packaging(win): update INSTALL.md + README.md for 0.3.0

- INSTALL.md: bump the setup filename to 0.3.0; add an end-user section
  on text chat + sending photos/files (inline images, file chips,
  Save/Download, 25 MB cap, session-only); note that both ends must run
  the same version under "won't connect".
- README.md: add a Version compatibility section (installer version
  tracks Cargo; a 0.x MINOR bump is a breaking wire change so everyone
  must reinstall; 0.3.0 can't talk to 0.2.x).

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.lock

@@ -4742,7 +4742,7 @@ checksum = "35fb2e5f958ec131621fdd531e9fc186ed768cbe395337403ae56c17a74c68ec"
 
 [[package]]
 name = "peerspeak"
-version = "0.2.0"
+version = "0.3.0"
 dependencies = [
  "anyhow",
  "async-trait",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "peerspeak"
-version = "0.2.0"
+version = "0.3.0"
 edition = "2024"
 # Application crate, not a crates.io library — refuse `cargo publish` and let
 # cargo-deny's [licenses.private] skip the missing-license check.

packaging/PKGBUILD

@@ -1,7 +1,7 @@
 # Maintainer: mollusk <jitty+lc1iz0dc@protonmail.com>
 pkgname=peerspeak-git
 _pkgname=peerspeak
-pkgver=0.1.0
+pkgver=0.2.0.r218.gcbba4b6
 pkgrel=1
 pkgdesc="Decentralized peer-to-peer voice chat (Rust/iroh/PipeWire/Opus/iced)"
 arch=('x86_64')

packaging/windows/INSTALL.md

@@ -8,7 +8,7 @@ it once, then you and I connect directly to each other.
 
 ## 1. Install it
 
-1. Double-click **`peerspeak-0.2.0-setup.exe`** (the file I sent you).
+1. Double-click **`peerspeak-0.3.0-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
@@ -69,13 +69,39 @@ Either way works the same; it just depends on who makes the 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.
+  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.
 

packaging/windows/README.md

@@ -9,6 +9,18 @@ notification chimes, and avatar presets are all embedded in the binary
 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 crate version in `Cargo.toml` (currently
+**0.3.0**) — keep `MyAppVersion` in `peerspeak.iss` in sync when it changes.
+
+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 |

packaging/windows/peerspeak.iss

@@ -12,7 +12,7 @@
 ; (x86_64-pc-windows-gnu, statically linked -- no extra DLLs needed).
 
 #define MyAppName "PeerSpeak"
-#define MyAppVersion "0.2.0"
+#define MyAppVersion "0.3.0"
 #define MyAppPublisher "mollusk"
 #define MyAppExeName "peerspeak.exe"
 

src/app/mod.rs

@@ -114,6 +114,19 @@ struct ChatEntry {
     /// Sender's node id string, used to key their avatar colour (W4). `None` only
     /// for any future system-generated lines.
     from: Option<String>,
+    /// Optional file attachment descriptor. The bytes (if fetched) live in
+    /// `AppState.attachment_data` keyed by `attachment.id`; the entry only holds
+    /// the descriptor so history stays cheap.
+    attachment: Option<crate::files::ChatAttachment>,
+}
+
+/// Fetch state of a chat attachment's bytes (session-only).
+#[derive(Debug, Clone)]
+enum AttachmentState {
+    /// Bytes in hand (image decoded-valid, or a file ready to save).
+    Ready(Vec<u8>),
+    /// Fetch or decode failed; carries a short reason for the UI.
+    Failed(String),
 }
 
 /// Cap on retained chat history so a long call can't grow it without bound.
@@ -208,6 +221,7 @@ pub enum AppMessage {
     ClearHotkey(HotkeyAction),
     PeerVolumeChanged(EndpointId, f32),
     PeerPanChanged(EndpointId, f32),
+    PeerGateChanged(EndpointId, f32),
     PeerEqChanged(EndpointId, EqBand, f32),
     /// Toggle local mute of a peer (silence them just for us).
     TogglePeerMute(EndpointId),
@@ -263,6 +277,12 @@ pub enum AppMessage {
     ToggleRecording,
     /// Live edits to the chat input line.
     ChatInputChanged(String),
+    /// Open the native picker to attach a file to the chat.
+    PickAttachmentFile,
+    /// Result of the attach picker: (filename, bytes), or None if cancelled.
+    AttachmentFilePicked(Option<(String, Vec<u8>)>),
+    /// Save (downloading first if needed) a received attachment to disk.
+    SaveAttachment(crate::files::AttachmentId),
     /// Send the current chat input line (Enter or the Send button).
     ChatSubmit,
     /// Open a clicked chat link in the system browser (A13).
@@ -290,6 +310,15 @@ pub enum AppMessage {
     /// Result of the avatar file picker: the chosen file's raw bytes, or `None`
     /// if the user cancelled.
     AvatarFilePicked(Option<Vec<u8>>),
+    /// Open the native file picker to choose a custom UI background image (W16).
+    PickBackgroundFile,
+    /// Result of the background file picker: the chosen file's raw bytes, or
+    /// `None` if the user cancelled.
+    BackgroundFilePicked(Option<Vec<u8>>),
+    /// Clear the custom background, reverting to the theme background (W16).
+    RemoveBackground,
+    /// Set the background legibility scrim strength (0.0..=1.0) (W16).
+    SetBackgroundDim(f32),
     /// Toggle the Chat drawer open/closed (drawer layout).
     ToggleDrawerChat,
     /// Start/stop sharing our own screen (spawns/kills a pixelpass host).
@@ -335,8 +364,11 @@ pub struct AppState {
     selected_input: Option<AudioDevice>,
     selected_output: Option<AudioDevice>,
     config: AppConfig,
+    /// Decoded bytes of the custom background image (W16), cached so `view()`
+    /// doesn't read the file from disk on every redraw. Loaded on startup and
+    /// refreshed when the background is changed/removed. `None` = no custom bg.
+    background_image: Option<bytes::Bytes>,
     peers: HashMap<EndpointId, PeerState>,
-    peer_volumes: HashMap<EndpointId, f32>,
     audio_levels: HashMap<EndpointId, f32>,
     /// Peers we've locally muted (their audio isn't mixed into our output).
     locally_muted: HashSet<EndpointId>,
@@ -349,6 +381,15 @@ pub struct AppState {
     /// Room text-chat history (newest last) and the pending input line.
     chat_messages: Vec<ChatEntry>,
     chat_input: String,
+    /// Fetched/failed state for chat attachments, keyed by attachment id.
+    /// Session-only (cleared on leave); never persisted.
+    attachment_data: HashMap<crate::files::AttachmentId, AttachmentState>,
+    /// Cached iced image handles for ready image attachments, keyed by id, so we
+    /// don't re-upload to the GPU every redraw (the e917c53 avatar flicker fix).
+    image_handle_cache: HashMap<crate::files::AttachmentId, iced::widget::image::Handle>,
+    /// Attachment ids the user asked to save before the bytes arrived; when the
+    /// fetch completes a save dialog is opened for them.
+    pending_saves: std::collections::HashSet<crate::files::AttachmentId>,
     /// Last known window size, tracked so divider clamps stay valid on resize.
     /// (The divider positions themselves are persisted in `config`.)
     window_size: Size,
@@ -461,6 +502,16 @@ impl Default for AppState {
                 let _ = controller.send(CoreCommand::SetPeerPan(id, *pan));
             }
         }
+        for (peer, volume) in &config.peer_volume {
+            if let Ok(id) = peer.parse::<EndpointId>() {
+                let _ = controller.send(CoreCommand::SetPeerVolume(id, *volume));
+            }
+        }
+        for (peer, threshold) in &config.peer_gate {
+            if let Ok(id) = peer.parse::<EndpointId>() {
+                let _ = controller.send(CoreCommand::SetPeerGate(id, *threshold));
+            }
+        }
         let pixelpass_available =
             crate::screenshare::is_available(config.pixelpass_path.as_deref());
         let all_devices = enumerate_audio_devices();
@@ -470,6 +521,7 @@ impl Default for AppState {
         let selected_input = input_devices.iter().find(|d| d.name == config.input_device).cloned();
         let selected_output = output_devices.iter().find(|d| d.name == config.output_device).cloned();
 
+        let background_image = load_background_bytes(&config);
 
         Self {
             // Pre-fill the nickname with the last one used (or "Peer" by default).
@@ -489,14 +541,17 @@ impl Default for AppState {
             selected_input,
             selected_output,
             config,
+            background_image,
             peers: HashMap::new(),
-            peer_volumes: HashMap::new(),
             audio_levels: HashMap::new(),
             locally_muted: HashSet::new(),
             call_started: None,
             recording: false,
             recording_started: None,
             chat_messages: Vec::new(),
+            attachment_data: HashMap::new(),
+            image_handle_cache: HashMap::new(),
+            pending_saves: std::collections::HashSet::new(),
             chat_input: String::new(),
             window_size: Size::new(ww, wh),
             layout_picker_open: false,
@@ -533,6 +588,15 @@ fn theme(state: &AppState) -> Theme {
     state.config.theme.base_theme()
 }
 
+/// Read the custom background PNG (W16) from disk into memory, if one is set and
+/// readable. Called once on startup and whenever the background changes, so the
+/// per-frame `view()` never touches the filesystem. A missing/unreadable file
+/// silently yields `None` (the UI falls back to the theme background).
+fn load_background_bytes(config: &AppConfig) -> Option<bytes::Bytes> {
+    let path = config.background.as_deref()?;
+    std::fs::read(path).ok().map(bytes::Bytes::from)
+}
+
 pub fn run_gui() -> iced::Result {
     // Restore the last window size (saved on close). Position is restored too,
     // but only on X11 — Wayland's xdg-shell gives clients no way to set their own
@@ -540,7 +604,7 @@ pub fn run_gui() -> iced::Result {
     let saved = AppConfig::load();
     let init_size = iced::Size::new(saved.window_width, saved.window_height);
     let init_position = initial_window_position(saved.window_x, saved.window_y, is_wayland());
-    iced::application(AppState::default, update, view)
+    iced::application(AppState::default, update, view_with_background)
         .title("PeerSpeak P2P Voice Chat")
         .theme(theme)
         .subscription(subscription)
@@ -720,6 +784,34 @@ fn set_peer_pan_config(config: &mut AppConfig, id: EndpointId, pan: f32) -> f32
     pan
 }
 
+/// Store the per-peer listener volume, clamped to the slider range. Unity gain
+/// (`1.0`) is the implicit default, so an at-unity entry is removed rather than
+/// stored to keep the config tidy. Returns the clamped value.
+fn set_peer_volume_config(config: &mut AppConfig, id: EndpointId, volume: f32) -> f32 {
+    let volume = volume.clamp(0.0, 2.0);
+    let key = id.to_string();
+    if (volume - 1.0).abs() <= 0.001 {
+        config.peer_volume.remove(&key);
+    } else {
+        config.peer_volume.insert(key, volume);
+    }
+    volume
+}
+
+/// Store the per-peer listener noise-gate threshold, clamped to the slider
+/// range. `0.0` means the gate is off, so an at-zero entry is removed rather
+/// than stored. Returns the clamped value.
+fn set_peer_gate_config(config: &mut AppConfig, id: EndpointId, threshold: f32) -> f32 {
+    let threshold = threshold.clamp(0.0, METER_MAX);
+    let key = id.to_string();
+    if threshold <= 0.0 {
+        config.peer_gate.remove(&key);
+    } else {
+        config.peer_gate.insert(key, threshold);
+    }
+    threshold
+}
+
 fn peer_eq_settings(config: &AppConfig, id: &EndpointId) -> EqSettings {
     config
         .peer_eq
@@ -935,19 +1027,45 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.recording_started = None;
                     state.status_message = format!("Saved recording → {path}");
                 }
-                UiEvent::ChatMessage { from, name, text } => {
+                UiEvent::ChatMessage { from, name, text, attachment } => {
                     // Incoming peer content is untrusted — sanitize name + text.
+                    // (The attachment filename was already sanitized in core.)
                     let text = sanitize_chat(&text);
-                    if !text.is_empty() {
+                    // Keep the message if it has visible text OR an attachment (an
+                    // image with no caption is still a real message).
+                    if !text.is_empty() || attachment.is_some() {
                         let name = sanitize_chat(&name);
                         push_chat(&mut state.chat_messages, ChatEntry {
                             name,
                             text,
                             mine: false,
                             from: Some(from),
+                            attachment,
                         });
                     }
                 }
+                UiEvent::AttachmentReady { id, data } => {
+                    // Bytes arrived. For images we can cache the iced handle now
+                    // (built once, not per redraw). If the user was waiting to save
+                    // this file, the save dialog is opened from update() below by
+                    // checking pending_saves — done lazily so this arm stays simple.
+                    if crate::files::validate_image_bytes(&data).is_some() {
+                        state.image_handle_cache.insert(
+                            id,
+                            iced::widget::image::Handle::from_bytes(data.clone()),
+                        );
+                    }
+                    let needs_save = state.pending_saves.remove(&id);
+                    state.attachment_data.insert(id, AttachmentState::Ready(data));
+                    if needs_save {
+                        save_attachment_to_disk(state, id);
+                    }
+                }
+                UiEvent::AttachmentFailed { id, error } => {
+                    state.pending_saves.remove(&id);
+                    state.attachment_data.insert(id, AttachmentState::Failed(error.clone()));
+                    state.status_message = format!("Attachment failed: {error}");
+                }
                 UiEvent::ScreenShareStarted => {
                     state.self_sharing = true;
                     state.status_message = "Sharing your screen".to_string();
@@ -1014,13 +1132,17 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
             state.config.save();
         }
         AppMessage::PeerVolumeChanged(id, vol) => {
-            state.peer_volumes.insert(id, vol);
+            let vol = set_peer_volume_config(&mut state.config, id, vol);
             let _ = state.controller.send(CoreCommand::SetPeerVolume(id, vol));
         }
         AppMessage::PeerPanChanged(id, pan) => {
             let pan = set_peer_pan_config(&mut state.config, id, pan);
             let _ = state.controller.send(CoreCommand::SetPeerPan(id, pan));
         }
+        AppMessage::PeerGateChanged(id, threshold) => {
+            let threshold = set_peer_gate_config(&mut state.config, id, threshold);
+            let _ = state.controller.send(CoreCommand::SetPeerGate(id, threshold));
+        }
         AppMessage::PeerEqChanged(id, band, gain_db) => {
             let settings = set_peer_eq_config(&mut state.config, id, band, gain_db);
             let _ = state.controller.send(CoreCommand::SetPeerEq(id, settings));
@@ -1347,6 +1469,73 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                 }
             }
         }
+        AppMessage::PickBackgroundFile => {
+            // Native picker off the UI thread; result returns as BackgroundFilePicked.
+            return Task::perform(
+                async {
+                    let handle = rfd::AsyncFileDialog::new()
+                        .add_filter("Images", &["png", "jpg", "jpeg", "webp", "bmp"])
+                        .set_title("Choose a background image")
+                        .pick_file()
+                        .await;
+                    match handle {
+                        Some(h) => Some(h.read().await),
+                        None => None,
+                    }
+                },
+                AppMessage::BackgroundFilePicked,
+            );
+        }
+        AppMessage::BackgroundFilePicked(picked) => {
+            if let Some(bytes) = picked {
+                match crate::background::process_background(&bytes) {
+                    Ok(png) => match AppConfig::background_path() {
+                        Some(path) => {
+                            if let Some(dir) = path.parent() {
+                                let _ = std::fs::create_dir_all(dir);
+                            }
+                            match std::fs::write(&path, &png) {
+                                Ok(()) => {
+                                    state.config.background =
+                                        Some(path.to_string_lossy().into_owned());
+                                    state.config.save();
+                                    // Refresh the in-memory cache from the bytes we
+                                    // just wrote (avoids re-reading from disk).
+                                    state.background_image = Some(bytes::Bytes::from(png));
+                                    state.status_message = "Background updated.".to_string();
+                                }
+                                Err(e) => {
+                                    state.status_message =
+                                        format!("Couldn't save background: {e}");
+                                }
+                            }
+                        }
+                        None => {
+                            state.status_message =
+                                "Couldn't find a config directory to save the background."
+                                    .to_string();
+                        }
+                    },
+                    Err(e) => {
+                        state.status_message = e;
+                    }
+                }
+            }
+        }
+        AppMessage::RemoveBackground => {
+            // Best-effort delete of our stored copy; clear the config + cache.
+            if let Some(path) = AppConfig::background_path() {
+                let _ = std::fs::remove_file(path);
+            }
+            state.config.background = None;
+            state.config.save();
+            state.background_image = None;
+            state.status_message = "Background removed.".to_string();
+        }
+        AppMessage::SetBackgroundDim(dim) => {
+            state.config.background_dim = dim.clamp(0.0, 1.0);
+            state.config.save();
+        }
         AppMessage::ToggleDrawerChat => {
             state.drawer_chat_open = !state.drawer_chat_open;
         }
@@ -1359,11 +1548,93 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     text: text.clone(),
                     mine: true,
                     from: Some(state.self_id.clone()),
+                    attachment: None,
                 });
                 let _ = state.controller.send(CoreCommand::SendChat(text));
                 state.chat_input.clear();
             }
         }
+        AppMessage::PickAttachmentFile => {
+            // Native picker off the UI thread; returns (filename, bytes).
+            return Task::perform(
+                async {
+                    let handle = rfd::AsyncFileDialog::new()
+                        .set_title("Attach a file to the chat")
+                        .pick_file()
+                        .await;
+                    match handle {
+                        Some(h) => Some((h.file_name(), h.read().await)),
+                        None => None,
+                    }
+                },
+                AppMessage::AttachmentFilePicked,
+            );
+        }
+        AppMessage::AttachmentFilePicked(picked) => {
+            if let Some((name, bytes)) = picked {
+                let size = bytes.len() as u64;
+                if !crate::files::size_within_cap(size) {
+                    state.status_message = format!(
+                        "File too large — max {}.",
+                        crate::files::human_size(crate::files::MAX_ATTACHMENT_BYTES)
+                    );
+                    return Task::none();
+                }
+                let kind = crate::files::classify(&bytes);
+                // Random 32-byte handle for this attachment.
+                let id: crate::files::AttachmentId = rand::random();
+                let att = crate::files::ChatAttachment {
+                    name: crate::files::sanitize_filename(&name),
+                    size,
+                    kind,
+                    id,
+                };
+                // Keep our own bytes locally so we see our own attachment inline
+                // immediately (others fetch it off the file plane).
+                if kind == crate::files::AttachmentKind::Image
+                    && crate::files::validate_image_bytes(&bytes).is_some()
+                {
+                    state
+                        .image_handle_cache
+                        .insert(id, iced::widget::image::Handle::from_bytes(bytes.clone()));
+                }
+                state
+                    .attachment_data
+                    .insert(id, AttachmentState::Ready(bytes.clone()));
+                push_chat(
+                    &mut state.chat_messages,
+                    ChatEntry {
+                        name: format!("{} (You)", state.name),
+                        text: String::new(),
+                        mine: true,
+                        from: Some(state.self_id.clone()),
+                        attachment: Some(att.clone()),
+                    },
+                );
+                let _ = state.controller.send(CoreCommand::SendChatFile {
+                    text: String::new(),
+                    attachment: att,
+                    data: bytes,
+                });
+            }
+        }
+        AppMessage::SaveAttachment(id) => {
+            // If we already have the bytes, save now; otherwise fetch from the
+            // sender and save when AttachmentReady arrives (pending_saves).
+            if matches!(state.attachment_data.get(&id), Some(AttachmentState::Ready(_))) {
+                save_attachment_to_disk(state, id);
+            } else if let Some((from, att)) = find_attachment_source(state, id) {
+                if let Ok(eid) = from.parse::<EndpointId>() {
+                    state.pending_saves.insert(id);
+                    state.status_message = format!("Downloading {}…", att.name);
+                    let _ = state
+                        .controller
+                        .send(CoreCommand::FetchAttachment { from: eid, attachment: att });
+                } else {
+                    state.status_message = "Can't download: unknown sender.".to_string();
+                }
+            }
+        }
         AppMessage::OpenUrl(url) => {
             // Defence in depth: only ever hand http(s) URLs to the opener. The
             // link span's href came from `linkify`, which only emits http/https,
@@ -1597,6 +1868,54 @@ fn push_chat(messages: &mut Vec<ChatEntry>, entry: ChatEntry) {
     }
 }
 
+/// Find the sender id + descriptor for a received attachment by its id, so a
+/// fetch can be addressed. Returns `None` for our own attachments or an unknown
+/// id.
+fn find_attachment_source(
+    state: &AppState,
+    id: crate::files::AttachmentId,
+) -> Option<(String, crate::files::ChatAttachment)> {
+    state.chat_messages.iter().find_map(|m| {
+        let att = m.attachment.as_ref()?;
+        if att.id == id && !m.mine {
+            Some((m.from.clone()?, att.clone()))
+        } else {
+            None
+        }
+    })
+}
+
+/// Write a ready attachment's bytes to a user-chosen location via a native save
+/// dialog. The default filename comes from the (already-sanitized) descriptor.
+/// No-op if the bytes aren't ready. Sync dialog: the brief block is acceptable
+/// for a deliberate save action.
+fn save_attachment_to_disk(state: &mut AppState, id: crate::files::AttachmentId) {
+    let Some(AttachmentState::Ready(data)) = state.attachment_data.get(&id) else {
+        return;
+    };
+    let data = data.clone();
+    let default_name = state
+        .chat_messages
+        .iter()
+        .find_map(|m| {
+            m.attachment
+                .as_ref()
+                .filter(|a| a.id == id)
+                .map(|a| a.name.clone())
+        })
+        .unwrap_or_else(|| "download".to_string());
+    if let Some(path) = rfd::FileDialog::new()
+        .set_file_name(default_name)
+        .set_title("Save attachment")
+        .save_file()
+    {
+        match std::fs::write(&path, &data) {
+            Ok(()) => state.status_message = format!("Saved {}", path.display()),
+            Err(e) => state.status_message = format!("Save failed: {e}"),
+        }
+    }
+}
+
 fn horizontal_space() -> iced::widget::Space {
     iced::widget::Space::new().width(iced::Length::Fill)
 }
@@ -2018,6 +2337,40 @@ fn friends_panel(state: &AppState) -> Element<'_, AppMessage> {
     .into()
 }
 
+/// Wrap the main [`view`] with the custom background layer (W16). When a
+/// background image is set, render `stack![ image(Cover), scrim, ui ]` so the
+/// photo sits behind the whole UI with a legibility scrim (the theme base colour
+/// at `background_dim` alpha) between them; otherwise return the UI untouched. The
+/// three screen roots go transparent (`root_bg` in `view`) so the image shows
+/// through the gaps between panels. This is the registered top-level view.
+fn view_with_background(state: &AppState) -> Element<'_, AppMessage> {
+    let content = view(state);
+    let Some(bytes) = state.background_image.clone() else {
+        return content;
+    };
+    let pal = state.config.theme.palette();
+    let dim = state.config.background_dim;
+    let image_layer = iced::widget::image(cached_image_handle(bytes))
+        .content_fit(iced::ContentFit::Cover)
+        .width(iced::Length::Fill)
+        .height(iced::Length::Fill);
+    let scrim = container(
+        iced::widget::Space::new()
+            .width(iced::Length::Fill)
+            .height(iced::Length::Fill),
+    )
+    .width(iced::Length::Fill)
+    .height(iced::Length::Fill)
+    .style(move |_: &Theme| container::Style {
+        background: Some(Background::Color(crate::background::scrim_color(pal.base, dim))),
+        ..Default::default()
+    });
+    iced::widget::stack![image_layer, scrim, content]
+        .width(iced::Length::Fill)
+        .height(iced::Length::Fill)
+        .into()
+}
+
 fn view(state: &AppState) -> Element<'_, AppMessage> {
     // Theme colours — sourced from the active palette (see `src/theme.rs`), so
     // all styling below re-themes when the user picks a different theme.
@@ -2036,6 +2389,16 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
     let color_green = pal.green;
     let color_yellow = pal.yellow;
 
+    // The window backdrop fill for the three screen roots. When a custom
+    // background image is set (W16), the root goes transparent so the image +
+    // scrim layered behind by `view_with_background` shows through the gaps
+    // between panels; otherwise it's the usual opaque `crust`.
+    let root_bg = if state.background_image.is_some() {
+        Color::TRANSPARENT
+    } else {
+        color_crust
+    };
+
     // Style Helpers
     let c_style = move |bg: Color, b_color: Color, radius: f32| {
         move |_theme: &Theme| container::Style {
@@ -2297,6 +2660,35 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
         .spacing(10)
         .width(iced::Length::Fill);
 
+        let remove_background: Element<'_, AppMessage> = if state.config.background.is_some() {
+            button(text("Remove background").size(13))
+                .on_press(AppMessage::RemoveBackground)
+                .style(b_style(color_surface, color_blue, color_text, 6.0))
+                .padding(8)
+                .into()
+        } else {
+            iced::widget::Space::new().width(0.0).height(0.0).into()
+        };
+        let background_section = column![
+            row![
+                button(text("Choose image…").size(13))
+                    .on_press(AppMessage::PickBackgroundFile)
+                    .style(b_style(color_surface, color_blue, color_text, 6.0))
+                    .padding(8),
+                remove_background,
+            ].spacing(8),
+            text(format!("Background dimming: {:.0}%", state.config.background_dim * 100.0))
+                .size(11)
+                .color(color_subtext),
+            slider(0.0..=1.0, state.config.background_dim, AppMessage::SetBackgroundDim)
+                .step(0.05),
+            text("Set a picture from your computer as the app background. Auto-resized; a dimming overlay keeps text readable. Applies live.")
+                .size(11)
+                .color(color_subtext),
+        ]
+        .spacing(10)
+        .width(iced::Length::Fill);
+
         // Inline avatar chooser (W4): the monogram fallback plus the bundled
         // presets, each a clickable tile. Same SelectAvatar message, applied live
         // + persisted (and re-announced to the room).
@@ -2645,6 +3037,9 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                 vertical_space(section_gap),
                 section_header("Theme"),
                 theme_section,
+                vertical_space(section_gap),
+                section_header("Background"),
+                background_section,
             ]
             .spacing(10)
             .width(iced::Length::Fill)
@@ -2830,7 +3225,7 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
             .height(iced::Length::Fill)
             .padding(24)
             .center_x(iced::Length::Fill)
-            .style(c_style(color_crust, Color::TRANSPARENT, 0.0));
+            .style(c_style(root_bg, Color::TRANSPARENT, 0.0));
 
         return with_regenerate_confirm(settings_screen.into(), state);
     }
@@ -2889,7 +3284,7 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
         )
             .width(iced::Length::Fill)
             .height(iced::Length::Fill)
-            .style(c_style(color_crust, Color::TRANSPARENT, 0.0));
+            .style(c_style(root_bg, Color::TRANSPARENT, 0.0));
 
         with_hotkey_info(with_layout_picker(home.into(), state), state)
     } else {
@@ -3181,11 +3576,18 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
             ].spacing(8);
 
             // Peer volume slider
-            let current_vol = state.peer_volumes.get(peer_id).copied().unwrap_or(1.0);
+            let current_vol = state
+                .config
+                .peer_volume
+                .get(&peer_id.to_string())
+                .copied()
+                .unwrap_or(1.0);
             card_content = card_content.push(
                 row![
                     text("Vol:").size(12).color(color_subtext),
                     slider(0.0..=2.0, current_vol, move |v| AppMessage::PeerVolumeChanged(peer_id_clone, v))
+                        .step(0.01)
+                        .on_release(AppMessage::PersistConfig)
                 ].spacing(8).align_y(iced::alignment::Vertical::Center)
             );
 
@@ -3204,6 +3606,28 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                 .align_y(iced::alignment::Vertical::Center),
             );
 
+            // Peer noise gate: suppress this peer's background noise on our end.
+            // Threshold is normalized RMS on the same 0..METER_MAX scale as the
+            // mic gate; 0 = off.
+            let current_gate = state.config.peer_gate.get(&peer_key).copied().unwrap_or(0.0);
+            let gate_label = if current_gate <= 0.0 {
+                "Off".to_string()
+            } else {
+                format!("{:.0}%", (current_gate / METER_MAX * 100.0).clamp(0.0, 100.0))
+            };
+            card_content = card_content.push(
+                row![
+                    text("Gate:").size(12).color(color_subtext),
+                    container(text(gate_label).size(11).color(color_subtext))
+                        .width(iced::Length::Fixed(58.0)),
+                    slider(0.0..=METER_MAX, current_gate, move |v| AppMessage::PeerGateChanged(peer_id_clone, v))
+                        .step(0.001)
+                        .on_release(AppMessage::PersistConfig),
+                ]
+                .spacing(8)
+                .align_y(iced::alignment::Vertical::Center),
+            );
+
             let eq = peer_eq_settings(&state.config, peer_id);
             let eq_row = |label: &'static str, band: EqBand, value: f32| -> Element<'_, AppMessage> {
                 row![
@@ -3456,6 +3880,59 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                     .spacing(8)
                     .align_y(iced::alignment::Vertical::Top),
                 );
+                // Attachment row (indented under the message), if any.
+                if let Some(att) = &m.attachment {
+                    let data = state.attachment_data.get(&att.id);
+                    let elem: Element<'_, AppMessage> =
+                        if let Some(AttachmentState::Failed(e)) = data {
+                            text(format!("⚠ {} — {e}", att.name))
+                                .size(12)
+                                .color(color_red)
+                                .into()
+                        } else if att.kind == crate::files::AttachmentKind::Image {
+                            match state.image_handle_cache.get(&att.id) {
+                                Some(handle) => iced::widget::image(handle.clone())
+                                    .width(iced::Length::Fixed(260.0))
+                                    .into(),
+                                None => text(format!("🖼 {} — loading…", att.name))
+                                    .size(12)
+                                    .color(color_subtext)
+                                    .into(),
+                            }
+                        } else {
+                            let ready =
+                                matches!(data, Some(AttachmentState::Ready(_)));
+                            let btn_label = if ready { "Save" } else { "Download" };
+                            row![
+                                text(format!(
+                                    "📎 {} ({})",
+                                    att.name,
+                                    crate::files::human_size(att.size)
+                                ))
+                                .size(12)
+                                .color(color_text),
+                                button(text(btn_label).size(12))
+                                    .on_press(AppMessage::SaveAttachment(att.id))
+                                    .style(b_style(
+                                        color_blue,
+                                        color_lavender,
+                                        color_crust,
+                                        6.0,
+                                    ))
+                                    .padding(6),
+                            ]
+                            .spacing(8)
+                            .align_y(iced::alignment::Vertical::Center)
+                            .into()
+                        };
+                    chat_col = chat_col.push(
+                        row![
+                            iced::widget::Space::new().width(iced::Length::Fixed(30.0)),
+                            elem
+                        ]
+                        .spacing(0),
+                    );
+                }
             }
         }
         let chat_scroll = scrollable(chat_col)
@@ -3463,6 +3940,10 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
             .height(iced::Length::Fill)
             .anchor_bottom();
         let chat_input_row = row![
+            button(text("📎").size(15))
+                .on_press(AppMessage::PickAttachmentFile)
+                .style(b_style(color_surface, color_overlay, color_text, 6.0))
+                .padding(8),
             text_input("Message the room…", &state.chat_input)
                 .on_input(AppMessage::ChatInputChanged)
                 .on_submit(AppMessage::ChatSubmit)
@@ -3590,7 +4071,7 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
         .padding(15)
         .width(iced::Length::Fill)
         .height(iced::Length::Fill)
-        .style(c_style(color_crust, Color::TRANSPARENT, 0.0));
+        .style(c_style(root_bg, Color::TRANSPARENT, 0.0));
 
         with_hotkey_info(
             with_pixelpass_help(with_layout_picker(room.into(), state), state),
@@ -4733,8 +5214,48 @@ impl Program<AppMessage> for Icon {
 mod tests {
     use super::{
         format_duration, initial_window_position, reconnect_attempt_chime, reconnected_chime,
-        GateMeter, METER_MAX,
+        set_peer_gate_config, set_peer_volume_config, AppConfig, GateMeter, METER_MAX,
     };
+    use iroh::SecretKey;
+
+    #[test]
+    fn peer_gate_persists_when_on_and_clears_when_off() {
+        let mut config = AppConfig::default();
+        let id = SecretKey::generate().public();
+
+        // A positive threshold is stored, clamped to the slider's METER_MAX ceiling.
+        let stored = set_peer_gate_config(&mut config, id, 0.05);
+        assert_eq!(stored, 0.05);
+        assert_eq!(config.peer_gate.get(&id.to_string()).copied(), Some(0.05));
+        assert_eq!(set_peer_gate_config(&mut config, id, 99.0), METER_MAX);
+
+        // Zero (or negative) means "gate off" — the entry is removed so the
+        // config doesn't carry a disabled gate.
+        let stored = set_peer_gate_config(&mut config, id, 0.0);
+        assert_eq!(stored, 0.0);
+        assert!(!config.peer_gate.contains_key(&id.to_string()));
+    }
+
+    #[test]
+    fn peer_volume_persists_non_unity_and_clears_at_unity() {
+        let mut config = AppConfig::default();
+        let id = SecretKey::generate().public();
+
+        // A non-unity value is clamped into range and stored.
+        let stored = set_peer_volume_config(&mut config, id, 1.5);
+        assert_eq!(stored, 1.5);
+        assert_eq!(config.peer_volume.get(&id.to_string()).copied(), Some(1.5));
+
+        // Out-of-range values clamp to the slider bounds.
+        assert_eq!(set_peer_volume_config(&mut config, id, 5.0), 2.0);
+        assert_eq!(set_peer_volume_config(&mut config, id, -1.0), 0.0);
+
+        // Returning to unity removes the entry (unity is the implicit default),
+        // so the config doesn't accumulate no-op entries.
+        let stored = set_peer_volume_config(&mut config, id, 1.0);
+        assert_eq!(stored, 1.0);
+        assert!(!config.peer_volume.contains_key(&id.to_string()));
+    }
 
     #[test]
     fn x11_restores_saved_window_position() {
@@ -5009,6 +5530,7 @@ mod tests {
             text: "Hello".to_string(),
             mine: true,
             from: None,
+            attachment: None,
         };
         push_chat(&mut messages, entry);
         assert_eq!(messages.len(), 1);
@@ -5029,6 +5551,7 @@ mod tests {
                     text: format!("Msg{}", i),
                     mine: i % 2 == 0,
                     from: None,
+                    attachment: None,
                 },
             );
         }
@@ -5052,6 +5575,7 @@ mod tests {
                     text: format!("Msg{}", i),
                     mine: i % 2 == 0,
                     from: None,
+                    attachment: None,
                 },
             );
         }

src/background.rs

@@ -0,0 +1,107 @@
+//! 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())
+}
+
+/// 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 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/config.rs

@@ -106,6 +106,10 @@ fn default_true() -> bool {
     true
 }
 
+fn default_background_dim() -> f32 {
+    crate::background::DEFAULT_DIM
+}
+
 fn default_volume() -> f32 {
     1.0
 }
@@ -185,6 +189,16 @@ pub struct AppConfig {
     /// Our chosen avatar (W4): monogram fallback or a bundled preset.
     #[serde(default)]
     pub avatar: crate::avatar::Avatar,
+    /// Custom UI background image (W16): path to the downscaled PNG we wrote into
+    /// the config dir (see `background_path`). `None` = use the theme background.
+    /// Local-only; never sent to peers.
+    #[serde(default)]
+    pub background: Option<String>,
+    /// Scrim strength drawn over the custom background for legibility (0.0 = image
+    /// at full strength, 1.0 = fully hidden behind the theme base). See
+    /// `crate::background::scrim_color`.
+    #[serde(default = "default_background_dim")]
+    pub background_dim: f32,
     /// What a call recording captures (mixed / per-peer stems / both).
     #[serde(default)]
     pub recording_mode: RecordingMode,
@@ -241,6 +255,15 @@ pub struct AppConfig {
     /// keyed by peer node id string. Local preference only.
     #[serde(default)]
     pub peer_pan: HashMap<String, f32>,
+    /// Per-peer listener-side volume/gain (`1.0` = unity), keyed by peer node id
+    /// string. Local preference only; never sent to peers. Absent entry = unity.
+    #[serde(default)]
+    pub peer_volume: HashMap<String, f32>,
+    /// Per-peer listener-side noise-gate threshold (normalized RMS, `0.0` = off),
+    /// keyed by peer node id string. Local preference only; never sent to peers.
+    /// Absent entry = gate disabled (pass-through).
+    #[serde(default)]
+    pub peer_gate: HashMap<String, f32>,
     /// Focused app-local keyboard shortcuts.
     #[serde(default)]
     pub hotkeys: crate::hotkeys::HotkeyMap,
@@ -280,6 +303,8 @@ impl Default for AppConfig {
             room_layout: RoomLayout::default(),
             theme: AppTheme::default(),
             avatar: crate::avatar::Avatar::default(),
+            background: None,
+            background_dim: default_background_dim(),
             recording_mode: RecordingMode::default(),
             custom_sound_self_join: None,
             custom_sound_peer_join: None,
@@ -301,6 +326,8 @@ impl Default for AppConfig {
             recents: Vec::new(),
             peer_eq: HashMap::new(),
             peer_pan: HashMap::new(),
+            peer_volume: HashMap::new(),
+            peer_gate: HashMap::new(),
             hotkeys: crate::hotkeys::HotkeyMap::default(),
             window_width: default_window_width(),
             window_height: default_window_height(),
@@ -348,6 +375,17 @@ impl AppConfig {
         })
     }
 
+    /// Path the processed custom-background PNG (W16) is written to, alongside
+    /// `config.json` in the app config dir. We store our own downscaled copy here
+    /// (rather than base64 in the config) so the JSON stays small.
+    pub fn background_path() -> Option<PathBuf> {
+        dirs::config_dir().map(|mut p| {
+            p.push("peerspeak");
+            p.push("background.png");
+            p
+        })
+    }
+
     pub fn load() -> Self {
         if let Some(path) = Self::config_path()
             && let Ok(contents) = fs::read_to_string(&path)
@@ -430,6 +468,8 @@ mod tests {
         // shortcut settings.
         assert!(deserialized.peer_eq.is_empty());
         assert!(deserialized.peer_pan.is_empty());
+        assert!(deserialized.peer_volume.is_empty());
+        assert!(deserialized.peer_gate.is_empty());
         assert_eq!(
             crate::hotkeys::format_binding(
                 deserialized

src/core/messages.rs

@@ -26,6 +26,10 @@ 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),
@@ -49,6 +53,14 @@ pub enum CoreCommand {
     SetRecordingMode(RecordingMode),
     /// Broadcast a room text-chat message. No-op when not in a call.
     SendChat(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.
+    SendChatFile { text: String, attachment: crate::files::ChatAttachment, data: 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 },
     /// Set the pixelpass binary location (config override, empty = use `$PATH`).
     /// Sent at startup so screen-share can resolve the binary.
     SetPixelpassPath(Option<String>),
@@ -105,7 +117,13 @@ pub enum UiEvent {
     /// 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 attachment id so the UI can match
+    /// it to the chat entry.
+    AttachmentReady { id: crate::files::AttachmentId, data: Vec<u8> },
+    /// An attachment fetch failed (sender gone, too large, decode error, etc.).
+    AttachmentFailed { id: crate::files::AttachmentId, error: String },
     /// Our own screen share started; the UI flips the Share button to "Stop".
     ScreenShareStarted,
     /// Our own screen share stopped (or failed to start).

src/core/mod.rs

@@ -8,7 +8,7 @@ use crate::codec::{AudioEncoder, opus_impl::OpusEncoder};
 use crate::core::jitter::{JitterBuffer, FRAME_SAMPLES};
 use crate::network::{
     NetworkTransport, RoomState, PeerState, RoomEvent, ConnEvent, PeerSpeakTicket,
-    iroh_impl::{IrohTransport, AudioRouter},
+    iroh_impl::{IrohTransport, AudioRouter, FileRouter},
     gossip::IrohGossipState,
 };
 use crate::core::messages::{CoreCommand, UiEvent};
@@ -578,6 +578,9 @@ struct NetStack {
     /// The persistent inbound-audio handler on `router`; per-join we bind the
     /// active session's transport into it, and clear it on leave.
     audio_router: AudioRouter,
+    /// The persistent chat-file-transfer handler on `router`; bound/cleared in
+    /// lock-step with `audio_router` (same session lifecycle).
+    file_router: FileRouter,
     /// In-memory address book (ticket + gossip fed), shared with every session.
     memory_lookup: iroh::address_lookup::memory::MemoryLookup,
 }
@@ -689,6 +692,7 @@ async fn build_net_stack(
         .spawn(endpoint.clone());
 
     let audio_router = AudioRouter::new();
+    let file_router = FileRouter::new();
     // The friends presence listener (W7 B2) rides this same persistent router as a
     // third ALPN — it MUST be a handler here, not a standalone accept loop, since
     // the router owns endpoint.accept(). Policy (who we answer / what room we
@@ -696,6 +700,7 @@ async fn build_net_stack(
     let router = Router::builder(endpoint.clone())
         .accept(iroh_gossip::net::GOSSIP_ALPN, gossip.clone())
         .accept(crate::protocol::AUDIO_ALPN, audio_router.clone())
+        .accept(crate::protocol::FILES_ALPN, file_router.clone())
         .accept(
             crate::presence_net::FRIENDS_ALPN,
             crate::presence_net::FriendsProtocol::new(friends_handler),
@@ -707,10 +712,49 @@ async fn build_net_stack(
         gossip,
         router,
         audio_router,
+        file_router,
         memory_lookup,
     })
 }
 
+/// Fetch a chat attachment's bytes from `from` over the file plane in a detached
+/// task, then report the result to the UI via [`UiEvent::AttachmentReady`] /
+/// [`UiEvent::AttachmentFailed`] keyed by the attachment id. For images
+/// (`is_image`) the bytes are defensively re-validated (decodable + within pixel
+/// limits) before being handed to the renderer; an "Image" that doesn't decode is
+/// reported as a failure rather than rendered.
+fn spawn_attachment_fetch(
+    transport: Arc<IrohTransport>,
+    ui_tx: mpsc::Sender<UiEvent>,
+    from: EndpointId,
+    att: crate::files::ChatAttachment,
+    is_image: bool,
+) {
+    tokio::spawn(async move {
+        match transport.fetch_attachment(from, &att).await {
+            Ok(data) => {
+                if is_image && crate::files::validate_image_bytes(&data).is_none() {
+                    let _ = ui_tx
+                        .send(UiEvent::AttachmentFailed {
+                            id: att.id,
+                            error: "received image failed to decode".to_string(),
+                        })
+                        .await;
+                    return;
+                }
+                let _ = ui_tx
+                    .send(UiEvent::AttachmentReady { id: att.id, data })
+                    .await;
+            }
+            Err(e) => {
+                let _ = ui_tx
+                    .send(UiEvent::AttachmentFailed { id: att.id, error: e.to_string() })
+                    .await;
+            }
+        }
+    });
+}
+
 /// Finalize and clear the active recording, if any, emitting `RecordingStopped`.
 /// No-op when not recording. Called on stop, room leave, and room switch so a
 /// recording is always closed cleanly (its WAV size fields patched).
@@ -869,6 +913,8 @@ async fn run_core_loop(
     let peer_volumes = Arc::new(Mutex::new(HashMap::<EndpointId, f32>::new()));
     let peer_eq = Arc::new(Mutex::new(HashMap::<EndpointId, EqSettings>::new()));
     let peer_pan = Arc::new(Mutex::new(HashMap::<EndpointId, f32>::new()));
+    // Listener-side per-peer noise-gate thresholds (normalized RMS, 0.0 = off).
+    let peer_gate = Arc::new(Mutex::new(HashMap::<EndpointId, f32>::new()));
     // Peers locally muted by us: decoded for level metering but not mixed.
     let locally_muted = Arc::new(Mutex::new(HashSet::<EndpointId>::new()));
     let mut current_name = "Anonymous".to_string();
@@ -1069,6 +1115,7 @@ async fn run_core_loop(
                 if let Some(session) = active_session.take() {
                     session.shutdown(audio_backend.clone()).await;
                     net.audio_router.clear();
+                    net.file_router.clear();
                 }
                 *current_room.lock().unwrap() = None;
 
@@ -1091,6 +1138,7 @@ async fn run_core_loop(
                     crate::log_msg("Shutting down existing active session");
                     session.shutdown(audio_backend.clone()).await;
                     net.audio_router.clear();
+                    net.file_router.clear();
                 }
 
                 // If a network-mode / identity change was deferred while a call was
@@ -1147,6 +1195,7 @@ async fn run_core_loop(
                 // NetStack; the session just subscribes its topic below.
                 let transport = Arc::new(IrohTransport::new(endpoint.clone()));
                 net.audio_router.bind(&transport);
+                net.file_router.bind(&transport);
 
                 let room_state = Arc::new(IrohGossipState::new(
                     endpoint.clone(),
@@ -1191,6 +1240,7 @@ async fn run_core_loop(
                     crate::log_msg(&format!("Error room_state.join failed: {:?}", e));
                     let _ = ui_tx.send(UiEvent::Error(format!("Failed to join room: {}", e))).await;
                     net.audio_router.clear();
+                    net.file_router.clear();
                     continue;
                 }
                 crate::log_msg("Joined room successfully via room_state");
@@ -1243,6 +1293,7 @@ async fn run_core_loop(
                     let _ = ui_tx.send(UiEvent::Error(format!("Failed to start capture: {}", e))).await;
                     let _ = room_state.leave().await;
                     net.audio_router.clear();
+                    net.file_router.clear();
                     continue;
                 }
 
@@ -1255,6 +1306,7 @@ async fn run_core_loop(
                     let _ = audio_backend.stop();
                     let _ = room_state.leave().await;
                     net.audio_router.clear();
+                    net.file_router.clear();
                     continue;
                 }
 
@@ -1397,6 +1449,7 @@ async fn run_core_loop(
                 let peer_volumes_mixer = peer_volumes.clone();
                 let peer_eq_mixer = peer_eq.clone();
                 let peer_pan_mixer = peer_pan.clone();
+                let peer_gate_mixer = peer_gate.clone();
                 let locally_muted_mixer = locally_muted.clone();
                 let output_gain_mixer = output_gain.clone();
                 let ui_tx_mixer = ui_tx.clone();
@@ -1413,6 +1466,11 @@ async fn run_core_loop(
                     // Per-peer EQ filter state. Settings are live-cloned each
                     // cycle; state is rebuilt only when a peer's EQ changes.
                     let mut peer_eqs: HashMap<EndpointId, Eq> = HashMap::new();
+                    // Per-peer noise-gate envelope state. The threshold is passed
+                    // per frame (live slider), so the gate is never rebuilt — only
+                    // created once per peer and dropped when the peer leaves.
+                    let mut peer_noise_gates: HashMap<EndpointId, crate::audio::gate::NoiseGate> =
+                        HashMap::new();
                     // When the ring is at/above target we have nothing to do; nap
                     // briefly and re-check. Short enough (relative to the ~60ms
                     // target and ~21ms device quantum) that we always refill well
@@ -1438,6 +1496,7 @@ async fn run_core_loop(
                         let current_volumes = peer_volumes_mixer.lock().await.clone();
                         let current_eq = peer_eq_mixer.lock().await.clone();
                         let current_pans = peer_pan_mixer.lock().await.clone();
+                        let current_gates = peer_gate_mixer.lock().await.clone();
                         let muted_peers = locally_muted_mixer.lock().await.clone();
                         let mut peer_frames: Vec<(Vec<i16>, f32)> = Vec::new();
                         let mut peers_seen = HashSet::new();
@@ -1463,6 +1522,26 @@ async fn run_core_loop(
                                     stems.push((peer_id, frame.clone()));
                                 }
 
+                                // Listener-side per-peer noise gate, applied to the
+                                // raw decoded frame (after the clean stem tap, before
+                                // volume/EQ) so the threshold tracks the peer's true
+                                // signal level regardless of our volume setting. The
+                                // gate's "should transmit" return is irrelevant here —
+                                // we only attenuate. Threshold 0 = off; the gate is
+                                // created lazily and dropped when disabled.
+                                let gate_threshold =
+                                    current_gates.get(&peer_id).copied().unwrap_or(0.0);
+                                if gate_threshold > 0.0 {
+                                    peer_noise_gates
+                                        .entry(peer_id)
+                                        .or_insert_with(|| {
+                                            crate::audio::gate::NoiseGate::new(48_000)
+                                        })
+                                        .process(&mut frame, gate_threshold);
+                                } else {
+                                    peer_noise_gates.remove(&peer_id);
+                                }
+
                                 let vol = current_volumes.get(&peer_id).copied().unwrap_or(1.0);
                                 apply_volume(&mut frame, vol);
 
@@ -1507,6 +1586,8 @@ async fn run_core_loop(
                             }
                         }
                         peer_eqs.retain(|id, _| peers_seen.contains(id) || current_eq.contains_key(id));
+                        peer_noise_gates
+                            .retain(|id, _| peers_seen.contains(id) || current_gates.contains_key(id));
 
                         // Lossless i32 sum, then the limiter applies the master
                         // output gain (in f32, so a boost past the ceiling is
@@ -1691,11 +1772,27 @@ async fn run_core_loop(
                                     .insert(peer_id, state.addr.clone());
                                 let _ = ui_tx_events.send(UiEvent::PeerUpdated { id: peer_id, state }).await;
                             }
-                            RoomEvent::ChatMessage { from, name, text, .. } => {
+                            RoomEvent::ChatMessage { from, name, text, ts: _, attachment } => {
+                                // Auto-fetch image attachments so they render inline
+                                // without a click; non-image files wait for an explicit
+                                // FetchAttachment (the "Save" chip). The descriptor was
+                                // already filename-sanitized + size-capped on ingest.
+                                if let Some(att) = attachment.clone()
+                                    && att.kind == crate::files::AttachmentKind::Image
+                                {
+                                    spawn_attachment_fetch(
+                                        transport_events.clone(),
+                                        ui_tx_events.clone(),
+                                        from,
+                                        att,
+                                        true,
+                                    );
+                                }
                                 let _ = ui_tx_events.send(UiEvent::ChatMessage {
                                     from: from.to_string(),
                                     name,
                                     text,
+                                    attachment,
                                 }).await;
                             }
                             RoomEvent::PeerConnectionLost(peer_id) => {
@@ -1798,6 +1895,7 @@ async fn run_core_loop(
                     session.shutdown(audio_backend.clone()).await;
                     // Stop routing inbound audio links — the endpoint/router stay up.
                     net.audio_router.clear();
+                    net.file_router.clear();
                     // No longer in a gathering — friends who ping see us as just online.
                     *current_room.lock().unwrap() = None;
                     let _ = ui_tx.send(UiEvent::RoomLeft).await;
@@ -1884,6 +1982,16 @@ async fn run_core_loop(
                 }
             }
 
+            CoreCommand::SetPeerGate(peer_id, threshold) => {
+                let threshold = threshold.clamp(0.0, 1.0);
+                let mut guard = peer_gate.lock().await;
+                if threshold <= 0.0 {
+                    guard.remove(&peer_id);
+                } else {
+                    guard.insert(peer_id, threshold);
+                }
+            }
+
             CoreCommand::SetPeerMuted(peer_id, muted) => {
                 let mut guard = locally_muted.lock().await;
                 if muted {
@@ -2167,12 +2275,38 @@ async fn run_core_loop(
 
             CoreCommand::SendChat(text) => {
                 if let Some(session) = &active_session
-                    && let Err(e) = session.room_state.send_chat(text).await
+                    && let Err(e) = session.room_state.send_chat(text, None).await
                 {
                     crate::log_msg(&format!("Failed to send chat: {e}"));
                 }
             }
 
+            CoreCommand::SendChatFile { text, attachment, data } => {
+                if let Some(session) = &active_session {
+                    // Make the bytes fetchable by room members, then broadcast the
+                    // descriptor alongside the (possibly empty) caption text.
+                    session
+                        .transport
+                        .serve_attachment(attachment.id, Arc::new(data));
+                    if let Err(e) = session.room_state.send_chat(text, Some(attachment)).await {
+                        crate::log_msg(&format!("Failed to send chat file: {e}"));
+                    }
+                }
+            }
+
+            CoreCommand::FetchAttachment { from, attachment } => {
+                if let Some(session) = &active_session {
+                    let is_image = attachment.kind == crate::files::AttachmentKind::Image;
+                    spawn_attachment_fetch(
+                        session.transport.clone(),
+                        ui_tx.clone(),
+                        from,
+                        attachment,
+                        is_image,
+                    );
+                }
+            }
+
             CoreCommand::SetPixelpassPath(path) => {
                 pixelpass_override = path.filter(|p| !p.trim().is_empty());
             }

src/files.rs

@@ -0,0 +1,295 @@
+//! 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;
+
+/// 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; turn other whitespace into single spaces later.
+    let cleaned: String = base
+        .chars()
+        .filter(|c| !c.is_control())
+        .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
+}
+
+/// 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 mut limits = image::Limits::default();
+    limits.max_image_width = Some(MAX_IMAGE_PX);
+    limits.max_image_height = Some(MAX_IMAGE_PX);
+    let reader = image::ImageReader::new(std::io::Cursor::new(bytes))
+        .with_guessed_format()
+        .ok()?;
+    let mut reader = reader;
+    reader.limits(limits);
+    let img = reader.decode().ok()?;
+    let (w, h) = (img.width(), img.height());
+    if w == 0 || h == 0 || w > MAX_IMAGE_PX || h > MAX_IMAGE_PX {
+        return None;
+    }
+    Some((w, h))
+}
+
+/// 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 classify_maps_sniff_to_kind() {
+        assert_eq!(classify(&[0xFF, 0xD8, 0xFF]), AttachmentKind::Image);
+        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 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 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/lib.rs

@@ -15,9 +15,11 @@ pub mod notify;
 pub mod screenshare;
 pub mod sanitize;
 pub mod avatar;
+pub mod background;
 pub mod recents;
 pub mod discovery;
 pub mod hotkeys;
+pub mod files;
 
 use std::fs::File;
 use std::path::{Path, PathBuf};

src/network/gossip.rs

@@ -184,9 +184,16 @@ fn compute_bootstrap(
 pub enum GossipMessage {
     Announce(PeerState),
     Leave,
-    /// A room text-chat message: the author's display name, the text, and a
-    /// sender-stamped millisecond timestamp.
-    Chat { name: String, text: String, ts: u64 },
+    /// A room text-chat message: the author's display name, the text, a
+    /// sender-stamped millisecond timestamp, and an optional file attachment
+    /// descriptor (the bytes are fetched off-gossip on the file plane).
+    Chat {
+        name: String,
+        text: String,
+        ts: u64,
+        #[serde(default)]
+        attachment: Option<crate::files::ChatAttachment>,
+    },
 }
 
 pub struct IrohGossipState {
@@ -438,13 +445,24 @@ impl RoomState for IrohGossipState {
                                             let _ = event_tx.send(RoomEvent::PeerLeft(payload.author)).await;
                                         }
                                     }
-                                    GossipMessage::Chat { name, text, ts } => {
+                                    GossipMessage::Chat { name, text, ts, attachment } => {
                                         crate::log_msg(&format!("Gossip chat from author={:?}", payload.author));
+                                        // Defensively normalize an untrusted attachment
+                                        // descriptor: sanitize the filename and drop it
+                                        // entirely if it declares an out-of-cap size.
+                                        let attachment = attachment.and_then(|mut a| {
+                                            if !crate::files::size_within_cap(a.size) {
+                                                return None;
+                                            }
+                                            a.name = crate::files::sanitize_filename(&a.name);
+                                            Some(a)
+                                        });
                                         let _ = event_tx.send(RoomEvent::ChatMessage {
                                             from: payload.author,
                                             name,
                                             text,
                                             ts,
+                                            attachment,
                                         }).await;
                                     }
                                 }
@@ -565,7 +583,11 @@ impl RoomState for IrohGossipState {
         }
     }
 
-    async fn send_chat(&self, text: String) -> Result<(), NetError> {
+    async fn send_chat(
+        &self,
+        text: String,
+        attachment: Option<crate::files::ChatAttachment>,
+    ) -> Result<(), NetError> {
         let name = {
             let guard = self.self_state.lock().unwrap();
             match guard.as_ref() {
@@ -582,7 +604,7 @@ impl RoomState for IrohGossipState {
                 &self.secret_key,
                 &topic,
                 ts,
-                GossipMessage::Chat { name, text, ts },
+                GossipMessage::Chat { name, text, ts, attachment },
             );
             if let Ok(bytes) = serde_json::to_vec(&payload) {
                 sender.broadcast(bytes.into()).await
@@ -744,13 +766,15 @@ mod tests {
             name: "Alice".to_string(),
             text: "Hello".to_string(),
             ts: 123456789,
+            attachment: None,
         };
         let serialized = serde_json::to_string(&original).unwrap();
         let deserialized: GossipMessage = serde_json::from_str(&serialized).unwrap();
-        if let GossipMessage::Chat { name, text, ts } = deserialized {
+        if let GossipMessage::Chat { name, text, ts, attachment } = deserialized {
             assert_eq!(name, "Alice");
             assert_eq!(text, "Hello");
             assert_eq!(ts, 123456789);
+            assert_eq!(attachment, None);
         } else {
             panic!("Expected GossipMessage::Chat");
         }
@@ -760,10 +784,11 @@ mod tests {
             name: "".to_string(),
             text: "".to_string(),
             ts: u64::MAX,
+            attachment: None,
         };
         let serialized_empty = serde_json::to_string(&original_empty).unwrap();
         let deserialized_empty: GossipMessage = serde_json::from_str(&serialized_empty).unwrap();
-        if let GossipMessage::Chat { name, text, ts } = deserialized_empty {
+        if let GossipMessage::Chat { name, text, ts, .. } = deserialized_empty {
             assert_eq!(name, "");
             assert_eq!(text, "");
             assert_eq!(ts, u64::MAX);
@@ -772,6 +797,40 @@ mod tests {
         }
     }
 
+    #[test]
+    fn test_gossip_chat_attachment_round_trip_and_back_compat() {
+        let att = crate::files::ChatAttachment {
+            name: "photo.png".to_string(),
+            size: 4096,
+            kind: crate::files::AttachmentKind::Image,
+            id: [42u8; 32],
+        };
+        let original = GossipMessage::Chat {
+            name: "Alice".to_string(),
+            text: "look at this".to_string(),
+            ts: 1,
+            attachment: Some(att.clone()),
+        };
+        let serialized = serde_json::to_string(&original).unwrap();
+        let deserialized: GossipMessage = serde_json::from_str(&serialized).unwrap();
+        if let GossipMessage::Chat { attachment, .. } = deserialized {
+            assert_eq!(attachment, Some(att));
+        } else {
+            panic!("Expected GossipMessage::Chat");
+        }
+
+        // A pre-v2 chat payload (no `attachment` field) must still deserialize,
+        // defaulting the attachment to None (serde(default)).
+        let legacy = r#"{"Chat":{"name":"Old","text":"hi","ts":7}}"#;
+        let parsed: GossipMessage = serde_json::from_str(legacy).unwrap();
+        if let GossipMessage::Chat { name, attachment, .. } = parsed {
+            assert_eq!(name, "Old");
+            assert_eq!(attachment, None);
+        } else {
+            panic!("Expected GossipMessage::Chat");
+        }
+    }
+
     #[test]
     fn test_gossip_payload_chat_round_trip() {
         let secret = SecretKey::generate();
@@ -784,6 +843,7 @@ mod tests {
                 name: "Bob".to_string(),
                 text: "Hi there".to_string(),
                 ts: 987654321,
+                attachment: None,
             },
         );
 
@@ -791,7 +851,7 @@ mod tests {
         let deserialized: GossipPayload = serde_json::from_str(&serialized).unwrap();
 
         assert_eq!(deserialized.author, secret.public());
-        if let GossipMessage::Chat { name, text, ts } = deserialized.msg {
+        if let GossipMessage::Chat { name, text, ts, .. } = deserialized.msg {
             assert_eq!(name, "Bob");
             assert_eq!(text, "Hi there");
             assert_eq!(ts, 987654321);
@@ -806,10 +866,11 @@ mod tests {
             name: "🎙 User".to_string(),
             text: "héllo 🎙 世界".to_string(),
             ts: 1717171717,
+            attachment: None,
         };
         let serialized = serde_json::to_string(&original).unwrap();
         let deserialized: GossipMessage = serde_json::from_str(&serialized).unwrap();
-        if let GossipMessage::Chat { name, text, ts } = deserialized {
+        if let GossipMessage::Chat { name, text, ts, .. } = deserialized {
             assert_eq!(name, "🎙 User");
             assert_eq!(text, "héllo 🎙 世界");
             assert_eq!(ts, 1717171717);
@@ -849,7 +910,7 @@ mod tests {
         let secret = SecretKey::generate();
         let topic = [4u8; 32];
         let mut p = sign_gossip(&secret, &topic, 5_000, GossipMessage::Leave);
-        p.msg = GossipMessage::Chat { name: "x".into(), text: "y".into(), ts: 5_000 };
+        p.msg = GossipMessage::Chat { name: "x".into(), text: "y".into(), ts: 5_000, attachment: None };
         assert_eq!(
             verify_gossip(&p, &topic, 5_000, GOSSIP_FRESHNESS_MS),
             Err(GossipReject::BadSignature)
@@ -922,8 +983,8 @@ mod tests {
     fn state_mutation_replay_gate_leaves_chat_ordering_untouched() {
         let author = fresh_id();
         let mut seen = HashMap::new();
-        let later_chat = GossipMessage::Chat { name: "A".into(), text: "later".into(), ts: 200 };
-        let earlier_chat = GossipMessage::Chat { name: "A".into(), text: "earlier".into(), ts: 100 };
+        let later_chat = GossipMessage::Chat { name: "A".into(), text: "later".into(), ts: 200, attachment: None };
+        let earlier_chat = GossipMessage::Chat { name: "A".into(), text: "earlier".into(), ts: 100, attachment: None };
 
         assert!(admit_state_mutation(&mut seen, author, &later_chat, 200));
         assert!(admit_state_mutation(&mut seen, author, &earlier_chat, 100));

src/network/iroh_impl.rs

@@ -9,7 +9,8 @@ use std::collections::{HashMap, HashSet};
 use std::time::Duration;
 use async_trait::async_trait;
 
-use crate::protocol::AUDIO_ALPN;
+use crate::protocol::{AUDIO_ALPN, FILES_ALPN};
+use crate::files::{AttachmentId, ChatAttachment};
 
 /// 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 +65,11 @@ 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.
+    served_files: StdMutex<HashMap<crate::files::AttachmentId, Arc<Vec<u8>>>>,
     incoming_tx: mpsc::Sender<(EndpointId, Bytes)>,
     /// Best-effort link-state notifications for the UI (connecting / connected).
     conn_events_tx: mpsc::Sender<ConnEvent>,
@@ -402,6 +412,88 @@ impl iroh::protocol::ProtocolHandler for AudioRouter {
     }
 }
 
+/// 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).cloned();
+            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();
+            Ok(())
+        }
+    }
+}
+
 pub struct IrohTransport {
     shared: Arc<Shared>,
     incoming_rx: tokio::sync::Mutex<Option<mpsc::Receiver<(EndpointId, Bytes)>>>,
@@ -426,6 +518,7 @@ 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(HashMap::new()),
             incoming_tx,
             conn_events_tx,
         });
@@ -455,6 +548,7 @@ 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 +577,59 @@ 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>>) {
+        self.shared.served_files.lock().unwrap().insert(id, bytes);
+    }
+
+    /// Fetch a chat attachment's bytes from its sender over the file plane. Dials
+    /// the sender on `FILES_ALPN` (preferring a known full address), writes the
+    /// 32-byte id, and reads the response bounded by the descriptor's declared
+    /// size (which the caller has already validated against the global cap). The
+    /// read limit means a malicious sender can't stream us more than advertised.
+    pub async fn fetch_attachment(
+        &self,
+        from: EndpointId,
+        att: &ChatAttachment,
+    ) -> Result<Vec<u8>, NetError> {
+        if !crate::files::size_within_cap(att.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(&att.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}")))?;
+
+        let read = recv.read_to_end(att.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()));
+        }
+        Ok(bytes)
+    }
 }
 
 #[async_trait]

src/network/mod.rs

@@ -57,7 +57,15 @@ pub enum RoomEvent {
     /// 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 },
+    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
@@ -206,8 +214,13 @@ pub trait RoomState: Send + Sync {
     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>;

src/protocol.rs

@@ -22,16 +22,26 @@ pub const FRIENDS_PROTO: u32 = 1;
 /// Gossip plane version (`GossipPayload`/`GossipMessage`/`PeerState`, signing,
 /// freshness). Bump on any change. Mirrored in [`GOSSIP_SIG_DOMAIN`] and folded
 /// into [`versioned_topic`].
-pub const GOSSIP_PROTO: u32 = 1;
+///
+/// v2 (0.3.0): `GossipMessage::Chat` gained an optional file attachment
+/// (`ChatAttachment`), so a pre-v2 peer can't interpret/serve chat files — bumped
+/// to fail fast rather than half-work.
+pub const GOSSIP_PROTO: u32 = 2;
+/// File-transfer plane version (chat attachment request/stream shape). Bump on
+/// any change. Mirrored in [`FILES_ALPN`].
+pub const FILES_PROTO: u32 = 1;
 
 /// ALPN for the audio datagram plane: `peerspeak/audio/<AUDIO_PROTO>`.
 pub const AUDIO_ALPN: &[u8] = b"peerspeak/audio/1";
 /// ALPN for the friends/presence plane: `peerspeak/friends/<FRIENDS_PROTO>`.
 pub const FRIENDS_ALPN: &[u8] = b"peerspeak/friends/1";
+/// ALPN for the file-transfer plane: `peerspeak/files/<FILES_PROTO>`. Carries
+/// chat attachment bytes via direct QUIC streams (not gossip).
+pub const FILES_ALPN: &[u8] = b"peerspeak/files/1";
 /// ed25519 gossip signature domain: `peerspeak-gossip-v<GOSSIP_PROTO>`. Carries
 /// the gossip protocol version into every signed payload — a version mismatch
 /// fails verification (cryptographic separation between gossip versions).
-pub const GOSSIP_SIG_DOMAIN: &str = "peerspeak-gossip-v1";
+pub const GOSSIP_SIG_DOMAIN: &str = "peerspeak-gossip-v2";
 
 /// Version-namespace a room topic so peers on different gossip protocol versions
 /// derive **different subscription topics from the same ticket** and therefore
@@ -62,6 +72,7 @@ mod tests {
     fn alpns_match_their_proto_versions() {
         assert_eq!(AUDIO_ALPN, format!("peerspeak/audio/{AUDIO_PROTO}").as_bytes());
         assert_eq!(FRIENDS_ALPN, format!("peerspeak/friends/{FRIENDS_PROTO}").as_bytes());
+        assert_eq!(FILES_ALPN, format!("peerspeak/files/{FILES_PROTO}").as_bytes());
         assert_eq!(GOSSIP_SIG_DOMAIN, format!("peerspeak-gossip-v{GOSSIP_PROTO}"));
     }