S8 (Pass 2): wire grace-aware audio-membership admission

Closes S8 (High): inbound audio was authenticated by identity (remote_id) but
NOT by room membership, so a former member who knew a current member's endpoint
could reconnect on the audio ALPN and inject into / eavesdrop on the mix while
invisible in the roster. Now audio is admitted only for live gossip-roster
members (the senior+user-resolved GRACE-AWARE policy).

Transport (src/network/iroh_impl.rs):
- New per-session admitted_audio: HashSet<EndpointId> on Shared (internal state,
  no wire/serialization change). Cleared on disconnect_all.
- AudioRouter::accept consults audio_sender_admitted BEFORE ensure_supervisor —
  a non-member never gets a supervisor, sender handle, datagram reader, or
  outbound mix. Brief StdMutex check, released before the await (no RT lock).
- Pure apply_audio_admission_event(roster, peer, event) with AudioAdmissionEvent
  {RosterPresent insert, TransientDropGrace no-op, Remove}. Grace deliberately
  cannot ADD membership — it only preserves an already-admitted peer — so an
  unknown peer can't sneak in via a grace event. +3 lifecycle tests (on top of
  Pass-1's 4 predicate tests).
- admit/keep_for_reconnect_grace/remove/query methods for core to drive.

Core (src/core/mod.rs) — authority is core's VERIFIED gossip-roster events, not
transport connect/disconnect:
- PeerJoined / PeerUpdated: admit_audio_sender before connect_peer.
- PeerConnectionLost: keep_audio_sender_for_reconnect_grace (preserve through the
  existing RECONNECT_GRACE window — no audio cut on transient blips).
- gossip PeerLeft, transport ConnEvent::Left, grace-timer expiry: remove_audio_sender
  before disconnect_peer + jitter removal (removal-before-teardown bounds the
  in-flight-datagram race).
- datagram receiver: audio_sender_admitted gate before any jitter buffer (defense
  in depth against a datagram racing a removal). Mixer stays off the hot path.

Mid-join: a peer who dials audio before we've verified their signed Announce is
dropped (no "pending" admission, which would reintroduce the eavesdrop); their
reconnect loop recovers once the Announce admits them.

tests/transport_loopback.rs: admit both ends before connecting, mirroring the
production room-event order.

313 lib / clippy --all-targets / transport_loopback 4 / reconnect_eviction 6 /
release — all re-run green by the senior. Former-member-rejection + mid-join
recovery are verifiable only in a 2-machine call (senior's to run).

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

src/app/mod.rs

@@ -955,13 +955,15 @@ fn update(state: &mut AppState, message: AppMessage) -> Task<AppMessage> {
                     state.friend_presence.insert(id, presence);
                 }
                 UiEvent::PresenceModeReverted { mode } => {
-                    // The Discoverable time-box elapsed; core dropped us back to
+                    // Core corrected the committed presence mode. Mirror + persist so
-                    // `mode` (Normal) and stopped publishing. Mirror + persist so the
+                    // the picker reflects the discovery state the endpoint actually has.
-                    // presence picker reflects it, and tell the user why it changed.
                     state.config.presence_mode = mode;
                     state.config.save();
-                    state.status_message =
+                    state.status_message = if mode == PresenceMode::Normal {
-                        "Discoverable timed out — back to Normal".to_string();
+                        "Discoverable timed out — back to Normal".to_string()
+                    } else {
+                        format!("Presence mode stayed {mode}")
+                    };
                 }
                 UiEvent::ShutdownComplete => {
                     if state.closing {

src/core/messages.rs

@@ -124,11 +124,10 @@ pub enum UiEvent {
     /// joinable gathering (with a one-click ticket). Emitted by the outbound ping
     /// scheduler; absence of a recent event = treat as offline.
     FriendPresence { id: EndpointId, presence: FriendPresence },
-    /// The Discoverable time-box elapsed (W7 P6): the core auto-reverted our presence
+    /// Core corrected the committed presence posture. Usually the Discoverable
-    /// posture to the carried `mode` (always `Normal`) and stopped publishing. The
+    /// time-box elapsed and the core auto-reverted to `Normal`; on discovery apply
-    /// GUI must mirror + persist this so its presence picker stops showing
+    /// failure, this carries the previous truthful mode. The GUI must mirror +
-    /// Discoverable. Distinct from a user-driven change so the GUI knows to update
+    /// persist this so its presence picker matches the endpoint's discovery state.
-    /// without having issued the command itself.
     PresenceModeReverted { mode: PresenceMode },
     /// Core finished orderly app shutdown and the GUI can exit.
     ShutdownComplete,

src/core/mod.rs

@@ -13,6 +13,7 @@ use crate::network::{
 use crate::core::messages::{CoreCommand, UiEvent};
 
 use crate::config::{NetworkMode, RecordingMode};
+use crate::presence::PresenceMode;
 use crate::audio::multitrack::MultitrackRecorder;
 use iroh::{Endpoint, EndpointAddr, EndpointId, RelayMode, SecretKey, endpoint::presets, protocol::Router};
 use iroh_gossip::net::Gossip;
@@ -69,10 +70,27 @@ const RECONNECT_GRACE: Duration = Duration::from_secs(45);
 /// 48 kHz / 60 ms frame) while bounding malicious datagram copy/decode churn.
 const MAX_OPUS_PAYLOAD: usize = 4000;
 
+/// If the Discoverable time-box tries to revert but discovery service reconfiguration
+/// fails, retry soon while keeping the UI in the still-possible publishing state.
+const DISCOVERY_REVERT_RETRY: Duration = Duration::from_secs(60);
+
 fn audio_datagram_len_ok(len: usize) -> bool {
     (4..=4 + MAX_OPUS_PAYLOAD).contains(&len)
 }
 
+fn arm_discovery_retry(
+    discovery_deadline: &mut Option<tokio::time::Instant>,
+    now: tokio::time::Instant,
+) {
+    let retry_deadline = now + DISCOVERY_REVERT_RETRY;
+    if discovery_deadline
+        .map(|current| current > retry_deadline)
+        .unwrap_or(true)
+    {
+        *discovery_deadline = Some(retry_deadline);
+    }
+}
+
 /// Per-peer reconnect grace timers (see [`RECONNECT_GRACE`]). Shared between the
 /// room-event task (which arms one on a transient drop and cancels it on a
 /// gossip rejoin) and the conn-event task (which cancels it when the audio link
@@ -119,6 +137,7 @@ fn arm_grace_timer(
     let handle = tokio::spawn(async move {
         tokio::time::sleep(grace).await;
         crate::log_msg(&format!("Reconnect grace expired; evicting peer {:?}", peer_id));
+        transport_evict.remove_audio_sender(peer_id);
         transport_evict.disconnect_peer(peer_id).await;
         jitter_evict.lock().await.remove(&peer_id);
         // Scrub our internal state *before* announcing the eviction, so anything
@@ -352,6 +371,7 @@ impl ConnEventHandler {
                 // until the grace timer or the slow gossip Leave.
                 cancel_grace_timer(&self.grace_timers, &id);
                 self.seen_connected.lock().unwrap().remove(&id);
+                self.transport.remove_audio_sender(id);
                 self.transport.disconnect_peer(id).await;
                 self.jitter.lock().await.remove(&id);
                 let _ = self.ui_tx.send(UiEvent::PeerLeft { id }).await;
@@ -466,12 +486,11 @@ impl NetStack {
 /// `DnsAddressLookup`, mirroring the `N0` preset) is added when `plan.resolver`; the
 /// n0 DNS *publisher* (`PkarrPublisher`) when `plan.publisher`.
 ///
-/// Idempotent and reversible: it clears the whole service set and reinstalls exactly
+/// Idempotent and reversible: it builds the replacement services first, then clears
-/// what the plan wants, so flipping `publisher` off simply drops the publisher (its
+/// the service set and reinstalls exactly what the plan wants. Flipping `publisher`
-/// republish task ends when the last clone is dropped, and the already-published
+/// off drops the publisher (its republish task ends when the last clone is dropped,
-/// record TTL-expires within ~30s) without an endpoint rebuild and without disturbing
+/// and the already-published record TTL-expires within ~30s) without an endpoint
-/// resolution. The brief clear→re-add window is a few synchronous calls; presence
+/// rebuild and without disturbing resolution.
-/// toggles are rare, so a concurrent dial racing it is not a practical concern.
 fn apply_discovery(
     endpoint: &Endpoint,
     memory_lookup: &iroh::address_lookup::memory::MemoryLookup,
@@ -482,16 +501,34 @@ fn apply_discovery(
         pkarr::{PkarrPublisher, PkarrResolver},
     };
     let services = endpoint.address_lookup()?;
+    let pkarr_resolver = if plan.resolver {
+        Some(PkarrResolver::n0_dns().into_address_lookup(endpoint)?)
+    } else {
+        None
+    };
+    let dns_resolver = if plan.resolver {
+        Some(DnsAddressLookup::n0_dns().into_address_lookup(endpoint)?)
+    } else {
+        None
+    };
+    let publisher = if plan.publisher {
+        Some(PkarrPublisher::n0_dns().into_address_lookup(endpoint)?)
+    } else {
+        None
+    };
+
     services.clear();
     // Always keep the local, server-free lookup (this is what ticket/gossip dialing
     // depends on — it must survive every posture, including DirectOnly).
     services.add(memory_lookup.clone());
-    if plan.resolver {
+    if let Some(pkarr_resolver) = pkarr_resolver {
-        services.add(PkarrResolver::n0_dns().into_address_lookup(endpoint)?);
+        services.add(pkarr_resolver);
-        services.add(DnsAddressLookup::n0_dns().into_address_lookup(endpoint)?);
     }
-    if plan.publisher {
+    if let Some(dns_resolver) = dns_resolver {
-        services.add(PkarrPublisher::n0_dns().into_address_lookup(endpoint)?);
+        services.add(dns_resolver);
+    }
+    if let Some(publisher) = publisher {
+        services.add(publisher);
     }
     Ok(())
 }
@@ -851,22 +888,64 @@ async fn run_core_loop(
             // W7 P6 time-box: Discoverable auto-reverts to Normal after DISCOVERY_TIMEBOX
             // so a publish beacon never stands indefinitely. The branch is disabled
             // (`if` guard) unless a deadline is armed; `unwrap_or_else` is unreachable
-            // belt-and-braces. On fire: stop publishing, drop to Normal, tell the GUI.
+            // belt-and-braces. On fire: stop publishing first, then commit Normal only
+            // if the endpoint's discovery services accepted the non-publishing plan.
             _ = tokio::time::sleep_until(
                 discovery_deadline.unwrap_or_else(tokio::time::Instant::now),
             ), if discovery_deadline.is_some() => {
-                discovery_deadline = None;
+                let previous_mode = *presence_mode.lock().unwrap();
-                *presence_mode.lock().unwrap() = crate::presence::PresenceMode::Normal;
+                if previous_mode != PresenceMode::Discoverable {
-                let plan = crate::discovery::lookup_plan(network_mode, false);
+                    discovery_deadline = None;
-                if let Err(e) = apply_discovery(&net.endpoint, &net.memory_lookup, plan) {
+                    continue;
-                    crate::log_msg(&format!("discovery: time-box revert failed: {e:#}"));
+                }
+
+                let requested_mode = PresenceMode::Normal;
+                let now = tokio::time::Instant::now();
+                let plan = crate::discovery::lookup_plan(
+                    network_mode,
+                    requested_mode.publishes_to_discovery(),
+                );
+                let apply_result = apply_discovery(&net.endpoint, &net.memory_lookup, plan);
+                let (committed_mode, transition_error) =
+                    crate::discovery::resolve_presence_transition(
+                        previous_mode,
+                        requested_mode,
+                        apply_result.is_ok(),
+                    );
+                *presence_mode.lock().unwrap() = committed_mode;
+                discovery_deadline = if committed_mode == PresenceMode::Discoverable {
+                    Some(now + DISCOVERY_REVERT_RETRY)
+                } else {
+                    None
+                };
+
+                match apply_result {
+                    Ok(()) => {
+                        crate::log_msg(
+                            "discovery: Discoverable time-box elapsed → reverting to Normal",
+                        );
+                        let _ = ui_tx
+                            .send(UiEvent::PresenceModeReverted {
+                                mode: PresenceMode::Normal,
+                            })
+                            .await;
+                    }
+                    Err(e) => {
+                        crate::log_msg(&format!("discovery: time-box revert failed: {e:#}"));
+                        if committed_mode != requested_mode {
+                            let _ = ui_tx
+                                .send(UiEvent::PresenceModeReverted {
+                                    mode: committed_mode,
+                                })
+                                .await;
+                        }
+                        if let Some(message) = transition_error {
+                            let _ = ui_tx
+                                .send(UiEvent::Error(format!("{message} ({e:#})")))
+                                .await;
+                        }
+                    }
                 }
-                crate::log_msg("discovery: Discoverable time-box elapsed → reverting to Normal");
-                let _ = ui_tx
-                    .send(UiEvent::PresenceModeReverted {
-                        mode: crate::presence::PresenceMode::Normal,
-                    })
-                    .await;
                 continue;
             }
         };
@@ -1162,6 +1241,9 @@ async fn run_core_loop(
                     };
 
                     while let Some((from_peer, bytes)) = datagram_rx.recv().await {
+                        if !transport_recv.audio_sender_admitted(from_peer) {
+                            continue;
+                        }
                         if !audio_datagram_len_ok(bytes.len()) {
                             // Malformed (< sequence header) or oversized Opus payload.
                             continue;
@@ -1396,6 +1478,7 @@ async fn run_core_loop(
                                 // A (re)join means the peer is back — cancel any
                                 // pending reconnect grace timer before re-adding it.
                                 cancel_grace_timer(&grace_timers_events, &peer_id);
+                                transport_events.admit_audio_sender(peer_id);
                                 // Establish the audio connection as soon as the peer
                                 // is known (the transport dedupes the full-mesh race).
                                 // Hand over the full address so reconnects can dial
@@ -1447,6 +1530,7 @@ async fn run_core_loop(
                                 {
                                     peers.remove(&peer_id);
                                 }
+                                transport_events.remove_audio_sender(peer_id);
                                 transport_events.disconnect_peer(peer_id).await;
                                 jitter_events.lock().await.remove(&peer_id);
                                 let _ = ui_tx_events.send(UiEvent::PeerLeft { id: peer_id }).await;
@@ -1459,6 +1543,7 @@ async fn run_core_loop(
                                 // it. Idempotent: an ordinary mute/unmute update just
                                 // re-records the same address.
                                 cancel_grace_timer(&grace_timers_events, &peer_id);
+                                transport_events.admit_audio_sender(peer_id);
                                 transport_events.connect_peer(state.addr.clone()).await;
                                 // Auto-heal a friend's saved address (W7) on the
                                 // re-announce too — this is the path that catches a
@@ -1500,6 +1585,7 @@ async fn run_core_loop(
                                 // hasn't recovered within RECONNECT_GRACE. A gossip
                                 // rejoin (PeerJoined/PeerUpdated) or a transport
                                 // reconnect (ConnEvent::Connected) cancels it first.
+                                transport_events.keep_audio_sender_for_reconnect_grace(peer_id);
                                 let _ = ui_tx_events.send(UiEvent::PeerConnecting { id: peer_id }).await;
                                 arm_grace_timer(
                                     &grace_timers_events,
@@ -1798,22 +1884,60 @@ async fn run_core_loop(
             }
 
             CoreCommand::SetPresenceMode(mode) => {
-                *presence_mode.lock().unwrap() = mode;
+                let previous_mode = *presence_mode.lock().unwrap();
-                // W7 P6: re-apply n0 DNS discovery for the new posture (publish on iff
+                let now = tokio::time::Instant::now();
-                // Discoverable). Runtime — no endpoint rebuild; clears + reinstalls the
+
-                // address-lookup services. The resolver stays on regardless so we can
+                if previous_mode == mode {
-                // still look up moved friends.
+                    // Same-mode requests are no-ops for discovery wiring, but keep the
-                let plan = crate::discovery::lookup_plan(network_mode, mode.publishes_to_discovery());
+                    // existing UX: re-selecting Discoverable restarts the clock.
-                if let Err(e) = apply_discovery(&net.endpoint, &net.memory_lookup, plan) {
+                    discovery_deadline = if mode == PresenceMode::Discoverable {
-                    crate::log_msg(&format!("discovery: apply failed: {e:#}"));
+                        Some(now + crate::discovery::DISCOVERY_TIMEBOX)
+                    } else {
+                        None
+                    };
+                    continue;
                 }
-                // Arm (Discoverable) or cancel (any other posture) the auto-revert
+
-                // time-box. Re-selecting Discoverable restarts the clock.
+                // W7 P6/S11: re-apply n0 DNS discovery for the requested posture
-                discovery_deadline = if mode == crate::presence::PresenceMode::Discoverable {
+                // first, then commit the presence mode only if the endpoint accepted
-                    Some(tokio::time::Instant::now() + crate::discovery::DISCOVERY_TIMEBOX)
+                // that discovery plan. This keeps the UI truthful when dropping the
+                // publisher fails.
+                let plan =
+                    crate::discovery::lookup_plan(network_mode, mode.publishes_to_discovery());
+                let apply_result = apply_discovery(&net.endpoint, &net.memory_lookup, plan);
+                let (committed_mode, transition_error) =
+                    crate::discovery::resolve_presence_transition(
+                        previous_mode,
+                        mode,
+                        apply_result.is_ok(),
+                    );
+                *presence_mode.lock().unwrap() = committed_mode;
+
+                if committed_mode == PresenceMode::Discoverable {
+                    if apply_result.is_ok() && mode == PresenceMode::Discoverable {
+                        discovery_deadline = Some(now + crate::discovery::DISCOVERY_TIMEBOX);
+                    } else {
+                        arm_discovery_retry(&mut discovery_deadline, now);
+                    }
                 } else {
-                    None
+                    discovery_deadline = None;
-                };
+                }
+
+                if let Err(e) = apply_result {
+                    crate::log_msg(&format!("discovery: apply failed: {e:#}"));
+                    if committed_mode != mode {
+                        let _ = ui_tx
+                            .send(UiEvent::PresenceModeReverted {
+                                mode: committed_mode,
+                            })
+                            .await;
+                    }
+                    if let Some(message) = transition_error {
+                        let _ = ui_tx
+                            .send(UiEvent::Error(format!("{message} ({e:#})")))
+                            .await;
+                    }
+                }
             }
 
             CoreCommand::SetRecordingMode(mode) => {

src/discovery.rs

@@ -8,14 +8,19 @@
 //! The model (from `docs/contacts-plan.md` P6, decided 2026-06-16):
 //! - **Resolving is always allowed on relay-capable modes** — a stationary friend
 //!   (typically in `Normal`) must be able to look up a friend who moved networks. A
-//!   resolve is a DNS query to n0 that publishes nothing; it only fires when a saved
+//!   resolve is a DNS query to n0 that publishes nothing, but still exposes query
-//!   address is stale and the dial falls through to discovery.
+//!   timing/source metadata to n0; it only fires when a saved address is stale and
+//!   the dial falls through to discovery.
 //! - **Publishing is gated on `Discoverable`** and asymmetric: only the mover
 //!   publishes their address to n0 DNS; everyone else just looks it up.
+//! - **Stopping publishing removes the local publisher service**; iroh does not
+//!   expose an explicit unpublish call here, so already-published pkarr records can
+//!   linger until their default ~30s TTL expires.
 //! - **`DirectOnly` is the explicit no-server posture** — neither resolve nor publish
 //!   ever touches n0 there, regardless of the Discoverable toggle.
 
 use crate::config::NetworkMode;
+use crate::presence::PresenceMode;
 use std::time::Duration;
 
 /// How long `Discoverable` stays on before auto-reverting to `Normal`. Discovery is
@@ -46,12 +51,43 @@ pub fn lookup_plan(network_mode: NetworkMode, want_publish: bool) -> LookupPlan
     match network_mode {
         // The explicit serverless posture: no n0 contact at all, even to resolve.
         // A Discoverable toggle here is intentionally inert.
-        NetworkMode::DirectOnly => LookupPlan { resolver: false, publisher: false },
+        NetworkMode::DirectOnly => LookupPlan {
+            resolver: false,
+            publisher: false,
+        },
         // Relay-capable: always resolve (so a stationary friend can find a mover);
         // publish only when the user opted into Discoverable.
-        NetworkMode::RelayNoDiscovery | NetworkMode::N0Full => {
+        NetworkMode::RelayNoDiscovery | NetworkMode::N0Full => LookupPlan {
-            LookupPlan { resolver: true, publisher: want_publish }
+            resolver: true,
-        }
+            publisher: want_publish,
+        },
+    }
+}
+
+/// Decide which presence mode may be committed after attempting to apply discovery
+/// services for `requested`.
+///
+/// On failure, keep the previous mode: it is the only locally truthful state because
+/// the endpoint's discovery services may still reflect the old posture. Same-mode
+/// requests are no-ops from a presence-truth perspective and do not surface an error.
+pub fn resolve_presence_transition(
+    previous: PresenceMode,
+    requested: PresenceMode,
+    apply_ok: bool,
+) -> (PresenceMode, Option<String>) {
+    if previous == requested {
+        return (previous, None);
+    }
+
+    if apply_ok {
+        (requested, None)
+    } else {
+        (
+            previous,
+            Some(format!(
+                "Couldn't update discovery mode; keeping {previous}."
+            )),
+        )
     }
 }
 
@@ -64,12 +100,18 @@ mod tests {
         for mode in [NetworkMode::RelayNoDiscovery, NetworkMode::N0Full] {
             assert_eq!(
                 lookup_plan(mode, false),
-                LookupPlan { resolver: true, publisher: false },
+                LookupPlan {
+                    resolver: true,
+                    publisher: false
+                },
                 "{mode:?}: resolve always on, no publish when not Discoverable"
             );
             assert_eq!(
                 lookup_plan(mode, true),
-                LookupPlan { resolver: true, publisher: true },
+                LookupPlan {
+                    resolver: true,
+                    publisher: true
+                },
                 "{mode:?}: Discoverable adds publish on top of resolve"
             );
         }
@@ -79,12 +121,18 @@ mod tests {
     fn direct_only_never_touches_n0_even_when_discoverable() {
         assert_eq!(
             lookup_plan(NetworkMode::DirectOnly, false),
-            LookupPlan { resolver: false, publisher: false }
+            LookupPlan {
+                resolver: false,
+                publisher: false
+            }
         );
         // The serverless posture overrides the Discoverable request entirely.
         assert_eq!(
             lookup_plan(NetworkMode::DirectOnly, true),
-            LookupPlan { resolver: false, publisher: false }
+            LookupPlan {
+                resolver: false,
+                publisher: false
+            }
         );
     }
 
@@ -92,4 +140,42 @@ mod tests {
     fn timebox_is_thirty_minutes() {
         assert_eq!(DISCOVERY_TIMEBOX, Duration::from_secs(1800));
     }
+
+    #[test]
+    fn presence_transition_commits_requested_mode_after_successful_apply() {
+        assert_eq!(
+            resolve_presence_transition(PresenceMode::Normal, PresenceMode::Discoverable, true),
+            (PresenceMode::Discoverable, None)
+        );
+    }
+
+    #[test]
+    fn presence_transition_keeps_previous_mode_when_apply_fails() {
+        let (mode, err) =
+            resolve_presence_transition(PresenceMode::Normal, PresenceMode::Discoverable, false);
+
+        assert_eq!(mode, PresenceMode::Normal);
+        assert!(err.unwrap().contains("keeping Normal"));
+    }
+
+    #[test]
+    fn presence_transition_keeps_discoverable_when_off_transition_fails() {
+        let (mode, err) =
+            resolve_presence_transition(PresenceMode::Discoverable, PresenceMode::Normal, false);
+
+        assert_eq!(mode, PresenceMode::Discoverable);
+        assert!(err.unwrap().contains("keeping Discoverable"));
+    }
+
+    #[test]
+    fn presence_transition_same_mode_is_noop_without_error() {
+        assert_eq!(
+            resolve_presence_transition(
+                PresenceMode::Discoverable,
+                PresenceMode::Discoverable,
+                false
+            ),
+            (PresenceMode::Discoverable, None)
+        );
+    }
 }

src/network/iroh_impl.rs

@@ -5,7 +5,7 @@ use bytes::Bytes;
 use tokio::sync::mpsc;
 use tokio::sync::mpsc::Receiver;
 use std::sync::{Arc, Mutex as StdMutex};
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet};
 use std::time::Duration;
 use async_trait::async_trait;
 
@@ -56,6 +56,10 @@ struct Shared {
     /// supervisor inserts its connection when the link comes up and removes it
     /// when the link dies.
     live_conns: StdMutex<HashMap<EndpointId, Connection>>,
+    /// Core-owned audio admission snapshot for this room session. It mirrors the
+    /// verified gossip roster plus peers still inside reconnect grace; transport
+    /// connections alone never mutate this set.
+    admitted_audio: StdMutex<HashSet<EndpointId>>,
     incoming_tx: mpsc::Sender<(EndpointId, Bytes)>,
     /// Best-effort link-state notifications for the UI (connecting / connected).
     conn_events_tx: mpsc::Sender<ConnEvent>,
@@ -112,6 +116,16 @@ impl Shared {
             crate::log_msg(&format!("Transport: stopped supervising peer {:?}", peer_id));
         }
     }
+
+    fn audio_sender_admitted(&self, peer_id: EndpointId) -> bool {
+        let roster = self.admitted_audio.lock().unwrap();
+        audio_sender_admitted(peer_id, &roster)
+    }
+
+    fn apply_audio_admission(&self, peer_id: EndpointId, event: AudioAdmissionEvent) {
+        let mut roster = self.admitted_audio.lock().unwrap();
+        apply_audio_admission_event(&mut roster, peer_id, event);
+    }
 }
 
 /// Why a peer's live-link wait woke up.
@@ -135,6 +149,41 @@ fn is_graceful_leave(err: &ConnectionError) -> bool {
     matches!(err, ConnectionError::ApplicationClosed(frame) if frame.error_code == VarInt::from_u32(GOODBYE_CODE))
 }
 
+/// Pure S8 membership decision: iroh already authenticated `remote` as the
+/// connection's endpoint id, so audio admission is exactly live roster membership.
+pub(crate) fn audio_sender_admitted(remote: EndpointId, roster: &HashSet<EndpointId>) -> bool {
+    roster.contains(&remote)
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub(crate) enum AudioAdmissionEvent {
+    /// A signed gossip Announce/Update says the peer is in the live room roster.
+    RosterPresent,
+    /// Gossip reported a transient drop; keep admission during reconnect grace.
+    TransientDropGrace,
+    /// Graceful leave, transport Left eviction, or reconnect-grace expiry.
+    Remove,
+}
+
+pub(crate) fn apply_audio_admission_event(
+    roster: &mut HashSet<EndpointId>,
+    peer_id: EndpointId,
+    event: AudioAdmissionEvent,
+) {
+    match event {
+        AudioAdmissionEvent::RosterPresent => {
+            roster.insert(peer_id);
+        }
+        AudioAdmissionEvent::TransientDropGrace => {
+            // Grace is not an authority to add membership; it only preserves an
+            // already-admitted peer until either rejoin or grace expiry.
+        }
+        AudioAdmissionEvent::Remove => {
+            roster.remove(&peer_id);
+        }
+    }
+}
+
 /// 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
@@ -333,10 +382,17 @@ impl iroh::protocol::ProtocolHandler for AudioRouter {
             if shared.self_id.to_string() < peer_id.to_string() {
                 return Ok(());
             }
+            if !shared.audio_sender_admitted(peer_id) {
+                crate::log_msg(&format!(
+                    "Transport: rejected inbound audio from non-member {}",
+                    crate::short_id(&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
+            // inbound link arrives after the signed gossip Announce admitted it).
-            // protocol handler from ever blocking; a full queue only happens if
+            // try_send keeps the protocol handler from ever blocking; a full queue
-            // links are churning, and the supervisor will get the next one.
+            // only happens if links are churning, and the supervisor gets the next one.
             let inbound_tx = shared.ensure_supervisor(peer_id).await;
             if inbound_tx.try_send(connection).is_err() {
                 crate::log_msg(&format!("Transport: dropped inbound link from {:?} (queue full)", peer_id));
@@ -369,6 +425,7 @@ impl IrohTransport {
             addrs: StdMutex::new(HashMap::new()),
             peers: tokio::sync::Mutex::new(HashMap::new()),
             live_conns: StdMutex::new(HashMap::new()),
+            admitted_audio: StdMutex::new(HashSet::new()),
             incoming_tx,
             conn_events_tx,
         });
@@ -397,11 +454,35 @@ impl IrohTransport {
         }
         self.shared.senders.lock().unwrap().clear();
         self.shared.addrs.lock().unwrap().clear();
+        self.shared.admitted_audio.lock().unwrap().clear();
         // Give the CONNECTION_CLOSE frames a moment to flush before the caller
         // shuts the endpoint/router down (the `conns` clones are still alive
         // here, so the endpoint can still transmit them).
         tokio::time::sleep(Duration::from_millis(150)).await;
     }
+
+    /// Admit a peer to this session's audio plane. Core calls this from verified
+    /// gossip roster events; the transport never derives membership on its own.
+    pub fn admit_audio_sender(&self, peer_id: EndpointId) {
+        self.shared
+            .apply_audio_admission(peer_id, AudioAdmissionEvent::RosterPresent);
+    }
+
+    /// Preserve an already-admitted peer through the reconnect grace window.
+    pub fn keep_audio_sender_for_reconnect_grace(&self, peer_id: EndpointId) {
+        self.shared
+            .apply_audio_admission(peer_id, AudioAdmissionEvent::TransientDropGrace);
+    }
+
+    /// Remove a peer from audio admission before tearing down transport/jitter state.
+    pub fn remove_audio_sender(&self, peer_id: EndpointId) {
+        self.shared
+            .apply_audio_admission(peer_id, AudioAdmissionEvent::Remove);
+    }
+
+    pub fn audio_sender_admitted(&self, peer_id: EndpointId) -> bool {
+        self.shared.audio_sender_admitted(peer_id)
+    }
 }
 
 #[async_trait]
@@ -443,3 +524,85 @@ impl NetworkTransport for IrohTransport {
             .ok_or_else(|| NetError::Other("Connection events already subscribed".to_string()))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use iroh::SecretKey;
+
+    fn endpoint_id() -> EndpointId {
+        SecretKey::generate().public()
+    }
+
+    #[test]
+    fn audio_sender_admission_accepts_roster_member() {
+        let member = endpoint_id();
+        let roster = HashSet::from([member]);
+
+        assert!(audio_sender_admitted(member, &roster));
+    }
+
+    #[test]
+    fn audio_sender_admission_rejects_unknown_sender() {
+        let member = endpoint_id();
+        let stranger = endpoint_id();
+        let roster = HashSet::from([member]);
+
+        assert!(!audio_sender_admitted(stranger, &roster));
+    }
+
+    #[test]
+    fn audio_sender_admission_rejects_former_member_after_roster_removal() {
+        let former = endpoint_id();
+        let mut roster = HashSet::from([former]);
+        assert!(audio_sender_admitted(former, &roster));
+
+        roster.remove(&former);
+
+        assert!(!audio_sender_admitted(former, &roster));
+    }
+
+    #[test]
+    fn audio_sender_admission_waits_for_mid_join_announce() {
+        let joining_peer = endpoint_id();
+        let mut roster = HashSet::new();
+
+        assert!(!audio_sender_admitted(joining_peer, &roster));
+
+        roster.insert(joining_peer);
+
+        assert!(audio_sender_admitted(joining_peer, &roster));
+    }
+
+    #[test]
+    fn audio_admission_lifecycle_keeps_peer_through_transient_grace() {
+        let peer = endpoint_id();
+        let mut roster = HashSet::new();
+
+        apply_audio_admission_event(&mut roster, peer, AudioAdmissionEvent::RosterPresent);
+        assert!(audio_sender_admitted(peer, &roster));
+
+        apply_audio_admission_event(&mut roster, peer, AudioAdmissionEvent::TransientDropGrace);
+        assert!(audio_sender_admitted(peer, &roster));
+    }
+
+    #[test]
+    fn audio_admission_lifecycle_does_not_add_unknown_peer_on_grace_event() {
+        let peer = endpoint_id();
+        let mut roster = HashSet::new();
+
+        apply_audio_admission_event(&mut roster, peer, AudioAdmissionEvent::TransientDropGrace);
+
+        assert!(!audio_sender_admitted(peer, &roster));
+    }
+
+    #[test]
+    fn audio_admission_lifecycle_removes_peer_on_leave_or_grace_expiry() {
+        let peer = endpoint_id();
+        let mut roster = HashSet::from([peer]);
+
+        apply_audio_admission_event(&mut roster, peer, AudioAdmissionEvent::Remove);
+
+        assert!(!audio_sender_admitted(peer, &roster));
+    }
+}

tests/transport_loopback.rs

@@ -169,6 +169,9 @@ async fn loopback_sequenced_audio_reaches_peer_and_decodes() {
     b.lookup.add_endpoint_info(a.endpoint.addr());
 
     let a_id = a.endpoint.id();
+    let b_id = b.endpoint.id();
+    a.transport.admit_audio_sender(b_id);
+    b.transport.admit_audio_sender(a_id);
 
     // Subscribe to incoming datagrams on B before any are sent.
     let mut b_rx = b.transport.receive_datagrams().await.expect("subscribe B");