feat: reconnect on transient link loss with per-peer supervisors

Audio links now survive a dropped QUIC connection instead of silently
dying until the peer leaves and rejoins the room.

Transport: each peer is owned by a single supervisor task running a
connect → run → reconnect loop. The deterministic-initiator rule (lower
id dials, higher accepts) holds on every reconnect, so one shared
connection re-forms each time; the dialer redials with capped backoff
and the acceptor awaits the inbound link, switching to a replacement
immediately if one arrives before its own close fires. Inbound
connections are routed to the supervisor via a per-peer channel.

Fixes a latent bug from the prior design: aborting a peer's tasks left
the detached send/read loops running, holding Connection clones so the
link never actually closed. The loops now live in abort-on-drop guards
scoped to the supervisor, so cancelling it releases the connection.

UX: a new ConnEvent stream surfaces per-peer link state to the UI, which
shows "Connecting…"/"Reconnecting…" with a yellow indicator and border
while a peer's audio link is down, returning to normal when it recovers.

Tests: the loopback test now runs through the supervisor path, plus a
new test drives a real drop (explicit close of a controlled peer
endpoint) and asserts the dialer re-dials the stable address and audio
resumes over the rebuilt connection.

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

src/app/mod.rs

@@ -10,7 +10,7 @@ use iced::{
     Color, Background, Border, Element, Subscription, Task, Theme, Event, keyboard,
 };
 use iroh::EndpointId;
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::sync::{Arc, OnceLock};
 use tokio::sync::Mutex;
 
@@ -80,6 +80,11 @@ pub struct AppState {
     peers: HashMap<EndpointId, PeerState>,
     peer_volumes: HashMap<EndpointId, f32>,
     audio_levels: HashMap<EndpointId, f32>,
+    /// Peers whose audio link is currently down (initial connect or reconnect).
+    connecting: HashSet<EndpointId>,
+    /// Peers we've had a live link to at least once — used to say "Reconnecting"
+    /// rather than "Connecting" the second time around.
+    ever_connected: HashSet<EndpointId>,
     controller: Arc<CoreController>,
     current_screen: Screen,
 }
@@ -121,6 +126,8 @@ impl Default for AppState {
             peers: HashMap::new(),
             peer_volumes: HashMap::new(),
             audio_levels: HashMap::new(),
+            connecting: HashSet::new(),
+            ever_connected: HashSet::new(),
             controller,
             current_screen: Screen::Home,
         }
@@ -206,6 +213,8 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.ticket = "".to_string();
                     state.peers.clear();
                     state.audio_levels.clear();
+                    state.connecting.clear();
+                    state.ever_connected.clear();
                     state.status_message = "Ready to connect".to_string();
                     state.current_screen = Screen::Home;
                 }
@@ -215,10 +224,19 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                 UiEvent::PeerLeft { id } => {
                     state.peers.remove(&id);
                     state.audio_levels.remove(&id);
+                    state.connecting.remove(&id);
+                    state.ever_connected.remove(&id);
                 }
                 UiEvent::PeerUpdated { id, state: peer_state } => {
                     state.peers.insert(id, peer_state);
                 }
+                UiEvent::PeerConnecting { id } => {
+                    state.connecting.insert(id);
+                }
+                UiEvent::PeerConnected { id } => {
+                    state.connecting.remove(&id);
+                    state.ever_connected.insert(id);
+                }
                 UiEvent::AudioLevels(levels) => {
                     for (id, val) in levels {
                         state.audio_levels.insert(id, val);
@@ -326,6 +344,7 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
     let color_red = Color::from_rgb8(243, 139, 168);
     let color_maroon = Color::from_rgb8(233, 146, 160);
     let color_green = Color::from_rgb8(166, 227, 161);
+    let color_yellow = Color::from_rgb8(249, 226, 175);
 
     // Style Helpers
     let c_style = move |bg: Color, b_color: Color, radius: f32| {
@@ -585,9 +604,17 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
 
         for (peer_id, peer) in &state.peers {
             let level = state.audio_levels.get(peer_id).copied().unwrap_or(0.0);
-            let is_speaking = level > 0.01;
+            let is_connecting = state.connecting.contains(peer_id);
+            let is_speaking = !is_connecting && level > 0.01;
 
-            let indicator = if peer.is_muted {
+            let indicator = if is_connecting {
+                let label = if state.ever_connected.contains(peer_id) {
+                    "[Reconnecting…]"
+                } else {
+                    "[Connecting…]"
+                };
+                text(label).size(14).color(color_yellow)
+            } else if peer.is_muted {
                 text("[Muted]").size(14).color(color_red)
             } else if is_speaking {
                 text("[Speaking]").size(14).color(color_green)
@@ -620,7 +647,7 @@ fn view(state: &AppState) -> Element<'_, AppMessage> {
             let card = container(card_content)
             .style(c_style(
                 if is_speaking { color_base } else { color_mantle },
-                if is_speaking { color_green } else { color_surface },
+                if is_connecting { color_yellow } else if is_speaking { color_green } else { color_surface },
                 6.0
             ))
             .padding(12);

src/core/messages.rs

@@ -24,6 +24,10 @@ pub enum UiEvent {
     PeerJoined { id: EndpointId, state: PeerState },
     PeerLeft { id: EndpointId },
     PeerUpdated { id: EndpointId, state: PeerState },
+    /// Audio link to a peer is being (re)established — show a connecting state.
+    PeerConnecting { id: EndpointId },
+    /// Audio link to a peer is up and carrying audio.
+    PeerConnected { id: EndpointId },
     AudioLevels(Vec<(EndpointId, f32)>),
     Error(String),
 }

src/core/mod.rs

@@ -5,7 +5,7 @@ use crate::audio::{AudioBackend, pipewire_impl::PipeWireBackend};
 use crate::codec::{AudioEncoder, opus_impl::OpusEncoder};
 use crate::core::jitter::{JitterBuffer, FRAME_SAMPLES};
 use crate::network::{
-    NetworkTransport, RoomState, PeerState, RoomEvent, PeerSpeakTicket,
+    NetworkTransport, RoomState, PeerState, RoomEvent, ConnEvent, PeerSpeakTicket,
     iroh_impl::IrohTransport,
     gossip::IrohGossipState,
 };
@@ -54,6 +54,7 @@ struct ActiveSession {
     datagram_task: tokio::task::JoinHandle<()>,
     mixer_task: tokio::task::JoinHandle<()>,
     event_task: tokio::task::JoinHandle<()>,
+    conn_event_task: tokio::task::JoinHandle<()>,
 }
 
 impl ActiveSession {
@@ -62,6 +63,7 @@ impl ActiveSession {
         self.datagram_task.abort();
         self.mixer_task.abort();
         self.event_task.abort();
+        self.conn_event_task.abort();
         crate::log_msg("Aborted tasks");
 
         let audio_backend_clone = audio_backend.clone();
@@ -413,6 +415,28 @@ async fn run_core_loop(
                     }
                 });
 
+                // 5. Connection-state forwarder: turns transport link state into
+                //    per-peer UI indicators (connecting / reconnecting vs. live).
+                let mut conn_events = match transport.subscribe_conn_events().await {
+                    Ok(rx) => rx,
+                    Err(e) => {
+                        let _ = ui_tx.send(UiEvent::Error(format!("Failed to subscribe conn events: {}", e))).await;
+                        continue;
+                    }
+                };
+                let ui_tx_conn = ui_tx.clone();
+                let conn_event_task = tokio::spawn(async move {
+                    while let Some(event) = conn_events.recv().await {
+                        let msg = match event {
+                            ConnEvent::Connecting(id) => UiEvent::PeerConnecting { id },
+                            ConnEvent::Connected(id) => UiEvent::PeerConnected { id },
+                        };
+                        if ui_tx_conn.send(msg).await.is_err() {
+                            break;
+                        }
+                    }
+                });
+
                 let session = ActiveSession {
                     endpoint: endpoint.clone(),
                     router,
@@ -421,6 +445,7 @@ async fn run_core_loop(
                     datagram_task,
                     mixer_task,
                     event_task,
+                    conn_event_task,
                 };
 
                 let self_id = endpoint.id().to_string();

src/network/iroh_impl.rs

@@ -1,4 +1,4 @@
-use crate::network::{NetworkTransport, NetError};
+use crate::network::{NetworkTransport, NetError, ConnEvent};
 use iroh::{Endpoint, EndpointId};
 use iroh::endpoint::Connection;
 use bytes::Bytes;
@@ -6,6 +6,7 @@ use tokio::sync::mpsc;
 use tokio::sync::mpsc::Receiver;
 use std::sync::{Arc, Mutex as StdMutex};
 use std::collections::HashMap;
+use std::time::Duration;
 use async_trait::async_trait;
 
 const AUDIO_ALPN: &[u8] = b"peerspeak-audio";
@@ -14,74 +15,212 @@ const AUDIO_ALPN: &[u8] = b"peerspeak-audio";
 /// useless latency — keep it shallow and drop the oldest frame when full.
 const SEND_QUEUE_DEPTH: usize = 8;
 
-/// State shared between the transport and its protocol handler so both inbound
+/// How many inbound connections we'll buffer for a single peer's supervisor.
-/// (accepted) and outbound (dialed) connections register the same way.
+/// During a healthy link the supervisor drains this promptly; a small buffer
+/// just covers the brief window between detecting a drop and re-awaiting.
+const INBOUND_QUEUE_DEPTH: usize = 4;
+
+/// Reconnect backoff bounds for the dialing side. Starts gentle so a momentary
+/// blip recovers almost instantly, and caps so a long outage doesn't hammer.
+const INITIAL_BACKOFF: Duration = Duration::from_millis(250);
+const MAX_BACKOFF: Duration = Duration::from_secs(5);
+
+/// 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 {
+    /// Used by dialer-side supervisors to (re)establish connections.
+    endpoint: Endpoint,
+    self_id: EndpointId,
     /// Sync-lockable send handles, so `broadcast` can fan out from the (non-async)
-    /// capture/encode thread without touching the Tokio runtime.
+    /// capture/encode thread without touching the Tokio runtime. A supervisor
+    /// inserts its handle when a link comes up and removes it when the link dies,
+    /// so `broadcast` only ever targets peers that are currently reachable.
     senders: StdMutex<HashMap<EndpointId, mpsc::Sender<Bytes>>>,
-    /// Per-peer task handles + a retained connection clone. Keeping the clone
+    /// One supervisor task per known peer.
-    /// alive is what stops iroh from closing an accepted connection once the
+    peers: tokio::sync::Mutex<HashMap<EndpointId, PeerHandle>>,
-    /// `accept()` future returns.
-    peers: tokio::sync::Mutex<HashMap<EndpointId, PeerTasks>>,
     incoming_tx: mpsc::Sender<(EndpointId, Bytes)>,
+    /// Best-effort link-state notifications for the UI (connecting / connected).
+    conn_events_tx: mpsc::Sender<ConnEvent>,
 }
 
-struct PeerTasks {
+struct PeerHandle {
-    send_task: tokio::task::JoinHandle<()>,
+    /// The supervisor owning this peer's connect → run → reconnect loop.
-    read_task: tokio::task::JoinHandle<()>,
+    supervisor: tokio::task::JoinHandle<()>,
-    _conn: Connection,
+    /// Inbound connections accepted for this peer are routed here so the
+    /// acceptor-side supervisor can pick them up (initial and reconnect).
+    inbound_tx: mpsc::Sender<Connection>,
+}
+
+/// Aborts a spawned task when dropped. The supervisor holds its send/read loops
+/// in these so that cancelling the supervisor (via `remove`'s `abort`) tears the
+/// loops down too — otherwise they'd keep their `Connection` clones alive and
+/// the link would never actually close.
+struct AbortOnDrop(tokio::task::JoinHandle<()>);
+
+impl Drop for AbortOnDrop {
+    fn drop(&mut self) {
+        self.0.abort();
+    }
 }
 
 impl Shared {
-    /// Register a live connection: spin up its send loop (datagrams out) and
+    /// Ensure a supervisor task exists for `peer_id`, returning its inbound
-    /// read loop (datagrams in). Idempotent — a second registration for an
+    /// connection sender. Idempotent: a second call for a known peer just hands
-    /// already-known peer is ignored so we never run duplicate loops.
+    /// back the existing sender. Both the reactive `connect_peer` path and the
-    async fn register(self: &Arc<Self>, peer_id: EndpointId, conn: Connection) {
+    /// inbound `accept()` path funnel through here, so whichever fires first
-        {
+    /// spins the peer up and the roles stay deterministic by id.
-            let peers = self.peers.lock().await;
+    async fn ensure_supervisor(self: &Arc<Self>, peer_id: EndpointId) -> mpsc::Sender<Connection> {
-            if peers.contains_key(&peer_id) {
+        let mut peers = self.peers.lock().await;
-                return;
+        if let Some(handle) = peers.get(&peer_id) {
+            return handle.inbound_tx.clone();
+        }
+
+        let (inbound_tx, inbound_rx) = mpsc::channel::<Connection>(INBOUND_QUEUE_DEPTH);
+        let shared = self.clone();
+        let supervisor = tokio::spawn(supervise(shared, peer_id, inbound_rx));
+        let inbound_tx_ret = inbound_tx.clone();
+        peers.insert(peer_id, PeerHandle { supervisor, inbound_tx });
+        crate::log_msg(&format!("Transport: supervising peer {:?}", peer_id));
+        inbound_tx_ret
+    }
+
+    /// Permanently retire a peer (it left the room). Stops its supervisor — which
+    /// cancels any in-flight dial or live link — and drops its send handle.
+    async fn remove(&self, peer_id: EndpointId) {
+        self.senders.lock().unwrap().remove(&peer_id);
+        if let Some(handle) = self.peers.lock().await.remove(&peer_id) {
+            handle.supervisor.abort();
+            crate::log_msg(&format!("Transport: stopped supervising peer {:?}", peer_id));
         }
     }
+}
+
+/// Why a peer's live-link wait woke up.
+enum Wake {
+    /// The QUIC connection closed (idle timeout or error) — need to reconnect.
+    Closed,
+    /// A fresh inbound connection arrived (acceptor side) — switch to it.
+    Replacement(Connection),
+    /// The peer was retired; tear down.
+    Shutdown,
+}
+
+/// Owns a single peer's connection lifecycle for as long as the peer is in the
+/// room: obtain a link, run the send/read loops, and on loss obtain a new one —
+/// with capped backoff on the dialing side. The deterministic-initiator rule
+/// (lower id dials, higher id accepts) is the same on first connect and every
+/// reconnect, so exactly one shared connection forms each time.
+async fn supervise(
+    shared: Arc<Shared>,
+    peer_id: EndpointId,
+    mut inbound_rx: mpsc::Receiver<Connection>,
+) {
+    let is_dialer = shared.self_id.to_string() < peer_id.to_string();
+    let mut backoff = INITIAL_BACKOFF;
+
+    // Show "connecting" until the first link is actually up.
+    let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
+
+    let mut conn = match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff).await {
+        Some(conn) => conn,
+        None => return, // retired before we ever connected
+    };
+
+    loop {
+        // A healthy link resets the dialer's backoff for the next outage.
+        backoff = INITIAL_BACKOFF;
 
         let (send_tx, mut send_rx) = mpsc::channel::<Bytes>(SEND_QUEUE_DEPTH);
+        shared.senders.lock().unwrap().insert(peer_id, send_tx);
+        let _ = shared.conn_events_tx.try_send(ConnEvent::Connected(peer_id));
+        crate::log_msg(&format!("Transport: peer {:?} link up", peer_id));
 
+        // Run until the link dies, a replacement arrives, or we're retired. The
+        // send/read loops are held in abort-on-drop guards scoped to this block,
+        // so however we leave it — normal exit or the supervisor being aborted
+        // mid-`select` — both loops stop and release their `Connection` clones.
+        let wake = {
             let conn_send = conn.clone();
-        let send_task = tokio::spawn(async move {
+            let _send_guard = AbortOnDrop(tokio::spawn(async move {
                 while let Some(data) = send_rx.recv().await {
                     if conn_send.send_datagram(data).is_err() {
                         break;
                     }
                 }
-        });
+            }));
 
             let conn_read = conn.clone();
-        let incoming_tx = self.incoming_tx.clone();
+            let incoming_tx = shared.incoming_tx.clone();
-        let read_task = tokio::spawn(async move {
+            let _read_guard = AbortOnDrop(tokio::spawn(async move {
                 while let Ok(bytes) = conn_read.read_datagram().await {
                     if incoming_tx.send((peer_id, bytes)).await.is_err() {
                         break;
                     }
                 }
-        });
+            }));
 
-        self.senders.lock().unwrap().insert(peer_id, send_tx);
+            // Only the acceptor watches for replacements: if the dialer notices
-        self.peers.lock().await.insert(
+            // the drop and re-dials before our own `closed()` fires, we switch to
-            peer_id,
+            // the new link immediately instead of waiting out the idle timeout.
-            PeerTasks { send_task, read_task, _conn: conn },
+            tokio::select! {
-        );
+                _ = conn.closed() => Wake::Closed,
-        crate::log_msg(&format!("Transport: registered peer {:?}", peer_id));
+                inbound = inbound_rx.recv(), if !is_dialer => match inbound {
+                    Some(new_conn) => Wake::Replacement(new_conn),
+                    None => Wake::Shutdown,
+                },
             }
+        };
 
-    async fn remove(&self, peer_id: EndpointId) {
+        // Dropping the send handle makes `broadcast` skip this peer until the
-        self.senders.lock().unwrap().remove(&peer_id);
+        // link is back, instead of piling frames into a dead connection.
-        if let Some(tasks) = self.peers.lock().await.remove(&peer_id) {
+        shared.senders.lock().unwrap().remove(&peer_id);
-            tasks.send_task.abort();
+
-            tasks.read_task.abort();
+        match wake {
-            // Dropping `_conn` (the last retained clone) closes the connection.
+            Wake::Shutdown => return,
-            crate::log_msg(&format!("Transport: removed peer {:?}", peer_id));
+            Wake::Replacement(new_conn) => {
+                crate::log_msg(&format!("Transport: peer {:?} replaced with new inbound link", peer_id));
+                let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
+                conn = new_conn;
             }
+            Wake::Closed => {
+                crate::log_msg(&format!("Transport: peer {:?} link dropped; reconnecting", peer_id));
+                let _ = shared.conn_events_tx.try_send(ConnEvent::Connecting(peer_id));
+                conn = match obtain_conn(&shared, peer_id, is_dialer, &mut inbound_rx, &mut backoff).await {
+                    Some(conn) => conn,
+                    None => return, // retired while reconnecting
+                };
+            }
+        }
+    }
+}
+
+/// Block until we hold a live connection to the peer, or `None` if the peer was
+/// retired first. The dialer redials with capped exponential backoff; the
+/// acceptor waits for the dialer to come to it (a closed `inbound_rx` means the
+/// supervisor was retired).
+async fn obtain_conn(
+    shared: &Arc<Shared>,
+    peer_id: EndpointId,
+    is_dialer: bool,
+    inbound_rx: &mut mpsc::Receiver<Connection>,
+    backoff: &mut Duration,
+) -> Option<Connection> {
+    if is_dialer {
+        loop {
+            match shared.endpoint.connect(peer_id, AUDIO_ALPN).await {
+                Ok(conn) => return Some(conn),
+                Err(e) => {
+                    crate::log_msg(&format!(
+                        "Transport: dial to {:?} failed: {:?}; retrying in {:?}",
+                        peer_id, e, backoff
+                    ));
+                    tokio::time::sleep(*backoff).await;
+                    *backoff = (*backoff * 2).min(MAX_BACKOFF);
+                }
+            }
+        }
+    } else {
+        inbound_rx.recv().await
     }
 }
 
@@ -104,38 +243,51 @@ impl iroh::protocol::ProtocolHandler for AudioProtocol {
         let peer_id = connection.remote_id();
         let shared = self.shared.clone();
         async move {
-            // Register and return: the retained connection clone in `PeerTasks`
+            // Deterministic roles: the lower id dials, the higher id accepts.
-            // keeps the connection open after this future resolves.
+            // If we're the dialer for this peer we never consume inbound links
-            shared.register(peer_id, connection).await;
+            // (we make our own), so just let this one drop.
+            if shared.self_id.to_string() < peer_id.to_string() {
+                return Ok(());
+            }
+            // Route the connection to this peer's supervisor (creating it if the
+            // inbound link beat the gossip join event). try_send keeps the
+            // protocol handler from ever blocking; a full queue only happens if
+            // links are churning, and the supervisor will get the next one.
+            let inbound_tx = shared.ensure_supervisor(peer_id).await;
+            if inbound_tx.try_send(connection).is_err() {
+                crate::log_msg(&format!("Transport: dropped inbound link from {:?} (queue full)", peer_id));
+            }
             Ok(())
         }
     }
 }
 
 pub struct IrohTransport {
-    endpoint: Endpoint,
-    self_id: EndpointId,
     shared: Arc<Shared>,
     incoming_rx: tokio::sync::Mutex<Option<mpsc::Receiver<(EndpointId, Bytes)>>>,
+    conn_events_rx: tokio::sync::Mutex<Option<mpsc::Receiver<ConnEvent>>>,
 }
 
 impl IrohTransport {
     pub fn new(endpoint: Endpoint) -> (Self, AudioProtocol) {
         let (incoming_tx, incoming_rx) = mpsc::channel(1000);
+        let (conn_events_tx, conn_events_rx) = mpsc::channel(100);
         let self_id = endpoint.id();
 
         let shared = Arc::new(Shared {
+            endpoint,
+            self_id,
             senders: StdMutex::new(HashMap::new()),
             peers: tokio::sync::Mutex::new(HashMap::new()),
             incoming_tx,
+            conn_events_tx,
         });
 
         let protocol = AudioProtocol { shared: shared.clone() };
         let transport = Self {
-            endpoint,
-            self_id,
             shared,
             incoming_rx: tokio::sync::Mutex::new(Some(incoming_rx)),
+            conn_events_rx: tokio::sync::Mutex::new(Some(conn_events_rx)),
         };
 
         (transport, protocol)
@@ -145,20 +297,9 @@ impl IrohTransport {
 #[async_trait]
 impl NetworkTransport for IrohTransport {
     async fn connect_peer(&self, peer_id: EndpointId) {
-        // Deterministic initiator: only the lexicographically-lower id dials, so
+        // Start (or confirm) the peer's supervisor. It owns dialing/accepting and
-        // a full-mesh pair forms exactly one shared connection instead of two
+        // reconnection from here on; this call is just the reactive trigger.
-        // racing ones. The higher id waits for the inbound `accept()`.
+        self.shared.ensure_supervisor(peer_id).await;
-        if self.self_id.to_string() >= peer_id.to_string() {
-            return;
-        }
-        if self.shared.peers.lock().await.contains_key(&peer_id) {
-            return;
-        }
-
-        match self.endpoint.connect(peer_id, AUDIO_ALPN).await {
-            Ok(conn) => self.shared.register(peer_id, conn).await,
-            Err(e) => crate::log_msg(&format!("Transport: dial to {:?} failed: {:?}", peer_id, e)),
-        }
     }
 
     async fn disconnect_peer(&self, peer_id: EndpointId) {
@@ -180,4 +321,11 @@ impl NetworkTransport for IrohTransport {
             .take()
             .ok_or_else(|| NetError::Other("Datagram receiver already subscribed".to_string()))
     }
+
+    async fn subscribe_conn_events(&self) -> Result<Receiver<ConnEvent>, NetError> {
+        let mut rx_guard = self.conn_events_rx.lock().await;
+        rx_guard
+            .take()
+            .ok_or_else(|| NetError::Other("Connection events already subscribed".to_string()))
+    }
 }

src/network/mod.rs

@@ -36,6 +36,18 @@ pub enum RoomEvent {
     PeerUpdated(EndpointId, PeerState),
 }
 
+/// Transport-level link state for a peer, surfaced so the UI can show when a
+/// peer's audio connection is being (re)established versus actually carrying
+/// audio. Distinct from `RoomEvent`: a peer can be present in the gossip room
+/// while its audio link is momentarily down and reconnecting.
+#[derive(Debug, Clone)]
+pub enum ConnEvent {
+    /// No live audio link yet — initial connect or reconnecting after a drop.
+    Connecting(EndpointId),
+    /// A live audio link is established and carrying datagrams.
+    Connected(EndpointId),
+}
+
 #[derive(Serialize, Deserialize, Clone, Debug)]
 pub struct PeerSpeakTicket {
     pub host_addr: iroh::EndpointAddr,
@@ -83,6 +95,9 @@ pub trait NetworkTransport: Send + Sync {
 
     /// Subscribes to incoming datagrams from any peer.
     async fn receive_datagrams(&self) -> Result<Receiver<(EndpointId, Bytes)>, NetError>;
+
+    /// Subscribes to per-peer link-state changes (connecting / connected).
+    async fn subscribe_conn_events(&self) -> Result<Receiver<ConnEvent>, NetError>;
 }
 
 #[async_trait]

tests/transport_loopback.rs

@@ -8,6 +8,8 @@
 use std::sync::Arc;
 use std::time::Duration;
 
+use tokio::sync::mpsc;
+
 use bytes::Bytes;
 use iroh::address_lookup::memory::MemoryLookup;
 use iroh::endpoint::presets;
@@ -15,10 +17,13 @@ use iroh::protocol::Router;
 use iroh::{Endpoint, RelayMode};
 use opus::{Application, Channels};
 
+use iroh::endpoint::Connection;
+use iroh::protocol::{AcceptError, ProtocolHandler};
+
 use peerspeak::codec::AudioEncoder;
 use peerspeak::codec::opus_impl::OpusEncoder;
 use peerspeak::core::jitter::{FRAME_SAMPLES, JitterBuffer};
-use peerspeak::network::NetworkTransport;
+use peerspeak::network::{ConnEvent, NetworkTransport};
 use peerspeak::network::iroh_impl::IrohTransport;
 
 const AUDIO_ALPN: &[u8] = b"peerspeak-audio";
@@ -31,9 +36,72 @@ struct Node {
 }
 
 async fn spawn_node() -> Node {
+    spawn_node_with_key(iroh::SecretKey::generate()).await
+}
+
+/// A minimal protocol handler for the reconnect test's "peer" side: it hands
+/// every accepted audio connection out through a channel so the test can hold
+/// it, read datagrams from it, and explicitly `close()` it to drive a drop —
+/// all on a single, stable endpoint address that the dialer can re-reach.
+#[derive(Clone)]
+struct CaptureProtocol {
+    conns_tx: mpsc::UnboundedSender<Connection>,
+}
+
+impl std::fmt::Debug for CaptureProtocol {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("CaptureProtocol").finish_non_exhaustive()
+    }
+}
+
+impl ProtocolHandler for CaptureProtocol {
+    fn accept(
+        &self,
+        connection: Connection,
+    ) -> impl std::future::Future<Output = Result<(), AcceptError>> + Send {
+        let conns_tx = self.conns_tx.clone();
+        async move {
+            // The channel retains the connection, which keeps it open after this
+            // future resolves (iroh closes accepted connections with no retained
+            // handle).
+            let _ = conns_tx.send(connection);
+            Ok(())
+        }
+    }
+}
+
+struct CapturePeer {
+    endpoint: Endpoint,
+    _router: Router,
+    lookup: MemoryLookup,
+    conns_rx: mpsc::UnboundedReceiver<Connection>,
+}
+
+async fn spawn_capture_peer(secret: iroh::SecretKey) -> CapturePeer {
     let lookup = MemoryLookup::new();
     let endpoint = Endpoint::builder(presets::Minimal)
-        .secret_key(iroh::SecretKey::generate())
+        .secret_key(secret)
+        .relay_mode(RelayMode::Disabled)
+        .address_lookup(lookup.clone())
+        .bind()
+        .await
+        .expect("bind capture peer");
+
+    let (conns_tx, conns_rx) = mpsc::unbounded_channel();
+    let router = Router::builder(endpoint.clone())
+        .accept(AUDIO_ALPN, CaptureProtocol { conns_tx })
+        .spawn();
+
+    CapturePeer { endpoint, _router: router, lookup, conns_rx }
+}
+
+/// Spawn a node with a specific secret key. Reusing a key gives the respawned
+/// node the same `EndpointId`, which is how we simulate a peer dropping off the
+/// network and coming back (new address, same identity) for the reconnect test.
+async fn spawn_node_with_key(secret: iroh::SecretKey) -> Node {
+    let lookup = MemoryLookup::new();
+    let endpoint = Endpoint::builder(presets::Minimal)
+        .secret_key(secret)
         // Direct-only: two endpoints on the same host reach each other via the
         // addresses we seed into each other's lookup, with no external relay.
         .relay_mode(RelayMode::Disabled)
@@ -68,6 +136,24 @@ fn packet(enc: &mut OpusEncoder, seq: u32) -> Bytes {
     Bytes::from(buf)
 }
 
+/// Drain link-state events until a `Connected` arrives, returning whether a
+/// `Connecting` was seen first (the down→up transition). Panics on timeout so a
+/// stuck reconnect fails loudly rather than hanging the suite.
+async fn await_reconnect(
+    rx: &mut mpsc::Receiver<ConnEvent>,
+    deadline: tokio::time::Instant,
+) -> bool {
+    let mut saw_connecting = false;
+    loop {
+        match tokio::time::timeout_at(deadline, rx.recv()).await {
+            Ok(Some(ConnEvent::Connecting(_))) => saw_connecting = true,
+            Ok(Some(ConnEvent::Connected(_))) => return saw_connecting,
+            Ok(None) => panic!("conn events channel closed unexpectedly"),
+            Err(_) => panic!("timed out waiting for Connected"),
+        }
+    }
+}
+
 #[tokio::test]
 async fn loopback_sequenced_audio_reaches_peer_and_decodes() {
     let a = spawn_node().await;
@@ -142,3 +228,94 @@ async fn loopback_sequenced_audio_reaches_peer_and_decodes() {
         "expected to decode ~{N} frames, got {decoded_frames} (received {received})"
     );
 }
+
+/// Read datagrams off a raw connection until `target` arrive or the deadline
+/// passes, asserting each carries the 4-byte sequence header.
+async fn count_audio(conn: &Connection, target: u32, deadline: tokio::time::Instant) -> u32 {
+    let mut received = 0;
+    while let Ok(Ok(bytes)) = tokio::time::timeout_at(deadline, conn.read_datagram()).await {
+        assert!(bytes.len() >= 4, "packet carries a sequence header");
+        received += 1;
+        if received >= target {
+            break;
+        }
+    }
+    received
+}
+
+#[tokio::test]
+async fn dialer_reconnects_after_link_drops() {
+    // The unit under test is the IrohTransport dialer. The peer is a hand-rolled
+    // endpoint we fully control, so we can explicitly close the live connection
+    // (which the dialer observes promptly, unlike a silent handle drop) and then
+    // accept the dialer's re-dial — all on one stable address it can re-reach.
+    //
+    // The dialer must hold the lower id so the transport's deterministic rule
+    // makes it dial, so order the two identities up front.
+    let s1 = iroh::SecretKey::generate();
+    let s2 = iroh::SecretKey::generate();
+    let (dialer_secret, peer_secret) = if s1.public().to_string() < s2.public().to_string() {
+        (s1, s2)
+    } else {
+        (s2, s1)
+    };
+
+    let dialer = spawn_node_with_key(dialer_secret).await;
+    let mut peer = spawn_capture_peer(peer_secret).await;
+
+    let dialer_id = dialer.endpoint.id();
+    let peer_id = peer.endpoint.id();
+    assert!(dialer_id.to_string() < peer_id.to_string());
+
+    // Seed addresses both ways and form the initial link.
+    dialer.lookup.add_endpoint_info(peer.endpoint.addr());
+    peer.lookup.add_endpoint_info(dialer.endpoint.addr());
+
+    let mut conn_events = dialer
+        .transport
+        .subscribe_conn_events()
+        .await
+        .expect("subscribe dialer conn events");
+    dialer.transport.connect_peer(peer_id).await;
+
+    // The peer accepts the dialer's initial connection.
+    let conn1 = tokio::time::timeout(Duration::from_secs(10), peer.conns_rx.recv())
+        .await
+        .expect("timed out awaiting initial connection")
+        .expect("connection channel closed");
+    assert!(
+        await_reconnect(&mut conn_events, tokio::time::Instant::now() + Duration::from_secs(10)).await,
+        "initial link should report Connecting then Connected"
+    );
+
+    // Drop the live link by closing it from the peer side. An explicit close
+    // sends a CONNECTION_CLOSE the dialer sees right away.
+    conn1.close(0u32.into(), b"transient drop");
+    drop(conn1);
+
+    // The dialer's supervisor should re-dial the (unchanged) peer address, and
+    // the peer accepts the fresh connection.
+    let conn2 = tokio::time::timeout(Duration::from_secs(15), peer.conns_rx.recv())
+        .await
+        .expect("timed out awaiting reconnect")
+        .expect("connection channel closed");
+    assert!(
+        await_reconnect(&mut conn_events, tokio::time::Instant::now() + Duration::from_secs(15)).await,
+        "dropped link should report Connecting (down) then Connected (recovered)"
+    );
+
+    // Audio must flow over the rebuilt link. Give the freshly-registered send
+    // path a beat, then stream frames and confirm they reach the peer on conn2.
+    tokio::time::sleep(Duration::from_millis(200)).await;
+    let mut enc = OpusEncoder::new(48000, Channels::Mono, Application::Voip).unwrap();
+    for seq in 0..30u32 {
+        dialer.transport.broadcast(packet(&mut enc, seq));
+        tokio::time::sleep(Duration::from_millis(5)).await;
+    }
+
+    let received = count_audio(&conn2, 25, tokio::time::Instant::now() + Duration::from_secs(3)).await;
+    assert!(
+        received >= 20,
+        "audio should resume after reconnect; got {received} frames"
+    );
+}