rsplit_once('.') else {
+        return false;
+    };
+    matches!(
+        extension.to_ascii_lowercase().as_str(),
+        "wav" | "mp3" | "ogg" | "oga" | "flac"
+    )
+}
+
+/// The attachment kind for some file bytes: [`AttachmentKind::Image`] if it
+/// sniffs as an image container, else [`AttachmentKind::File`].
+pub fn classify(bytes: &[u8]) -> AttachmentKind {
+    if is_probably_image(bytes) {
+        AttachmentKind::Image
+    } else {
+        AttachmentKind::File
+    }
+}
+
+/// Defensively decode image bytes under strict pixel limits to confirm they're a
+/// real, sane image before we hand them to the renderer. Returns the decoded
+/// dimensions on success. Guards against decode-bombs (small file → huge bitmap)
+/// regardless of [`MAX_ATTACHMENT_BYTES`]. Only PNG/JPEG are buildable in our
+/// `image` feature set; anything else returns `None` and the caller shows a chip.
+pub fn validate_image_bytes(bytes: &[u8]) -> Option<(u32, u32)> {
+    let img = decode_image_bounded(bytes)?;
+    Some((img.width(), img.height()))
+}
+
+/// Shared bounded decode: header-check the dimensions (per-side AND total-pixel
+/// limits) BEFORE decoding, then decode under `image::Limits` as defense in
+/// depth. The precheck reads only the container header, so an over-limit bomb is
+/// rejected without paying its decode cost.
+fn decode_image_bounded(bytes: &[u8]) -> Option<image::DynamicImage> {
+    let reader = image::ImageReader::new(std::io::Cursor::new(bytes))
+        .with_guessed_format()
+        .ok()?;
+    let (w, h) = reader.into_dimensions().ok()?;
+    if w == 0 || h == 0 || w > MAX_IMAGE_PX || h > MAX_IMAGE_PX {
+        return None;
+    }
+    if u64::from(w) * u64::from(h) > MAX_IMAGE_TOTAL_PIXELS {
+        return None;
+    }
+    let mut limits = image::Limits::default();
+    limits.max_image_width = Some(MAX_IMAGE_PX);
+    limits.max_image_height = Some(MAX_IMAGE_PX);
+    let mut reader = image::ImageReader::new(std::io::Cursor::new(bytes))
+        .with_guessed_format()
+        .ok()?;
+    reader.limits(limits);
+    let img = reader.decode().ok()?;
+    // Decoded size must match the header the precheck approved.
+    if img.width() != w || img.height() != h {
+        return None;
+    }
+    Some(img)
+}
+
+/// A decoded, display-ready inline preview: RGBA pixels downscaled so neither
+/// side exceeds [`IMAGE_PREVIEW_MAX_SIDE`]. `rgba.len() == width * height * 4`,
+/// which is also the preview's decoded-budget weight in the attachment cache.
+pub struct ImagePreview {
+    pub width: u32,
+    pub height: u32,
+    pub rgba: Vec<u8>,
+}
+
+/// Decode image bytes under the same limits as [`validate_image_bytes`] and
+/// build the downscaled inline preview. The full-resolution bitmap exists only
+/// transiently here; the renderer is never handed more than
+/// [`IMAGE_PREVIEW_MAX_SIDE`]² pixels. Returns `None` for anything that fails
+/// validation (caller falls back to a chip / failure row).
+pub fn decode_preview(bytes: &[u8]) -> Option<ImagePreview> {
+    let img = decode_image_bounded(bytes)?;
+    let img = if img.width() > IMAGE_PREVIEW_MAX_SIDE || img.height() > IMAGE_PREVIEW_MAX_SIDE {
+        // `thumbnail` preserves aspect ratio within the bounding box.
+        img.thumbnail(IMAGE_PREVIEW_MAX_SIDE, IMAGE_PREVIEW_MAX_SIDE)
+    } else {
+        img
+    };
+    let rgba = img.into_rgba8();
+    let (width, height) = (rgba.width(), rgba.height());
+    Some(ImagePreview {
+        width,
+        height,
+        rgba: rgba.into_raw(),
+    })
+}
+
+/// Estimated decoded RGBA cost of a preview, the weight counted against the
+/// attachment cache's decoded-byte budget (`width * height * 4`).
+pub fn preview_rgba_cost(width: u32, height: u32) -> usize {
+    (width as usize)
+        .saturating_mul(height as usize)
+        .saturating_mul(4)
+}
+
+/// Read at most [`MAX_ATTACHMENT_BYTES`] bytes from `r`. Returns `Ok(None)` if
+/// the source holds even one byte more (detected by reading cap + 1), so a huge
+/// or unbounded source is never fully buffered. Pure over `Read` for tests; the
+/// picker wraps it via [`read_file_capped`].
+pub fn read_capped<R: std::io::Read>(r: R) -> std::io::Result<Option<Vec<u8>>> {
+    use std::io::Read as _;
+    let mut buf = Vec::new();
+    let mut limited = r.take(MAX_ATTACHMENT_BYTES + 1);
+    limited.read_to_end(&mut buf)?;
+    if buf.len() as u64 > MAX_ATTACHMENT_BYTES {
+        return Ok(None);
+    }
+    Ok(Some(buf))
+}
+
+/// Read a picked file, bounded by [`MAX_ATTACHMENT_BYTES`]. Checks metadata
+/// first to reject an obviously-oversized file without opening it, but keeps the
+/// bounded read regardless — metadata can race (the file can grow after the
+/// check) or be unavailable through a portal. `Ok(None)` = over the cap.
+pub fn read_file_capped(path: &std::path::Path) -> std::io::Result<Option<Vec<u8>>> {
+    if let Ok(meta) = std::fs::metadata(path)
+        && meta.len() > MAX_ATTACHMENT_BYTES
+    {
+        return Ok(None);
+    }
+    read_capped(std::fs::File::open(path)?)
+}
+
+/// Cap on how many blobs the session serve store retains at once (sent chat
+/// attachments plus the current/next broadcast music tracks).
+pub const SERVED_FILES_MAX_ENTRIES: usize = 16;
+
+/// Byte budget for the serve store. Without it, a sender's own session could
+/// grow unbounded at up to [`MAX_ATTACHMENT_BYTES`] per send (Phase 3C).
+pub const SERVED_FILES_MAX_BYTES: usize = 128 * 1024 * 1024;
+
+/// Count- and byte-budgeted FIFO store of blobs we serve to room members over
+/// the file plane. Evicting an id makes a later request for it read as an empty
+/// body — the existing "sender no longer has the file" response — never stale
+/// or aliased bytes. Pure (no locks/IO) so budgets are unit-testable; the
+/// transport wraps it in its own mutex.
+#[derive(Debug, Default)]
+pub struct ServeStore {
+    entries: std::collections::HashMap<AttachmentId, std::sync::Arc<Vec<u8>>>,
+    /// Present ids in insertion order; the front is the eviction candidate.
+    order: std::collections::VecDeque<AttachmentId>,
+    total_bytes: usize,
+}
+
+impl ServeStore {
+    /// Insert or replace a blob, evicting oldest entries until the count and
+    /// byte budgets fit. Replacement keeps the id's age and subtracts the old
+    /// bytes before the new ones are counted. Returns `false` for a blob that
+    /// alone exceeds the byte budget (not stored; an existing entry under the
+    /// id is dropped rather than left stale).
+    pub fn insert(&mut self, id: AttachmentId, bytes: std::sync::Arc<Vec<u8>>) -> bool {
+        if let Some(old) = self.entries.get(&id) {
+            self.total_bytes -= old.len();
+        }
+        if bytes.len() > SERVED_FILES_MAX_BYTES {
+            if self.entries.remove(&id).is_some() {
+                self.order.retain(|k| k != &id);
+            }
+            return false;
+        }
+        let replacing = self.entries.contains_key(&id);
+        loop {
+            let count_full = !replacing && self.entries.len() >= SERVED_FILES_MAX_ENTRIES;
+            let bytes_full = self.total_bytes + bytes.len() > SERVED_FILES_MAX_BYTES;
+            if !count_full && !bytes_full {
+                break;
+            }
+            let Some(victim) = self.order.iter().find(|k| **k != id).copied() else {
+                break;
+            };
+            self.remove(&victim);
+        }
+        if !replacing {
+            self.order.push_back(id);
+        }
+        self.total_bytes += bytes.len();
+        self.entries.insert(id, bytes);
+        true
+    }
+
+    pub fn get(&self, id: &AttachmentId) -> Option<std::sync::Arc<Vec<u8>>> {
+        self.entries.get(id).cloned()
+    }
+
+    pub fn remove(&mut self, id: &AttachmentId) {
+        if let Some(old) = self.entries.remove(id) {
+            self.total_bytes -= old.len();
+            self.order.retain(|k| k != id);
+        }
+    }
+
+    pub fn clear(&mut self) {
+        self.entries.clear();
+        self.order.clear();
+        self.total_bytes = 0;
+    }
+
+    #[cfg(test)]
+    fn len(&self) -> usize {
+        self.entries.len()
+    }
+}
+
+/// Parse a file-plane request: it must be exactly one [`AttachmentId`] (32
+/// bytes). Anything else is rejected so a peer can't send a malformed/oversized
+/// request frame. Pure half of the serve handler.
+pub fn parse_request(bytes: &[u8]) -> Option<AttachmentId> {
+    if bytes.len() != 32 {
+        return None;
+    }
+    let mut id = [0u8; 32];
+    id.copy_from_slice(bytes);
+    Some(id)
+}
+
+/// A human-readable size like `2.3 MB` / `812 KB` / `40 B` for the file chip.
+pub fn human_size(bytes: u64) -> String {
+    const KB: u64 = 1024;
+    const MB: u64 = 1024 * KB;
+    if bytes >= MB {
+        format!("{:.1} MB", bytes as f64 / MB as f64)
+    } else if bytes >= KB {
+        format!("{:.0} KB", bytes as f64 / KB as f64)
+    } else {
+        format!("{bytes} B")
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn sanitize_strips_directory_traversal() {
+        assert_eq!(sanitize_filename("../../etc/passwd"), "passwd");
+        assert_eq!(sanitize_filename("/abs/path/photo.png"), "photo.png");
+        assert_eq!(sanitize_filename(r"C:\Users\me\secret.doc"), "secret.doc");
+        assert_eq!(sanitize_filename("a/b/c/"), "c");
+    }
+
+    #[test]
+    fn sanitize_rejects_dot_traps_and_empty() {
+        assert_eq!(sanitize_filename(""), "file");
+        assert_eq!(sanitize_filename("."), "file");
+        assert_eq!(sanitize_filename(".."), "file");
+        assert_eq!(sanitize_filename("   "), "file");
+        assert_eq!(sanitize_filename("/"), "file");
+    }
+
+    #[test]
+    fn sanitize_removes_control_chars_and_collapses_ws() {
+        // Control chars (incl. tab/newline) are stripped entirely.
+        assert_eq!(sanitize_filename("my\tphoto\n.png"), "myphoto.png");
+        assert_eq!(sanitize_filename("a\u{0000}b.txt"), "ab.txt");
+        // Real spaces are collapsed but preserved.
+        assert_eq!(sanitize_filename("my  photo .png"), "my photo .png");
+    }
+
+    #[test]
+    fn sanitize_caps_length_preserving_extension() {
+        let long_stem = "x".repeat(200);
+        let name = format!("{long_stem}.png");
+        let out = sanitize_filename(&name);
+        assert!(
+            out.chars().count() <= MAX_FILENAME_LEN,
+            "len was {}",
+            out.chars().count()
+        );
+        assert!(out.ends_with(".png"), "extension preserved: {out}");
+    }
+
+    #[test]
+    fn size_cap_bounds() {
+        assert!(!size_within_cap(0));
+        assert!(size_within_cap(1));
+        assert!(size_within_cap(MAX_ATTACHMENT_BYTES));
+        assert!(!size_within_cap(MAX_ATTACHMENT_BYTES + 1));
+    }
+
+    #[test]
+    fn image_sniffing_recognizes_containers() {
+        assert!(is_probably_image(&[
+            0x89, b'P', b'N', b'G', 0x0D, 0x0A, 0x1A, 0x0A, 0, 0
+        ]));
+        assert!(is_probably_image(&[0xFF, 0xD8, 0xFF, 0xE0]));
+        assert!(is_probably_image(b"GIF89a...."));
+        let mut webp = b"RIFF".to_vec();
+        webp.extend_from_slice(&[0, 0, 0, 0]);
+        webp.extend_from_slice(b"WEBP");
+        assert!(is_probably_image(&webp));
+        assert!(!is_probably_image(b"%PDF-1.7"));
+        assert!(!is_probably_image(b""));
+    }
+
+    #[test]
+    fn audio_sniffing_recognizes_supported_containers() {
+        assert!(is_probably_audio(b"fLaC\0\0\0\x22"));
+        assert!(is_probably_audio(b"OggS\0\x02"));
+
+        let mut wav = b"RIFF".to_vec();
+        wav.extend_from_slice(&[0, 0, 0, 0]);
+        wav.extend_from_slice(b"WAVE");
+        assert!(is_probably_audio(&wav));
+
+        assert!(is_probably_audio(b"ID3\x04\0\0"));
+        assert!(is_probably_audio(&[0xFF, 0xFB, 0x90, 0x64]));
+    }
+
+    #[test]
+    fn audio_sniffing_disambiguates_wav_from_webp() {
+        let mut wav = b"RIFF".to_vec();
+        wav.extend_from_slice(&[0, 0, 0, 0]);
+        wav.extend_from_slice(b"WAVE");
+        assert!(is_probably_audio(&wav));
+        assert!(!is_probably_image(&wav));
+
+        let mut webp = b"RIFF".to_vec();
+        webp.extend_from_slice(&[0, 0, 0, 0]);
+        webp.extend_from_slice(b"WEBP");
+        assert!(is_probably_image(&webp));
+        assert!(!is_probably_audio(&webp));
+    }
+
+    #[test]
+    fn audio_sniffing_rejects_non_audio() {
+        assert!(!is_probably_audio(b"%PDF-1.7"));
+        assert!(!is_probably_audio(&[0x89, b'P', b'N', b'G']));
+        assert!(!is_probably_audio(&[]));
+        assert!(!is_probably_audio(&[0xFF]));
+    }
+
+    #[test]
+    fn audio_name_detection_is_case_insensitive() {
+        for name in ["clip.wav", "clip.mp3", "clip.ogg", "clip.oga", "clip.flac"] {
+            assert!(looks_like_audio_name(name), "{name}");
+        }
+        assert!(looks_like_audio_name("VOICE.MP3"));
+        assert!(looks_like_audio_name("mix.FlAc"));
+        assert!(!looks_like_audio_name("recording"));
+        assert!(!looks_like_audio_name("notes.pdf"));
+        assert!(!looks_like_audio_name("photo.webp"));
+    }
+
+    #[test]
+    fn classify_maps_sniff_to_kind() {
+        assert_eq!(classify(&[0xFF, 0xD8, 0xFF]), AttachmentKind::Image);
+        assert_eq!(classify(b"fLaC\0\0\0\x22"), AttachmentKind::File);
+        assert_eq!(classify(b"plain text"), AttachmentKind::File);
+    }
+
+    #[test]
+    fn parse_request_requires_exact_32_bytes() {
+        assert_eq!(parse_request(&[7u8; 32]), Some([7u8; 32]));
+        assert_eq!(parse_request(&[7u8; 31]), None);
+        assert_eq!(parse_request(&[7u8; 33]), None);
+        assert_eq!(parse_request(&[]), None);
+    }
+
+    #[test]
+    fn validate_image_rejects_garbage() {
+        assert_eq!(validate_image_bytes(b"not an image"), None);
+        assert_eq!(validate_image_bytes(&[]), None);
+    }
+
+    #[test]
+    fn validate_image_accepts_a_real_png() {
+        // Encode a tiny PNG in-memory, then validate it.
+        let img = image::RgbImage::from_pixel(4, 3, image::Rgb([10, 20, 30]));
+        let mut buf = std::io::Cursor::new(Vec::new());
+        image::DynamicImage::ImageRgb8(img)
+            .write_to(&mut buf, image::ImageFormat::Png)
+            .unwrap();
+        assert_eq!(validate_image_bytes(&buf.into_inner()), Some((4, 3)));
+    }
+
+    #[test]
+    fn sanitize_strips_bidi_and_zero_width_spoofing_chars() {
+        // U+202E would visually reverse the tail, disguising the extension.
+        assert_eq!(sanitize_filename("photo\u{202E}gnp.exe"), "photognp.exe");
+        assert_eq!(sanitize_filename("a\u{200B}b\u{FEFF}.txt"), "ab.txt");
+        // Ordinary Unicode filenames pass through.
+        assert_eq!(sanitize_filename("família_fotos.png"), "família_fotos.png");
+        assert_eq!(sanitize_filename("日本語.pdf"), "日本語.pdf");
+    }
+
+    /// Encode a solid PNG of the given dimensions for limit tests.
+    fn png_bytes(w: u32, h: u32) -> Vec<u8> {
+        let img = image::RgbImage::from_pixel(w, h, image::Rgb([10, 20, 30]));
+        let mut buf = std::io::Cursor::new(Vec::new());
+        image::DynamicImage::ImageRgb8(img)
+            .write_to(&mut buf, image::ImageFormat::Png)
+            .unwrap();
+        buf.into_inner()
+    }
+
+    #[test]
+    fn validate_image_rejects_excessive_total_pixels() {
+        // Both sides within MAX_IMAGE_PX, but 4096 * 4096 > MAX_IMAGE_TOTAL_PIXELS.
+        assert!(u64::from(MAX_IMAGE_PX) * u64::from(MAX_IMAGE_PX) > MAX_IMAGE_TOTAL_PIXELS);
+        assert_eq!(validate_image_bytes(&png_bytes(4096, 4096)), None);
+        // A 12 MP phone-photo shape passes both limits.
+        assert_eq!(
+            validate_image_bytes(&png_bytes(4032, 3024)),
+            Some((4032, 3024))
+        );
+    }
+
+    #[test]
+    fn preview_downscales_to_max_side_preserving_aspect() {
+        // Wide: 3200x400 → 1600x200.
+        let p = decode_preview(&png_bytes(3200, 400)).unwrap();
+        assert_eq!((p.width, p.height), (1600, 200));
+        assert_eq!(p.rgba.len(), preview_rgba_cost(1600, 200));
+        // Tall: 400x3200 → 200x1600.
+        let p = decode_preview(&png_bytes(400, 3200)).unwrap();
+        assert_eq!((p.width, p.height), (200, 1600));
+        // Square over the side cap: 2000x2000 → 1600x1600.
+        let p = decode_preview(&png_bytes(2000, 2000)).unwrap();
+        assert_eq!((p.width, p.height), (1600, 1600));
+        // At/under the cap is untouched.
+        let p = decode_preview(&png_bytes(1600, 900)).unwrap();
+        assert_eq!((p.width, p.height), (1600, 900));
+        let p = decode_preview(&png_bytes(4, 3)).unwrap();
+        assert_eq!((p.width, p.height), (4, 3));
+        assert_eq!(p.rgba.len(), preview_rgba_cost(4, 3));
+    }
+
+    #[test]
+    fn preview_rejects_what_validation_rejects() {
+        assert!(decode_preview(b"not an image").is_none());
+        assert!(decode_preview(&png_bytes(4096, 4096)).is_none());
+    }
+
+    #[test]
+    fn read_capped_stops_at_cap_plus_one() {
+        // Under the cap: full read.
+        let small = vec![7u8; 1024];
+        assert_eq!(
+            read_capped(std::io::Cursor::new(&small))
+                .unwrap()
+                .as_deref(),
+            Some(&small[..])
+        );
+        // Exactly at the cap: accepted. `repeat` is endless, `take` proves the
+        // reader is bounded rather than draining the source.
+        let at_cap = std::io::Read::take(std::io::repeat(1), MAX_ATTACHMENT_BYTES);
+        let got = read_capped(at_cap).unwrap().unwrap();
+        assert_eq!(got.len() as u64, MAX_ATTACHMENT_BYTES);
+        // One byte over: rejected, and only cap + 1 bytes were ever buffered
+        // (an unbounded source returns instead of allocating forever).
+        let over = std::io::Read::take(std::io::repeat(1), MAX_ATTACHMENT_BYTES + 1);
+        assert_eq!(read_capped(over).unwrap(), None);
+        let endless = std::io::repeat(1);
+        assert_eq!(read_capped(endless).unwrap(), None);
+    }
+
+    #[test]
+    fn human_size_units() {
+        assert_eq!(human_size(40), "40 B");
+        assert_eq!(human_size(2048), "2 KB");
+        assert_eq!(human_size(3 * 1024 * 1024 + 300 * 1024), "3.3 MB");
+    }
+
+    #[test]
+    fn serve_store_count_and_byte_eviction_fifo() {
+        use std::sync::Arc;
+        let mut s = ServeStore::default();
+        let blob = |n: u8, len: usize| ([n; 32], Arc::new(vec![n; len]));
+        // Count cap: entry 0 is evicted when the 17th arrives.
+        for n in 0..=SERVED_FILES_MAX_ENTRIES as u8 {
+            let (id, b) = blob(n, 8);
+            assert!(s.insert(id, b));
+        }
+        assert_eq!(s.len(), SERVED_FILES_MAX_ENTRIES);
+        assert!(s.get(&[0u8; 32]).is_none(), "oldest evicted by count");
+        assert!(s.get(&[1u8; 32]).is_some());
+        // Byte budget: two ~half-budget blobs evict everything older.
+        let half = SERVED_FILES_MAX_BYTES / 2;
+        let (a, ab) = blob(100, half);
+        let (b, bb) = blob(101, half);
+        assert!(s.insert(a, ab));
+        assert!(s.insert(b, bb));
+        assert!(s.get(&a).is_some());
+        assert!(s.get(&b).is_some());
+        assert!(s.get(&[1u8; 32]).is_none(), "evicted for byte budget");
+        // A third half-budget blob evicts `a` (oldest), keeps `b`.
+        let (c, cb) = blob(102, half);
+        assert!(s.insert(c, cb));
+        assert!(s.get(&a).is_none());
+        assert!(s.get(&b).is_some());
+        assert!(s.get(&c).is_some());
+    }
+
+    #[test]
+    fn serve_store_replacement_accounting_and_remove_clear() {
+        use std::sync::Arc;
+        let mut s = ServeStore::default();
+        let id = [9u8; 32];
+        assert!(s.insert(id, Arc::new(vec![1; SERVED_FILES_MAX_BYTES - 10])));
+        // Replacing the near-budget blob must subtract its old bytes first —
+        // otherwise this same-id replacement would evict itself.
+        assert!(s.insert(id, Arc::new(vec![2; SERVED_FILES_MAX_BYTES - 5])));
+        assert_eq!(s.get(&id).unwrap()[0], 2);
+        assert_eq!(s.len(), 1);
+        s.remove(&id);
+        assert!(s.get(&id).is_none());
+        // Removed bytes were released: the budget admits a full-size blob again.
+        assert!(s.insert(id, Arc::new(vec![3; SERVED_FILES_MAX_BYTES])));
+        s.clear();
+        assert_eq!(s.len(), 0);
+        assert!(s.insert(id, Arc::new(vec![4; SERVED_FILES_MAX_BYTES])));
+    }
+
+    #[test]
+    fn serve_store_rejects_individually_overweight_blob() {
+        use std::sync::Arc;
+        let mut s = ServeStore::default();
+        let id = [7u8; 32];
+        assert!(s.insert(id, Arc::new(vec![1; 8])));
+        assert!(!s.insert(id, Arc::new(vec![2; SERVED_FILES_MAX_BYTES + 1])));
+        // The stale small blob is gone too — a fetch reads "no longer has it",
+        // never old bytes under a replaced id.
+        assert!(s.get(&id).is_none());
+        assert_eq!(s.len(), 0);
+    }
+
+    #[test]
+    fn attachment_descriptor_round_trips_json() {
+        let a = ChatAttachment {
+            name: "photo.png".to_string(),
+            size: 12345,
+            kind: AttachmentKind::Image,
+            id: [9u8; 32],
+        };
+        let bytes = serde_json::to_vec(&a).unwrap();
+        let back: ChatAttachment = serde_json::from_slice(&bytes).unwrap();
+        assert_eq!(a, back);
+    }
+}

src/friends.rs

@@ -66,7 +66,11 @@ impl FriendStore {
         if self.contains(&id) {
             return false;
         }
-        self.friends.push(Friend { id, name, last_addr: addr });
+        self.friends.push(Friend {
+            id,
+            name,
+            last_addr: addr,
+        });
         true
     }
 
@@ -118,21 +122,24 @@ pub fn friends_path() -> Option<PathBuf> {
 /// *parse* error bubbles up so a hand-edit being debugged isn't silently
 /// overwritten with an empty list.
 pub fn load() -> Result<FriendStore> {
-    let path = friends_path().context("could not determine a config directory for the friends list")?;
+    let path =
+        friends_path().context("could not determine a config directory for the friends list")?;
     load_at(&path)
 }
 
 /// Save the store. Atomic via tempfile-in-same-dir + rename.
 pub fn save(store: &FriendStore) -> Result<()> {
-    let path = friends_path().context("could not determine a config directory for the friends list")?;
+    let path =
+        friends_path().context("could not determine a config directory for the friends list")?;
     save_at(&path, store)
 }
 
 /// Path-injectable core of [`load`], so the round-trip is testable in a temp dir.
 fn load_at(path: &Path) -> Result<FriendStore> {
     match fs::read_to_string(path) {
-        Ok(s) => serde_json::from_str(&s)
-            .with_context(|| format!("failed to parse {}", path.display())),
+        Ok(s) => {
+            serde_json::from_str(&s).with_context(|| format!("failed to parse {}", path.display()))
+        }
         Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(FriendStore::default()),
         Err(e) => Err(e).with_context(|| format!("failed to read {}", path.display())),
     }
@@ -141,11 +148,14 @@ fn load_at(path: &Path) -> Result<FriendStore> {
 /// Path-injectable core of [`save`]. Atomic write: tempfile-in-same-dir, then
 /// rename, so a crash mid-write can't leave a truncated list.
 fn save_at(path: &Path, store: &FriendStore) -> Result<()> {
-    let parent = path.parent().context("friends path has no parent directory")?;
+    let parent = path
+        .parent()
+        .context("friends path has no parent directory")?;
     fs::create_dir_all(parent).with_context(|| format!("failed to create {}", parent.display()))?;
     let json = serde_json::to_string_pretty(store).context("failed to encode the friends list")?;
     let tmp = parent.join(format!(".friends.json.tmp.{}", std::process::id()));
-    fs::write(&tmp, json.as_bytes()).with_context(|| format!("failed to write {}", tmp.display()))?;
+    fs::write(&tmp, json.as_bytes())
+        .with_context(|| format!("failed to write {}", tmp.display()))?;
     fs::rename(&tmp, path)
         .with_context(|| format!("failed to rename {} -> {}", tmp.display(), path.display()))?;
     Ok(())
@@ -219,7 +229,11 @@ mod tests {
     /// A unique temp path; `save_at` creates the nested dir (exercises create_dir_all).
     fn temp_path(tag: &str) -> PathBuf {
         let mut p = std::env::temp_dir();
-        p.push(format!("peerspeak-friendstest-{}-{}", std::process::id(), tag));
+        p.push(format!(
+            "peerspeak-friendstest-{}-{}",
+            std::process::id(),
+            tag
+        ));
         p.push("friends.json");
         p
     }

src/game/detector.rs

@@ -0,0 +1,280 @@
+//! The detector service (§5): one cancellable background worker that polls the OS
+//! adapters, runs the pure matcher + debouncer, and publishes the stable detected
+//! game on a watch channel — only when it changes, so a flapping detector can't
+//! spam `PeerState` re-announces.
+//!
+//! All the OS reads (Steam files / registry, the process scan) are blocking, so
+//! the worker is a dedicated `std::thread`, not a tokio task; it owns the
+//! [`SteamProbe`] cache and the [`Debouncer`] across ticks. The per-tick decision
+//! is factored into the pure [`poll_once`] so the wiring of resolve + match +
+//! debounce is unit-tested without any I/O.
+
+use super::scan;
+use super::steam::SteamProbe;
+use super::{Debouncer, DetectedGame, ManualOverride, builtin_denylist, match_processes, resolve};
+use std::collections::BTreeMap;
+use std::io;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
+use std::thread::JoinHandle;
+use std::time::Duration;
+use tokio::sync::watch;
+
+/// How often the detector samples Steam state + the process list.
+pub const POLL_INTERVAL: Duration = Duration::from_secs(3);
+/// Granularity of the cancellable sleep between polls, so a stop request is
+/// honored promptly instead of after a full [`POLL_INTERVAL`].
+const SLEEP_TICK: Duration = Duration::from_millis(200);
+
+/// Apply one poll's worth of inputs to the debouncer, returning the new published
+/// value **iff it changed** (the signal to re-announce presence / switch the
+/// background). Pure: the caller supplies the already-fetched Steam detection and
+/// process list, so resolve + match + debounce are testable with zero I/O.
+pub fn poll_once(
+    debouncer: &mut Debouncer,
+    override_: &ManualOverride,
+    steam: Option<DetectedGame>,
+    processes: &[String],
+    process_map: &BTreeMap<String, String>,
+    denylist: &std::collections::BTreeSet<&str>,
+) -> Option<Option<DetectedGame>> {
+    let matched = match_processes(processes, process_map, denylist);
+    let res = resolve(override_, steam, &matched);
+    if debouncer.observe(res.game, res.immediate) {
+        Some(debouncer.current().cloned())
+    } else {
+        None
+    }
+}
+
+/// Shared, live-updatable inputs to the detector, written by core (manual override
+/// changes, config edits to the process map) and read each poll by the worker.
+#[derive(Default)]
+pub struct DetectorInputs {
+    pub override_: Mutex<ManualOverride>,
+    pub process_map: Mutex<BTreeMap<String, String>>,
+}
+
+/// A running detector service. Holds the watch receiver for detected-game changes
+/// and the shared inputs; dropping it (or calling [`stop`](Self::stop)) ends the
+/// worker thread.
+pub struct GameDetector {
+    inputs: Arc<DetectorInputs>,
+    rx: watch::Receiver<Option<DetectedGame>>,
+    stop: Arc<AtomicBool>,
+    worker: Option<JoinHandle<()>>,
+}
+
+impl GameDetector {
+    /// Spawn the detector worker. `process_map` seeds the non-Steam mappings;
+    /// `override_` seeds the manual override (usually `Auto`). The worker runs
+    /// until [`stop`](Self::stop) or the returned `GameDetector` is dropped.
+    pub fn spawn(
+        override_: ManualOverride,
+        process_map: BTreeMap<String, String>,
+    ) -> io::Result<Self> {
+        let inputs = Arc::new(DetectorInputs {
+            override_: Mutex::new(override_),
+            process_map: Mutex::new(process_map),
+        });
+        let (tx, rx) = watch::channel(None);
+        let stop = Arc::new(AtomicBool::new(false));
+
+        let worker_inputs = inputs.clone();
+        let worker_stop = stop.clone();
+        let worker = std::thread::Builder::new()
+            .name("game-detector".to_string())
+            .spawn(move || worker_loop(worker_inputs, tx, worker_stop))?;
+
+        Ok(Self {
+            inputs,
+            rx,
+            stop,
+            worker: Some(worker),
+        })
+    }
+
+    /// A clone of the watch receiver for detected-game changes. The current value
+    /// is `None` until the first non-empty detection is debounced in.
+    pub fn subscribe(&self) -> watch::Receiver<Option<DetectedGame>> {
+        self.rx.clone()
+    }
+
+    /// Replace the manual override (applied on the next poll, immediately,
+    /// bypassing debounce).
+    pub fn set_override(&self, override_: ManualOverride) {
+        *self.inputs.override_.lock().unwrap() = override_;
+    }
+
+    /// Replace the user process→name mappings (e.g. after a Settings edit).
+    pub fn set_process_map(&self, map: BTreeMap<String, String>) {
+        *self.inputs.process_map.lock().unwrap() = map;
+    }
+
+    /// Signal the worker to exit. Idempotent; also happens on drop.
+    pub fn stop(&self) {
+        self.stop.store(true, Ordering::Relaxed);
+    }
+}
+
+impl Drop for GameDetector {
+    fn drop(&mut self) {
+        self.stop();
+        if let Some(worker) = self.worker.take() {
+            let _ = worker.join();
+        }
+    }
+}
+
+/// The blocking worker loop: probe, decide, publish on change, sleep (cancellably).
+fn worker_loop(
+    inputs: Arc<DetectorInputs>,
+    tx: watch::Sender<Option<DetectedGame>>,
+    stop: Arc<AtomicBool>,
+) {
+    let denylist = builtin_denylist();
+    let mut steam = SteamProbe::new();
+    let mut debouncer = Debouncer::default();
+
+    while !stop.load(Ordering::Relaxed) {
+        let override_ = inputs.override_.lock().unwrap().clone();
+        let process_map = inputs.process_map.lock().unwrap().clone();
+
+        let steam_game = steam.detect();
+        let processes = scan::running_executables();
+
+        if let Some(new_current) = poll_once(
+            &mut debouncer,
+            &override_,
+            steam_game,
+            &processes,
+            &process_map,
+            &denylist,
+        ) {
+            // A closed receiver means core shut down; stop quietly.
+            if tx.send(new_current).is_err() {
+                return;
+            }
+        }
+
+        // Cancellable sleep: wake promptly on a stop request.
+        let mut slept = Duration::ZERO;
+        while slept < POLL_INTERVAL && !stop.load(Ordering::Relaxed) {
+            std::thread::sleep(SLEEP_TICK);
+            slept += SLEEP_TICK;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::super::GameSource;
+    use super::*;
+
+    fn game(id: &str, name: &str, source: GameSource) -> DetectedGame {
+        DetectedGame {
+            id: id.into(),
+            name: Some(name.into()),
+            source,
+        }
+    }
+
+    fn map(pairs: &[(&str, &str)]) -> BTreeMap<String, String> {
+        pairs
+            .iter()
+            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .collect()
+    }
+
+    #[test]
+    fn poll_once_debounces_steam_detection() {
+        let deny = builtin_denylist();
+        let mut d = Debouncer::default();
+        let steam = game("steam:730", "CS2", GameSource::Steam);
+        let empty = BTreeMap::new();
+
+        // First poll: detected but not yet published (needs two hits).
+        assert_eq!(
+            poll_once(
+                &mut d,
+                &ManualOverride::Auto,
+                Some(steam.clone()),
+                &[],
+                &empty,
+                &deny
+            ),
+            None
+        );
+        // Second poll: published.
+        assert_eq!(
+            poll_once(
+                &mut d,
+                &ManualOverride::Auto,
+                Some(steam.clone()),
+                &[],
+                &empty,
+                &deny
+            ),
+            Some(Some(steam))
+        );
+        // Third identical poll: no change event.
+        assert_eq!(
+            poll_once(
+                &mut d,
+                &ManualOverride::Auto,
+                Some(game("steam:730", "CS2", GameSource::Steam)),
+                &[],
+                &empty,
+                &deny
+            ),
+            None
+        );
+    }
+
+    #[test]
+    fn poll_once_matches_process_when_no_steam() {
+        let deny = builtin_denylist();
+        let mut d = Debouncer::default();
+        let procs = vec!["/games/hl2_linux".to_string()];
+        let user = map(&[("hl2_linux", "Half-Life 2")]);
+
+        poll_once(&mut d, &ManualOverride::Auto, None, &procs, &user, &deny);
+        let change = poll_once(&mut d, &ManualOverride::Auto, None, &procs, &user, &deny);
+        let published = change
+            .expect("should publish on second hit")
+            .expect("a game");
+        assert_eq!(published.id, "exe:hl2_linux");
+        assert_eq!(published.name.as_deref(), Some("Half-Life 2"));
+    }
+
+    #[test]
+    fn poll_once_manual_override_is_immediate() {
+        let deny = builtin_denylist();
+        let mut d = Debouncer::default();
+        let forced = game("steam:220", "HL2", GameSource::Steam);
+        // Even with a live Steam detection of something else, the override wins now.
+        let other = game("steam:730", "CS2", GameSource::Steam);
+        let change = poll_once(
+            &mut d,
+            &ManualOverride::Force(forced.clone()),
+            Some(other),
+            &[],
+            &BTreeMap::new(),
+            &deny,
+        );
+        assert_eq!(change, Some(Some(forced)));
+    }
+
+    #[test]
+    fn spawn_and_stop_is_clean() {
+        // Smoke test the lifecycle: spawning and stopping must not panic, and the
+        // initial published value is None.
+        let det = GameDetector::spawn(ManualOverride::Auto, BTreeMap::new()).unwrap();
+        assert_eq!(*det.subscribe().borrow(), None);
+        det.set_override(ManualOverride::ForceNone);
+        det.set_process_map(map(&[("x", "X")]));
+        det.stop();
+        // Dropping also stops; no hang/panic.
+        drop(det);
+    }
+}

src/game/mod.rs

@@ -0,0 +1,514 @@
+//! Game detection, game-presence, and game-reactive backgrounds.
+//!
+//! A single local "what game is running" detector feeds two consumers:
+//! 1. **Local** — a per-game UI background that auto-switches (extends W16).
+//! 2. **Broadcast** — a `Playing <name>` status next to our avatar in every peer's
+//!    roster, riding the gossip presence plane like nickname + avatar.
+//!
+//! This module is structured testable-seams-first: the *pure* logic lives here
+//! (the stable-id scheme, the priority [`resolve`] matcher, the [`Debouncer`], and
+//! the process-name [`match_processes`] mapping), unit-tested with zero I/O. The OS
+//! edges — Steam state/file reads ([`steam`]) and the running-process scan
+//! ([`scan`]) — feed already-parsed values into these pure functions, and the
+//! cancellable poll service ([`detector`]) wires them together.
+
+pub mod detector;
+pub mod scan;
+pub mod steam;
+pub mod vdf;
+
+use std::collections::{BTreeMap, BTreeSet};
+
+/// Where a detected game came from. Encodes the trust/priority tier directly:
+/// a manual override beats live Steam state, which beats a matched process. Used
+/// only for prioritization and as a presentation hint — never trusted as identity.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum GameSource {
+    /// The user forced a specific game (or "none") via the manual override.
+    Manual,
+    /// Steam's live `RunningAppID` resolved against an `appmanifest`.
+    Steam,
+    /// A running process matched against the user's process→name mappings.
+    Process,
+}
+
+/// A game the local detector currently believes is running.
+///
+/// `id` is the stable, namespaced identity used as the config key for backgrounds
+/// (`steam:730`, `exe:hl2_linux`) — **never** the mutable display name. `name` is
+/// the human label shown locally and broadcast as presence; it is `None` only for
+/// the Steam appid-without-manifest case, where the background can still switch by
+/// `id` but nothing is broadcast (per the "don't invent `Steam App 123`" rule).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct DetectedGame {
+    /// Stable namespaced identity. Config-key safe; survives renames.
+    pub id: String,
+    /// Trustworthy human name; `None` = id-only (Steam manifest unavailable).
+    pub name: Option<String>,
+    /// Provenance / priority tier.
+    pub source: GameSource,
+}
+
+impl DetectedGame {
+    /// The Steam namespaced id for an appid: `steam:<appid>`.
+    pub fn steam_id(app_id: u32) -> String {
+        format!("steam:{app_id}")
+    }
+
+    /// The process namespaced id for an executable identity: `exe:<normalized>`.
+    pub fn exe_id(exe: &str) -> String {
+        format!("exe:{}", normalize_exe(exe))
+    }
+}
+
+/// The user's manual override sitting above both detectors (D2). Small by design.
+#[derive(Debug, Clone, PartialEq, Eq, Default)]
+pub enum ManualOverride {
+    /// Trust the auto-detector (default).
+    #[default]
+    Auto,
+    /// Force "not playing anything" regardless of what is detected.
+    ForceNone,
+    /// Force a specific game (the user picked it from the known-games list).
+    Force(DetectedGame),
+}
+
+/// The outcome of [`resolve`]: the chosen game (if any) plus whether the choice is
+/// a manual override and so should **bypass the [`Debouncer`]** (apply immediately).
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct Resolution {
+    pub game: Option<DetectedGame>,
+    /// `true` when a manual override (`ForceNone`/`Force`) decided the value.
+    pub immediate: bool,
+}
+
+/// Apply the detector priority (D2 / §5): **manual override → Steam → mapped
+/// process → none**. Pure; the adapters resolve `steam`/`processes` into
+/// `DetectedGame`s and this only picks the winner. `processes` is in the adapter's
+/// deterministic priority order (see [`match_processes`]); its first entry wins.
+pub fn resolve(
+    override_: &ManualOverride,
+    steam: Option<DetectedGame>,
+    processes: &[DetectedGame],
+) -> Resolution {
+    match override_ {
+        ManualOverride::ForceNone => Resolution {
+            game: None,
+            immediate: true,
+        },
+        ManualOverride::Force(g) => Resolution {
+            game: Some(g.clone()),
+            immediate: true,
+        },
+        ManualOverride::Auto => {
+            let game = steam.or_else(|| processes.first().cloned());
+            Resolution {
+                game,
+                immediate: false,
+            }
+        }
+    }
+}
+
+/// Samples required before a *new* game is accepted/switched to.
+pub const ACCEPT_HITS: u32 = 2;
+/// Consecutive "no game" samples before a currently-shown game is cleared. At the
+/// ~3 s poll cadence this is ~9 s, absorbing a brief Steam stale/crash blip.
+pub const CLEAR_MISSES: u32 = 3;
+
+/// Debounces a stream of raw per-poll detections into a stable published value, so
+/// a flapping detector can't repeatedly re-announce the entire `PeerState` (which
+/// can carry the ~48 KB avatar). Pure state machine — the service feeds it samples
+/// and re-announces only when [`observe`](Debouncer::observe) reports a change.
+///
+/// A switch to a different game needs [`ACCEPT_HITS`] matching samples; clearing a
+/// game needs [`CLEAR_MISSES`] consecutive misses. A manual override
+/// (`immediate = true`) applies at once, bypassing both counters.
+#[derive(Debug, Clone, Default)]
+pub struct Debouncer {
+    current: Option<DetectedGame>,
+    pending: Option<DetectedGame>,
+    pending_hits: u32,
+    misses: u32,
+}
+
+impl Debouncer {
+    /// The currently published, debounced value.
+    pub fn current(&self) -> Option<&DetectedGame> {
+        self.current.as_ref()
+    }
+
+    /// Feed one poll result. `immediate` (a manual override is active) bypasses the
+    /// debounce. Returns `true` iff the published [`current`](Self::current) value
+    /// changed — the signal for the service to re-announce presence / switch the
+    /// background.
+    pub fn observe(&mut self, sample: Option<DetectedGame>, immediate: bool) -> bool {
+        if immediate {
+            let changed = self.current != sample;
+            self.current = sample;
+            self.pending = None;
+            self.pending_hits = 0;
+            self.misses = 0;
+            return changed;
+        }
+        match sample {
+            Some(game) => {
+                self.misses = 0;
+                if self.current.as_ref() == Some(&game) {
+                    // Already publishing this game; drop any half-counted switch.
+                    self.pending = None;
+                    self.pending_hits = 0;
+                    false
+                } else {
+                    if self.pending.as_ref() == Some(&game) {
+                        self.pending_hits += 1;
+                    } else {
+                        self.pending = Some(game);
+                        self.pending_hits = 1;
+                    }
+                    if self.pending_hits >= ACCEPT_HITS {
+                        self.current = self.pending.take();
+                        self.pending_hits = 0;
+                        true
+                    } else {
+                        false
+                    }
+                }
+            }
+            None => {
+                // A miss never counts toward a *switch*; drop any pending candidate.
+                self.pending = None;
+                self.pending_hits = 0;
+                if self.current.is_some() {
+                    self.misses += 1;
+                    if self.misses >= CLEAR_MISSES {
+                        self.current = None;
+                        self.misses = 0;
+                        true
+                    } else {
+                        false
+                    }
+                } else {
+                    false
+                }
+            }
+        }
+    }
+}
+
+/// Normalize a raw executable name/path to a stable identity for matching and ids:
+/// take the final path component (handling both `/` and `\\` separators) and
+/// lowercase it. Keeps any extension (`minecraft.exe` stays distinct from a
+/// hypothetical `minecraft`), trims surrounding whitespace.
+pub fn normalize_exe(raw: &str) -> String {
+    raw.rsplit(['/', '\\'])
+        .next()
+        .unwrap_or(raw)
+        .trim()
+        .to_lowercase()
+}
+
+/// Launcher/helper executables that must NEVER be reported as a game even if a
+/// mapping names them — defense against a mis-entered mapping turning the launcher
+/// itself into "the game". Normalized (lowercase basename) for comparison.
+const BUILTIN_DENYLIST: &[&str] = &[
+    "steam",
+    "steam.exe",
+    "steamwebhelper",
+    "steamwebhelper.exe",
+    "steamerrorreporter",
+    "gameoverlayui",
+    "reaper",
+    "lutris",
+    "heroic",
+    "heroic.exe",
+    "legendary",
+    "gogdl",
+    "wine",
+    "wine64",
+    "wineserver",
+    "wine-preloader",
+    "proton",
+    "pressure-vessel-wrap",
+    "explorer.exe",
+    "services.exe",
+    "svchost.exe",
+];
+
+/// The built-in launcher/helper denylist as a set, for membership checks.
+pub fn builtin_denylist() -> BTreeSet<&'static str> {
+    BUILTIN_DENYLIST.iter().copied().collect()
+}
+
+/// Match the currently-running executables against the user's explicit
+/// process→display-name mappings, returning detected games in **deterministic
+/// priority order** (sorted by stable id) with duplicates removed.
+///
+/// Conservative by construction (§3): only exact normalized-basename matches to a
+/// user mapping count — we never guess that an arbitrary long-running process is a
+/// game. Any executable on `denylist` is rejected even if mapped, so a launcher or
+/// helper can't be promoted to "the game".
+///
+/// `user_map` keys are matched against the normalized basename of each running
+/// entry; the key itself is normalized too, so the caller may store either
+/// `Half-Life 2` style display values keyed by `hl2_linux` or `HL2_Linux`.
+pub fn match_processes(
+    running: &[String],
+    user_map: &BTreeMap<String, String>,
+    denylist: &BTreeSet<&str>,
+) -> Vec<DetectedGame> {
+    // Normalize the user map once so lookups are basename/case-insensitive.
+    let normalized_map: BTreeMap<String, &String> = user_map
+        .iter()
+        .map(|(k, v)| (normalize_exe(k), v))
+        .collect();
+
+    let mut seen: BTreeSet<String> = BTreeSet::new();
+    let mut out: Vec<DetectedGame> = Vec::new();
+    for raw in running {
+        let norm = normalize_exe(raw);
+        if norm.is_empty() || denylist.contains(norm.as_str()) {
+            continue;
+        }
+        if let Some(name) = normalized_map.get(&norm) {
+            let id = format!("exe:{norm}");
+            if seen.insert(id.clone()) {
+                out.push(DetectedGame {
+                    id,
+                    name: Some((*name).clone()),
+                    source: GameSource::Process,
+                });
+            }
+        }
+    }
+    // Deterministic priority: stable order independent of process-scan order.
+    out.sort_by(|a, b| a.id.cmp(&b.id));
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn steam_game(app_id: u32, name: &str) -> DetectedGame {
+        DetectedGame {
+            id: DetectedGame::steam_id(app_id),
+            name: Some(name.to_string()),
+            source: GameSource::Steam,
+        }
+    }
+
+    // --- ids / normalization ----------------------------------------------
+
+    #[test]
+    fn stable_ids_are_namespaced() {
+        assert_eq!(DetectedGame::steam_id(730), "steam:730");
+        assert_eq!(
+            DetectedGame::exe_id("/usr/games/hl2_linux"),
+            "exe:hl2_linux"
+        );
+        assert_eq!(
+            DetectedGame::exe_id("C:\\Games\\Minecraft.exe"),
+            "exe:minecraft.exe"
+        );
+    }
+
+    #[test]
+    fn normalize_handles_both_separators_and_case() {
+        assert_eq!(normalize_exe("/opt/Foo/Bar.x86_64"), "bar.x86_64");
+        assert_eq!(normalize_exe("D:\\a\\b\\GAME.EXE"), "game.exe");
+        assert_eq!(normalize_exe("  spaced.bin  "), "spaced.bin");
+        assert_eq!(normalize_exe("bare"), "bare");
+    }
+
+    // --- resolve priority --------------------------------------------------
+
+    #[test]
+    fn resolve_prefers_steam_over_process_in_auto() {
+        let steam = steam_game(730, "CS2");
+        let procs = vec![DetectedGame {
+            id: "exe:foo".into(),
+            name: Some("Foo".into()),
+            source: GameSource::Process,
+        }];
+        let r = resolve(&ManualOverride::Auto, Some(steam.clone()), &procs);
+        assert_eq!(r.game, Some(steam));
+        assert!(!r.immediate);
+    }
+
+    #[test]
+    fn resolve_falls_back_to_first_process_then_none() {
+        let procs = vec![
+            DetectedGame {
+                id: "exe:a".into(),
+                name: Some("A".into()),
+                source: GameSource::Process,
+            },
+            DetectedGame {
+                id: "exe:b".into(),
+                name: Some("B".into()),
+                source: GameSource::Process,
+            },
+        ];
+        let r = resolve(&ManualOverride::Auto, None, &procs);
+        assert_eq!(r.game.as_ref().unwrap().id, "exe:a");
+        let none = resolve(&ManualOverride::Auto, None, &[]);
+        assert_eq!(none.game, None);
+        assert!(!none.immediate);
+    }
+
+    #[test]
+    fn resolve_manual_override_wins_and_is_immediate() {
+        let steam = steam_game(730, "CS2");
+        // ForceNone overrides a live Steam detection, immediately.
+        let r = resolve(&ManualOverride::ForceNone, Some(steam.clone()), &[]);
+        assert_eq!(r.game, None);
+        assert!(r.immediate);
+        // Force(x) overrides too.
+        let forced = steam_game(220, "HL2");
+        let r = resolve(&ManualOverride::Force(forced.clone()), Some(steam), &[]);
+        assert_eq!(r.game, Some(forced));
+        assert!(r.immediate);
+    }
+
+    // --- debounce ----------------------------------------------------------
+
+    #[test]
+    fn debounce_requires_two_hits_to_switch() {
+        let mut d = Debouncer::default();
+        let g = steam_game(730, "CS2");
+        // First sighting: not yet published.
+        assert!(!d.observe(Some(g.clone()), false));
+        assert_eq!(d.current(), None);
+        // Second consecutive sighting: now published.
+        assert!(d.observe(Some(g.clone()), false));
+        assert_eq!(d.current(), Some(&g));
+        // Steady state: same game, no further change events.
+        assert!(!d.observe(Some(g.clone()), false));
+    }
+
+    #[test]
+    fn debounce_requires_three_misses_to_clear() {
+        let mut d = Debouncer::default();
+        let g = steam_game(730, "CS2");
+        d.observe(Some(g.clone()), false);
+        d.observe(Some(g.clone()), false);
+        assert_eq!(d.current(), Some(&g));
+        // Two misses: still shown (absorbs a transient blip).
+        assert!(!d.observe(None, false));
+        assert!(!d.observe(None, false));
+        assert_eq!(d.current(), Some(&g));
+        // Third miss: cleared.
+        assert!(d.observe(None, false));
+        assert_eq!(d.current(), None);
+    }
+
+    #[test]
+    fn debounce_blip_during_clear_resets_miss_count() {
+        let mut d = Debouncer::default();
+        let g = steam_game(730, "CS2");
+        d.observe(Some(g.clone()), false);
+        d.observe(Some(g.clone()), false);
+        // Miss, miss, then the game reappears: miss count resets, stays published.
+        d.observe(None, false);
+        d.observe(None, false);
+        assert!(!d.observe(Some(g.clone()), false));
+        assert_eq!(d.current(), Some(&g));
+        // It now takes a fresh run of three misses to clear.
+        d.observe(None, false);
+        d.observe(None, false);
+        assert!(d.observe(None, false));
+        assert_eq!(d.current(), None);
+    }
+
+    #[test]
+    fn debounce_immediate_bypasses_counters() {
+        let mut d = Debouncer::default();
+        let g = steam_game(730, "CS2");
+        // A manual override publishes on the first sample.
+        assert!(d.observe(Some(g.clone()), true));
+        assert_eq!(d.current(), Some(&g));
+        // ForceNone clears immediately.
+        assert!(d.observe(None, true));
+        assert_eq!(d.current(), None);
+        // Re-issuing the same immediate value is not a change.
+        d.observe(Some(g.clone()), true);
+        assert!(!d.observe(Some(g.clone()), true));
+    }
+
+    #[test]
+    fn debounce_switching_games_needs_two_hits_of_the_new_one() {
+        let mut d = Debouncer::default();
+        let a = steam_game(1, "A");
+        let b = steam_game(2, "B");
+        d.observe(Some(a.clone()), false);
+        d.observe(Some(a.clone()), false);
+        assert_eq!(d.current(), Some(&a));
+        // One sample of B does not switch.
+        assert!(!d.observe(Some(b.clone()), false));
+        assert_eq!(d.current(), Some(&a));
+        // Second consecutive B switches.
+        assert!(d.observe(Some(b.clone()), false));
+        assert_eq!(d.current(), Some(&b));
+    }
+
+    // --- process matching --------------------------------------------------
+
+    fn map(pairs: &[(&str, &str)]) -> BTreeMap<String, String> {
+        pairs
+            .iter()
+            .map(|(k, v)| (k.to_string(), v.to_string()))
+            .collect()
+    }
+
+    #[test]
+    fn match_processes_matches_only_explicit_mappings() {
+        let user = map(&[("hl2_linux", "Half-Life 2")]);
+        let deny = builtin_denylist();
+        let running = vec![
+            "/usr/bin/firefox".to_string(),
+            "/games/Half-Life 2/hl2_linux".to_string(),
+            "/usr/bin/htop".to_string(),
+        ];
+        let got = match_processes(&running, &user, &deny);
+        assert_eq!(got.len(), 1);
+        assert_eq!(got[0].id, "exe:hl2_linux");
+        assert_eq!(got[0].name.as_deref(), Some("Half-Life 2"));
+        assert_eq!(got[0].source, GameSource::Process);
+    }
+
+    #[test]
+    fn match_processes_rejects_denylisted_even_if_mapped() {
+        // A mis-entered mapping naming the Steam client must not win.
+        let user = map(&[("steam", "Steam (oops)"), ("mygame", "My Game")]);
+        let deny = builtin_denylist();
+        let running = vec!["/usr/bin/steam".into(), "/opt/mygame".into()];
+        let got = match_processes(&running, &user, &deny);
+        assert_eq!(got.len(), 1);
+        assert_eq!(got[0].id, "exe:mygame");
+    }
+
+    #[test]
+    fn match_processes_is_deterministic_and_deduped() {
+        let user = map(&[("zed", "Zed"), ("alpha", "Alpha")]);
+        let deny = builtin_denylist();
+        // Same game twice (two processes) + reverse discovery order.
+        let running = vec!["/b/zed".into(), "/a/alpha".into(), "/c/alpha".into()];
+        let got = match_processes(&running, &user, &deny);
+        // Deduped to two, sorted by id (alpha before zed) regardless of scan order.
+        assert_eq!(
+            got.iter().map(|g| g.id.as_str()).collect::<Vec<_>>(),
+            vec!["exe:alpha", "exe:zed"]
+        );
+    }
+
+    #[test]
+    fn match_processes_ignores_unmapped_and_case_folds() {
+        let user = map(&[("Game.x86_64", "The Game")]);
+        let deny = builtin_denylist();
+        let running = vec!["/x/GAME.X86_64".into(), "/y/random".into()];
+        let got = match_processes(&running, &user, &deny);
+        assert_eq!(got.len(), 1);
+        assert_eq!(got[0].name.as_deref(), Some("The Game"));
+    }
+}

src/game/scan.rs

@@ -0,0 +1,123 @@
+//! Running-process enumeration for the non-Steam detection fallback (D6/D7):
+//! native adapters only — `/proc` on Linux, Toolhelp on Windows — so there is no
+//! `sysinfo` dependency and the audit surface stays small.
+//!
+//! This module is *just the OS edge*: it returns the list of running executable
+//! paths/names. The trustworthy part — turning that list into a game via the
+//! user's explicit mappings and the launcher denylist — is the pure
+//! [`match_processes`](super::match_processes), unit-tested in the parent module.
+
+/// Enumerate the executables of currently-running processes as paths/basenames.
+/// Best-effort: processes we can't introspect (other users') are skipped rather
+/// than erroring. The result is fed to [`match_processes`](super::match_processes),
+/// which normalizes each entry to a basename before matching.
+pub fn running_executables() -> Vec<String> {
+    #[cfg(target_os = "linux")]
+    {
+        linux_proc_executables()
+    }
+    #[cfg(windows)]
+    {
+        windows_toolhelp_executables()
+    }
+    #[cfg(not(any(target_os = "linux", windows)))]
+    {
+        Vec::new()
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn linux_proc_executables() -> Vec<String> {
+    let mut out = Vec::new();
+    let Ok(entries) = std::fs::read_dir("/proc") else {
+        return out;
+    };
+    for entry in entries.flatten() {
+        let name = entry.file_name();
+        let Some(name) = name.to_str() else { continue };
+        // Only numeric entries are processes.
+        if !name.bytes().all(|b| b.is_ascii_digit()) {
+            continue;
+        }
+        let proc_dir = entry.path();
+        // Prefer the real exe path (full, untruncated); fall back to `comm`, which
+        // is readable for all processes but truncated to 15 bytes.
+        if let Ok(exe) = std::fs::read_link(proc_dir.join("exe"))
+            && let Some(s) = exe.to_str()
+        {
+            out.push(s.to_string());
+            continue;
+        }
+        if let Ok(comm) = std::fs::read_to_string(proc_dir.join("comm")) {
+            let trimmed = comm.trim();
+            if !trimmed.is_empty() {
+                out.push(trimmed.to_string());
+            }
+        }
+    }
+    out
+}
+
+#[cfg(windows)]
+fn windows_toolhelp_executables() -> Vec<String> {
+    use windows_sys::Win32::Foundation::{CloseHandle, INVALID_HANDLE_VALUE};
+    use windows_sys::Win32::System::Diagnostics::ToolHelp::{
+        CreateToolhelp32Snapshot, PROCESSENTRY32W, Process32FirstW, Process32NextW,
+        TH32CS_SNAPPROCESS,
+    };
+
+    let mut out = Vec::new();
+    // SAFETY: standard Toolhelp snapshot of all processes; handle checked below.
+    let snapshot = unsafe { CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0) };
+    if snapshot == INVALID_HANDLE_VALUE {
+        return out;
+    }
+    let mut entry: PROCESSENTRY32W = unsafe { std::mem::zeroed() };
+    entry.dwSize = std::mem::size_of::<PROCESSENTRY32W>() as u32;
+    // SAFETY: entry is zeroed with dwSize set, as Process32FirstW requires.
+    let mut ok = unsafe { Process32FirstW(snapshot, &mut entry) };
+    while ok != 0 {
+        // szExeFile is a NUL-terminated UTF-16 array (the basename, e.g. game.exe).
+        let end = entry
+            .szExeFile
+            .iter()
+            .position(|&c| c == 0)
+            .unwrap_or(entry.szExeFile.len());
+        let name = String::from_utf16_lossy(&entry.szExeFile[..end]);
+        if !name.is_empty() {
+            out.push(name);
+        }
+        // SAFETY: same valid snapshot + entry struct.
+        ok = unsafe { Process32NextW(snapshot, &mut entry) };
+    }
+    // SAFETY: snapshot handle came from CreateToolhelp32Snapshot above.
+    unsafe { CloseHandle(snapshot) };
+    out
+}
+
+#[cfg(test)]
+mod tests {
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn enumerates_at_least_this_process() {
+        // The test runner itself is a process, so /proc enumeration must be
+        // non-empty and include something that normalizes to our own exe basename.
+        let exes = super::running_executables();
+        assert!(
+            !exes.is_empty(),
+            "expected to see running processes via /proc"
+        );
+        // Our own /proc/self/exe basename should appear among them.
+        let me = std::fs::read_link("/proc/self/exe")
+            .ok()
+            .and_then(|p| p.file_name().map(|f| f.to_string_lossy().into_owned()));
+        if let Some(me) = me {
+            let me_norm = super::super::normalize_exe(&me);
+            assert!(
+                exes.iter()
+                    .any(|e| super::super::normalize_exe(e) == me_norm),
+                "running list should include our own executable {me_norm:?}"
+            );
+        }
+    }
+}

src/game/steam.rs

@@ -0,0 +1,581 @@
+//! Steam detection adapter: the primary signal (D1). Reads Steam's live
+//! `RunningAppID` and resolves it to a display name via the plain-text
+//! `appmanifest_<appid>.acf`, with no dependency on the binary `appinfo.vdf`.
+//!
+//! The *parsing* is pure and unit-tested ([`parse_running_app_id`],
+//! [`parse_library_paths`], [`parse_app_name`], all over file contents). The fs /
+//! Windows-registry reads are the thin edge, and [`SteamProbe`] caches roots,
+//! library list, and resolved names — invalidating by mtime — so the 3 s detector
+//! poll does not rescan every library each tick (Codex hardening).
+
+use super::vdf::{self, Value};
+use super::{DetectedGame, GameSource};
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::time::SystemTime;
+
+/// Max bytes read from any single Steam state file. These are small text files
+/// (a manifest is a few KB); the cap stops a corrupt/hostile giant file from being
+/// slurped into memory before the parser's own depth guard kicks in.
+const MAX_STEAM_FILE_BYTES: u64 = 4 * 1024 * 1024;
+/// SteamPath is a local filesystem path. Four KiB is deliberately generous and
+/// prevents a corrupt registry length from driving an enormous allocation.
+#[cfg(any(windows, test))]
+const MAX_STEAM_PATH_BYTES: u32 = 4 * 1024;
+
+#[cfg(any(windows, test))]
+fn validate_reg_len(len: u32) -> Option<usize> {
+    (len != 0 && len.is_multiple_of(2) && len <= MAX_STEAM_PATH_BYTES).then_some(len as usize / 2)
+}
+
+#[cfg(any(windows, test))]
+fn decode_reg_sz(mut buf: Vec<u16>, returned_bytes: u32) -> Option<String> {
+    let units = validate_reg_len(returned_bytes)?;
+    if units > buf.len() {
+        return None;
+    }
+    buf.truncate(units);
+    while buf.last() == Some(&0) {
+        buf.pop();
+    }
+    Some(String::from_utf16_lossy(&buf))
+}
+
+/// Parse the live `RunningAppID` out of a Steam `registry.vdf` (the Linux/macOS
+/// client's emulated-registry text file). Returns the appid only when present and
+/// nonzero — `0`/absent is the "no game" state. Pure.
+pub fn parse_running_app_id(registry_vdf: &str) -> Option<u32> {
+    let root = vdf::parse(registry_vdf).ok()?;
+    let raw = root
+        .get_path(&[
+            "Registry",
+            "HKCU",
+            "Software",
+            "Valve",
+            "Steam",
+            "RunningAppID",
+        ])
+        .and_then(Value::as_str)?;
+    let id: u32 = raw.trim().parse().ok()?;
+    (id != 0).then_some(id)
+}
+
+/// Parse the library folder paths out of a `libraryfolders.vdf`, handling **both**
+/// the current shape (`"0" { "path" "..." }`) and the legacy shape
+/// (`"1" "/path"`, the path as a direct string value). Non-numeric keys
+/// (`contentstatsid`, …) are skipped. Pure; paths are returned as-is (escapes
+/// already decoded by the VDF parser), including ones on offline drives — the
+/// caller checks existence.
+pub fn parse_library_paths(libraryfolders_vdf: &str) -> Vec<PathBuf> {
+    let Ok(root) = vdf::parse(libraryfolders_vdf) else {
+        return Vec::new();
+    };
+    // The root may or may not wrap entries in a "libraryfolders" object.
+    let container = root.get("libraryfolders").unwrap_or(&root);
+    let mut out = Vec::new();
+    for (key, val) in container.entries() {
+        // Only numeric-keyed entries are library folders.
+        if key.parse::<u32>().is_err() {
+            continue;
+        }
+        let path = match val {
+            Value::Str(s) => Some(s.as_str()),
+            Value::Obj(_) => val.get("path").and_then(Value::as_str),
+        };
+        if let Some(p) = path
+            && !p.is_empty()
+        {
+            out.push(PathBuf::from(p));
+        }
+    }
+    out
+}
+
+/// Parse the human `name` out of an `appmanifest_<appid>.acf`. Pure.
+pub fn parse_app_name(appmanifest_acf: &str) -> Option<String> {
+    let root = vdf::parse(appmanifest_acf).ok()?;
+    root.get_path(&["AppState", "name"])
+        .and_then(Value::as_str)
+        .map(|s| s.to_string())
+        .filter(|s| !s.is_empty())
+}
+
+/// Read at most [`MAX_STEAM_FILE_BYTES`] of a file as UTF-8 (lossy), or `None` if
+/// it is missing/unreadable. The thin fs edge under the pure parsers above.
+fn read_capped(path: &Path) -> Option<String> {
+    use std::io::Read;
+    let file = std::fs::File::open(path).ok()?;
+    let mut buf = Vec::new();
+    file.take(MAX_STEAM_FILE_BYTES).read_to_end(&mut buf).ok()?;
+    Some(String::from_utf8_lossy(&buf).into_owned())
+}
+
+fn mtime_of(path: &Path) -> Option<SystemTime> {
+    std::fs::metadata(path).ok()?.modified().ok()
+}
+
+/// A library list cached against its source file's mtime.
+#[derive(Default)]
+struct CachedLibraries {
+    source: Option<PathBuf>,
+    mtime: Option<SystemTime>,
+    paths: Vec<PathBuf>,
+}
+
+/// A per-appid resolved name cached against the manifest's mtime. `name` is `None`
+/// when the manifest exists but carries no usable name, or wasn't found.
+struct CachedManifest {
+    mtime: Option<SystemTime>,
+    name: Option<String>,
+}
+
+/// Stateful Steam probe with mtime-invalidated caches. Construct once and call
+/// [`detect`](Self::detect) each poll; all reads are blocking, so the detector
+/// service runs it off the async worker.
+pub struct SteamProbe {
+    roots: Vec<PathBuf>,
+    libraries: CachedLibraries,
+    manifests: HashMap<u32, CachedManifest>,
+}
+
+impl Default for SteamProbe {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl SteamProbe {
+    pub fn new() -> Self {
+        Self {
+            roots: discover_roots(),
+            libraries: CachedLibraries::default(),
+            manifests: HashMap::new(),
+        }
+    }
+
+    /// One detection pass: read the live `RunningAppID`, and if a game is running,
+    /// resolve its name from the appmanifest (cached). Returns a `DetectedGame`
+    /// with `name: None` when the appid is known but no manifest name is available
+    /// — the background can still switch by id, but presence must not invent a name.
+    pub fn detect(&mut self) -> Option<DetectedGame> {
+        let app_id = self.running_app_id()?;
+        let name = self.app_name(app_id);
+        Some(DetectedGame {
+            id: DetectedGame::steam_id(app_id),
+            name,
+            source: GameSource::Steam,
+        })
+    }
+
+    /// The live RunningAppID (nonzero), or `None`.
+    ///
+    /// Platform notes: on **Windows** the real registry's `RunningAppID` is updated
+    /// live, so we read it. On **Linux** the client's `registry.vdf` is only
+    /// rewritten on Steam *shutdown* — it's stale while a game runs — so the live
+    /// signal is the running game process's `SteamAppId` environment variable
+    /// (`/proc/<pid>/environ`, readable for our own processes; the same approach
+    /// MangoHud uses); `registry.vdf` stays as a best-effort fallback. Other Unix
+    /// (macOS) only has the `registry.vdf` fallback for now.
+    fn running_app_id(&self) -> Option<u32> {
+        #[cfg(windows)]
+        {
+            win::running_app_id()
+        }
+        #[cfg(target_os = "linux")]
+        {
+            running_app_id_from_environ().or_else(registry_running_app_id)
+        }
+        #[cfg(not(any(windows, target_os = "linux")))]
+        {
+            registry_running_app_id()
+        }
+    }
+
+    /// Resolve (and cache) the display name for an appid by locating its
+    /// `appmanifest_<appid>.acf` across the known libraries.
+    fn app_name(&mut self, app_id: u32) -> Option<String> {
+        let manifest = self.find_manifest(app_id)?;
+        let mtime = mtime_of(&manifest);
+        if let Some(cached) = self.manifests.get(&app_id)
+            && cached.mtime == mtime
+        {
+            return cached.name.clone();
+        }
+        let name = read_capped(&manifest).and_then(|c| parse_app_name(&c));
+        self.manifests.insert(
+            app_id,
+            CachedManifest {
+                mtime,
+                name: name.clone(),
+            },
+        );
+        name
+    }
+
+    /// The path to an appid's manifest, if it exists in any library.
+    fn find_manifest(&mut self, app_id: u32) -> Option<PathBuf> {
+        let filename = format!("appmanifest_{app_id}.acf");
+        for lib in self.library_paths() {
+            let candidate = lib.join("steamapps").join(&filename);
+            if candidate.exists() {
+                return Some(candidate);
+            }
+        }
+        None
+    }
+
+    /// All Steam library folder paths, cached and refreshed only when the source
+    /// `libraryfolders.vdf` changes (mtime). Discovered from the known roots.
+    fn library_paths(&mut self) -> Vec<PathBuf> {
+        // Locate the libraryfolders.vdf to watch (first existing across roots).
+        let source = self
+            .roots
+            .iter()
+            .map(|r| r.join("steamapps").join("libraryfolders.vdf"))
+            .find(|p| p.exists());
+
+        let mtime = source.as_deref().and_then(mtime_of);
+        if self.libraries.source == source && self.libraries.mtime == mtime && source.is_some() {
+            return self.libraries.paths.clone();
+        }
+
+        let mut paths = Vec::new();
+        if let Some(ref src) = source
+            && let Some(contents) = read_capped(src)
+        {
+            paths = parse_library_paths(&contents);
+        }
+        // Always include the roots themselves: the install dir is an implicit
+        // library even if libraryfolders.vdf is missing or lists only extras.
+        for root in &self.roots {
+            if !paths.contains(root) {
+                paths.push(root.clone());
+            }
+        }
+        self.libraries = CachedLibraries {
+            source,
+            mtime,
+            paths: paths.clone(),
+        };
+        paths
+    }
+}
+
+/// Candidate Steam install roots that actually exist on this machine (each is a
+/// directory containing a `steamapps` folder). Covers native, Flatpak, and Snap
+/// layouts on Linux; on Windows the install path comes from the registry.
+fn discover_roots() -> Vec<PathBuf> {
+    let mut roots = Vec::new();
+
+    #[cfg(windows)]
+    {
+        if let Some(p) = win::install_path() {
+            roots.push(p);
+        }
+    }
+
+    #[cfg(not(windows))]
+    {
+        if let Some(home) = dirs::home_dir() {
+            for rel in [
+                ".steam/steam",
+                ".steam/root",
+                ".local/share/Steam",
+                ".var/app/com.valvesoftware.Steam/.local/share/Steam",
+                "snap/steam/common/.local/share/Steam",
+            ] {
+                roots.push(home.join(rel));
+            }
+        }
+    }
+
+    // Keep only roots that exist and look like a Steam install.
+    roots.retain(|p| p.join("steamapps").is_dir());
+    roots.sort();
+    roots.dedup();
+    roots
+}
+
+/// Candidate `registry.vdf` locations (Linux/macOS emulated registry).
+#[cfg(not(windows))]
+fn registry_vdf_candidates() -> Vec<PathBuf> {
+    let mut out = Vec::new();
+    if let Some(home) = dirs::home_dir() {
+        out.push(home.join(".steam/registry.vdf"));
+        out.push(home.join(".steam/steam/registry.vdf"));
+        out.push(home.join(".var/app/com.valvesoftware.Steam/.steam/registry.vdf"));
+        out.push(home.join("snap/steam/common/.steam/registry.vdf"));
+    }
+    out
+}
+
+/// Best-effort `RunningAppID` from the on-disk `registry.vdf`. ⚠️ Stale while a
+/// game runs (Steam rewrites the file only on shutdown), so this is a *fallback*
+/// behind the live `/proc` `SteamAppId` scan on Linux — not the primary signal.
+#[cfg(not(windows))]
+fn registry_running_app_id() -> Option<u32> {
+    for path in registry_vdf_candidates() {
+        if let Some(contents) = read_capped(&path)
+            && let Some(id) = parse_running_app_id(&contents)
+        {
+            return Some(id);
+        }
+    }
+    None
+}
+
+/// Parse a Steam appid out of a process's raw `environ` blob (NUL-separated
+/// `KEY=VALUE` pairs), reading the `SteamAppId` variable Steam exports to every
+/// game process. Returns the appid only when present and nonzero. Pure +
+/// unit-tested; the `/proc` iteration is the thin edge in
+/// [`running_app_id_from_environ`].
+#[cfg(target_os = "linux")]
+pub fn parse_steam_app_id_from_environ(environ: &[u8]) -> Option<u32> {
+    for kv in environ.split(|&b| b == 0) {
+        if let Some(val) = kv.strip_prefix(b"SteamAppId=")
+            && let Ok(s) = std::str::from_utf8(val)
+            && let Ok(id) = s.trim().parse::<u32>()
+            && id != 0
+        {
+            return Some(id);
+        }
+    }
+    None
+}
+
+/// The live Steam appid of a running game, found by scanning `/proc/<pid>/environ`
+/// for the `SteamAppId` Steam exports to the game's process tree. `environ` is
+/// readable only for our own processes — exactly the ones a Steam game we launched
+/// runs as — and we skip the rest. The live signal that replaces the stale
+/// on-disk `registry.vdf` on Linux.
+#[cfg(target_os = "linux")]
+fn running_app_id_from_environ() -> Option<u32> {
+    let entries = std::fs::read_dir("/proc").ok()?;
+    for entry in entries.flatten() {
+        let name = entry.file_name();
+        let Some(name) = name.to_str() else { continue };
+        if !name.bytes().all(|b| b.is_ascii_digit()) {
+            continue;
+        }
+        // Cap the read: an environ is small; this bounds a pathological case.
+        if let Some(environ) = read_capped(&entry.path().join("environ"))
+            && let Some(id) = parse_steam_app_id_from_environ(environ.as_bytes())
+        {
+            return Some(id);
+        }
+    }
+    None
+}
+
+#[cfg(windows)]
+mod win {
+    //! Windows registry reads via direct Win32 FFI (windows-sys), no `winreg`
+    //! crate. Steam stores both the live `RunningAppID` and its install path under
+    //! `HKCU\Software\Valve\Steam`.
+    use super::{decode_reg_sz, validate_reg_len};
+    use std::path::PathBuf;
+    use windows_sys::Win32::Foundation::ERROR_SUCCESS;
+    use windows_sys::Win32::System::Registry::{
+        HKEY, HKEY_CURRENT_USER, KEY_READ, REG_DWORD, REG_SZ, RegCloseKey, RegOpenKeyExW,
+        RegQueryValueExW,
+    };
+
+    /// UTF-16, NUL-terminated, for a Win32 wide-string argument.
+    fn wide(s: &str) -> Vec<u16> {
+        s.encode_utf16().chain(std::iter::once(0)).collect()
+    }
+
+    /// Open `HKCU\Software\Valve\Steam` for reading; `None` if absent.
+    fn open_steam_key() -> Option<HKEY> {
+        let subkey = wide("Software\\Valve\\Steam");
+        let mut hkey: HKEY = std::ptr::null_mut();
+        // SAFETY: valid HKEY constant, NUL-terminated subkey, out-param for the handle.
+        let rc =
+            unsafe { RegOpenKeyExW(HKEY_CURRENT_USER, subkey.as_ptr(), 0, KEY_READ, &mut hkey) };
+        (rc == ERROR_SUCCESS).then_some(hkey)
+    }
+
+    /// The live `RunningAppID` REG_DWORD, nonzero, or `None`.
+    pub fn running_app_id() -> Option<u32> {
+        let hkey = open_steam_key()?;
+        let name = wide("RunningAppID");
+        let mut kind: u32 = 0;
+        let mut data: u32 = 0;
+        let mut len = std::mem::size_of::<u32>() as u32;
+        // SAFETY: out-params sized for a DWORD; data buffer is a u32 we own.
+        let rc = unsafe {
+            RegQueryValueExW(
+                hkey,
+                name.as_ptr(),
+                std::ptr::null(),
+                &mut kind,
+                &mut data as *mut u32 as *mut u8,
+                &mut len,
+            )
+        };
+        // SAFETY: handle came from RegOpenKeyExW above.
+        unsafe { RegCloseKey(hkey) };
+        if rc == ERROR_SUCCESS && kind == REG_DWORD && data != 0 {
+            Some(data)
+        } else {
+            None
+        }
+    }
+
+    /// The Steam install directory from `HKCU\...\Steam\SteamPath`, if it exists.
+    pub fn install_path() -> Option<PathBuf> {
+        let hkey = open_steam_key()?;
+        let name = wide("SteamPath");
+        let mut kind: u32 = 0;
+        let mut len: u32 = 0;
+        // First query the size.
+        // SAFETY: null data ptr with a zeroed len asks for the required size.
+        let rc = unsafe {
+            RegQueryValueExW(
+                hkey,
+                name.as_ptr(),
+                std::ptr::null(),
+                &mut kind,
+                std::ptr::null_mut(),
+                &mut len,
+            )
+        };
+        if rc != ERROR_SUCCESS || kind != REG_SZ {
+            // SAFETY: valid handle.
+            unsafe { RegCloseKey(hkey) };
+            return None;
+        }
+        let Some(units) = validate_reg_len(len) else {
+            // SAFETY: valid handle.
+            unsafe { RegCloseKey(hkey) };
+            return None;
+        };
+        let mut buf = vec![0u16; units];
+        let mut len2 = len;
+        // SAFETY: buffer sized to the queried byte length.
+        let rc = unsafe {
+            RegQueryValueExW(
+                hkey,
+                name.as_ptr(),
+                std::ptr::null(),
+                &mut kind,
+                buf.as_mut_ptr() as *mut u8,
+                &mut len2,
+            )
+        };
+        // SAFETY: valid handle.
+        unsafe { RegCloseKey(hkey) };
+        if rc != ERROR_SUCCESS || kind != REG_SZ || len2 > len {
+            return None;
+        }
+        Some(PathBuf::from(decode_reg_sz(buf, len2)?))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn registry_string_lengths_are_bounded_and_trimmed() {
+        assert_eq!(
+            validate_reg_len(5),
+            None,
+            "odd byte lengths are invalid UTF-16"
+        );
+        assert_eq!(validate_reg_len(MAX_STEAM_PATH_BYTES + 2), None);
+        assert_eq!(validate_reg_len(8), Some(4));
+
+        let raw = "C:\\Steam\0ignored".encode_utf16().collect::<Vec<_>>();
+        let returned_bytes = ("C:\\Steam\0".encode_utf16().count() * 2) as u32;
+        assert_eq!(
+            decode_reg_sz(raw, returned_bytes).as_deref(),
+            Some("C:\\Steam")
+        );
+    }
+
+    #[test]
+    fn running_app_id_reads_nonzero_and_rejects_zero() {
+        let running = r#""Registry" { "HKCU" { "Software" { "Valve" { "Steam" {
+            "RunningAppID" "440"
+        } } } } }"#;
+        assert_eq!(parse_running_app_id(running), Some(440));
+        let idle = r#""Registry" { "HKCU" { "Software" { "Valve" { "Steam" {
+            "RunningAppID" "0"
+        } } } } }"#;
+        assert_eq!(parse_running_app_id(idle), None);
+        // Missing key / garbage → None, no panic.
+        assert_eq!(parse_running_app_id(r#""Registry" { }"#), None);
+        assert_eq!(parse_running_app_id("not vdf at all {{{"), None);
+    }
+
+    #[test]
+    fn library_paths_handles_current_and_legacy_shapes() {
+        let current = r#""libraryfolders" {
+            "0" { "path" "/home/eric/.local/share/Steam" "label" "" }
+            "1" { "path" "/mnt/games/SteamLibrary" }
+            "contentstatsid" "12345"
+        }"#;
+        let got = parse_library_paths(current);
+        assert_eq!(
+            got,
+            vec![
+                PathBuf::from("/home/eric/.local/share/Steam"),
+                PathBuf::from("/mnt/games/SteamLibrary"),
+            ]
+        );
+
+        // Legacy shape: numeric keys map straight to path strings.
+        let legacy = r#""LibraryFolders" {
+            "TimeNextStatsReport" "9999"
+            "ContentStatsID" "42"
+            "1" "/mnt/old/SteamLibrary"
+        }"#;
+        let got = parse_library_paths(legacy);
+        assert_eq!(got, vec![PathBuf::from("/mnt/old/SteamLibrary")]);
+    }
+
+    #[test]
+    fn library_paths_empty_on_garbage() {
+        assert!(parse_library_paths("totally broken {{{").is_empty());
+    }
+
+    #[cfg(target_os = "linux")]
+    #[test]
+    fn steam_app_id_parsed_from_environ_blob() {
+        // A realistic NUL-separated environ with SteamAppId among other vars.
+        let environ = b"PATH=/usr/bin\0SteamAppId=440\0HOME=/home/x\0SteamGameId=440\0";
+        assert_eq!(parse_steam_app_id_from_environ(environ), Some(440));
+        // Nonzero requirement: SteamAppId=0 (the launcher itself) is ignored.
+        assert_eq!(
+            parse_steam_app_id_from_environ(b"SteamAppId=0\0FOO=bar\0"),
+            None
+        );
+        // Absent → None (a non-Steam process).
+        assert_eq!(
+            parse_steam_app_id_from_environ(b"PATH=/usr/bin\0HOME=/home/x\0"),
+            None
+        );
+        // Not fooled by a different var that merely contains the substring.
+        assert_eq!(
+            parse_steam_app_id_from_environ(b"MY_SteamAppId=999\0"),
+            None
+        );
+        // Garbage value → None, no panic.
+        assert_eq!(
+            parse_steam_app_id_from_environ(b"SteamAppId=notanumber\0"),
+            None
+        );
+    }
+
+    #[test]
+    fn app_name_extracts_and_filters_empty() {
+        let acf = r#""AppState" { "appid" "440" "name" "Team Fortress 2" }"#;
+        assert_eq!(parse_app_name(acf), Some("Team Fortress 2".to_string()));
+        // Empty name → None (don't broadcast a blank).
+        let blank = r#""AppState" { "appid" "440" "name" "" }"#;
+        assert_eq!(parse_app_name(blank), None);
+        // Missing name → None.
+        assert_eq!(parse_app_name(r#""AppState" { "appid" "440" }"#), None);
+    }
+}

src/game/vdf.rs

@@ -0,0 +1,366 @@
+//! A small, defensive parser for Valve's KeyValues / VDF text format, used by
+//! `appmanifest_<appid>.acf`, `libraryfolders.vdf`, and `~/.steam/registry.vdf`.
+//!
+//! Pure (operates on already-read file *contents*) and unit-tested, per the
+//! testable-seams-first workflow — the file I/O and size caps live in the Steam
+//! adapter. Deliberately a real recursive-descent KeyValues parser rather than a
+//! `"name"`-line regex: escapes, nesting, and truncation will eventually break a
+//! regex (Codex's "use a real VDF parser" hardening). Hardened against hostile
+//! input with a recursion-depth cap, so a deeply nested file errors instead of
+//! overflowing the stack, and never panics on malformed/truncated input.
+
+/// Max object nesting depth accepted before bailing out. Real Steam files nest a
+/// handful of levels (`registry.vdf` is the deepest at ~6); this is generous while
+/// still bounding a malicious file.
+const MAX_DEPTH: usize = 32;
+
+/// A parsed KeyValues value: either a leaf string or a nested object. Child order
+/// is preserved and duplicate keys are kept (KeyValues permits them); lookups
+/// return the first match.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum Value {
+    Str(String),
+    Obj(Vec<(String, Value)>),
+}
+
+impl Value {
+    /// The leaf string at this node, if it is a string (not an object).
+    pub fn as_str(&self) -> Option<&str> {
+        match self {
+            Value::Str(s) => Some(s),
+            Value::Obj(_) => None,
+        }
+    }
+
+    /// The first child value under `key`, if this is an object containing it.
+    /// Case-insensitive on the key (KeyValues keys are conventionally
+    /// case-insensitive, and Steam is inconsistent, e.g. `AppState`/`appid`).
+    pub fn get(&self, key: &str) -> Option<&Value> {
+        match self {
+            Value::Obj(pairs) => pairs
+                .iter()
+                .find(|(k, _)| k.eq_ignore_ascii_case(key))
+                .map(|(_, v)| v),
+            Value::Str(_) => None,
+        }
+    }
+
+    /// Follow a chain of object keys, returning the value at the end of the path.
+    /// `root.get_path(&["AppState", "name"])`.
+    pub fn get_path<'a>(&'a self, path: &[&str]) -> Option<&'a Value> {
+        let mut cur = self;
+        for key in path {
+            cur = cur.get(key)?;
+        }
+        Some(cur)
+    }
+
+    /// Iterate the (key, value) child pairs if this is an object.
+    pub fn entries(&self) -> &[(String, Value)] {
+        match self {
+            Value::Obj(pairs) => pairs,
+            Value::Str(_) => &[],
+        }
+    }
+}
+
+/// Parse KeyValues/VDF text into a top-level object (the sequence of root
+/// key→value pairs). Returns `Err` on unbalanced braces, a key with no value, or
+/// nesting past [`MAX_DEPTH`]. Never panics.
+pub fn parse(input: &str) -> Result<Value, String> {
+    let mut lexer = Lexer { rest: input };
+    let obj = parse_object(&mut lexer, 0, true)?;
+    Ok(Value::Obj(obj))
+}
+
+/// Parse a run of `key value` pairs. `top_level` parses until EOF; otherwise it
+/// parses until a closing `}` (which it consumes).
+fn parse_object(
+    lexer: &mut Lexer,
+    depth: usize,
+    top_level: bool,
+) -> Result<Vec<(String, Value)>, String> {
+    if depth > MAX_DEPTH {
+        return Err("VDF nesting too deep".to_string());
+    }
+    let mut pairs = Vec::new();
+    loop {
+        match lexer.next_token()? {
+            None => {
+                if top_level {
+                    return Ok(pairs);
+                }
+                return Err("unexpected end of input inside object".to_string());
+            }
+            Some(Token::Close) => {
+                if top_level {
+                    return Err("unexpected '}' at top level".to_string());
+                }
+                return Ok(pairs);
+            }
+            Some(Token::Open) => {
+                return Err("expected key, found '{'".to_string());
+            }
+            Some(Token::Str(key)) => {
+                // A key must be followed by a value: a string or a nested object.
+                match lexer.next_token()? {
+                    Some(Token::Str(val)) => pairs.push((key, Value::Str(val))),
+                    Some(Token::Open) => {
+                        let child = parse_object(lexer, depth + 1, false)?;
+                        pairs.push((key, Value::Obj(child)));
+                    }
+                    Some(Token::Close) => {
+                        return Err(format!("key '{key}' has no value (found '}}')"));
+                    }
+                    None => return Err(format!("key '{key}' has no value (end of input)")),
+                }
+            }
+        }
+    }
+}
+
+enum Token {
+    Open,
+    Close,
+    Str(String),
+}
+
+struct Lexer<'a> {
+    rest: &'a str,
+}
+
+impl Lexer<'_> {
+    /// Produce the next token, skipping whitespace and `//` line comments.
+    fn next_token(&mut self) -> Result<Option<Token>, String> {
+        loop {
+            self.rest = self.rest.trim_start();
+            if self.rest.is_empty() {
+                return Ok(None);
+            }
+            // Line comments: `//` to end of line.
+            if let Some(after) = self.rest.strip_prefix("//") {
+                match after.find('\n') {
+                    Some(nl) => self.rest = &after[nl + 1..],
+                    None => {
+                        self.rest = "";
+                        return Ok(None);
+                    }
+                }
+                continue;
+            }
+            let mut chars = self.rest.char_indices();
+            let (_, first) = chars.next().expect("non-empty checked above");
+            return match first {
+                '{' => {
+                    self.advance_bytes(first.len_utf8());
+                    Ok(Some(Token::Open))
+                }
+                '}' => {
+                    self.advance_bytes(first.len_utf8());
+                    Ok(Some(Token::Close))
+                }
+                '"' => self.lex_quoted(),
+                _ => Ok(Some(self.lex_bareword())),
+            };
+        }
+    }
+
+    fn advance_bytes(&mut self, n: usize) {
+        self.rest = &self.rest[n..];
+    }
+
+    /// Lex a `"..."` string, decoding `\\ \" \n \t` escapes. Errors if unterminated.
+    fn lex_quoted(&mut self) -> Result<Option<Token>, String> {
+        // Skip the opening quote.
+        self.advance_bytes(1);
+        let mut out = String::new();
+        let mut chars = self.rest.char_indices();
+        while let Some((i, c)) = chars.next() {
+            match c {
+                '"' => {
+                    // Consume through the closing quote.
+                    self.rest = &self.rest[i + 1..];
+                    return Ok(Some(Token::Str(out)));
+                }
+                '\\' => {
+                    // Decode the escape.
+                    match chars.next() {
+                        Some((_, esc)) => out.push(match esc {
+                            'n' => '\n',
+                            't' => '\t',
+                            'r' => '\r',
+                            // `\\`, `\"`, and anything else: take the literal char.
+                            other => other,
+                        }),
+                        None => return Err("unterminated escape in quoted string".to_string()),
+                    }
+                }
+                other => out.push(other),
+            }
+        }
+        Err("unterminated quoted string".to_string())
+    }
+
+    /// Lex an unquoted token: run of non-whitespace, non-brace, non-quote chars.
+    fn lex_bareword(&mut self) -> Token {
+        let end = self
+            .rest
+            .find(|c: char| c.is_whitespace() || matches!(c, '{' | '}' | '"'))
+            .unwrap_or(self.rest.len());
+        let word = self.rest[..end].to_string();
+        self.rest = &self.rest[end..];
+        Token::Str(word)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_appmanifest_name() {
+        // A trimmed-down real appmanifest_<id>.acf.
+        let acf = r#"
+"AppState"
+{
+	"appid"		"730"
+	"name"		"Counter-Strike 2"
+	"StateFlags"		"4"
+	"installdir"		"Counter-Strike Global Offensive"
+	"UserConfig"
+	{
+		"language"		"english"
+	}
+}
+"#;
+        let root = parse(acf).unwrap();
+        assert_eq!(
+            root.get_path(&["AppState", "name"]).and_then(Value::as_str),
+            Some("Counter-Strike 2")
+        );
+        assert_eq!(
+            root.get_path(&["AppState", "appid"])
+                .and_then(Value::as_str),
+            Some("730")
+        );
+        // Case-insensitive key lookup.
+        assert_eq!(
+            root.get_path(&["appstate", "NAME"]).and_then(Value::as_str),
+            Some("Counter-Strike 2")
+        );
+    }
+
+    #[test]
+    fn parses_libraryfolders_paths_with_escaped_backslashes() {
+        // Windows paths arrive with doubled backslashes (escaped).
+        let vdf = r#"
+"libraryfolders"
+{
+	"0"
+	{
+		"path"		"C:\\Program Files (x86)\\Steam"
+		"apps"
+		{
+			"730"		"35000000000"
+		}
+	}
+	"1"
+	{
+		"path"		"/home/eric/.local/share/Steam"
+	}
+}
+"#;
+        let root = parse(vdf).unwrap();
+        let lf = root.get("libraryfolders").unwrap();
+        assert_eq!(
+            lf.get_path(&["0", "path"]).and_then(Value::as_str),
+            Some(r"C:\Program Files (x86)\Steam")
+        );
+        assert_eq!(
+            lf.get_path(&["1", "path"]).and_then(Value::as_str),
+            Some("/home/eric/.local/share/Steam")
+        );
+        // The library folder ids are iterable for discovery.
+        let ids: Vec<&str> = lf.entries().iter().map(|(k, _)| k.as_str()).collect();
+        assert_eq!(ids, vec!["0", "1"]);
+    }
+
+    #[test]
+    fn parses_registry_running_appid_deep_path() {
+        let reg = r#"
+"Registry"
+{
+	"HKCU"
+	{
+		"Software"
+		{
+			"Valve"
+			{
+				"Steam"
+				{
+					"RunningAppID"		"570"
+					"language"		"english"
+				}
+			}
+		}
+	}
+}
+"#;
+        let root = parse(reg).unwrap();
+        let appid = root
+            .get_path(&[
+                "Registry",
+                "HKCU",
+                "Software",
+                "Valve",
+                "Steam",
+                "RunningAppID",
+            ])
+            .and_then(Value::as_str);
+        assert_eq!(appid, Some("570"));
+    }
+
+    #[test]
+    fn handles_comments_and_barewords() {
+        let vdf = "// a comment\n\"root\"\n{\n\tbarekey barevalue // trailing\n}\n";
+        let root = parse(vdf).unwrap();
+        assert_eq!(
+            root.get_path(&["root", "barekey"]).and_then(Value::as_str),
+            Some("barevalue")
+        );
+    }
+
+    #[test]
+    fn rejects_malformed_without_panicking() {
+        // Unbalanced braces.
+        assert!(parse("\"a\" {").is_err());
+        // Stray closing brace.
+        assert!(parse("}").is_err());
+        // Key with no value at EOF.
+        assert!(parse("\"lonely\"").is_err());
+        // Unterminated quoted string.
+        assert!(parse("\"key\" \"unterminated").is_err());
+    }
+
+    #[test]
+    fn rejects_pathologically_deep_nesting() {
+        // Build MAX_DEPTH+5 nested objects; must error, not overflow the stack.
+        let mut s = String::new();
+        for i in 0..(MAX_DEPTH + 5) {
+            s.push_str(&format!("\"k{i}\" {{"));
+        }
+        for _ in 0..(MAX_DEPTH + 5) {
+            s.push('}');
+        }
+        assert!(parse(&s).is_err());
+    }
+
+    #[test]
+    fn missing_keys_return_none_not_error() {
+        let root = parse("\"AppState\" { \"appid\" \"1\" }").unwrap();
+        assert_eq!(root.get_path(&["AppState", "name"]), None);
+        assert_eq!(root.get_path(&["Nope"]), None);
+        // Treating a string as an object yields None rather than panicking.
+        assert_eq!(root.get_path(&["AppState", "appid", "deeper"]), None);
+    }
+}

src/hotkeys.rs

@@ -89,9 +89,9 @@ impl HotkeyAction {
 
     pub fn tier(self) -> HotkeyTier {
         match self {
-            HotkeyAction::ToggleMute
-            | HotkeyAction::ToggleDeafen
-            | HotkeyAction::OpenSettings => HotkeyTier::AppWide,
+            HotkeyAction::ToggleMute | HotkeyAction::ToggleDeafen | HotkeyAction::OpenSettings => {
+                HotkeyTier::AppWide
+            }
             HotkeyAction::PushToTalk | HotkeyAction::LeaveRoom => HotkeyTier::RoomOnly,
         }
     }
@@ -278,7 +278,10 @@ mod tests {
 
     #[test]
     fn parse_single_character_case_folds() {
-        assert_eq!(parse_binding("M"), Some(KeyBinding::Character("m".to_string())));
+        assert_eq!(
+            parse_binding("M"),
+            Some(KeyBinding::Character("m".to_string()))
+        );
         assert_eq!(format_binding(parse_binding("m").as_ref()), "M");
     }
 }

src/identity.rs

@@ -41,7 +41,8 @@ pub fn identity_path() -> Option<PathBuf> {
 /// A *missing* file (first ever run, or right after a reset) is the normal
 /// create path.
 pub fn load_or_create() -> Result<SecretKey> {
-    let path = identity_path().context("could not determine a config directory for the identity key")?;
+    let path =
+        identity_path().context("could not determine a config directory for the identity key")?;
     load_or_create_at(&path)
 }
 
@@ -49,7 +50,8 @@ pub fn load_or_create() -> Result<SecretKey> {
 /// deliberate "Regenerate identity" / unlink action — the old id is discarded and
 /// unrecoverable, so callers should confirm with the user first.
 pub fn regenerate() -> Result<SecretKey> {
-    let path = identity_path().context("could not determine a config directory for the identity key")?;
+    let path =
+        identity_path().context("could not determine a config directory for the identity key")?;
     let key = SecretKey::generate();
     save_at(&path, &key)?;
     Ok(key)
@@ -57,7 +59,8 @@ pub fn regenerate() -> Result<SecretKey> {
 
 /// Atomic, `0600` write at the default identity path. See [`save_at`].
 pub fn save(key: &SecretKey) -> Result<()> {
-    let path = identity_path().context("could not determine a config directory for the identity key")?;
+    let path =
+        identity_path().context("could not determine a config directory for the identity key")?;
     save_at(&path, key)
 }
 
@@ -80,13 +83,15 @@ fn load_or_create_at(path: &std::path::Path) -> Result<SecretKey> {
 /// perms are applied before the rename so the secret is never briefly
 /// world-readable.
 fn save_at(path: &std::path::Path, key: &SecretKey) -> Result<()> {
-    let parent = path.parent().context("identity path has no parent directory")?;
+    let parent = path
+        .parent()
+        .context("identity path has no parent directory")?;
     fs::create_dir_all(parent).with_context(|| format!("failed to create {}", parent.display()))?;
 
     let tmp = parent.join(format!(".identity.key.tmp.{}", std::process::id()));
     {
-        let mut f =
-            fs::File::create(&tmp).with_context(|| format!("failed to create {}", tmp.display()))?;
+        let mut f = fs::File::create(&tmp)
+            .with_context(|| format!("failed to create {}", tmp.display()))?;
         #[cfg(unix)]
         {
             use std::os::unix::fs::PermissionsExt;

src/lib.rs

@@ -1,23 +1,28 @@
-pub mod audio;
-pub mod codec;
-pub mod dsp;
-pub mod network;
-pub mod protocol;
-pub mod core;
 pub mod app;
+pub mod audio;
+pub mod avatar;
+pub mod background;
+pub mod codec;
 pub mod config;
-pub mod identity;
+pub mod core;
+pub mod discovery;
+pub mod dsp;
+pub mod files;
 pub mod friends;
+pub mod game;
+pub mod hotkeys;
+pub mod identity;
+pub mod network;
+pub mod notify;
+pub mod playlist;
 pub mod presence;
 pub mod presence_net;
-pub mod theme;
-pub mod notify;
-pub mod screenshare;
-pub mod sanitize;
-pub mod avatar;
+pub mod protocol;
 pub mod recents;
-pub mod discovery;
-pub mod hotkeys;
+pub mod sanitize;
+pub mod screenshare;
+pub mod theme;
+pub mod widget;
 
 use std::fs::File;
 use std::path::{Path, PathBuf};
@@ -70,7 +75,8 @@ pub fn redact_for_log(value: &str) -> String {
 }
 
 pub fn short_bytes_hex(bytes: &[u8]) -> String {
-    bytes.iter()
+    bytes
+        .iter()
         .take(6)
         .map(|b| format!("{b:02x}"))
         .collect::<Vec<_>>()
@@ -78,7 +84,10 @@ pub fn short_bytes_hex(bytes: &[u8]) -> String {
 }
 
 fn rotated_log_path(path: &Path) -> PathBuf {
-    let file_name = path.file_name().and_then(|n| n.to_str()).unwrap_or("peerspeak.log");
+    let file_name = path
+        .file_name()
+        .and_then(|n| n.to_str())
+        .unwrap_or("peerspeak.log");
     path.with_file_name(format!("{file_name}.1"))
 }
 
@@ -95,7 +104,10 @@ fn prepare_log_file_with_limit(path: &Path, max_bytes: u64) -> std::io::Result<F
         let rotated = rotated_log_path(path);
         let _ = std::fs::remove_file(&rotated);
         if std::fs::rename(path, &rotated).is_err() {
-            let _ = std::fs::OpenOptions::new().write(true).truncate(true).open(path);
+            let _ = std::fs::OpenOptions::new()
+                .write(true)
+                .truncate(true)
+                .open(path);
         }
     }
 

src/main.rs

@@ -1,3 +1,7 @@
+// On Windows, suppress the extra console window for release GUI builds while
+// keeping it in debug builds so stderr/panics stay visible during development.
+#![cfg_attr(not(debug_assertions), windows_subsystem = "windows")]
+
 fn main() {
     if let Err(e) = peerspeak::app::run_gui() {
         eprintln!("Error running GUI: {:?}", e);

src/network/iroh_impl.rs

@@ -1,15 +1,16 @@
-use crate::network::{NetworkTransport, NetError, ConnEvent};
-use iroh::{Endpoint, EndpointId};
-use iroh::endpoint::{Connection, ConnectionError, VarInt};
+use crate::network::{ConnEvent, NetError, NetworkTransport};
+use async_trait::async_trait;
 use bytes::Bytes;
+use iroh::endpoint::{Connection, ConnectionError, VarInt};
+use iroh::{Endpoint, EndpointId};
+use std::collections::{HashMap, HashSet};
+use std::sync::{Arc, Mutex as StdMutex};
+use std::time::Duration;
 use tokio::sync::mpsc;
 use tokio::sync::mpsc::Receiver;
-use std::sync::{Arc, Mutex as StdMutex};
-use std::collections::{HashMap, HashSet};
-use std::time::Duration;
-use async_trait::async_trait;
 
-use crate::protocol::AUDIO_ALPN;
+use crate::files::{AttachmentId, ChatAttachment};
+use crate::protocol::{AUDIO_ALPN, FILES_ALPN};
 
 /// Per-peer datagram send queue depth. Audio is real-time, so a backlog is
 /// useless latency — keep it shallow and drop the oldest frame when full.
@@ -31,6 +32,10 @@ const MAX_BACKOFF: Duration = Duration::from_secs(5);
 /// already means "the peer closed this on purpose."
 const GOODBYE_CODE: u32 = 1;
 
+/// Bound on each phase (connect, read) of a chat-attachment fetch, so a slow or
+/// stalled sender can't hang the fetch indefinitely.
+const FILE_FETCH_TIMEOUT: Duration = Duration::from_secs(30);
+
 /// State shared between the transport, its protocol handler, and every per-peer
 /// supervisor task. One supervisor owns a peer's whole connection lifecycle.
 struct Shared {
@@ -60,6 +65,13 @@ struct Shared {
     /// verified gossip roster plus peers still inside reconnect grace; transport
     /// connections alone never mutate this set.
     admitted_audio: StdMutex<HashSet<EndpointId>>,
+    /// Chat file attachments we're serving to room members this session, keyed by
+    /// the random attachment id. Populated when we send a chat file; read by the
+    /// file protocol handler to answer a member's fetch. Cleared on leave. Each
+    /// blob is already byte-capped at send time.
+    /// Blobs we serve to room members, bounded by count and byte budgets
+    /// (Phase 3C) — an evicted id reads as "sender no longer has the file".
+    served_files: StdMutex<crate::files::ServeStore>,
     incoming_tx: mpsc::Sender<(EndpointId, Bytes)>,
     /// Best-effort link-state notifications for the UI (connecting / connected).
     conn_events_tx: mpsc::Sender<ConnEvent>,
@@ -101,7 +113,13 @@ impl Shared {
         let shared = self.clone();
         let supervisor = tokio::spawn(supervise(shared, peer_id, inbound_rx));
         let inbound_tx_ret = inbound_tx.clone();
-        peers.insert(peer_id, PeerHandle { supervisor, inbound_tx });
+        peers.insert(
+            peer_id,
+            PeerHandle {
+                supervisor,
+                inbound_tx,
+            },
+        );
         crate::log_msg(&format!("Transport: supervising peer {:?}", peer_id));
         inbound_tx_ret
     }
@@ -113,7 +131,10 @@ impl Shared {
         self.addrs.lock().unwrap().remove(&peer_id);
         if let Some(handle) = self.peers.lock().await.remove(&peer_id) {
             handle.supervisor.abort();
-            crate::log_msg(&format!("Transport: stopped supervising peer {:?}", peer_id));
+            crate::log_msg(&format!(
+                "Transport: stopped supervising peer {:?}",
+                peer_id
+            ));
         }
     }
 
@@ -198,12 +219,15 @@ async fn supervise(
     let mut backoff = INITIAL_BACKOFF;
 
     // Show "connecting" until the first link is actually up.
-    let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
+    let _ = shared
+        .conn_events_tx
+        .try_send(ConnEvent::Connecting(peer_id));
 
-    let mut conn = match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff).await {
-        Some(conn) => conn,
-        None => return, // retired before we ever connected
-    };
+    let mut conn =
+        match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff).await {
+            Some(conn) => conn,
+            None => return, // retired before we ever connected
+        };
 
     loop {
         // A healthy link resets the dialer's backoff for the next outage.
@@ -213,8 +237,14 @@ async fn supervise(
         shared.senders.lock().unwrap().insert(peer_id, send_tx);
         // Publish the live connection so an intentional leave can close it with
         // the goodbye code.
-        shared.live_conns.lock().unwrap().insert(peer_id, conn.clone());
-        let _ = shared.conn_events_tx.try_send(ConnEvent::Connected(peer_id));
+        shared
+            .live_conns
+            .lock()
+            .unwrap()
+            .insert(peer_id, conn.clone());
+        let _ = shared
+            .conn_events_tx
+            .try_send(ConnEvent::Connected(peer_id));
         crate::log_msg(&format!("Transport: peer {:?} link up", peer_id));
 
         // Run until the link dies, a replacement arrives, or we're retired. The
@@ -262,21 +292,36 @@ async fn supervise(
         match wake {
             Wake::Shutdown => return,
             Wake::Replacement(new_conn) => {
-                crate::log_msg(&format!("Transport: peer {:?} replaced with new inbound link", peer_id));
-                let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
+                crate::log_msg(&format!(
+                    "Transport: peer {:?} replaced with new inbound link",
+                    peer_id
+                ));
+                let _ = shared
+                    .conn_events_tx
+                    .try_send(ConnEvent::Connecting(peer_id));
                 conn = new_conn;
             }
             Wake::Closed(reason) => {
                 // A graceful application close means the peer left on purpose —
                 // don't reconnect; tell the core to evict it now.
                 if is_graceful_leave(&reason) {
-                    crate::log_msg(&format!("Transport: peer {:?} left gracefully ({:?})", peer_id, reason));
+                    crate::log_msg(&format!(
+                        "Transport: peer {:?} left gracefully ({:?})",
+                        peer_id, reason
+                    ));
                     let _ = shared.conn_events_tx.try_send(ConnEvent::Left(peer_id));
                     return;
                 }
-                crate::log_msg(&format!("Transport: peer {:?} link dropped; reconnecting", peer_id));
-                let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
-                conn = match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff).await {
+                crate::log_msg(&format!(
+                    "Transport: peer {:?} link dropped; reconnecting",
+                    peer_id
+                ));
+                let _ = shared
+                    .conn_events_tx
+                    .try_send(ConnEvent::Connecting(peer_id));
+                conn = match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff)
+                    .await
+                {
                     Some(conn) => conn,
                     None => return, // retired while reconnecting
                 };
@@ -395,13 +440,107 @@ impl iroh::protocol::ProtocolHandler for AudioRouter {
             // only happens if links are churning, and the supervisor gets the next one.
             let inbound_tx = shared.ensure_supervisor(peer_id).await;
             if inbound_tx.try_send(connection).is_err() {
-                crate::log_msg(&format!("Transport: dropped inbound link from {:?} (queue full)", peer_id));
+                crate::log_msg(&format!(
+                    "Transport: dropped inbound link from {:?} (queue full)",
+                    peer_id
+                ));
             }
             Ok(())
         }
     }
 }
 
+/// Protocol handler for the file-transfer plane (`FILES_ALPN`). Mirrors
+/// [`AudioRouter`]: it's persistent on the router and bound to the active
+/// session's [`Shared`] on join. On an inbound stream it authenticates the peer
+/// (iroh ALPN handshake gives us `remote_id`), gates on **live room membership**
+/// (same invariant as audio admission, so a former member can't pull files),
+/// reads a single 32-byte attachment id, and streams back the matching blob from
+/// the session serve store — or nothing if the id is unknown.
+#[derive(Clone, Default)]
+pub struct FileRouter {
+    current: Arc<StdMutex<Option<Arc<Shared>>>>,
+}
+
+impl std::fmt::Debug for FileRouter {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("FileRouter").finish_non_exhaustive()
+    }
+}
+
+impl FileRouter {
+    pub fn new() -> Self {
+        Self::default()
+    }
+
+    /// Route inbound file fetches to `transport`'s session (called on join).
+    pub fn bind(&self, transport: &IrohTransport) {
+        *self.current.lock().unwrap() = Some(transport.shared.clone());
+    }
+
+    /// Stop serving files until the next [`bind`](Self::bind) (called on leave).
+    pub fn clear(&self) {
+        *self.current.lock().unwrap() = None;
+    }
+}
+
+/// Max bytes we'll read for a fetch *request* frame. A request is exactly one
+/// 32-byte id; this small ceiling rejects a peer trying to stream us a huge
+/// "request" as a cheap DoS.
+const FILE_REQUEST_MAX: usize = 64;
+
+impl iroh::protocol::ProtocolHandler for FileRouter {
+    fn accept(
+        &self,
+        connection: Connection,
+    ) -> impl std::future::Future<Output = Result<(), iroh::protocol::AcceptError>> + Send {
+        let peer_id = connection.remote_id();
+        let shared = self.current.lock().unwrap().clone();
+        async move {
+            // No active call → nothing to serve.
+            let Some(shared) = shared else {
+                return Ok(());
+            };
+            // Member gating: only current room members may fetch our files. Reuses
+            // the audio admission roster (the authoritative room membership set).
+            if !shared.audio_sender_admitted(peer_id) {
+                crate::log_msg(&format!(
+                    "Transport: rejected file fetch from non-member {}",
+                    crate::short_id(&peer_id.to_string())
+                ));
+                return Ok(());
+            }
+            // Accept one bidirectional stream: read the id, write the bytes.
+            let Ok((mut send, mut recv)) = connection.accept_bi().await else {
+                return Ok(());
+            };
+            let Ok(req) = recv.read_to_end(FILE_REQUEST_MAX).await else {
+                return Ok(());
+            };
+            let Some(id) = crate::files::parse_request(&req) else {
+                return Ok(());
+            };
+            let blob = shared.served_files.lock().unwrap().get(&id);
+            if let Some(blob) = blob {
+                let _ = send.write_all(&blob).await;
+            }
+            // Finish either way: an unknown id closes with an empty body, which
+            // the fetcher reads as a zero-length result and treats as "gone".
+            let _ = send.finish();
+            // CRITICAL: `finish()` only marks the stream's EOF — it does NOT wait
+            // for the written bytes to be delivered and acknowledged. If we return
+            // here the `connection` drops, and its CONNECTION_CLOSE can race ahead
+            // of the still-in-flight stream data, so the fetcher's read aborts with
+            // "connection lost". Wait for the fetcher to receive everything and
+            // close the connection itself (it drops `conn` right after read_to_end);
+            // that close is our signal the transfer landed. Bounded so a fetcher
+            // that vanishes can't pin this task forever.
+            let _ = tokio::time::timeout(FILE_FETCH_TIMEOUT, connection.closed()).await;
+            Ok(())
+        }
+    }
+}
+
 pub struct IrohTransport {
     shared: Arc<Shared>,
     incoming_rx: tokio::sync::Mutex<Option<mpsc::Receiver<(EndpointId, Bytes)>>>,
@@ -426,6 +565,7 @@ impl IrohTransport {
             peers: tokio::sync::Mutex::new(HashMap::new()),
             live_conns: StdMutex::new(HashMap::new()),
             admitted_audio: StdMutex::new(HashSet::new()),
+            served_files: StdMutex::new(crate::files::ServeStore::default()),
             incoming_tx,
             conn_events_tx,
         });
@@ -443,7 +583,14 @@ impl IrohTransport {
     /// all supervisors so none linger redialing the about-to-close endpoint.
     /// Call this before shutting the router down.
     pub async fn leave(&self) {
-        let conns: Vec<Connection> = self.shared.live_conns.lock().unwrap().drain().map(|(_, c)| c).collect();
+        let conns: Vec<Connection> = self
+            .shared
+            .live_conns
+            .lock()
+            .unwrap()
+            .drain()
+            .map(|(_, c)| c)
+            .collect();
         for conn in &conns {
             conn.close(VarInt::from_u32(GOODBYE_CODE), b"leave");
         }
@@ -455,6 +602,7 @@ impl IrohTransport {
         self.shared.senders.lock().unwrap().clear();
         self.shared.addrs.lock().unwrap().clear();
         self.shared.admitted_audio.lock().unwrap().clear();
+        self.shared.served_files.lock().unwrap().clear();
         // Give the CONNECTION_CLOSE frames a moment to flush before the caller
         // shuts the endpoint/router down (the `conns` clones are still alive
         // here, so the endpoint can still transmit them).
@@ -483,6 +631,137 @@ impl IrohTransport {
     pub fn audio_sender_admitted(&self, peer_id: EndpointId) -> bool {
         self.shared.audio_sender_admitted(peer_id)
     }
+
+    /// Make `bytes` available to room members under `id` for the rest of this
+    /// session (served by the [`FileRouter`] handler). Called by core when we
+    /// send a chat file. The blob is cleared on leave.
+    pub fn serve_attachment(&self, id: AttachmentId, bytes: Arc<Vec<u8>>) {
+        if !self.shared.served_files.lock().unwrap().insert(id, bytes) {
+            crate::log_msg("Transport: refused to serve an over-budget blob");
+        }
+    }
+
+    /// Drop a previously-served blob (e.g. a music track no longer current-or-next).
+    pub fn forget_attachment(&self, id: AttachmentId) {
+        self.shared.served_files.lock().unwrap().remove(&id);
+    }
+
+    /// Fetch `size` bytes stored under `id` from peer `from` over the files plane.
+    /// Shared core of `fetch_attachment` and music-track fetching: dials
+    /// `FILES_ALPN`, writes the 32-byte id, and reads bounded by `size`.
+    pub async fn fetch_blob(
+        &self,
+        from: EndpointId,
+        id: AttachmentId,
+        size: u64,
+    ) -> Result<Vec<u8>, NetError> {
+        if !crate::files::size_within_cap(size) {
+            return Err(NetError::Other("attachment size out of range".to_string()));
+        }
+        let addr = self.shared.addrs.lock().unwrap().get(&from).cloned();
+        let connect = async {
+            match addr {
+                Some(addr) => self.shared.endpoint.connect(addr, FILES_ALPN).await,
+                None => self.shared.endpoint.connect(from, FILES_ALPN).await,
+            }
+        };
+        let conn = tokio::time::timeout(FILE_FETCH_TIMEOUT, connect)
+            .await
+            .map_err(|_| NetError::Other("file fetch: connect timed out".to_string()))?
+            .map_err(|e| NetError::Other(format!("file fetch: connect failed: {e}")))?;
+
+        let (mut send, mut recv) = conn
+            .open_bi()
+            .await
+            .map_err(|e| NetError::Other(format!("file fetch: open stream failed: {e}")))?;
+        send.write_all(&id)
+            .await
+            .map_err(|e| NetError::Other(format!("file fetch: request write failed: {e}")))?;
+        send.finish()
+            .map_err(|e| NetError::Other(format!("file fetch: request finish failed: {e}")))?;
+
+        // `read_to_end(size)` errors if the stream exceeds `size`, rejecting an
+        // overlong transfer; the exact-length check below rejects a short one.
+        let read = recv.read_to_end(size as usize);
+        let bytes = tokio::time::timeout(FILE_FETCH_TIMEOUT, read)
+            .await
+            .map_err(|_| NetError::Other("file fetch: read timed out".to_string()))?
+            .map_err(|e| NetError::Other(format!("file fetch: read failed: {e}")))?;
+        if bytes.is_empty() {
+            return Err(NetError::Other(
+                "file fetch: sender no longer has the file".to_string(),
+            ));
+        }
+        // Exact transfer required (Phase 3C): a truncated body must not be
+        // cached/saved/decoded as if it were the declared attachment.
+        if bytes.len() as u64 != size {
+            return Err(NetError::Other(format!(
+                "file fetch: incomplete transfer ({} of {size} bytes)",
+                bytes.len()
+            )));
+        }
+        Ok(bytes)
+    }
+
+    /// Snapshot the selected QUIC path of every live audio connection, for the
+    /// UI's per-peer connection badge (direct/relay, RTT, loss, bitrate).
+    /// Cheap and lock-light: the `live_conns` guard is released before touching
+    /// any connection, and `Connection::paths()` reads shared state without I/O.
+    pub fn connection_stats(&self) -> Vec<(EndpointId, crate::network::PathSnapshot)> {
+        // Clone the connections out so the map lock isn't held while we inspect
+        // paths (a supervisor inserts/removes entries as links come and go).
+        let conns: Vec<(EndpointId, Connection)> = self
+            .shared
+            .live_conns
+            .lock()
+            .unwrap()
+            .iter()
+            .map(|(id, conn)| (*id, conn.clone()))
+            .collect();
+        conns
+            .into_iter()
+            .filter_map(|(id, conn)| {
+                let paths = conn.paths();
+                // The selected path is the one carrying application data. In the
+                // brief window where none is flagged (e.g. mid-migration), fall
+                // back to the first open path rather than dropping the badge.
+                let path = paths
+                    .iter()
+                    .find(|p| p.is_selected())
+                    .or_else(|| paths.iter().next())?;
+                let stats = path.stats();
+                // Per-variant display: `TransportAddr`'s own `Display` prefixes
+                // a scheme ("ip:1.2.3.4:5") that's noise next to the badge's
+                // Direct/Relay label.
+                let remote_addr = match path.remote_addr() {
+                    iroh::TransportAddr::Ip(sock) => sock.to_string(),
+                    iroh::TransportAddr::Relay(url) => url.to_string(),
+                    other => other.to_string(),
+                };
+                Some((
+                    id,
+                    crate::network::PathSnapshot {
+                        is_relay: path.remote_addr().is_relay(),
+                        remote_addr,
+                        rtt: stats.rtt,
+                        tx_bytes: stats.udp_tx.bytes,
+                        rx_bytes: stats.udp_rx.bytes,
+                        tx_datagrams: stats.udp_tx.datagrams,
+                        lost_packets: stats.lost_packets,
+                    },
+                ))
+            })
+            .collect()
+    }
+
+    /// Fetch a chat attachment's bytes from its sender over the file plane.
+    pub async fn fetch_attachment(
+        &self,
+        from: EndpointId,
+        att: &ChatAttachment,
+    ) -> Result<Vec<u8>, NetError> {
+        self.fetch_blob(from, att.id, att.size).await
+    }
 }
 
 #[async_trait]

src/network/mod.rs

@@ -1,10 +1,10 @@
-use iroh::{EndpointId, EndpointAddr};
+use async_trait::async_trait;
 use bytes::Bytes;
+use iroh::{EndpointAddr, EndpointId};
+use serde::{Deserialize, Serialize};
+use std::str::FromStr;
 use thiserror::Error;
 use tokio::sync::mpsc::Receiver;
-use async_trait::async_trait;
-use serde::{Serialize, Deserialize};
-use std::str::FromStr;
 
 #[derive(Error, Debug)]
 pub enum NetError {
@@ -22,6 +22,38 @@ pub enum NetError {
     Other(String),
 }
 
+/// A peer's currently-broadcast music track + playback timeline (W22). Rides
+/// gossip presence so listeners can tune in, follow track changes, and keep in
+/// sync. Untrusted like `name`/`game`: the `name` is sanitized and `size` is
+/// cap-checked at gossip ingest. Bytes never ride gossip — they are fetched
+/// point-to-point over the files plane by `id`, exactly like a chat attachment.
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct MusicPresence {
+    /// Files-plane handle to fetch this track's bytes (minted per track by the DJ).
+    pub id: crate::files::AttachmentId,
+    /// Sanitized display name (track filename). Untrusted; cleaned at ingest.
+    pub name: String,
+    /// Byte length, bounds the listener's fetch. Must be `<= MAX_ATTACHMENT_BYTES`.
+    pub size: u64,
+    /// True while the DJ has the track paused.
+    pub paused: bool,
+    /// Wall-clock ms (UNIX epoch) of the timeline anchor. While playing, the true
+    /// playhead is `position_ms + (now_ms - anchor_ms)`; while paused it is
+    /// frozen at `position_ms`. Re-stamped on every play/pause/seek.
+    pub anchor_ms: u64,
+    /// Playhead position (ms) at `anchor_ms`.
+    pub position_ms: u64,
+    /// Files-plane handle for the DJ's NEXT track, so listeners can prefetch it
+    /// for a gapless skip. `None` when there is no distinct next track (single
+    /// item playlist) or the DJ isn't ready. Equals a future `id` once that
+    /// track plays.
+    #[serde(default)]
+    pub next_id: Option<crate::files::AttachmentId>,
+    /// Byte length of the next track; bounds the prefetch. Cap-checked at ingest.
+    #[serde(default)]
+    pub next_size: Option<u64>,
+}
+
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub struct PeerState {
     pub name: String,
@@ -39,6 +71,65 @@ pub struct PeerState {
     /// peers/configs that predate the field still deserialize (→ monogram).
     #[serde(default)]
     pub avatar: crate::avatar::Avatar,
+    /// The game this peer is currently playing, as a display string only (shown as
+    /// `Playing <name>` next to their avatar). Opt-in and **untrusted** like
+    /// `name`: sanitized + length-capped at the gossip ingest boundary. `None` when
+    /// the peer isn't sharing a game (feature off / nothing detected). Only the
+    /// display string rides the wire — never the appid or detection source, to
+    /// avoid fingerprinting and coupling the protocol to detector internals.
+    /// Defaulted so peers/configs predating the field still deserialize.
+    #[serde(default)]
+    pub game: Option<String>,
+    /// This peer's currently-broadcast music track and playback timeline, or
+    /// `None` when not broadcasting. Defaulted so pre-W22 peers deserialize.
+    #[serde(default)]
+    pub music: Option<MusicPresence>,
+}
+
+/// The locally-owned, "sticky" pieces of our own presence: the identity fields
+/// that change only on explicit user action and persist for the whole core
+/// session. The remaining `PeerState` fields are *volatile* — mute state, current
+/// `addr`, and the active screen-share ticket are read fresh at each announce — so
+/// they are passed into [`SelfPresence::to_state`] rather than stored here.
+///
+/// This is the single source of truth for building our own `PeerState`: core
+/// reconstructs self-state in several command branches (join, mute toggle, avatar
+/// change, screen-share start/stop), and centralizing the `PeerState` literal here
+/// means a new presence field is added in exactly one place instead of at every
+/// call site.
+#[derive(Debug, Clone, Default)]
+pub struct SelfPresence {
+    pub name: String,
+    pub avatar: crate::avatar::Avatar,
+    /// The display label of the game we're currently broadcasting, or `None` when
+    /// game presence is off / nothing is detected. Already sanitized + capped
+    /// (see `crate::sanitize::sanitize_game_label`) before being stored here, so
+    /// the outgoing announce carries a safe value.
+    pub game: Option<String>,
+    /// Our current broadcast timeline, or `None` when not broadcasting / not playing.
+    pub music: Option<MusicPresence>,
+}
+
+impl SelfPresence {
+    /// Combine the sticky identity fields with the volatile per-announce fields
+    /// (`is_muted`, current `addr`, active-share `sharing` ticket) into a full
+    /// `PeerState` ready to announce over the gossip presence plane.
+    pub fn to_state(
+        &self,
+        is_muted: bool,
+        addr: iroh::EndpointAddr,
+        sharing: Option<String>,
+    ) -> PeerState {
+        PeerState {
+            name: self.name.clone(),
+            is_muted,
+            addr,
+            sharing,
+            avatar: self.avatar.clone(),
+            game: self.game.clone(),
+            music: self.music.clone(),
+        }
+    }
 }
 
 #[derive(Debug, Clone)]
@@ -54,10 +145,26 @@ pub enum RoomEvent {
     /// from `PeerLeft` precisely so a momentary `NeighborDown` can't tear down the
     /// reconnect path the way it used to.
     PeerConnectionLost(EndpointId),
-    /// A peer sent a room text-chat message. Carries the sender's id, their
-    /// display name (embedded so it shows even without a presence entry), the
-    /// text, and a sender-stamped millisecond timestamp.
-    ChatMessage { from: EndpointId, name: String, text: String, ts: u64 },
+    /// A validly signed gossip payload was rejected only because its timestamp is
+    /// outside the replay-protection window. The peer is not in the roster yet,
+    /// so this surfaces as a room-level warning instead of a peer-card state.
+    ClockSkewSuspected {
+        author: EndpointId,
+        skew_ms: i64,
+    },
+    /// A peer sent a room text-chat message. Carries the sender's id, the
+    /// sender-CLAIMED display name (untrusted; the core replaces it with the
+    /// roster-bound name before the UI sees it — chat-hardening Phase 2), the
+    /// text, and the signed envelope timestamp (display only, never ordering).
+    ChatMessage {
+        from: EndpointId,
+        name: String,
+        text: String,
+        ts: u64,
+        /// Optional file attachment descriptor; the bytes are fetched off-gossip
+        /// on the file plane. Already filename-sanitized + size-capped on ingest.
+        attachment: Option<crate::files::ChatAttachment>,
+    },
 }
 
 /// Transport-level link state for a peer, surfaced so the UI can show when a
@@ -78,6 +185,32 @@ pub enum ConnEvent {
     Left(EndpointId),
 }
 
+/// Owned snapshot of a peer's *selected* QUIC path (the one currently carrying
+/// application data), taken from the live audio connection for the UI's
+/// connection-transparency badge. Counters are cumulative for the path's
+/// lifetime; rate/loss derivation over a poll window happens in
+/// `core::connstats` (which also detects path switches via `remote_addr`).
+#[derive(Debug, Clone, PartialEq)]
+pub struct PathSnapshot {
+    /// True when the path runs through a relay server, false for a direct
+    /// (holepunched or local) IP path.
+    pub is_relay: bool,
+    /// The path's remote transport address: `ip:port` for a direct path, the
+    /// relay URL for a relayed one.
+    pub remote_addr: String,
+    /// Current QUIC round-trip-time estimate for the path.
+    pub rtt: std::time::Duration,
+    /// Cumulative bytes sent in UDP datagrams on the path.
+    pub tx_bytes: u64,
+    /// Cumulative bytes received in UDP datagrams on the path.
+    pub rx_bytes: u64,
+    /// Cumulative UDP datagrams sent on the path (the loss denominator: for our
+    /// small voice frames these map ~1:1 to QUIC packets).
+    pub tx_datagrams: u64,
+    /// Cumulative packets detected lost on the path.
+    pub lost_packets: u64,
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct PeerSpeakTicket {
     pub host_addr: iroh::EndpointAddr,
@@ -100,10 +233,12 @@ impl PeerSpeakTicket {
     /// is idempotent.
     pub fn restamp(ticket_str: &str, my_addr: iroh::EndpointAddr) -> String {
         match ticket_str.parse::<PeerSpeakTicket>() {
-            Ok(t) => {
-                PeerSpeakTicket { host_addr: my_addr, topic_id: t.topic_id, name: t.name }
-                    .to_string()
+            Ok(t) => PeerSpeakTicket {
+                host_addr: my_addr,
+                topic_id: t.topic_id,
+                name: t.name,
             }
+            .to_string(),
             Err(_) => ticket_str.to_string(),
         }
     }
@@ -112,7 +247,10 @@ impl PeerSpeakTicket {
     /// can't be parsed or carries no label. Pure; used to label the gathering both
     /// in the room UI and in the presence we report to friends.
     pub fn label_of(ticket_str: &str) -> String {
-        ticket_str.parse::<PeerSpeakTicket>().map(|t| t.name).unwrap_or_default()
+        ticket_str
+            .parse::<PeerSpeakTicket>()
+            .map(|t| t.name)
+            .unwrap_or_default()
     }
 
     /// The room's `topic_id` embedded in a ticket string, or `None` if the ticket
@@ -120,7 +258,10 @@ impl PeerSpeakTicket {
     /// the recents list (the host address and label change between members/sessions,
     /// but the topic uniquely identifies the gathering).
     pub fn topic_of(ticket_str: &str) -> Option<[u8; 32]> {
-        ticket_str.parse::<PeerSpeakTicket>().ok().map(|t| t.topic_id)
+        ticket_str
+            .parse::<PeerSpeakTicket>()
+            .ok()
+            .map(|t| t.topic_id)
     }
 }
 
@@ -143,8 +284,8 @@ impl FromStr for PeerSpeakTicket {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         let decoded = base64::Engine::decode(&base64::engine::general_purpose::URL_SAFE_NO_PAD, s)
             .map_err(|e| NetError::InvalidTicket(e.to_string()))?;
-        let ticket: PeerSpeakTicket = serde_json::from_slice(&decoded)
-            .map_err(|e| NetError::InvalidTicket(e.to_string()))?;
+        let ticket: PeerSpeakTicket =
+            serde_json::from_slice(&decoded).map_err(|e| NetError::InvalidTicket(e.to_string()))?;
         Ok(ticket)
     }
 }
@@ -194,9 +335,25 @@ pub trait RoomState: Send + Sync {
     /// Updates our local state (e.g. when user mutes/unmutes) and broadcasts it.
     async fn update_self_state(&self, self_state: PeerState) -> Result<(), NetError>;
 
+    /// Ask the active gossip topic to connect to retained peer addresses without
+    /// leaving or replacing the subscription. This is a recovery primitive only:
+    /// it does not add peers to the authenticated room roster. A peer becomes
+    /// active only after its normal signed `Announce` is received and verified.
+    async fn rebootstrap_peers(&self, peers: Vec<EndpointAddr>) -> Result<(), NetError>;
+
+    /// Remove a peer from the authenticated live roster before background
+    /// recovery. This only revokes membership; a fresh verified `Announce` is
+    /// required to add the peer again.
+    fn mark_peer_disconnected(&self, peer_id: EndpointId);
+
     /// Broadcasts a room text-chat message authored by us (our display name is
-    /// taken from the current self-state).
-    async fn send_chat(&self, text: String) -> Result<(), NetError>;
+    /// taken from the current self-state), optionally carrying a file attachment
+    /// descriptor whose bytes are served separately on the file plane.
+    async fn send_chat(
+        &self,
+        text: String,
+        attachment: Option<crate::files::ChatAttachment>,
+    ) -> Result<(), NetError>;
 
     /// Leaves the room and announces departure.
     async fn leave(&self) -> Result<(), NetError>;
@@ -208,13 +365,13 @@ pub trait RoomState: Send + Sync {
     async fn subscribe_events(&self) -> Result<Receiver<RoomEvent>, NetError>;
 }
 
-pub mod iroh_impl;
 pub mod gossip;
+pub mod iroh_impl;
 
 #[cfg(test)]
 mod tests {
     use super::*;
-    use iroh::{SecretKey, EndpointAddr};
+    use iroh::{EndpointAddr, SecretKey};
 
     fn sample_peer_state() -> PeerState {
         let secret = SecretKey::generate();
@@ -226,6 +383,8 @@ mod tests {
             addr,
             sharing: None,
             avatar: crate::avatar::Avatar::default(),
+            game: None,
+            music: None,
         }
     }
 
@@ -250,9 +409,12 @@ mod tests {
         let host = SecretKey::generate().public();
         let topic_id = [3u8; 32];
         // A labelled ticket: restamp keeps the label, label_of reads it.
-        let labelled =
-            PeerSpeakTicket { host_addr: EndpointAddr::from(host), topic_id, name: "HangOut".into() }
-                .to_string();
+        let labelled = PeerSpeakTicket {
+            host_addr: EndpointAddr::from(host),
+            topic_id,
+            name: "HangOut".into(),
+        }
+        .to_string();
         assert_eq!(PeerSpeakTicket::label_of(&labelled), "HangOut");
         let member = SecretKey::generate().public();
         let restamped = PeerSpeakTicket::restamp(&labelled, EndpointAddr::from(member));
@@ -289,10 +451,8 @@ mod tests {
 
         // valid URL-safe-base64 that decodes to non-JSON bytes
         let bad_json = b"hello world";
-        let encoded = base64::Engine::encode(
-            &base64::engine::general_purpose::URL_SAFE_NO_PAD,
-            bad_json,
-        );
+        let encoded =
+            base64::Engine::encode(&base64::engine::general_purpose::URL_SAFE_NO_PAD, bad_json);
         let res3 = encoded.parse::<PeerSpeakTicket>();
         assert!(matches!(res3, Err(NetError::InvalidTicket(_))));
     }
@@ -303,9 +463,12 @@ mod tests {
         let host = SecretKey::generate().public();
         let member = SecretKey::generate().public();
         let topic_id = [42u8; 32];
-        let original =
-            PeerSpeakTicket { host_addr: EndpointAddr::from(host), topic_id, name: "HangOut".into() }
-                .to_string();
+        let original = PeerSpeakTicket {
+            host_addr: EndpointAddr::from(host),
+            topic_id,
+            name: "HangOut".into(),
+        }
+        .to_string();
 
         let restamped_str = PeerSpeakTicket::restamp(&original, EndpointAddr::from(member));
         let restamped = restamped_str.parse::<PeerSpeakTicket>().unwrap();
@@ -320,18 +483,51 @@ mod tests {
     fn test_restamp_is_idempotent_for_same_addr() {
         let me = SecretKey::generate().public();
         let topic_id = [7u8; 32];
-        let mine =
-            PeerSpeakTicket { host_addr: EndpointAddr::from(me), topic_id, name: String::new() }
-                .to_string();
+        let mine = PeerSpeakTicket {
+            host_addr: EndpointAddr::from(me),
+            topic_id,
+            name: String::new(),
+        }
+        .to_string();
         // Re-stamping my own ticket with my own addr changes nothing.
-        assert_eq!(PeerSpeakTicket::restamp(&mine, EndpointAddr::from(me)), mine);
+        assert_eq!(
+            PeerSpeakTicket::restamp(&mine, EndpointAddr::from(me)),
+            mine
+        );
     }
 
     #[test]
     fn test_restamp_passes_through_unparseable() {
         let me = SecretKey::generate().public();
         // A malformed ticket is returned unchanged (the join will fail anyway).
-        assert_eq!(PeerSpeakTicket::restamp("not-a-ticket", EndpointAddr::from(me)), "not-a-ticket");
+        assert_eq!(
+            PeerSpeakTicket::restamp("not-a-ticket", EndpointAddr::from(me)),
+            "not-a-ticket"
+        );
+    }
+
+    #[test]
+    fn self_presence_builds_peer_state_with_volatile_fields() {
+        let addr = EndpointAddr::from(SecretKey::generate().public());
+        let presence = SelfPresence {
+            name: "Alice".to_string(),
+            avatar: crate::avatar::Avatar::default(),
+            game: Some("Half-Life 2".to_string()),
+            music: None,
+        };
+        // Volatile fields come from the call; sticky fields from the struct.
+        let muted = presence.to_state(true, addr.clone(), Some("ticket".to_string()));
+        assert_eq!(muted.name, "Alice");
+        assert!(muted.is_muted);
+        assert_eq!(muted.addr.id, addr.id);
+        assert_eq!(muted.sharing.as_deref(), Some("ticket"));
+        assert_eq!(muted.avatar, crate::avatar::Avatar::default());
+        assert_eq!(muted.game.as_deref(), Some("Half-Life 2"));
+        // The same sticky presence yields different volatile fields per announce.
+        let unmuted = presence.to_state(false, addr.clone(), None);
+        assert!(!unmuted.is_muted);
+        assert_eq!(unmuted.sharing, None);
+        assert_eq!(unmuted.name, muted.name);
     }
 
     #[test]
@@ -341,5 +537,21 @@ mod tests {
         let deserialized: PeerState = serde_json::from_str(&serialized).unwrap();
         assert_eq!(original, deserialized);
     }
-}
 
+    #[test]
+    fn music_presence_serde_round_trip() {
+        let original = MusicPresence {
+            id: [3u8; 32],
+            name: "track.ogg".to_string(),
+            size: 1234,
+            paused: false,
+            anchor_ms: 1_700_000_000_000,
+            position_ms: 42_000,
+            next_id: None,
+            next_size: None,
+        };
+        let serialized = serde_json::to_string(&original).unwrap();
+        let deserialized: MusicPresence = serde_json::from_str(&serialized).unwrap();
+        assert_eq!(original, deserialized);
+    }
+}

src/notify.rs

@@ -3,19 +3,24 @@
 //!
 //! The WAVs are embedded in the binary (`include_bytes!`) so a deployed single
 //! binary is self-contained — no asset directory to ship alongside it. On first
-//! use each sound is written once to a temp file, then played fire-and-forget
-//! via `pw-play` (PipeWire-native; falls back to `paplay`/`aplay`). Playback runs
-//! on a detached thread that waits on the child, so it never blocks the UI and
-//! never leaves a zombie. Any failure (no player, no audio) is silent by design —
-//! a missing chime should never disrupt a call.
+//! use each sound is written once to a temp file, then played fire-and-forget.
+//! Linux uses `pw-play` (PipeWire-native; falls back to `paplay`/`aplay`);
+//! Windows uses PowerShell's `System.Media.SoundPlayer`. Playback runs on a
+//! detached thread that waits on the child, so it never blocks the UI and never
+//! leaves a zombie. Any failure (no player, no audio) is silent by design — a
+//! missing chime should never disrupt a call.
 
 use std::collections::HashMap;
+use std::fs::OpenOptions;
+use std::io::Write;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
-use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU64, Ordering};
 use std::sync::{Mutex, OnceLock};
+use std::time::{SystemTime, UNIX_EPOCH};
 
 static ENABLED: AtomicBool = AtomicBool::new(true);
+static TEMP_WAV_COUNTER: AtomicU64 = AtomicU64::new(0);
 
 /// Per-sound enable flags (W6), indexed by `Sound::index`. The master `ENABLED`
 /// toggle gates everything; these silence individual events while the master
@@ -56,7 +61,6 @@ pub fn should_play(master_enabled: bool, sound_enabled: bool) -> bool {
     master_enabled && sound_enabled
 }
 
-
 /// A notification event with a distinct chime.
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum Sound {
@@ -76,6 +80,14 @@ pub enum Sound {
     MicToggle,
     /// Reconnect failed / peer evicted.
     ReconnectFailed,
+    /// One of our chat messages was broadcast to the room.
+    ChatSent,
+    /// A chat message from another participant was admitted.
+    ChatReceived,
+    /// A saved contact was detected online on the home screen.
+    ContactOnline,
+    /// A saved contact previously seen online went offline on the home screen.
+    ContactOffline,
 }
 
 impl Sound {
@@ -89,10 +101,14 @@ impl Sound {
         Sound::SelfLeave,
         Sound::MicToggle,
         Sound::ReconnectFailed,
+        Sound::ChatSent,
+        Sound::ChatReceived,
+        Sound::ContactOnline,
+        Sound::ContactOffline,
     ];
 
     /// Number of distinct notification events.
-    pub const COUNT: usize = 8;
+    pub const COUNT: usize = 12;
 
     /// Stable 0-based index into the per-sound flag array. Must match `ALL`.
     fn index(self) -> usize {
@@ -105,6 +121,10 @@ impl Sound {
             Sound::SelfLeave => 5,
             Sound::MicToggle => 6,
             Sound::ReconnectFailed => 7,
+            Sound::ChatSent => 8,
+            Sound::ChatReceived => 9,
+            Sound::ContactOnline => 10,
+            Sound::ContactOffline => 11,
         }
     }
 
@@ -119,6 +139,10 @@ impl Sound {
             Sound::SelfLeave => include_bytes!("../assets/sounds/self-leave.wav"),
             Sound::MicToggle => include_bytes!("../assets/sounds/mic-toggle.wav"),
             Sound::ReconnectFailed => include_bytes!("../assets/sounds/reconnect-failed.wav"),
+            Sound::ChatSent => include_bytes!("../assets/sounds/chat-sent.wav"),
+            Sound::ChatReceived => include_bytes!("../assets/sounds/chat-received.wav"),
+            Sound::ContactOnline => include_bytes!("../assets/sounds/contact-online.wav"),
+            Sound::ContactOffline => include_bytes!("../assets/sounds/contact-offline.wav"),
         }
     }
 
@@ -133,6 +157,10 @@ impl Sound {
             Sound::SelfLeave => "self-leave",
             Sound::MicToggle => "mic-toggle",
             Sound::ReconnectFailed => "reconnect-failed",
+            Sound::ChatSent => "chat-sent",
+            Sound::ChatReceived => "chat-received",
+            Sound::ContactOnline => "contact-online",
+            Sound::ContactOffline => "contact-offline",
         }
     }
 }
@@ -194,16 +222,46 @@ fn cached_path(sound: Sound) -> Option<PathBuf> {
     if let Some(path) = guard.get(sound.name()) {
         return Some(path.clone());
     }
-    let path = std::env::temp_dir().join(format!("peerspeak-{}.wav", sound.name()));
-    if std::fs::write(&path, sound.bytes()).is_err() {
-        return None;
-    }
+    let path = match write_private_wav(&std::env::temp_dir(), sound.name(), sound.bytes()) {
+        Ok(path) => path,
+        Err(_) => return None,
+    };
     guard.insert(sound.name(), path.clone());
     Some(path)
 }
 
+fn write_private_wav(dir: &Path, stem: &str, bytes: &[u8]) -> std::io::Result<PathBuf> {
+    let counter = TEMP_WAV_COUNTER.fetch_add(1, Ordering::Relaxed);
+    let nanos = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_nanos();
+    let path = dir.join(format!(
+        "peerspeak-{stem}-{}-{counter}-{nanos}.wav",
+        std::process::id()
+    ));
+
+    let mut options = OpenOptions::new();
+    options.write(true).create_new(true);
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::OpenOptionsExt;
+        options.mode(0o600);
+    }
+
+    let mut file = options.open(&path)?;
+    file.write_all(bytes)?;
+    Ok(path)
+}
+
+#[cfg(any(windows, test))]
+fn escape_powershell_single_quoted(s: &str) -> String {
+    s.replace('\'', "''")
+}
+
 /// Try each available player in turn, waiting on the first that starts (which
 /// reaps the child). Runs on a detached thread, so the wait is harmless.
+#[cfg(not(windows))]
 fn spawn_player(path: &Path) {
     for player in ["pw-play", "paplay", "aplay"] {
         let started = Command::new(player)
@@ -221,10 +279,40 @@ fn spawn_player(path: &Path) {
     }
 }
 
+/// Play through Windows' built-in WAV player. Runs on a detached thread, so
+/// `PlaySync()` blocking for the sound duration is fine.
+#[cfg(windows)]
+fn spawn_player(path: &Path) {
+    let path = escape_powershell_single_quoted(&path.display().to_string());
+    let command = format!("(New-Object System.Media.SoundPlayer '{path}').PlaySync()");
+    let _ = Command::new("powershell")
+        .arg("-NoProfile")
+        .arg("-NonInteractive")
+        .arg("-Command")
+        .arg(command)
+        .stdin(Stdio::null())
+        .stdout(Stdio::null())
+        .stderr(Stdio::null())
+        .status();
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    static TEST_TEMP_COUNTER: AtomicU64 = AtomicU64::new(0);
+
+    fn temp_wav_dir(tag: &str) -> PathBuf {
+        let counter = TEST_TEMP_COUNTER.fetch_add(1, Ordering::Relaxed);
+        let dir = std::env::temp_dir().join(format!(
+            "peerspeak-notifytest-{}-{tag}-{counter}",
+            std::process::id()
+        ));
+        let _ = std::fs::remove_dir_all(&dir);
+        std::fs::create_dir_all(&dir).unwrap();
+        dir
+    }
+
     #[test]
     fn test_should_play_truth_table() {
         // Plays only when BOTH the master and the per-sound flag are on.
@@ -234,6 +322,15 @@ mod tests {
         assert!(!should_play(false, false));
     }
 
+    #[test]
+    fn test_powershell_single_quote_escape() {
+        assert_eq!(
+            escape_powershell_single_quoted(r"C:\Users\O'Brien\chime.wav"),
+            r"C:\Users\O''Brien\chime.wav"
+        );
+        assert_eq!(escape_powershell_single_quoted("a'b'c"), "a''b''c");
+    }
+
     #[test]
     fn test_sound_indices_unique_and_match_all() {
         // `index()` must be a 0..COUNT bijection in `ALL` order, or the flag
@@ -261,7 +358,10 @@ mod tests {
             // bare `~` -> home dir
             assert_eq!(expand_tilde("~"), home);
             // `~/sub/dir/file.wav` -> home joined with `sub/dir/file.wav`
-            assert_eq!(expand_tilde("~/sub/dir/file.wav"), home.join("sub/dir/file.wav"));
+            assert_eq!(
+                expand_tilde("~/sub/dir/file.wav"),
+                home.join("sub/dir/file.wav")
+            );
         }
         // absolute path (`/etc/foo.wav`) -> unchanged
         assert_eq!(expand_tilde("/etc/foo.wav"), PathBuf::from("/etc/foo.wav"));
@@ -274,10 +374,19 @@ mod tests {
         // leading/trailing whitespace is trimmed
         if let Some(home) = dirs::home_dir() {
             assert_eq!(expand_tilde("  ~  "), home);
-            assert_eq!(expand_tilde("  ~/sub/dir/file.wav  "), home.join("sub/dir/file.wav"));
+            assert_eq!(
+                expand_tilde("  ~/sub/dir/file.wav  "),
+                home.join("sub/dir/file.wav")
+            );
         }
-        assert_eq!(expand_tilde("  /etc/foo.wav  "), PathBuf::from("/etc/foo.wav"));
-        assert_eq!(expand_tilde("  foo/bar.wav  "), PathBuf::from("foo/bar.wav"));
+        assert_eq!(
+            expand_tilde("  /etc/foo.wav  "),
+            PathBuf::from("/etc/foo.wav")
+        );
+        assert_eq!(
+            expand_tilde("  foo/bar.wav  "),
+            PathBuf::from("foo/bar.wav")
+        );
     }
 
     #[test]
@@ -296,4 +405,61 @@ mod tests {
         // a `~`-prefixed path that resolves to a non-existent file -> Some(false)
         assert_eq!(validate_custom_path("~/non/existent/file.wav"), Some(false));
     }
+
+    #[test]
+    fn write_private_wav_writes_exact_bytes() {
+        let dir = temp_wav_dir("writes");
+        let bytes = b"RIFFpeerspeak-test";
+
+        let path = write_private_wav(&dir, "unit", bytes).unwrap();
+
+        assert!(path.exists());
+        assert_eq!(std::fs::read(&path).unwrap(), bytes);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn write_private_wav_creates_0600_file() {
+        use std::os::unix::fs::PermissionsExt;
+
+        let dir = temp_wav_dir("mode");
+        let path = write_private_wav(&dir, "unit", b"mode").unwrap();
+
+        let mode = std::fs::metadata(&path).unwrap().permissions().mode() & 0o777;
+        assert_eq!(mode, 0o600);
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn write_private_wav_uses_unique_paths() {
+        let dir = temp_wav_dir("unique");
+
+        let first = write_private_wav(&dir, "same-stem", b"first").unwrap();
+        let second = write_private_wav(&dir, "same-stem", b"second").unwrap();
+
+        assert_ne!(first, second);
+        assert!(first.exists());
+        assert!(second.exists());
+        assert_eq!(std::fs::read(&first).unwrap(), b"first");
+        assert_eq!(std::fs::read(&second).unwrap(), b"second");
+        let _ = std::fs::remove_dir_all(&dir);
+    }
+
+    #[test]
+    fn create_new_refuses_existing_path() {
+        let dir = temp_wav_dir("create-new");
+        let path = dir.join("preexisting.wav");
+        std::fs::write(&path, b"original").unwrap();
+
+        let err = std::fs::OpenOptions::new()
+            .write(true)
+            .create_new(true)
+            .open(&path)
+            .unwrap_err();
+
+        assert_eq!(err.kind(), std::io::ErrorKind::AlreadyExists);
+        assert_eq!(std::fs::read(&path).unwrap(), b"original");
+        let _ = std::fs::remove_dir_all(&dir);
+    }
 }

src/playlist.rs

@@ -0,0 +1,115 @@
+use std::path::{Path, PathBuf};
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+pub enum PlaylistKind {
+    M3u,
+    Pls,
+}
+
+/// Classify a path by extension into a playlist kind, or None if it is not a
+/// recognized playlist file. Case-insensitive: m3u/m3u8 -> M3u, pls -> Pls.
+pub fn playlist_kind(path: &Path) -> Option<PlaylistKind> {
+    let ext = path.extension()?.to_string_lossy();
+    match ext.to_ascii_lowercase().as_str() {
+        "m3u" | "m3u8" => Some(PlaylistKind::M3u),
+        "pls" => Some(PlaylistKind::Pls),
+        _ => None,
+    }
+}
+
+/// Parse an m3u/m3u8 or pls playlist into local audio file paths. Remote entries
+/// (http/https/ftp URLs) and non-audio entries are skipped; relative paths are
+/// resolved against `base_dir` (the playlist file's parent directory). Order is
+/// preserved. Does not touch the filesystem.
+pub fn parse_playlist(contents: &str, base_dir: &Path, kind: PlaylistKind) -> Vec<PathBuf> {
+    let entries: Vec<&str> = match kind {
+        PlaylistKind::M3u => contents
+            .lines()
+            .map(str::trim)
+            .filter(|line| !line.is_empty() && !line.starts_with('#'))
+            .collect(),
+        PlaylistKind::Pls => contents
+            .lines()
+            .filter_map(|line| {
+                let (key, value) = line.split_once('=')?;
+                key.trim()
+                    .to_ascii_lowercase()
+                    .starts_with("file")
+                    .then_some(value.trim())
+            })
+            .filter(|line| !line.is_empty())
+            .collect(),
+    };
+
+    entries
+        .into_iter()
+        .filter_map(|entry| playlist_entry_path(entry, base_dir))
+        .collect()
+}
+
+fn playlist_entry_path(entry: &str, base_dir: &Path) -> Option<PathBuf> {
+    let lower = entry.to_ascii_lowercase();
+    if lower.starts_with("http://") || lower.starts_with("https://") || lower.starts_with("ftp://")
+    {
+        return None;
+    }
+
+    let path = Path::new(entry);
+    let resolved = if path.is_absolute() {
+        path.to_path_buf()
+    } else {
+        base_dir.join(path)
+    };
+    let file_name = resolved.file_name()?.to_string_lossy();
+    crate::files::looks_like_audio_name(&file_name).then_some(resolved)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn m3u_skips_comments_and_remote_urls() {
+        let base = Path::new("/music/lists");
+        let contents = "\
+#EXTM3U
+#EXTINF:123,Artist - Song
+tracks/song.ogg
+https://example.com/stream.mp3
+";
+        assert_eq!(
+            parse_playlist(contents, base, PlaylistKind::M3u),
+            vec![PathBuf::from("/music/lists/tracks/song.ogg")]
+        );
+    }
+
+    #[test]
+    fn pls_keeps_file_values_and_skips_non_audio() {
+        let base = Path::new("/music");
+        let contents = "\
+[playlist]
+File1=one.flac
+Title1=One
+File2=notes.txt
+File3=/var/audio/two.MP3
+";
+        assert_eq!(
+            parse_playlist(contents, base, PlaylistKind::Pls),
+            vec![
+                PathBuf::from("/music/one.flac"),
+                PathBuf::from("/var/audio/two.MP3"),
+            ]
+        );
+    }
+
+    #[test]
+    fn playlist_kind_is_case_insensitive() {
+        assert_eq!(playlist_kind(Path::new("mix.M3U")), Some(PlaylistKind::M3u));
+        assert_eq!(
+            playlist_kind(Path::new("mix.m3u8")),
+            Some(PlaylistKind::M3u)
+        );
+        assert_eq!(playlist_kind(Path::new("mix.PLS")), Some(PlaylistKind::Pls));
+        assert_eq!(playlist_kind(Path::new("mix.txt")), None);
+    }
+}

src/presence.rs

@@ -36,8 +36,11 @@ pub enum PresenceMode {
 
 impl PresenceMode {
     /// All postures, default first — the option list for the Settings/home picker.
-    pub const ALL: [PresenceMode; 3] =
-        [PresenceMode::Normal, PresenceMode::Invisible, PresenceMode::Discoverable];
+    pub const ALL: [PresenceMode; 3] = [
+        PresenceMode::Normal,
+        PresenceMode::Invisible,
+        PresenceMode::Discoverable,
+    ];
 
     /// Whether this posture publishes to discovery (the only mode that does).
     pub fn publishes_to_discovery(self) -> bool {
@@ -100,7 +103,11 @@ pub fn should_answer(from: &EndpointId, friends: &FriendStore, mode: PresenceMod
     mode.answers_pings() && friends.contains(from)
 }
 
-/// What we learned about a friend from a successful ping reply.
+/// What we learned about a friend's reachability. `Online`/`InRoom` come from a
+/// successful ping reply (see [`interpret_pong`]); `Offline` is produced by the
+/// presence scheduler when a probe fails or the friend has no known address, so a
+/// friend who drops or leaves is *actively* downgraded rather than left showing a
+/// stale status. The UI also treats a missing entry as offline.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub enum FriendPresence {
     /// Online, but not in a gathering we can join.
@@ -108,6 +115,8 @@ pub enum FriendPresence {
     /// Online and in a joinable gathering (name already sanitized, ticket already
     /// validated as parseable).
     InRoom { name: String, ticket: String },
+    /// Unreachable: the probe failed, or we have no address to probe yet.
+    Offline,
 }
 
 /// Interpret a peer's reply defensively. `from` must be the connection's
@@ -140,6 +149,20 @@ pub fn interpret_pong(msg: &ControlMsg, from: EndpointId) -> Option<FriendPresen
     }
 }
 
+/// Map a single probe outcome to a definitive [`FriendPresence`], used by the
+/// presence scheduler. `Some((reply, from))` is a received message from the
+/// authenticated remote `from`; `None` means the probe failed (offline /
+/// unreachable / refused). Anything that doesn't interpret as a real presence —
+/// a probe error, or a non-`Pong` reply — becomes [`FriendPresence::Offline`], so
+/// a friend who drops is actively downgraded instead of keeping a stale status.
+/// Pure so the scheduler's downgrade behaviour is unit-testable without a network.
+pub fn presence_from_probe(reply: Option<(&ControlMsg, EndpointId)>) -> FriendPresence {
+    match reply {
+        Some((msg, from)) => interpret_pong(msg, from).unwrap_or(FriendPresence::Offline),
+        None => FriendPresence::Offline,
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -173,7 +196,11 @@ mod tests {
         assert!(!should_answer(&friend, &friends, PresenceMode::Invisible));
         // Stranger is NEVER answered, in any mode.
         assert!(!should_answer(&stranger, &friends, PresenceMode::Normal));
-        assert!(!should_answer(&stranger, &friends, PresenceMode::Discoverable));
+        assert!(!should_answer(
+            &stranger,
+            &friends,
+            PresenceMode::Discoverable
+        ));
         assert!(!should_answer(&stranger, &friends, PresenceMode::Invisible));
     }
 
@@ -194,7 +221,10 @@ mod tests {
             ControlMsg::Ping,
             ControlMsg::Pong { room: None },
             ControlMsg::Pong {
-                room: Some(RoomPresence { name: "HangOut".into(), ticket: "abc".into() }),
+                room: Some(RoomPresence {
+                    name: "HangOut".into(),
+                    ticket: "abc".into(),
+                }),
             },
         ];
         for msg in cases {
@@ -225,19 +255,37 @@ mod tests {
         );
         // Valid ticket -> InRoom with a sanitized name.
         let t = valid_ticket(friend);
-        let got = interpret_pong(&ControlMsg::Pong {
-            room: Some(RoomPresence { name: "HangOut".into(), ticket: t.clone() }),
-        }, friend);
-        assert_eq!(got, Some(FriendPresence::InRoom { name: "HangOut".into(), ticket: t }));
+        let got = interpret_pong(
+            &ControlMsg::Pong {
+                room: Some(RoomPresence {
+                    name: "HangOut".into(),
+                    ticket: t.clone(),
+                }),
+            },
+            friend,
+        );
+        assert_eq!(
+            got,
+            Some(FriendPresence::InRoom {
+                name: "HangOut".into(),
+                ticket: t
+            })
+        );
     }
 
     #[test]
     fn interpret_pong_downgrades_a_garbage_ticket_to_online() {
         // A friend reporting a room with an unparseable ticket is treated as just
         // Online — no dead/hostile Join button is surfaced.
-        let got = interpret_pong(&ControlMsg::Pong {
-            room: Some(RoomPresence { name: "Trap".into(), ticket: "not-a-ticket".into() }),
-        }, id());
+        let got = interpret_pong(
+            &ControlMsg::Pong {
+                room: Some(RoomPresence {
+                    name: "Trap".into(),
+                    ticket: "not-a-ticket".into(),
+                }),
+            },
+            id(),
+        );
         assert_eq!(got, Some(FriendPresence::Online));
     }
 
@@ -246,20 +294,67 @@ mod tests {
         let friend = id();
         let attacker = id();
         let t = valid_ticket(attacker);
-        let got = interpret_pong(&ControlMsg::Pong {
-            room: Some(RoomPresence { name: "Redirect".into(), ticket: t }),
-        }, friend);
+        let got = interpret_pong(
+            &ControlMsg::Pong {
+                room: Some(RoomPresence {
+                    name: "Redirect".into(),
+                    ticket: t,
+                }),
+            },
+            friend,
+        );
         assert_eq!(got, Some(FriendPresence::Online));
     }
 
+    #[test]
+    fn presence_from_probe_maps_outcomes_to_definitive_status() {
+        let friend = id();
+        // A failed probe (no reply) is an explicit downgrade to Offline, so the UI
+        // clears a friend who has dropped instead of keeping a stale status.
+        assert_eq!(presence_from_probe(None), FriendPresence::Offline);
+        // A successful Pong with no room is Online.
+        assert_eq!(
+            presence_from_probe(Some((&ControlMsg::Pong { room: None }, friend))),
+            FriendPresence::Online
+        );
+        // A successful Pong advertising the friend's own room is InRoom.
+        let t = valid_ticket(friend);
+        assert_eq!(
+            presence_from_probe(Some((
+                &ControlMsg::Pong {
+                    room: Some(RoomPresence {
+                        name: "Den".into(),
+                        ticket: t.clone()
+                    })
+                },
+                friend,
+            ))),
+            FriendPresence::InRoom {
+                name: "Den".into(),
+                ticket: t
+            }
+        );
+        // A non-reply (a stray Ping) is not a presence -> Offline, never a false Online.
+        assert_eq!(
+            presence_from_probe(Some((&ControlMsg::Ping, friend))),
+            FriendPresence::Offline
+        );
+    }
+
     #[test]
     fn interpret_pong_sanitizes_a_hostile_room_name() {
         // Control/bidi characters in a peer-supplied name are stripped.
         let friend = id();
         let t = valid_ticket(friend);
-        let got = interpret_pong(&ControlMsg::Pong {
-            room: Some(RoomPresence { name: "Hang\u{202e}Out\u{0007}".into(), ticket: t.clone() }),
-        }, friend);
+        let got = interpret_pong(
+            &ControlMsg::Pong {
+                room: Some(RoomPresence {
+                    name: "Hang\u{202e}Out\u{0007}".into(),
+                    ticket: t.clone(),
+                }),
+            },
+            friend,
+        );
         match got {
             Some(FriendPresence::InRoom { name, .. }) => {
                 assert!(!name.contains('\u{202e}'), "bidi override must be stripped");