release: 0.6.6

The live-edge catch-up (8c4f4a0, b4a4c00) landed after the v0.6.5 tag, so
the 0.6.5 artifacts do not contain it — the same gap that left the fix out
of v0.6.4. Cut 0.6.6 so the published build actually carries it.

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

601 lib tests green, clippy clean.

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

CHANGELOG.md

@@ -4,6 +4,53 @@ All notable changes to PeerSpeak are documented here.
 
 ## [Unreleased]
 
+## [0.6.6] — 2026-07-19
+
+### Fixed
+- **A screen share that falls behind now catches back up.** On a lossy
+  connection (satellite links are the worst case) the share could settle several
+  seconds behind the host and simply stay there for the rest of the call. The
+  viewer now notices a deep buffer and plays imperceptibly fast until it is back
+  at the live edge — the audio stays in tune and in sync while it does. This
+  replaces the previous attempt at the problem, which measurement showed did not
+  help. Applies to the Low latency setting; Smooth intentionally keeps its
+  larger buffer.
+
+### Changed
+- **Low latency now keeps a tighter viewer buffer.** The screen-share cache
+  setting is a size in megabytes, which at a given bitrate quietly decides how
+  many *seconds* behind a viewer can drift — a 2 MB buffer turned out to hold
+  about six seconds of a typical share. Low latency now caps that buffer at 1 MB
+  regardless of the setting, which halved how far behind a share fell on a bad
+  connection before anything else kicked in. Smooth still honors the value you
+  choose, since a deep buffer is the point of that mode.
+
+## [0.6.5] — 2026-07-19
+
+### Added
+- **Chat message sounds.** Successful outgoing messages and admitted incoming
+  messages now have distinct notification chimes, each with its own enable
+  toggle and optional custom WAV path in Notifications settings.
+- **Contact presence sounds.** The home-screen contacts list now announces a
+  contact becoming online or offline. Initial online contacts are announced;
+  initial offline results stay silent. Both events have independent toggles and
+  optional custom WAV paths.
+- **Notification sound browser.** Every notification event now has a native
+  Browse button for choosing a custom WAV instead of typing its path manually.
+
+### Changed
+- **Tidier per-participant audio controls.** The equalizer bands and noise gate
+  for each participant now live behind an **"Advanced audio"** foldout instead
+  of being expanded all the time, so a call with several people no longer fills
+  the panel with sliders. The controls themselves are unchanged.
+
+### Fixed
+- **Low-latency screen sharing stays near the live edge again.** mpv's
+  timestamp pacing could let stale frames accumulate across the reliable
+  PixelPass transport until a share was 7–10 seconds behind. Low-latency mode
+  now presents decoded frames immediately; Smooth mode retains timestamp pacing
+  when keeping shared-video audio and video synchronized matters more.
+
 ## [0.6.4] — 2026-07-18
 
 ### Added

Cargo.lock

@@ -4871,7 +4871,7 @@ checksum = "35fb2e5f958ec131621fdd531e9fc186ed768cbe395337403ae56c17a74c68ec"
 
 [[package]]
 name = "peerspeak"
-version = "0.6.4"
+version = "0.6.6"
 dependencies = [
  "anyhow",
  "async-trait",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "peerspeak"
-version = "0.6.4"
+version = "0.6.6"
 edition = "2024"
 description = "Decentralized peer-to-peer voice chat (Rust/iroh/PipeWire/Opus/iced)"
 license = "MIT"

assets/sounds/generate_chimes.py

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

packaging/windows/peerspeak.iss

@@ -12,7 +12,7 @@
 ; (x86_64-pc-windows-gnu, statically linked -- no extra DLLs needed).
 
 #define MyAppName "PeerSpeak"
-#define MyAppVersion "0.6.4"
+#define MyAppVersion "0.6.6"
 #define MyAppPublisher "mollusk"
 #define MyAppExeName "peerspeak.exe"
 

src/app/mod.rs

@@ -700,6 +700,8 @@ pub enum AppMessage {
     PeerPanChanged(EndpointId, f32),
     PeerGateChanged(EndpointId, f32),
     PeerEqChanged(EndpointId, EqBand, f32),
+    /// Show or hide the secondary audio controls on one participant card.
+    TogglePeerAdvancedAudio(EndpointId),
     /// Toggle local mute of a peer (silence them just for us).
     TogglePeerMute(EndpointId),
     InputDeviceSelected(AudioDevice),
@@ -758,6 +760,10 @@ pub enum AppMessage {
     ToggleNotifications(bool),
     ToggleEchoCancellation(bool),
     CustomSoundPathChanged(Sound, String),
+    /// Open a native WAV picker for one notification event.
+    BrowseCustomSound(Sound),
+    /// Result of the notification WAV picker (`None` = cancelled).
+    CustomSoundFilePicked(Sound, Option<std::path::PathBuf>),
     /// Toggle the per-sound enable flag for a single chime (W6).
     ToggleSoundEnabled(Sound, bool),
     /// Open / cancel the "Regenerate identity?" confirm modal (W7).
@@ -1047,6 +1053,9 @@ pub struct AppState {
     conn_stats: HashMap<EndpointId, crate::core::connstats::PeerConnInfo>,
     /// Peers we've locally muted (their audio isn't mixed into our output).
     locally_muted: HashSet<EndpointId>,
+    /// Participant cards whose volume/pan/gate/EQ foldout is open. Session-only:
+    /// a fresh room starts compact, regardless of the previous room's UI state.
+    peer_audio_expanded: HashSet<EndpointId>,
     /// When we joined the current room, for the in-room call-duration timer.
     call_started: Option<std::time::Instant>,
     /// Whether a local call recording is in progress (confirmed by the core).
@@ -1240,6 +1249,7 @@ impl AppState {
         self.audio_levels.clear();
         self.conn_stats.clear();
         self.locally_muted.clear();
+        self.peer_audio_expanded.clear();
         self.chat_messages.clear();
         // Unsent queue + retry bytes die with the room's transcript. The pacer
         // and id counter deliberately survive: receivers' per-author buckets
@@ -1333,16 +1343,20 @@ impl AppState {
     /// so Retry can re-dispatch, unless the entry is already gone (history
     /// eviction / room reset), in which case the payload is dropped so its map
     /// can't leak. Either way an id with no matching entry is a harmless no-op.
-    fn apply_send_result(&mut self, local_id: u64, error: Option<String>) {
+    /// Returns `true` only when a successful result matched a live local echo,
+    /// which is the boundary used for the outgoing-message notification.
+    fn apply_send_result(&mut self, local_id: u64, error: Option<String>) -> bool {
         match error {
             None => {
-                self.set_send_status(local_id, SendStatus::Broadcast);
+                let matched = self.set_send_status(local_id, SendStatus::Broadcast);
                 self.send_payloads.remove(&local_id);
+                matched
             }
             Some(e) => {
                 if !self.set_send_status(local_id, SendStatus::Failed(e)) {
                     self.send_payloads.remove(&local_id);
                 }
+                false
             }
         }
     }
@@ -1373,9 +1387,30 @@ impl AppState {
             Sound::SelfLeave => &self.config.custom_sound_self_leave,
             Sound::MicToggle => &self.config.custom_sound_mic_toggle,
             Sound::ReconnectFailed => &self.config.custom_sound_reconnect_failed,
+            Sound::ChatSent => &self.config.custom_sound_chat_sent,
+            Sound::ChatReceived => &self.config.custom_sound_chat_received,
+            Sound::ContactOnline => &self.config.custom_sound_contact_online,
+            Sound::ContactOffline => &self.config.custom_sound_contact_offline,
         };
         opt.as_deref().unwrap_or("")
     }
+
+    fn set_custom_sound_path(&mut self, sound: Sound, path: Option<String>) {
+        match sound {
+            Sound::SelfJoin => self.config.custom_sound_self_join = path,
+            Sound::PeerJoin => self.config.custom_sound_peer_join = path,
+            Sound::PeerLeave => self.config.custom_sound_peer_leave = path,
+            Sound::ReconnectAttempt => self.config.custom_sound_reconnect_attempt = path,
+            Sound::Reconnected => self.config.custom_sound_reconnected = path,
+            Sound::SelfLeave => self.config.custom_sound_self_leave = path,
+            Sound::MicToggle => self.config.custom_sound_mic_toggle = path,
+            Sound::ReconnectFailed => self.config.custom_sound_reconnect_failed = path,
+            Sound::ChatSent => self.config.custom_sound_chat_sent = path,
+            Sound::ChatReceived => self.config.custom_sound_chat_received = path,
+            Sound::ContactOnline => self.config.custom_sound_contact_online = path,
+            Sound::ContactOffline => self.config.custom_sound_contact_offline = path,
+        }
+    }
 }
 
 impl Default for AppState {
@@ -1502,6 +1537,7 @@ impl Default for AppState {
             audio_levels: HashMap::new(),
             conn_stats: HashMap::new(),
             locally_muted: HashSet::new(),
+            peer_audio_expanded: HashSet::new(),
             call_started: None,
             recording: false,
             recording_started: None,
@@ -1864,6 +1900,47 @@ fn reconnected_chime(
     was_reconnect.then_some(Sound::Reconnected)
 }
 
+/// Return the landing-page contact chime for one definitive presence update.
+/// An initial online result is an arrival (so contacts already online at app
+/// startup are announced), while an initial offline result is silent. Online
+/// includes both plain `Online` and `InRoom`; moving between those two states is
+/// not a connection transition. Updates continue to populate the presence map
+/// off-home, but notification sounds are intentionally limited to the home page.
+fn friend_presence_notification(
+    screen: Screen,
+    previous: Option<&crate::presence::FriendPresence>,
+    next: &crate::presence::FriendPresence,
+) -> Option<Sound> {
+    if screen != Screen::Home {
+        return None;
+    }
+
+    let online = |presence: &crate::presence::FriendPresence| {
+        matches!(
+            presence,
+            crate::presence::FriendPresence::Online
+                | crate::presence::FriendPresence::InRoom { .. }
+        )
+    };
+    match (previous.map(online), online(next)) {
+        (None | Some(false), true) => Some(Sound::ContactOnline),
+        (Some(true), false) => Some(Sound::ContactOffline),
+        _ => None,
+    }
+}
+
+/// Convert a native picker result into the persisted notification path. The
+/// dialog filter is advisory on some desktops, so enforce WAV here as well.
+/// `None` (cancel) and a non-WAV selection leave the existing setting untouched.
+fn selected_wav_path(picked: Option<std::path::PathBuf>) -> Option<String> {
+    let path = picked?;
+    let is_wav = path
+        .extension()
+        .and_then(|ext| ext.to_str())
+        .is_some_and(|ext| ext.eq_ignore_ascii_case("wav"));
+    is_wav.then(|| path.to_string_lossy().into_owned())
+}
+
 fn in_call(state: &AppState) -> bool {
     !state.ticket.is_empty()
 }
@@ -2217,6 +2294,7 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.peers.remove(&id);
                     state.audio_levels.remove(&id);
                     state.locally_muted.remove(&id);
+                    state.peer_audio_expanded.remove(&id);
                     state.connecting.remove(&id);
                     state.ever_connected.remove(&id);
                     if state.music_listening_to == Some(id) {
@@ -2238,6 +2316,7 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.peers.remove(&id);
                     state.audio_levels.remove(&id);
                     state.locally_muted.remove(&id);
+                    state.peer_audio_expanded.remove(&id);
                     state.connecting.remove(&id);
                     state.ever_connected.remove(&id);
                     notify::play(
@@ -2301,7 +2380,12 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     // failure it's retained for Retry — unless the entry is gone
                     // (history eviction / room reset), in which case drop it so
                     // the payload map can't leak.
-                    state.apply_send_result(local_id, error);
+                    if state.apply_send_result(local_id, error) {
+                        notify::play(
+                            Sound::ChatSent,
+                            state.config.custom_sound_chat_sent.as_deref(),
+                        );
+                    }
                 }
                 UiEvent::ChatMessage {
                     from,
@@ -2334,6 +2418,10 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                                 local_send: None,
                             },
                         );
+                        notify::play(
+                            Sound::ChatReceived,
+                            state.config.custom_sound_chat_received.as_deref(),
+                        );
                     }
                 }
                 UiEvent::AttachmentReady { from, id, data } => {
@@ -2503,7 +2591,15 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.friends_read_only = read_only;
                 }
                 UiEvent::FriendPresence { id, presence } => {
+                    let sound = friend_presence_notification(
+                        state.current_screen,
+                        state.friend_presence.get(&id),
+                        &presence,
+                    );
                     state.friend_presence.insert(id, presence);
+                    if let Some(sound) = sound {
+                        notify::play(sound, Some(state.custom_sound_path(sound)));
+                    }
                 }
                 UiEvent::FriendsRescanned => {
                     // The manual pass finished. Stamp the time for the live "scanned
@@ -2588,6 +2684,11 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
             let settings = set_peer_eq_config(&mut state.config, id, band, gain_db);
             let _ = state.controller.send(CoreCommand::SetPeerEq(id, settings));
         }
+        AppMessage::TogglePeerAdvancedAudio(id) => {
+            if !state.peer_audio_expanded.remove(&id) && state.peers.contains_key(&id) {
+                state.peer_audio_expanded.insert(id);
+            }
+        }
         AppMessage::TogglePeerMute(id) => {
             let now_muted = if state.locally_muted.contains(&id) {
                 state.locally_muted.remove(&id);
@@ -2873,15 +2974,36 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
             } else {
                 Some(path)
             };
-            match sound {
-                Sound::SelfJoin => state.config.custom_sound_self_join = path_opt,
-                Sound::PeerJoin => state.config.custom_sound_peer_join = path_opt,
-                Sound::PeerLeave => state.config.custom_sound_peer_leave = path_opt,
-                Sound::ReconnectAttempt => state.config.custom_sound_reconnect_attempt = path_opt,
-                Sound::Reconnected => state.config.custom_sound_reconnected = path_opt,
-                Sound::SelfLeave => state.config.custom_sound_self_leave = path_opt,
-                Sound::MicToggle => state.config.custom_sound_mic_toggle = path_opt,
-                Sound::ReconnectFailed => state.config.custom_sound_reconnect_failed = path_opt,
+            state.set_custom_sound_path(sound, path_opt);
+        }
+        AppMessage::BrowseCustomSound(sound) => {
+            let initial_dir = {
+                let current = state.custom_sound_path(sound);
+                (!current.trim().is_empty())
+                    .then(|| notify::expand_tilde(current))
+                    .and_then(|path| path.parent().map(std::path::Path::to_path_buf))
+                    .filter(|path| path.is_dir())
+            };
+            return Task::perform(
+                async move {
+                    let mut dialog = rfd::AsyncFileDialog::new()
+                        .add_filter("WAV audio", &["wav"])
+                        .set_title("Choose a notification sound");
+                    if let Some(dir) = initial_dir {
+                        dialog = dialog.set_directory(dir);
+                    }
+                    dialog
+                        .pick_file()
+                        .await
+                        .map(|handle| handle.path().to_path_buf())
+                },
+                move |picked| AppMessage::CustomSoundFilePicked(sound, picked),
+            );
+        }
+        AppMessage::CustomSoundFilePicked(sound, picked) => {
+            if let Some(path) = selected_wav_path(picked) {
+                state.set_custom_sound_path(sound, Some(path));
+                state.config.save();
             }
         }
         AppMessage::ToggleSoundEnabled(sound, enabled) => {
@@ -5268,10 +5390,19 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                 ]
                 .spacing(6)
                 .align_y(iced::alignment::Vertical::Center),
-                context_input("Default (embedded)...", path)
-                    .on_input(move |val| AppMessage::CustomSoundPathChanged(sound, val))
-                    .style(t_style)
-                    .padding(8)
+                row![
+                    context_input("Default (embedded)...", path)
+                        .on_input(move |val| AppMessage::CustomSoundPathChanged(sound, val))
+                        .style(t_style)
+                        .padding(8)
+                        .width(iced::Length::Fill),
+                    button(text("Browse…").size(11))
+                        .on_press(AppMessage::BrowseCustomSound(sound))
+                        .style(b_style(color_surface, color_blue, color_text, 5.0))
+                        .padding([8, 10]),
+                ]
+                .spacing(6)
+                .width(iced::Length::Fill)
             ]
             .spacing(4)
             .width(iced::Length::Fill)
@@ -6021,6 +6152,14 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                         path_field("Mic Toggle", Sound::MicToggle),
                         path_field("Reconnect Failed", Sound::ReconnectFailed),
                     ].spacing(20).width(iced::Length::Fill),
+                    row![
+                        path_field("Chat Sent", Sound::ChatSent),
+                        path_field("Chat Received", Sound::ChatReceived),
+                    ].spacing(20).width(iced::Length::Fill),
+                    row![
+                        path_field("Contact Online", Sound::ContactOnline),
+                        path_field("Contact Offline", Sound::ContactOffline),
+                    ].spacing(20).width(iced::Length::Fill),
                 ].spacing(8).width(iced::Length::Fill),
             ]
             .spacing(10)
@@ -6748,15 +6887,48 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
             ]
             .spacing(8);
 
-            // Peer volume slider
-            let current_vol = state
-                .config
-                .peer_volume
-                .get(&peer_id.to_string())
-                .copied()
-                .unwrap_or(1.0);
+            let advanced_audio_open = state.peer_audio_expanded.contains(peer_id);
+            let foldout_symbol = if advanced_audio_open { "▾" } else { "▸" };
             card_content = card_content.push(
-                row![
+                button(
+                    row![
+                        text(foldout_symbol).size(13).color(color_subtext),
+                        text("Advanced audio").size(12).color(color_text),
+                    ]
+                    .spacing(6)
+                    .align_y(iced::alignment::Vertical::Center),
+                )
+                .on_press(AppMessage::TogglePeerAdvancedAudio(peer_id_clone))
+                .style(b_style(color_surface, color_blue, color_text, 6.0))
+                .padding([6, 8])
+                .width(iced::Length::Fill),
+            );
+
+            if advanced_audio_open {
+                let peer_key = peer_id.to_string();
+                let current_vol = state
+                    .config
+                    .peer_volume
+                    .get(&peer_key)
+                    .copied()
+                    .unwrap_or(1.0);
+                let current_pan = state.config.peer_pan.get(&peer_key).copied().unwrap_or(0.0);
+                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)
+                    )
+                };
+
+                let volume_row = row![
                     text("Vol:").size(12).color(color_subtext),
                     slider(0.0..=2.0, current_vol, move |v| {
                         AppMessage::PeerVolumeChanged(peer_id_clone, v)
@@ -6765,47 +6937,24 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                     .on_release(AppMessage::PersistConfig)
                 ]
                 .spacing(8)
-                .align_y(iced::alignment::Vertical::Center),
-            );
+                .align_y(iced::alignment::Vertical::Center);
 
-            let peer_key = peer_id.to_string();
-            let current_pan = state.config.peer_pan.get(&peer_key).copied().unwrap_or(0.0);
-            card_content = card_content.push(
-                row![
+                let pan_row = row![
                     text("Pan:").size(12).color(color_subtext),
                     container(text(pan_label(current_pan)).size(11).color(color_subtext))
                         .width(iced::Length::Fixed(58.0)),
-                    slider(
-                        -1.0..=1.0,
-                        current_pan,
-                        move |v| AppMessage::PeerPanChanged(peer_id_clone, v)
-                    )
+                    slider(-1.0..=1.0, current_pan, move |v| {
+                        AppMessage::PeerPanChanged(peer_id_clone, v)
+                    })
                     .step(0.05)
                     .on_release(AppMessage::PersistConfig),
                 ]
                 .spacing(8)
-                .align_y(iced::alignment::Vertical::Center),
-            );
+                .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![
+                // Peer noise gate: suppress this peer's background noise on our
+                // end. Threshold is on the mic meter's 0..METER_MAX scale; 0 = off.
+                let gate_row = row![
                     text("Gate:").size(12).color(color_subtext),
                     container(text(gate_label).size(11).color(color_subtext))
                         .width(iced::Length::Fixed(58.0)),
@@ -6816,38 +6965,45 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
                     .on_release(AppMessage::PersistConfig),
                 ]
                 .spacing(8)
-                .align_y(iced::alignment::Vertical::Center),
-            );
+                .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![
-                        container(
-                            text(format!("{label} {value:+.1} dB"))
-                                .size(11)
-                                .color(color_subtext)
-                        )
-                        .width(iced::Length::Fixed(86.0)),
-                        slider(EQ_GAIN_DB_MIN..=EQ_GAIN_DB_MAX, value, move |v| {
-                            AppMessage::PeerEqChanged(peer_id_clone, band, v)
-                        })
-                        .step(0.5)
-                        .on_release(AppMessage::PersistConfig),
-                    ]
-                    .spacing(8)
-                    .align_y(iced::alignment::Vertical::Center)
-                    .into()
-                };
-            card_content = card_content.push(
-                column![
+                let eq = peer_eq_settings(&state.config, peer_id);
+                let eq_row =
+                    |label: &'static str, band: EqBand, value: f32| -> Element<'_, AppMessage> {
+                        row![
+                            container(
+                                text(format!("{label} {value:+.1} dB"))
+                                    .size(11)
+                                    .color(color_subtext)
+                            )
+                            .width(iced::Length::Fixed(86.0)),
+                            slider(EQ_GAIN_DB_MIN..=EQ_GAIN_DB_MAX, value, move |v| {
+                                AppMessage::PeerEqChanged(peer_id_clone, band, v)
+                            })
+                            .step(0.5)
+                            .on_release(AppMessage::PersistConfig),
+                        ]
+                        .spacing(8)
+                        .align_y(iced::alignment::Vertical::Center)
+                        .into()
+                    };
+                let advanced_audio = column![
+                    volume_row,
+                    pan_row,
+                    gate_row,
                     text("EQ").size(11).color(color_subtext),
                     eq_row("Low", EqBand::Low, eq.low_gain_db),
                     eq_row("Mid", EqBand::Mid, eq.mid_gain_db),
                     eq_row("High", EqBand::High, eq.high_gain_db),
                 ]
-                .spacing(4),
-            );
+                .spacing(6);
+                card_content = card_content.push(
+                    container(advanced_audio)
+                        .style(c_style(color_crust, color_surface, 6.0))
+                        .padding(10)
+                        .width(iced::Length::Fill),
+                );
+            }
 
             let card = container(card_content)
                 .style(c_style(
@@ -9513,12 +9669,12 @@ mod tests {
     use super::sendqueue::{self, LocalSend, SendStatus};
     use super::{
         AppConfig, AppMessage, AppState, AttachmentCache, AttachmentState,
-        CLOCK_SKEW_WARNING_VISIBLE_SECS, ChatEntry, ClockSkewBanner, GateMeter, METER_MAX,
+        CLOCK_SKEW_WARNING_VISIBLE_SECS, ChatEntry, ClockSkewBanner, GateMeter, METER_MAX, Screen,
         ScreenBounds, UiEvent, attachment_default_name, clamp_window_position,
         clear_expired_clock_skew_warning, format_clock_skew_duration, format_duration,
-        format_relative_ago, initial_window_position, now_playing_label, reconnect_attempt_chime,
-        reconnected_chime, set_peer_gate_config, set_peer_volume_config, show_clock_skew_warning,
-        update,
+        format_relative_ago, friend_presence_notification, initial_window_position,
+        now_playing_label, reconnect_attempt_chime, reconnected_chime, selected_wav_path,
+        set_peer_gate_config, set_peer_volume_config, show_clock_skew_warning, update,
     };
     use iroh::SecretKey;
     use std::collections::VecDeque;
@@ -9776,6 +9932,7 @@ mod tests {
         );
         state.audio_levels.insert(peer, 0.5);
         state.locally_muted.insert(peer);
+        state.peer_audio_expanded.insert(peer);
         state.chat_messages.push(ChatEntry {
             name: "Peer".to_string(),
             text: "old room".to_string(),
@@ -9837,6 +9994,7 @@ mod tests {
         assert!(state.peers.is_empty());
         assert!(state.audio_levels.is_empty());
         assert!(state.locally_muted.is_empty());
+        assert!(state.peer_audio_expanded.is_empty());
         assert!(state.chat_messages.is_empty());
         assert!(state.chat_input.is_empty());
         assert!(state.attachments.len() == 0);
@@ -9886,6 +10044,34 @@ mod tests {
         panic!("clip player did not stop during room reset");
     }
 
+    #[test]
+    fn peer_advanced_audio_toggle_is_per_peer_and_rejects_stale_ids() {
+        let mut state = AppState::default();
+        let peer = SecretKey::generate().public();
+        state.peers.insert(
+            peer,
+            crate::network::PeerState {
+                name: "Peer".to_string(),
+                is_muted: false,
+                addr: iroh::EndpointAddr::from(peer),
+                sharing: None,
+                avatar: crate::avatar::Avatar::default(),
+                game: None,
+                music: None,
+            },
+        );
+
+        let _ = update(&mut state, AppMessage::TogglePeerAdvancedAudio(peer));
+        assert!(state.peer_audio_expanded.contains(&peer));
+
+        let _ = update(&mut state, AppMessage::TogglePeerAdvancedAudio(peer));
+        assert!(!state.peer_audio_expanded.contains(&peer));
+
+        let stale = SecretKey::generate().public();
+        let _ = update(&mut state, AppMessage::TogglePeerAdvancedAudio(stale));
+        assert!(!state.peer_audio_expanded.contains(&stale));
+    }
+
     #[test]
     fn clock_skew_warning_shows_dismisses_and_expires() {
         let mut state = AppState::default();
@@ -10579,6 +10765,91 @@ mod tests {
 
     const W: f32 = 200.0;
 
+    #[test]
+    fn initial_contact_presence_announces_only_online() {
+        use crate::presence::FriendPresence;
+
+        assert_eq!(
+            friend_presence_notification(Screen::Home, None, &FriendPresence::Online),
+            Some(Sound::ContactOnline)
+        );
+        assert_eq!(
+            friend_presence_notification(Screen::Home, None, &FriendPresence::Offline),
+            None
+        );
+    }
+
+    #[test]
+    fn contact_presence_chimes_only_on_online_boundary() {
+        use crate::presence::FriendPresence;
+
+        let in_room = FriendPresence::InRoom {
+            name: "Game night".to_string(),
+            ticket: "ticket".to_string(),
+        };
+        assert_eq!(
+            friend_presence_notification(Screen::Home, Some(&FriendPresence::Offline), &in_room,),
+            Some(Sound::ContactOnline)
+        );
+        assert_eq!(
+            friend_presence_notification(
+                Screen::Home,
+                Some(&FriendPresence::Online),
+                &FriendPresence::Offline,
+            ),
+            Some(Sound::ContactOffline)
+        );
+        assert_eq!(
+            friend_presence_notification(Screen::Home, Some(&FriendPresence::Online), &in_room,),
+            None
+        );
+        assert_eq!(
+            friend_presence_notification(
+                Screen::Home,
+                Some(&FriendPresence::Offline),
+                &FriendPresence::Offline,
+            ),
+            None
+        );
+    }
+
+    #[test]
+    fn contact_presence_is_silent_away_from_landing_page() {
+        use crate::presence::FriendPresence;
+
+        assert_eq!(
+            friend_presence_notification(Screen::Room, None, &FriendPresence::Online),
+            None
+        );
+        assert_eq!(
+            friend_presence_notification(
+                Screen::Settings,
+                Some(&FriendPresence::Online),
+                &FriendPresence::Offline,
+            ),
+            None
+        );
+    }
+
+    #[test]
+    fn selected_notification_sound_accepts_wav_and_preserves_cancel() {
+        use std::path::PathBuf;
+
+        assert_eq!(selected_wav_path(None), None);
+        assert_eq!(
+            selected_wav_path(Some(PathBuf::from("/tmp/notify.mp3"))),
+            None
+        );
+        assert_eq!(
+            selected_wav_path(Some(PathBuf::from("/tmp/notify.wav"))),
+            Some("/tmp/notify.wav".to_string())
+        );
+        assert_eq!(
+            selected_wav_path(Some(PathBuf::from("/tmp/notify.WAV"))),
+            Some("/tmp/notify.WAV".to_string())
+        );
+    }
+
     #[test]
     fn gate_drag_maps_left_edge_to_zero() {
         assert_eq!(GateMeter::x_to_threshold(0.0, W), 0.0);
@@ -10862,7 +11133,7 @@ mod tests {
         // Empty queue + a fresh full pacer → dispatched immediately.
         assert_eq!(status_of(&state, id), Some(SendStatus::Pending));
         assert!(state.send_payloads.contains_key(&id));
-        state.apply_send_result(id, None);
+        assert!(state.apply_send_result(id, None));
         assert_eq!(status_of(&state, id), Some(SendStatus::Broadcast));
         // A completed send releases its retry payload.
         assert!(!state.send_payloads.contains_key(&id));
@@ -10873,7 +11144,7 @@ mod tests {
         let mut state = AppState::default();
         let id = push_own(&mut state, "yo");
         state.submit_send(id, PendingSend::Text("yo".to_string()));
-        state.apply_send_result(id, Some("not in a room".to_string()));
+        assert!(!state.apply_send_result(id, Some("not in a room".to_string())));
         assert_eq!(
             status_of(&state, id),
             Some(SendStatus::Failed("not in a room".to_string()))
@@ -10889,11 +11160,11 @@ mod tests {
         state.submit_send(a, PendingSend::Text("a".to_string()));
         let b = push_own(&mut state, "b");
         state.submit_send(b, PendingSend::Text("b".to_string()));
-        state.apply_send_result(a, None);
+        assert!(state.apply_send_result(a, None));
         assert_eq!(status_of(&state, a), Some(SendStatus::Broadcast));
         assert_eq!(status_of(&state, b), Some(SendStatus::Pending));
         // A result for an id with no matching entry is a harmless no-op.
-        state.apply_send_result(9999, None);
+        assert!(!state.apply_send_result(9999, None));
         assert_eq!(status_of(&state, b), Some(SendStatus::Pending));
     }
 
@@ -10907,7 +11178,7 @@ mod tests {
         state
             .chat_messages
             .retain(|m| m.local_send.as_ref().map(|s| s.id) != Some(id));
-        state.apply_send_result(id, Some("dead".to_string()));
+        assert!(!state.apply_send_result(id, Some("dead".to_string())));
         // No entry to mark → the payload must not leak.
         assert!(!state.send_payloads.contains_key(&id));
     }
@@ -10922,7 +11193,7 @@ mod tests {
         assert!(state.send_queue.is_empty());
         assert!(state.send_payloads.is_empty());
         // A late result for the pre-reset send touches nothing and adds no entry.
-        state.apply_send_result(id, None);
+        assert!(!state.apply_send_result(id, None));
         assert!(state.chat_messages.is_empty());
         assert!(state.send_payloads.is_empty());
     }

src/config.rs

@@ -478,6 +478,14 @@ pub struct AppConfig {
     pub custom_sound_mic_toggle: Option<String>,
     #[serde(default)]
     pub custom_sound_reconnect_failed: Option<String>,
+    #[serde(default)]
+    pub custom_sound_chat_sent: Option<String>,
+    #[serde(default)]
+    pub custom_sound_chat_received: Option<String>,
+    #[serde(default)]
+    pub custom_sound_contact_online: Option<String>,
+    #[serde(default)]
+    pub custom_sound_contact_offline: Option<String>,
     /// Per-sound enable flags (W6). The master `notifications_enabled` toggle
     /// gates ALL chimes; these let the user silence individual events while the
     /// master stays on. A chime plays only if the master AND its flag are true.
@@ -498,6 +506,14 @@ pub struct AppConfig {
     pub sound_mic_toggle_enabled: bool,
     #[serde(default = "default_true")]
     pub sound_reconnect_failed_enabled: bool,
+    #[serde(default = "default_true")]
+    pub sound_chat_sent_enabled: bool,
+    #[serde(default = "default_true")]
+    pub sound_chat_received_enabled: bool,
+    #[serde(default = "default_true")]
+    pub sound_contact_online_enabled: bool,
+    #[serde(default = "default_true")]
+    pub sound_contact_offline_enabled: bool,
     /// Optional override for the `pixelpass` binary location (screen share).
     /// Empty / unset = look it up on `$PATH`. Hand-editable; no Settings UI yet.
     #[serde(default)]
@@ -601,6 +617,10 @@ impl Default for AppConfig {
             custom_sound_self_leave: None,
             custom_sound_mic_toggle: None,
             custom_sound_reconnect_failed: None,
+            custom_sound_chat_sent: None,
+            custom_sound_chat_received: None,
+            custom_sound_contact_online: None,
+            custom_sound_contact_offline: None,
             sound_self_join_enabled: true,
             sound_peer_join_enabled: true,
             sound_peer_leave_enabled: true,
@@ -609,6 +629,10 @@ impl Default for AppConfig {
             sound_self_leave_enabled: true,
             sound_mic_toggle_enabled: true,
             sound_reconnect_failed_enabled: true,
+            sound_chat_sent_enabled: true,
+            sound_chat_received_enabled: true,
+            sound_contact_online_enabled: true,
+            sound_contact_offline_enabled: true,
             pixelpass_path: None,
             screen_share: ScreenShareSettings::default(),
             recents: Vec::new(),
@@ -639,6 +663,10 @@ impl AppConfig {
             Sound::SelfLeave => self.sound_self_leave_enabled,
             Sound::MicToggle => self.sound_mic_toggle_enabled,
             Sound::ReconnectFailed => self.sound_reconnect_failed_enabled,
+            Sound::ChatSent => self.sound_chat_sent_enabled,
+            Sound::ChatReceived => self.sound_chat_received_enabled,
+            Sound::ContactOnline => self.sound_contact_online_enabled,
+            Sound::ContactOffline => self.sound_contact_offline_enabled,
         }
     }
 
@@ -653,6 +681,10 @@ impl AppConfig {
             Sound::SelfLeave => self.sound_self_leave_enabled = enabled,
             Sound::MicToggle => self.sound_mic_toggle_enabled = enabled,
             Sound::ReconnectFailed => self.sound_reconnect_failed_enabled = enabled,
+            Sound::ChatSent => self.sound_chat_sent_enabled = enabled,
+            Sound::ChatReceived => self.sound_chat_received_enabled = enabled,
+            Sound::ContactOnline => self.sound_contact_online_enabled = enabled,
+            Sound::ContactOffline => self.sound_contact_offline_enabled = enabled,
         }
     }
 
@@ -940,6 +972,10 @@ mod tests {
         assert!(deserialized.custom_sound_self_leave.is_none());
         assert!(deserialized.custom_sound_mic_toggle.is_none());
         assert!(deserialized.custom_sound_reconnect_failed.is_none());
+        assert!(deserialized.custom_sound_chat_sent.is_none());
+        assert!(deserialized.custom_sound_chat_received.is_none());
+        assert!(deserialized.custom_sound_contact_online.is_none());
+        assert!(deserialized.custom_sound_contact_offline.is_none());
         assert_eq!(deserialized.screen_share, ScreenShareSettings::default());
         assert_eq!(deserialized.screen_share.quality, ShareQuality::Auto);
         assert_eq!(deserialized.screen_share.player, SharePlayer::Mpv);

src/notify.rs

@@ -80,6 +80,14 @@ pub enum Sound {
     MicToggle,
     /// Reconnect failed / peer evicted.
     ReconnectFailed,
+    /// One of our chat messages was broadcast to the room.
+    ChatSent,
+    /// A chat message from another participant was admitted.
+    ChatReceived,
+    /// A saved contact was detected online on the home screen.
+    ContactOnline,
+    /// A saved contact previously seen online went offline on the home screen.
+    ContactOffline,
 }
 
 impl Sound {
@@ -93,10 +101,14 @@ impl Sound {
         Sound::SelfLeave,
         Sound::MicToggle,
         Sound::ReconnectFailed,
+        Sound::ChatSent,
+        Sound::ChatReceived,
+        Sound::ContactOnline,
+        Sound::ContactOffline,
     ];
 
     /// Number of distinct notification events.
-    pub const COUNT: usize = 8;
+    pub const COUNT: usize = 12;
 
     /// Stable 0-based index into the per-sound flag array. Must match `ALL`.
     fn index(self) -> usize {
@@ -109,6 +121,10 @@ impl Sound {
             Sound::SelfLeave => 5,
             Sound::MicToggle => 6,
             Sound::ReconnectFailed => 7,
+            Sound::ChatSent => 8,
+            Sound::ChatReceived => 9,
+            Sound::ContactOnline => 10,
+            Sound::ContactOffline => 11,
         }
     }
 
@@ -123,6 +139,10 @@ impl Sound {
             Sound::SelfLeave => include_bytes!("../assets/sounds/self-leave.wav"),
             Sound::MicToggle => include_bytes!("../assets/sounds/mic-toggle.wav"),
             Sound::ReconnectFailed => include_bytes!("../assets/sounds/reconnect-failed.wav"),
+            Sound::ChatSent => include_bytes!("../assets/sounds/chat-sent.wav"),
+            Sound::ChatReceived => include_bytes!("../assets/sounds/chat-received.wav"),
+            Sound::ContactOnline => include_bytes!("../assets/sounds/contact-online.wav"),
+            Sound::ContactOffline => include_bytes!("../assets/sounds/contact-offline.wav"),
         }
     }
 
@@ -137,6 +157,10 @@ impl Sound {
             Sound::SelfLeave => "self-leave",
             Sound::MicToggle => "mic-toggle",
             Sound::ReconnectFailed => "reconnect-failed",
+            Sound::ChatSent => "chat-sent",
+            Sound::ChatReceived => "chat-received",
+            Sound::ContactOnline => "contact-online",
+            Sound::ContactOffline => "contact-offline",
         }
     }
 }

src/screenshare/livesync.rs

@@ -0,0 +1,314 @@
+//! Live-edge catch-up for the screen-share viewer.
+//!
+//! PixelPass carries the share as MPEG-TS over a reliable, ordered transport. On
+//! a lossy link (satellite handovers are the pathological case) every loss burst
+//! becomes retransmission plus head-of-line blocking, and the viewer absorbs the
+//! stall as buffered latency. Nothing in the chain ever trims that buffer back,
+//! so the picture ends up seconds behind the host and stays there.
+//!
+//! Measured on a `tc netem` rig that simulates a satellite link (40 ms +/- 20 ms
+//! jitter, 0.5% loss, a 250 ms/30%-loss handover burst every 15 s): a viewer with
+//! ordinary timestamp pacing settles ~1.24 s behind. mpv's `--untimed` does NOT
+//! help (~1.38 s, marginally worse) because it only removes pacing at
+//! *presentation* while audio still drains at 1x the DAC rate, so an accumulated
+//! buffer never shrinks. Returning to the live edge requires consuming the
+//! backlog faster than it arrives.
+//!
+//! So we nudge playback slightly faster than realtime while the buffer is deep,
+//! and drop back to 1x once it has drained. mpv's default pitch correction
+//! (`scaletempo2`) keeps a 5% speedup inaudible, and because audio and video are
+//! sped up together A/V sync is preserved — unlike `--untimed`.
+//!
+//! The control law and the JSON-IPC message handling are pure functions with
+//! tests; the only I/O is [`drive`], which talks to mpv's `--input-ipc-server`
+//! socket.
+
+use std::path::{Path, PathBuf};
+use std::time::Duration;
+
+/// Buffer depth (seconds) above which we start draining.
+pub const CACHE_HIGH_S: f64 = 1.0;
+/// Buffer depth (seconds) below which we return to realtime.
+pub const CACHE_LOW_S: f64 = 0.4;
+/// The buffer depth we aim to sit at; the drain rate is proportional to how far
+/// above this the buffer actually is.
+pub const CACHE_TARGET_S: f64 = 0.5;
+/// Extra playback rate per second of excess buffer.
+pub const CATCHUP_GAIN: f64 = 0.05;
+/// Hard ceiling on the drain rate. Beyond this the speedup stops being
+/// unnoticeable, and a share that far behind is better served by the operator
+/// restarting it than by a chipmunk impression.
+pub const MAX_CATCHUP_SPEED: f64 = 1.15;
+/// Normal realtime playback.
+pub const NORMAL_SPEED: f64 = 1.0;
+/// How often we sample the buffer depth.
+pub const POLL_INTERVAL: Duration = Duration::from_millis(500);
+/// Smallest rate change worth sending to the player.
+pub const SPEED_EPSILON: f64 = 0.005;
+
+/// The property we watch on the viewer.
+const CACHE_PROPERTY: &str = "demuxer-cache-duration";
+
+/// Decide the playback rate for the next interval.
+///
+/// Proportional, because a fixed small speedup cannot recover a large backlog in
+/// any reasonable time: draining 6 s at 1.05x takes two minutes, which a viewer
+/// experiences as "still broken". The drain rate instead scales with how deep
+/// the buffer is, so a bad handover is cleared in tens of seconds while a small
+/// excursion still gets only a gentle, inaudible nudge.
+///
+/// Deliberately hysteretic: between [`CACHE_LOW_S`] and [`CACHE_HIGH_S`] the
+/// current rate is held, so a buffer hovering near a single threshold cannot
+/// oscillate the speed (and with it the audio pitch) every poll. Pure.
+///
+/// A non-finite reading (mpv reports `null` before playback starts, and the
+/// caller maps that to NaN) holds the current rate rather than guessing.
+pub fn catchup_speed(cache_s: f64, current: f64) -> f64 {
+    if !cache_s.is_finite() {
+        return current;
+    }
+    if cache_s < CACHE_LOW_S {
+        return NORMAL_SPEED;
+    }
+    if cache_s <= CACHE_HIGH_S {
+        return current;
+    }
+    let excess = cache_s - CACHE_TARGET_S;
+    (NORMAL_SPEED + CATCHUP_GAIN * excess).clamp(NORMAL_SPEED, MAX_CATCHUP_SPEED)
+}
+
+/// Where mpv should create its IPC socket. Kept separate from the runtime
+/// lookup so tests can pin a directory. Pure.
+pub fn socket_path(dir: &Path, token: u64) -> PathBuf {
+    dir.join(format!("peerspeak-mpv-{token}.sock"))
+}
+
+/// The directory for the IPC socket: the XDG runtime dir when the session
+/// provides one (tmpfs, user-private, cleaned at logout), else the temp dir.
+pub fn socket_dir() -> PathBuf {
+    std::env::var_os("XDG_RUNTIME_DIR")
+        .map(PathBuf::from)
+        .unwrap_or_else(std::env::temp_dir)
+}
+
+/// A `get_property` request for the buffer depth. Pure.
+pub fn get_cache_request(request_id: u64) -> String {
+    format!(r#"{{"command":["get_property","{CACHE_PROPERTY}"],"request_id":{request_id}}}"#)
+}
+
+/// A `set_property` request for the playback rate. Pure.
+pub fn set_speed_request(request_id: u64, speed: f64) -> String {
+    format!(r#"{{"command":["set_property","speed",{speed}],"request_id":{request_id}}}"#)
+}
+
+/// Extract the buffer depth from one line of mpv's IPC output.
+///
+/// mpv interleaves unsolicited event lines with command replies, so a line is
+/// only ours when it carries the matching `request_id`. Returns:
+/// - `Some(Some(secs))` — our reply, with a usable number,
+/// - `Some(None)` — our reply, but no number (mpv sends `"data":null` before
+///   playback starts, and reports `error` while the demuxer has no cache yet),
+/// - `None` — not our reply (an event, or another command's response).
+///
+/// Pure.
+pub fn parse_cache_response(line: &str, request_id: u64) -> Option<Option<f64>> {
+    let value: serde_json::Value = serde_json::from_str(line.trim()).ok()?;
+    let id = value.get("request_id")?.as_u64()?;
+    if id != request_id {
+        return None;
+    }
+    if value.get("error").and_then(|e| e.as_str()) != Some("success") {
+        return Some(None);
+    }
+    Some(value.get("data").and_then(|d| d.as_f64()))
+}
+
+/// Drive one mpv viewer's playback rate over its JSON IPC socket.
+///
+/// Runs until mpv exits (the socket dies), so it is spawned detached alongside
+/// the player and needs no shutdown signal. Every failure path just ends the
+/// task: catch-up is an optimization, and a viewer that never gets it still
+/// plays, exactly as before this existed.
+#[cfg(unix)]
+pub async fn drive(socket: PathBuf) {
+    use tokio::io::{AsyncBufReadExt, AsyncWriteExt, BufReader};
+    use tokio::net::UnixStream;
+
+    // mpv creates the socket a moment after exec, so the first connects race it.
+    let mut stream = None;
+    for _ in 0..40 {
+        match UnixStream::connect(&socket).await {
+            Ok(s) => {
+                stream = Some(s);
+                break;
+            }
+            Err(_) => tokio::time::sleep(Duration::from_millis(250)).await,
+        }
+    }
+    let Some(stream) = stream else {
+        crate::log_msg("livesync: mpv IPC socket never appeared; catch-up disabled");
+        return;
+    };
+
+    let (read_half, mut write_half) = stream.into_split();
+    let mut lines = BufReader::new(read_half).lines();
+    let mut request_id: u64 = 0;
+    let mut speed = NORMAL_SPEED;
+
+    loop {
+        tokio::time::sleep(POLL_INTERVAL).await;
+
+        request_id += 1;
+        let query = format!("{}\n", get_cache_request(request_id));
+        if write_half.write_all(query.as_bytes()).await.is_err() {
+            break;
+        }
+
+        // Skip event lines until our reply arrives.
+        let cache = loop {
+            match lines.next_line().await {
+                Ok(Some(line)) => {
+                    if let Some(value) = parse_cache_response(&line, request_id) {
+                        break value;
+                    }
+                }
+                // Socket closed or unreadable: mpv is gone.
+                _ => return,
+            }
+        };
+
+        let cache = cache.unwrap_or(f64::NAN);
+        let next = catchup_speed(cache, speed);
+        // A proportional law would otherwise re-send on every wobble of the
+        // reading; only a change worth hearing is worth a round trip.
+        if (next - speed).abs() > SPEED_EPSILON {
+            speed = next;
+            request_id += 1;
+            let set = format!("{}\n", set_speed_request(request_id, speed));
+            if write_half.write_all(set.as_bytes()).await.is_err() {
+                break;
+            }
+            crate::log_msg(&format!(
+                "livesync: cache {cache:.2}s -> playback speed {speed}x"
+            ));
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn deep_buffer_speeds_up_and_drained_buffer_returns_to_realtime() {
+        assert!(catchup_speed(1.5, NORMAL_SPEED) > NORMAL_SPEED);
+        assert_eq!(catchup_speed(0.1, MAX_CATCHUP_SPEED), NORMAL_SPEED);
+    }
+
+    #[test]
+    fn drain_rate_scales_with_how_far_behind_we_are() {
+        // The point of the proportional law: a small excursion gets a gentle
+        // nudge, a deep backlog gets real recovery.
+        let small = catchup_speed(1.5, NORMAL_SPEED);
+        let large = catchup_speed(4.0, NORMAL_SPEED);
+        assert!(
+            large > small,
+            "deeper buffer must drain faster: {small} vs {large}"
+        );
+        assert!(
+            (small - 1.05).abs() < 1e-9,
+            "1.5s buffer -> 1.05x, got {small}"
+        );
+    }
+
+    #[test]
+    fn drain_rate_is_capped_so_it_never_sounds_absurd() {
+        // The ~6 s standing buffer measured on the netem rig, and far worse.
+        assert_eq!(catchup_speed(6.0, NORMAL_SPEED), MAX_CATCHUP_SPEED);
+        assert_eq!(catchup_speed(600.0, NORMAL_SPEED), MAX_CATCHUP_SPEED);
+    }
+
+    #[test]
+    fn hysteresis_band_holds_the_current_speed() {
+        // Between the marks nothing changes, whichever side we came from —
+        // this is what stops the rate (and audio pitch) oscillating.
+        for cache in [CACHE_LOW_S, 0.7, CACHE_HIGH_S] {
+            assert_eq!(catchup_speed(cache, NORMAL_SPEED), NORMAL_SPEED);
+            assert_eq!(catchup_speed(cache, MAX_CATCHUP_SPEED), MAX_CATCHUP_SPEED);
+        }
+    }
+
+    #[test]
+    fn unknown_cache_holds_the_current_speed() {
+        assert_eq!(
+            catchup_speed(f64::NAN, MAX_CATCHUP_SPEED),
+            MAX_CATCHUP_SPEED
+        );
+        assert_eq!(catchup_speed(f64::INFINITY, NORMAL_SPEED), NORMAL_SPEED);
+    }
+
+    #[test]
+    fn a_full_handover_cycle_drains_then_settles() {
+        // Buffer grows through a loss burst, then drains as we play faster.
+        let mut speed = NORMAL_SPEED;
+        for cache in [0.2, 0.5, 1.2, 3.4, 1.4, 0.9, 0.6, 0.3, 0.2] {
+            speed = catchup_speed(cache, speed);
+        }
+        assert_eq!(
+            speed, NORMAL_SPEED,
+            "should be back at realtime once drained"
+        );
+    }
+
+    #[test]
+    fn requests_are_valid_json_with_their_ids() {
+        let get: serde_json::Value = serde_json::from_str(&get_cache_request(7)).unwrap();
+        assert_eq!(get["request_id"], 7);
+        assert_eq!(get["command"][0], "get_property");
+        assert_eq!(get["command"][1], CACHE_PROPERTY);
+
+        let set: serde_json::Value = serde_json::from_str(&set_speed_request(8, 1.05)).unwrap();
+        assert_eq!(set["request_id"], 8);
+        assert_eq!(set["command"][0], "set_property");
+        assert_eq!(set["command"][1], "speed");
+        assert_eq!(set["command"][2], 1.05);
+    }
+
+    #[test]
+    fn parses_our_reply_only() {
+        assert_eq!(
+            parse_cache_response(r#"{"error":"success","data":1.25,"request_id":3}"#, 3),
+            Some(Some(1.25))
+        );
+        // Another command's reply, and an unsolicited event, are not ours.
+        assert_eq!(
+            parse_cache_response(r#"{"error":"success","data":1.25,"request_id":4}"#, 3),
+            None
+        );
+        assert_eq!(
+            parse_cache_response(r#"{"event":"playback-restart"}"#, 3),
+            None
+        );
+        assert_eq!(parse_cache_response("not json", 3), None);
+    }
+
+    #[test]
+    fn reply_without_a_usable_number_is_ours_but_empty() {
+        // mpv before playback starts, and while the demuxer has no cache.
+        assert_eq!(
+            parse_cache_response(r#"{"error":"success","data":null,"request_id":1}"#, 1),
+            Some(None)
+        );
+        assert_eq!(
+            parse_cache_response(r#"{"error":"property unavailable","request_id":1}"#, 1),
+            Some(None)
+        );
+    }
+
+    #[test]
+    fn socket_path_is_scoped_to_its_token() {
+        let a = socket_path(Path::new("/run/user/1000"), 42);
+        assert_eq!(a, Path::new("/run/user/1000/peerspeak-mpv-42.sock"));
+        assert_ne!(a, socket_path(Path::new("/run/user/1000"), 43));
+    }
+}

src/screenshare/mod.rs

@@ -21,6 +21,8 @@ use std::time::Duration;
 use tokio::io::{AsyncBufReadExt, BufReader};
 use tokio::process::{Child, Command};
 
+pub mod livesync;
+
 use crate::config::{ScreenShareSettings, ShareBuffering, SharePlayer, ShareQuality};
 
 /// The binary we shell out to. Looked up on `$PATH` unless a config override
@@ -45,6 +47,12 @@ const MAX_TICKET_LEN: usize = 512;
 /// are short ("Firefox", "mpv"); this only guards against a pathological value.
 const MAX_APP_NAME_LEN: usize = 256;
 
+/// Ceiling on the viewer's demuxer byte cache in the Low latency posture. The
+/// cache is a *byte* budget, so at a given bitrate it sets the worst-case
+/// backlog in seconds; keeping it tight is what stops a lossy link parking the
+/// viewer seconds behind before [`livesync`] even gets a chance to drain it.
+const LOW_LATENCY_CACHE_CAP_MB: u32 = 1;
+
 /// How long to wait for the host to emit its ticket / the viewer to connect
 /// before giving up and killing the child. Startup is normally sub-second; this
 /// is only a safety net so a hung pixelpass can't wedge the caller forever.
@@ -607,16 +615,28 @@ fn event_for_log(ev: &PixelpassEvent) -> String {
 /// player is reaped in a background task so it doesn't linger as a zombie when
 /// its window closes.
 ///
-/// The flags keep latency low while preserving A/V sync. We deliberately do
-/// NOT pass mpv's `--untimed`: that displays each video frame the instant it
-/// decodes, ignoring audio timestamps, which makes a shared *video* drift
-/// progressively out of sync with its audio. Pacing to the audio clock costs a
-/// little latency (negligible for pointing at a desktop) and keeps a shared
-/// video in sync. We also leave hwdec at the `low-latency` default (software
-/// decode): forcing `--hwdec=auto` froze some viewers on frame 1 while audio
-/// kept playing.
+/// The buffering posture chooses the latency/A/V-sync tradeoff. Low latency
+/// keeps the viewer at the live edge: mpv gets an IPC socket and [`livesync`]
+/// drains a lagging buffer by playing slightly fast (pitch-corrected, so A/V
+/// sync is preserved). Smooth leaves a deeper buffer alone, trading live
+/// latency for immunity to jitter. Hardware decoding remains opt-in: forcing
+/// `--hwdec=auto` froze some viewers on frame 1 while audio kept playing.
 fn launch_player(url: &str, settings: &ScreenShareSettings) -> std::io::Result<()> {
-    let mpv_args = mpv_args(settings);
+    // One socket per viewer launch, so overlapping shares can't collide on it.
+    // Unix only: mpv's IPC is a named pipe on Windows, which `livesync` does not
+    // speak, and an unusable socket path on the argv would help nobody.
+    #[cfg(unix)]
+    let ipc_socket = Some(livesync::socket_path(
+        &livesync::socket_dir(),
+        std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .map(|d| d.as_nanos() as u64)
+            .unwrap_or(0),
+    ));
+    #[cfg(not(unix))]
+    let ipc_socket: Option<PathBuf> = None;
+
+    let mpv_args = mpv_args(settings, ipc_socket.as_deref());
     let vlc_args = vlc_args(settings);
     let first = match settings.player {
         SharePlayer::Mpv => ("mpv", &mpv_args),
@@ -627,15 +647,32 @@ fn launch_player(url: &str, settings: &ScreenShareSettings) -> std::io::Result<(
         SharePlayer::Vlc => ("mpv", &mpv_args),
     };
 
-    let child = match spawn_player(first.0, first.1, url) {
-        Ok(c) => c,
-        Err(_) => spawn_player(second.0, second.1, url).map_err(|_| {
-            std::io::Error::new(
-                std::io::ErrorKind::NotFound,
-                "no media player found — install mpv or vlc to watch screen shares",
-            )
-        })?,
+    let (launched, child) = match spawn_player(first.0, first.1, url) {
+        Ok(c) => (first.0, c),
+        Err(_) => (
+            second.0,
+            spawn_player(second.0, second.1, url).map_err(|_| {
+                std::io::Error::new(
+                    std::io::ErrorKind::NotFound,
+                    "no media player found — install mpv or vlc to watch screen shares",
+                )
+            })?,
+        ),
     };
+
+    // Only when the socket actually reached the argv: mpv (VLC has no
+    // equivalent IPC) in the Low latency posture. The driver ends by itself when
+    // the player exits, so it needs no shutdown path.
+    #[cfg(unix)]
+    if launched == "mpv"
+        && settings.buffering == ShareBuffering::LowLatency
+        && let Some(socket) = ipc_socket
+    {
+        tokio::spawn(livesync::drive(socket));
+    }
+    #[cfg(not(unix))]
+    let _ = launched;
+
     tokio::spawn(async move {
         let mut child = child;
         let _ = child.wait().await;
@@ -643,11 +680,23 @@ fn launch_player(url: &str, settings: &ScreenShareSettings) -> std::io::Result<(
     Ok(())
 }
 
-pub fn mpv_args(settings: &ScreenShareSettings) -> Vec<String> {
+/// Build the argv for an mpv viewer.
+///
+/// `ipc_socket` is where mpv should expose its JSON IPC socket so [`livesync`]
+/// can drain a lagging buffer. It is wired up for Low latency only: Smooth
+/// deliberately holds a ~2 s readahead, which the catch-up thresholds would
+/// fight on every poll.
+pub fn mpv_args(settings: &ScreenShareSettings, ipc_socket: Option<&Path>) -> Vec<String> {
     let mut args = Vec::new();
     match settings.buffering {
         ShareBuffering::LowLatency => {
             args.push("--profile=low-latency".to_string());
+            // Pixelpass carries MPEG-TS through reliable ordered QUIC/TCP, so a
+            // lossy link turns every retransmission into buffered latency that
+            // nothing trims back. `--untimed` does NOT fix that (measured
+            // marginally worse: it only unpaces *presentation*, while audio
+            // still drains at 1x, so the backlog never shrinks) — the viewer
+            // instead drains it by playing slightly fast, see `livesync`.
             args.push("--audio-buffer=0.2".to_string());
             args.push("--demuxer-readahead-secs=0.5".to_string());
         }
@@ -656,10 +705,25 @@ pub fn mpv_args(settings: &ScreenShareSettings) -> Vec<String> {
             args.push("--demuxer-readahead-secs=2".to_string());
         }
     }
-    args.push(format!("--demuxer-max-bytes={}M", settings.cache_mb));
+    // The byte cap is what bounds how far behind a viewer can silently fall:
+    // a demuxer allowed 2 MiB will happily sit on ~6 s of a 2.5 Mbps share (as
+    // measured on the netem rig) and call it a buffer. Low latency therefore
+    // gets a tighter ceiling than the user's Smooth-oriented setting, so the
+    // catch-up has less to claw back after a bad patch of link.
+    let cache_mb = match settings.buffering {
+        ShareBuffering::LowLatency => settings.cache_mb.min(LOW_LATENCY_CACHE_CAP_MB),
+        ShareBuffering::Smooth => settings.cache_mb,
+    };
+    args.push(format!("--demuxer-max-bytes={cache_mb}M"));
     if settings.hardware_decode {
         args.push("--hwdec=auto".to_string());
     }
+    if let Some(socket) = ipc_socket
+        && settings.buffering == ShareBuffering::LowLatency
+    {
+        args.push(format!("--input-ipc-server={}", socket.display()));
+    }
+    // Extra args stay last so a user override wins over everything above.
     args.extend(split_extra_args(&settings.extra_mpv_args));
     args
 }
@@ -825,16 +889,86 @@ mod tests {
     #[test]
     fn mpv_args_default_matches_low_latency_software_decode() {
         assert_eq!(
-            mpv_args(&ScreenShareSettings::default()),
+            mpv_args(&ScreenShareSettings::default(), None),
             vec![
                 "--profile=low-latency",
                 "--audio-buffer=0.2",
                 "--demuxer-readahead-secs=0.5",
-                "--demuxer-max-bytes=2M",
+                "--demuxer-max-bytes=1M",
             ]
         );
     }
 
+    #[test]
+    fn low_latency_gets_the_ipc_socket_for_live_edge_catch_up() {
+        let args = mpv_args(
+            &ScreenShareSettings::default(),
+            Some(Path::new("/run/user/1000/peerspeak-mpv-1.sock")),
+        );
+        assert!(
+            args.contains(&"--input-ipc-server=/run/user/1000/peerspeak-mpv-1.sock".to_string()),
+            "low latency drains a lagging buffer over mpv IPC: {args:?}"
+        );
+        // The flag that used to hold this posture at the live edge measured no
+        // better than pacing, and cost A/V sync — it must not come back.
+        assert!(!args.contains(&"--untimed".to_string()));
+    }
+
+    #[test]
+    fn smooth_keeps_its_deep_buffer_and_gets_no_ipc_socket() {
+        let settings = ScreenShareSettings {
+            buffering: ShareBuffering::Smooth,
+            ..ScreenShareSettings::default()
+        };
+        let args = mpv_args(
+            &settings,
+            Some(Path::new("/run/user/1000/peerspeak-mpv-1.sock")),
+        );
+        assert!(
+            !args.iter().any(|a| a.starts_with("--input-ipc-server")),
+            "catch-up would fight Smooth's deliberate ~2s readahead: {args:?}"
+        );
+    }
+
+    #[test]
+    fn low_latency_caps_the_byte_cache_but_smooth_keeps_the_user_value() {
+        // The cache is a byte budget, so at a given bitrate it sets the
+        // worst-case backlog: 2 MiB held ~6 s of a 2.5 Mbps share on the rig.
+        let generous = ScreenShareSettings {
+            cache_mb: 32,
+            ..ScreenShareSettings::default()
+        };
+        assert!(
+            mpv_args(&generous, None)
+                .contains(&format!("--demuxer-max-bytes={LOW_LATENCY_CACHE_CAP_MB}M")),
+            "low latency must bound how far behind the viewer can silently fall"
+        );
+
+        let smooth = ScreenShareSettings {
+            cache_mb: 32,
+            buffering: ShareBuffering::Smooth,
+            ..ScreenShareSettings::default()
+        };
+        assert!(
+            mpv_args(&smooth, None).contains(&"--demuxer-max-bytes=32M".to_string()),
+            "smooth is the posture where the user asked for a deep buffer"
+        );
+    }
+
+    #[test]
+    fn user_extra_args_still_come_last() {
+        let settings = ScreenShareSettings {
+            extra_mpv_args: "--no-osc".to_string(),
+            ..ScreenShareSettings::default()
+        };
+        let args = mpv_args(&settings, Some(Path::new("/tmp/s.sock")));
+        assert_eq!(
+            args.last().map(String::as_str),
+            Some("--no-osc"),
+            "a user override has to win over everything we add: {args:?}"
+        );
+    }
+
     #[test]
     fn mpv_args_smooth_hwdecode_and_extra_args_last() {
         let settings = ScreenShareSettings {
@@ -846,7 +980,7 @@ mod tests {
         };
 
         assert_eq!(
-            mpv_args(&settings),
+            mpv_args(&settings, None),
             vec![
                 "--cache=yes",
                 "--demuxer-readahead-secs=2",