refactor: extract shared engine helpers, federation clone-before-send, constants

Engine deduplication (PRD-engine-dedup.md):
- build_call_config(): shared CallConfig construction (was 23 lines × 2)
- codec_to_profile(): shared CodecId → QualityProfile mapping (was 19 lines × 2)
- run_signal_task(): shared signal handler (was 48 lines × 2)
- Net -39 lines from engine.rs, 6 duplicated blocks → single-line calls

Quick wins from REFACTOR-codebase-audit.md:
- 6 magic number constants extracted (CAPTURE_POLL_MS, RECV_TIMEOUT_MS, etc.)
- DRED_POLL_INTERVAL moved from 2 local defs to 1 module-level const
- federation.rs: forward_to_peers, broadcast_signal, send_signal_to_peer
  now clone peer list and release lock before sending (was holding Mutex
  across async I/O — last lock-during-send pattern eliminated)
- main.rs: close_transport() helper replaces 12 silent .ok() calls with
  debug-level logging

314 tests passing, 0 regressions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-relay/src/federation.rs

@@ -213,16 +213,19 @@ impl FederationManager {
     /// `origin_relay_fp` against its own fp and drops self-sourced
     /// forwards.
     pub async fn broadcast_signal(&self, msg: &wzp_proto::SignalMessage) -> usize {
-        let links = self.peer_links.lock().await;
+        let peers: Vec<(String, String, Arc<QuinnTransport>)> = {
+            let links = self.peer_links.lock().await;
+            links.iter().map(|(fp, l)| (fp.clone(), l.label.clone(), l.transport.clone())).collect()
+        };  // lock released
         let mut count = 0;
-        for (fp, link) in links.iter() {
-            match link.transport.send_signal(msg).await {
+        for (fp, label, transport) in &peers {
+            match transport.send_signal(msg).await {
                 Ok(()) => {
                     count += 1;
-                    tracing::debug!(peer = %link.label, %fp, "federation: broadcast signal ok");
+                    tracing::debug!(peer = %label, %fp, "federation: broadcast signal ok");
                 }
                 Err(e) => {
-                    tracing::warn!(peer = %link.label, %fp, error = %e, "federation: broadcast signal failed");
+                    tracing::warn!(peer = %label, %fp, error = %e, "federation: broadcast signal failed");
                 }
             }
         }
@@ -243,10 +246,12 @@ impl FederationManager {
         msg: &wzp_proto::SignalMessage,
     ) -> Result<(), String> {
         let normalized = normalize_fp(peer_relay_fp);
-        let links = self.peer_links.lock().await;
-        match links.get(&normalized) {
-            Some(link) => link
-                .transport
+        let transport = {
+            let links = self.peer_links.lock().await;
+            links.get(&normalized).map(|l| l.transport.clone())
+        };  // lock released
+        match transport {
+            Some(t) => t
                 .send_signal(msg)
                 .await
                 .map_err(|e| format!("send to peer {normalized}: {e}")),
@@ -403,20 +408,22 @@ impl FederationManager {
     /// or rate limiting; the body currently forwards on `room_hash` alone
     /// because that's what the wire format carries.
     pub async fn forward_to_peers(&self, _room_name: &str, room_hash: &[u8; 8], media_data: &Bytes) {
-        let links = self.peer_links.lock().await;
-        if links.is_empty() {
-            return;
-        }
-        for (_fp, link) in links.iter() {
+        let peers: Vec<(String, Arc<QuinnTransport>)> = {
+            let links = self.peer_links.lock().await;
+            if links.is_empty() { return; }
+            links.values().map(|l| (l.label.clone(), l.transport.clone())).collect()
+        };  // lock released
+
+        for (label, transport) in &peers {
             let mut tagged = Vec::with_capacity(8 + media_data.len());
             tagged.extend_from_slice(room_hash);
             tagged.extend_from_slice(media_data);
-            match link.transport.send_raw_datagram(&tagged) {
+            match transport.send_raw_datagram(&tagged) {
                 Ok(()) => {
                     self.metrics.federation_packets_forwarded
-                        .with_label_values(&[&link.label, "out"]).inc();
+                        .with_label_values(&[label, "out"]).inc();
                 }
-                Err(e) => warn!(peer = %link.label, "federation send error: {e}"),
+                Err(e) => warn!(peer = %label, "federation send error: {e}"),
             }
         }
     }
@@ -483,9 +490,12 @@ async fn run_room_event_dispatcher(
                     let participants = fm.room_mgr.local_participant_list(&room);
                     info!(room = %room, count = participants.len(), "global room now active, announcing to peers");
                     let msg = SignalMessage::GlobalRoomActive { room, participants };
-                    let links = fm.peer_links.lock().await;
-                    for link in links.values() {
-                        let _ = link.transport.send_signal(&msg).await;
+                    let transports: Vec<Arc<QuinnTransport>> = {
+                        let links = fm.peer_links.lock().await;
+                        links.values().map(|l| l.transport.clone()).collect()
+                    };
+                    for t in &transports {
+                        let _ = t.send_signal(&msg).await;
                     }
                 }
             }
@@ -493,9 +503,12 @@ async fn run_room_event_dispatcher(
                 if fm.is_global_room(&room) {
                     info!(room = %room, "global room now inactive, announcing to peers");
                     let msg = SignalMessage::GlobalRoomInactive { room };
-                    let links = fm.peer_links.lock().await;
-                    for link in links.values() {
-                        let _ = link.transport.send_signal(&msg).await;
+                    let transports: Vec<Arc<QuinnTransport>> = {
+                        let links = fm.peer_links.lock().await;
+                        links.values().map(|l| l.transport.clone()).collect()
+                    };
+                    for t in &transports {
+                        let _ = t.send_signal(&msg).await;
                     }
                 }
             }

crates/wzp-relay/src/main.rs

@@ -23,6 +23,13 @@ use wzp_relay::presence::PresenceRegistry;
 use wzp_relay::room::{self, RoomManager};
 use wzp_relay::session_mgr::SessionManager;
 
+/// Close a transport gracefully, logging any error at debug level.
+async fn close_transport(t: &dyn wzp_proto::MediaTransport, context: &str) {
+    if let Err(e) = t.close().await {
+        tracing::debug!(context, error = %e, "transport close (non-fatal)");
+    }
+}
+
 /// Parsed CLI result — config + identity path.
 struct CliResult {
     config: RelayConfig,
@@ -908,7 +915,7 @@ async fn main() -> anyhow::Result<()> {
                         }
                     }
                 }
-                transport.close().await.ok();
+                close_transport(&*transport, "cleanup").await;
                 return;
             }
 
@@ -1475,7 +1482,7 @@ async fn main() -> anyhow::Result<()> {
                     reg.unregister_local(&client_fp);
                 }
 
-                transport.close().await.ok();
+                close_transport(&*transport, "cleanup").await;
                 return;
             }
 
@@ -1499,14 +1506,14 @@ async fn main() -> anyhow::Result<()> {
                             Err(e) => {
                                 metrics.auth_attempts.with_label_values(&["fail"]).inc();
                                 error!(%addr, "auth failed: {e}");
-                                transport.close().await.ok();
+                                close_transport(&*transport, "cleanup").await;
                                 return;
                             }
                         }
                     }
                     Ok(Some(_)) => {
                         error!(%addr, "expected AuthToken as first signal, got something else");
-                        transport.close().await.ok();
+                        close_transport(&*transport, "cleanup").await;
                         return;
                     }
                     Ok(None) => {
@@ -1515,7 +1522,7 @@ async fn main() -> anyhow::Result<()> {
                     }
                     Err(e) => {
                         error!(%addr, "signal recv error during auth: {e}");
-                        transport.close().await.ok();
+                        close_transport(&*transport, "cleanup").await;
                         return;
                     }
                 }
@@ -1537,7 +1544,7 @@ async fn main() -> anyhow::Result<()> {
                 }
                 Err(e) => {
                     error!(%addr, "handshake failed: {e}");
-                    transport.close().await.ok();
+                    close_transport(&*transport, "cleanup").await;
                     return;
                 }
             };
@@ -1561,7 +1568,7 @@ async fn main() -> anyhow::Result<()> {
                 };
                 if !authorized {
                     warn!(%addr, room = %room_name, fp = %participant_fp, "rejected: not authorized for this call room");
-                    transport.close().await.ok();
+                    close_transport(&*transport, "cleanup").await;
                     return;
                 }
                 info!(%addr, room = %room_name, fp = %participant_fp, "authorized for call room");
@@ -1602,7 +1609,7 @@ async fn main() -> anyhow::Result<()> {
 
                 tokio::select! { _ = up => {} _ = dn => {} }
                 stats_handle.abort();
-                transport.close().await.ok();
+                close_transport(&*transport, "cleanup").await;
             } else {
                 // Room mode — enforce max sessions, then join room
                 let session_id = {
@@ -1611,7 +1618,7 @@ async fn main() -> anyhow::Result<()> {
                         Ok(id) => id,
                         Err(e) => {
                             error!(%addr, room = %room_name, "session rejected: {e}");
-                            transport.close().await.ok();
+                            close_transport(&*transport, "cleanup").await;
                             return;
                         }
                     }
@@ -1626,7 +1633,7 @@ async fn main() -> anyhow::Result<()> {
                         metrics.active_sessions.dec();
                         let mut smgr = session_mgr.lock().await;
                         smgr.remove_session(session_id);
-                        transport.close().await.ok();
+                        close_transport(&*transport, "cleanup").await;
                         return;
                     }
                 }
@@ -1676,7 +1683,7 @@ async fn main() -> anyhow::Result<()> {
                             metrics.active_sessions.dec();
                             let mut smgr = session_mgr.lock().await;
                             smgr.remove_session(session_id);
-                            transport.close().await.ok();
+                            close_transport(&*transport, "cleanup").await;
                             return;
                         }
                     }
@@ -1731,7 +1738,7 @@ async fn main() -> anyhow::Result<()> {
                     smgr.remove_session(session_id);
                 }
 
-                transport.close().await.ok();
+                close_transport(&*transport, "cleanup").await;
             }
         });
     }

desktop/src-tauri/src/engine.rs

@@ -30,6 +30,14 @@ use wzp_proto::traits::{AudioDecoder, QualityController};
 use wzp_proto::{AdaptiveQualityController, CodecId, MediaTransport, QualityProfile};
 
 const FRAME_SAMPLES_40MS: usize = 1920;
+const CAPTURE_POLL_MS: u64 = 5;
+const RECV_TIMEOUT_MS: u64 = 100;
+const SIGNAL_TIMEOUT_MS: u64 = 200;
+#[cfg_attr(not(target_os = "android"), allow(dead_code))]
+const CONNECT_TIMEOUT_SECS: u64 = 10;
+#[cfg_attr(not(target_os = "android"), allow(dead_code))]
+const HEARTBEAT_INTERVAL_SECS: u64 = 2;
+const DRED_POLL_INTERVAL: u32 = 25;
 
 /// Profile index mapping for the AtomicU8 adaptive-quality bridge.
 const PROFILE_NO_CHANGE: u8 = 0xFF;
@@ -78,6 +86,101 @@ fn resolve_quality(quality: &str) -> Option<QualityProfile> {
     }
 }
 
+/// Build a CallConfig from a quality string. Used by both Android and desktop send tasks.
+fn build_call_config(quality: &str) -> CallConfig {
+    let profile = resolve_quality(quality);
+    match profile {
+        Some(p) => CallConfig {
+            noise_suppression: false,
+            suppression_enabled: false,
+            ..CallConfig::from_profile(p)
+        },
+        None => CallConfig {
+            noise_suppression: false,
+            suppression_enabled: false,
+            ..CallConfig::default()
+        },
+    }
+}
+
+/// Map a received codec ID to the corresponding QualityProfile.
+/// Used by recv tasks when the peer switches codecs.
+fn codec_to_profile(codec: CodecId) -> QualityProfile {
+    match codec {
+        CodecId::Opus24k => QualityProfile::GOOD,
+        CodecId::Opus6k => QualityProfile::DEGRADED,
+        CodecId::Opus32k => QualityProfile::STUDIO_32K,
+        CodecId::Opus48k => QualityProfile::STUDIO_48K,
+        CodecId::Opus64k => QualityProfile::STUDIO_64K,
+        CodecId::Codec2_1200 => QualityProfile::CATASTROPHIC,
+        CodecId::Codec2_3200 => QualityProfile {
+            codec: CodecId::Codec2_3200,
+            fec_ratio: 0.5,
+            frame_duration_ms: 20,
+            frames_per_block: 5,
+        },
+        other => QualityProfile { codec: other, ..QualityProfile::GOOD },
+    }
+}
+
+/// Signal handler task -- shared between Android and desktop.
+/// Handles RoomUpdate (participant list), QualityDirective (relay-pushed
+/// codec switch), and Hangup from the relay signal stream.
+async fn run_signal_task(
+    transport: Arc<wzp_transport::QuinnTransport>,
+    running: Arc<AtomicBool>,
+    pending_profile: Arc<AtomicU8>,
+    participants: Arc<Mutex<Vec<ParticipantInfo>>>,
+    event_cb: Arc<dyn Fn(&str, &str) + Send + Sync>,
+) {
+    loop {
+        if !running.load(Ordering::Relaxed) {
+            break;
+        }
+        match tokio::time::timeout(
+            std::time::Duration::from_millis(SIGNAL_TIMEOUT_MS),
+            transport.recv_signal(),
+        )
+        .await
+        {
+            Ok(Ok(Some(wzp_proto::SignalMessage::RoomUpdate {
+                participants: parts,
+                ..
+            }))) => {
+                let mut seen = std::collections::HashSet::new();
+                let unique: Vec<ParticipantInfo> = parts
+                    .into_iter()
+                    .filter(|p| seen.insert((p.fingerprint.clone(), p.alias.clone())))
+                    .map(|p| ParticipantInfo {
+                        fingerprint: p.fingerprint,
+                        alias: p.alias,
+                        relay_label: p.relay_label,
+                    })
+                    .collect();
+                let count = unique.len();
+                *participants.lock().await = unique;
+                event_cb("room-update", &format!("{count} participants"));
+            }
+            Ok(Ok(Some(wzp_proto::SignalMessage::QualityDirective {
+                recommended_profile,
+                reason,
+            }))) => {
+                let idx = profile_to_index(&recommended_profile);
+                info!(
+                    codec = ?recommended_profile.codec,
+                    reason = reason.as_deref().unwrap_or(""),
+                    "relay quality directive: switching profile"
+                );
+                pending_profile.store(idx, Ordering::Release);
+            }
+            Ok(Ok(Some(_))) => {}
+            Ok(Ok(None)) => break,
+            Ok(Err(_)) => break,
+            Err(_) => {}
+        }
+    }
+}
+
 /// Wrapper to make non-Sync audio handles safe to store in shared state.
 /// The audio handle is only accessed from the thread that created it (drop),
 /// never shared across threads — Sync is safe.
@@ -395,7 +498,7 @@ impl CallEngine {
             };
             let client_config = wzp_transport::client_config();
             let conn = match tokio::time::timeout(
-                std::time::Duration::from_secs(10),
+                std::time::Duration::from_secs(CONNECT_TIMEOUT_SECS),
                 wzp_transport::connect(&endpoint, relay_addr, &room, client_config),
             ).await {
                 Ok(Ok(c)) => c,
@@ -404,8 +507,8 @@ impl CallEngine {
                     return Err(e.into());
                 }
                 Err(_) => {
-                    error!("connect TIMED OUT after 10s — QUIC handshake never completed. Relay may be unreachable from this endpoint.");
-                    return Err(anyhow::anyhow!("QUIC connect timeout (10s)"));
+                    error!("connect TIMED OUT after {CONNECT_TIMEOUT_SECS}s — QUIC handshake never completed. Relay may be unreachable from this endpoint.");
+                    return Err(anyhow::anyhow!("QUIC connect timeout ({CONNECT_TIMEOUT_SECS}s)"));
                 }
             };
             info!(t_ms = call_t0.elapsed().as_millis(), "first-join diag: QUIC connection established, performing handshake");
@@ -525,19 +628,7 @@ impl CallEngine {
         let send_app = app.clone();
         let send_pending_profile = pending_profile.clone();
         tokio::spawn(async move {
-            let profile = resolve_quality(&send_quality);
-            let config = match profile {
-                Some(p) => CallConfig {
-                    noise_suppression: false,
-                    suppression_enabled: false,
-                    ..CallConfig::from_profile(p)
-                },
-                None => CallConfig {
-                    noise_suppression: false,
-                    suppression_enabled: false,
-                    ..CallConfig::default()
-                },
-            };
+            let config = build_call_config(&send_quality);
             let mut frame_samples = (config.profile.frame_duration_ms as usize) * 48;
             info!(codec = ?config.profile.codec, frame_samples, t_ms = send_t0.elapsed().as_millis(), "first-join diag: send task spawned (android/oboe)");
             *send_tx_codec.lock().await = format!("{:?}", config.profile.codec);
@@ -552,7 +643,6 @@ impl CallEngine {
             // expected-loss hint based on real-time network conditions.
             let mut dred_tuner = wzp_proto::DredTuner::new(config.profile.codec);
             let mut frames_since_dred_poll: u32 = 0;
-            const DRED_POLL_INTERVAL: u32 = 25;
 
             let mut heartbeat = std::time::Instant::now();
             let mut last_rms: u32 = 0;
@@ -576,7 +666,7 @@ impl CallEngine {
                 // like Opus6k to produce ~11 frames/s instead of 25).
                 if crate::wzp_native::audio_capture_available() < frame_samples {
                     short_reads += 1;
-                    tokio::time::sleep(std::time::Duration::from_millis(5)).await;
+                    tokio::time::sleep(std::time::Duration::from_millis(CAPTURE_POLL_MS)).await;
                     continue;
                 }
                 let read = crate::wzp_native::audio_read_capture(&mut buf[..frame_samples]);
@@ -693,7 +783,7 @@ impl CallEngine {
                 }
 
                 // Heartbeat every 2s with capture+encode+send state
-                if heartbeat.elapsed() >= std::time::Duration::from_secs(2) {
+                if heartbeat.elapsed() >= std::time::Duration::from_secs(HEARTBEAT_INTERVAL_SECS) {
                     let fs = send_fs.load(Ordering::Relaxed);
                     let drops = send_drops.load(Ordering::Relaxed);
                     info!(
@@ -810,7 +900,7 @@ impl CallEngine {
                     break;
                 }
                 match tokio::time::timeout(
-                    std::time::Duration::from_millis(100),
+                    std::time::Duration::from_millis(RECV_TIMEOUT_MS),
                     recv_t.recv_media(),
                 )
                 .await
@@ -849,19 +939,7 @@ impl CallEngine {
                                 if *rx != codec_name { *rx = codec_name; }
                             }
                             if pkt.header.codec_id != current_codec {
-                                let new_profile = match pkt.header.codec_id {
-                                    CodecId::Opus24k => QualityProfile::GOOD,
-                                    CodecId::Opus6k => QualityProfile::DEGRADED,
-                                    CodecId::Opus32k => QualityProfile::STUDIO_32K,
-                                    CodecId::Opus48k => QualityProfile::STUDIO_48K,
-                                    CodecId::Opus64k => QualityProfile::STUDIO_64K,
-                                    CodecId::Codec2_1200 => QualityProfile::CATASTROPHIC,
-                                    CodecId::Codec2_3200 => QualityProfile {
-                                        codec: CodecId::Codec2_3200,
-                                        fec_ratio: 0.5, frame_duration_ms: 20, frames_per_block: 5,
-                                    },
-                                    other => QualityProfile { codec: other, ..QualityProfile::GOOD },
-                                };
+                                let new_profile = codec_to_profile(pkt.header.codec_id);
                                 info!(from = ?current_codec, to = ?pkt.header.codec_id, "recv: switching decoder");
                                 let _ = decoder.set_profile(new_profile);
                                 current_profile = new_profile;
@@ -1015,7 +1093,7 @@ impl CallEngine {
                 }
 
                 // Heartbeat every 2s with decode+playout state
-                if heartbeat.elapsed() >= std::time::Duration::from_secs(2) {
+                if heartbeat.elapsed() >= std::time::Duration::from_secs(HEARTBEAT_INTERVAL_SECS) {
                     let fr = recv_fr.load(Ordering::Relaxed);
                     if wzp_codec::dred_verbose_logs() {
                         info!(
@@ -1124,60 +1202,14 @@ impl CallEngine {
         });
 
         // Signal task (presence + quality directives).
-        let sig_t = transport.clone();
-        let sig_r = running.clone();
-        let sig_p = participants.clone();
-        let sig_pending_profile = pending_profile.clone();
         let event_cb = Arc::new(event_cb);
-        let sig_cb = event_cb.clone();
-        tokio::spawn(async move {
-            loop {
-                if !sig_r.load(Ordering::Relaxed) {
-                    break;
-                }
-                match tokio::time::timeout(
-                    std::time::Duration::from_millis(200),
-                    sig_t.recv_signal(),
-                )
-                .await
-                {
-                    Ok(Ok(Some(wzp_proto::SignalMessage::RoomUpdate {
-                        participants: parts,
-                        ..
-                    }))) => {
-                        let mut seen = std::collections::HashSet::new();
-                        let unique: Vec<ParticipantInfo> = parts
-                            .into_iter()
-                            .filter(|p| seen.insert((p.fingerprint.clone(), p.alias.clone())))
-                            .map(|p| ParticipantInfo {
-                                fingerprint: p.fingerprint,
-                                alias: p.alias,
-                                relay_label: p.relay_label,
-                            })
-                            .collect();
-                        let count = unique.len();
-                        *sig_p.lock().await = unique;
-                        sig_cb("room-update", &format!("{count} participants"));
-                    }
-                    Ok(Ok(Some(wzp_proto::SignalMessage::QualityDirective {
-                        recommended_profile,
-                        reason,
-                    }))) => {
-                        let idx = profile_to_index(&recommended_profile);
-                        info!(
-                            codec = ?recommended_profile.codec,
-                            reason = reason.as_deref().unwrap_or(""),
-                            "relay quality directive: switching profile"
-                        );
-                        sig_pending_profile.store(idx, Ordering::Release);
-                    }
-                    Ok(Ok(Some(_))) => {}
-                    Ok(Ok(None)) => break,
-                    Ok(Err(_)) => break,
-                    Err(_) => {}
-                }
-            }
-        });
+        tokio::spawn(run_signal_task(
+            transport.clone(),
+            running.clone(),
+            pending_profile.clone(),
+            participants.clone(),
+            event_cb.clone(),
+        ));
 
         Ok(Self {
             running,
@@ -1349,19 +1381,7 @@ impl CallEngine {
         let send_tx_codec = tx_codec.clone();
         let send_pending_profile = pending_profile.clone();
         tokio::spawn(async move {
-            let profile = resolve_quality(&send_quality);
-            let config = match profile {
-                Some(p) => CallConfig {
-                    noise_suppression: false,
-                    suppression_enabled: false,
-                    ..CallConfig::from_profile(p)
-                },
-                None => CallConfig {
-                    noise_suppression: false,
-                    suppression_enabled: false,
-                    ..CallConfig::default()
-                },
-            };
+            let config = build_call_config(&send_quality);
             let mut frame_samples = (config.profile.frame_duration_ms as usize) * 48;
             info!(codec = ?config.profile.codec, frame_samples, "send task starting");
             *send_tx_codec.lock().await = format!("{:?}", config.profile.codec);
@@ -1372,14 +1392,13 @@ impl CallEngine {
             // Continuous DRED tuning (same as Android send task).
             let mut dred_tuner = wzp_proto::DredTuner::new(config.profile.codec);
             let mut frames_since_dred_poll: u32 = 0;
-            const DRED_POLL_INTERVAL: u32 = 25;
 
             loop {
                 if !send_r.load(Ordering::Relaxed) {
                     break;
                 }
                 if capture_ring.available() < frame_samples {
-                    tokio::time::sleep(std::time::Duration::from_millis(5)).await;
+                    tokio::time::sleep(std::time::Duration::from_millis(CAPTURE_POLL_MS)).await;
                     continue;
                 }
                 capture_ring.read(&mut buf[..frame_samples]);
@@ -1470,7 +1489,7 @@ impl CallEngine {
                     break;
                 }
                 match tokio::time::timeout(
-                    std::time::Duration::from_millis(100),
+                    std::time::Duration::from_millis(RECV_TIMEOUT_MS),
                     recv_t.recv_media(),
                 )
                 .await
@@ -1485,19 +1504,7 @@ impl CallEngine {
                             }
                             // Auto-switch decoder if incoming codec differs
                             if pkt.header.codec_id != current_codec {
-                                let new_profile = match pkt.header.codec_id {
-                                    CodecId::Opus24k => QualityProfile::GOOD,
-                                    CodecId::Opus6k => QualityProfile::DEGRADED,
-                                    CodecId::Opus32k => QualityProfile::STUDIO_32K,
-                                    CodecId::Opus48k => QualityProfile::STUDIO_48K,
-                                    CodecId::Opus64k => QualityProfile::STUDIO_64K,
-                                    CodecId::Codec2_1200 => QualityProfile::CATASTROPHIC,
-                                    CodecId::Codec2_3200 => QualityProfile {
-                                        codec: CodecId::Codec2_3200,
-                                        fec_ratio: 0.5, frame_duration_ms: 20, frames_per_block: 5,
-                                    },
-                                    other => QualityProfile { codec: other, ..QualityProfile::GOOD },
-                                };
+                                let new_profile = codec_to_profile(pkt.header.codec_id);
                                 info!(from = ?current_codec, to = ?pkt.header.codec_id, "recv: switching decoder");
                                 let _ = decoder.set_profile(new_profile);
                                 current_profile = new_profile;
@@ -1560,60 +1567,14 @@ impl CallEngine {
         });
 
         // Signal task (presence + quality directives)
-        let sig_t = transport.clone();
-        let sig_r = running.clone();
-        let sig_p = participants.clone();
-        let sig_pending_profile = pending_profile.clone();
         let event_cb = Arc::new(event_cb);
-        let sig_cb = event_cb.clone();
-        tokio::spawn(async move {
-            loop {
-                if !sig_r.load(Ordering::Relaxed) {
-                    break;
-                }
-                match tokio::time::timeout(
-                    std::time::Duration::from_millis(200),
-                    sig_t.recv_signal(),
-                )
-                .await
-                {
-                    Ok(Ok(Some(wzp_proto::SignalMessage::RoomUpdate {
-                        participants: parts,
-                        ..
-                    }))) => {
-                        let mut seen = std::collections::HashSet::new();
-                        let unique: Vec<ParticipantInfo> = parts
-                            .into_iter()
-                            .filter(|p| seen.insert((p.fingerprint.clone(), p.alias.clone())))
-                            .map(|p| ParticipantInfo {
-                                fingerprint: p.fingerprint,
-                                alias: p.alias,
-                                relay_label: p.relay_label,
-                            })
-                            .collect();
-                        let count = unique.len();
-                        *sig_p.lock().await = unique;
-                        sig_cb("room-update", &format!("{count} participants"));
-                    }
-                    Ok(Ok(Some(wzp_proto::SignalMessage::QualityDirective {
-                        recommended_profile,
-                        reason,
-                    }))) => {
-                        let idx = profile_to_index(&recommended_profile);
-                        info!(
-                            codec = ?recommended_profile.codec,
-                            reason = reason.as_deref().unwrap_or(""),
-                            "relay quality directive: switching profile"
-                        );
-                        sig_pending_profile.store(idx, Ordering::Release);
-                    }
-                    Ok(Ok(Some(_))) => {}
-                    Ok(Ok(None)) => break,
-                    Ok(Err(_)) => break,
-                    Err(_) => {}
-                }
-            }
-        });
+        tokio::spawn(run_signal_task(
+            transport.clone(),
+            running.clone(),
+            pending_profile.clone(),
+            participants.clone(),
+            event_cb.clone(),
+        ));
 
         Ok(Self {
             running,

docs/PRD-engine-dedup.md

@@ -0,0 +1,132 @@
+# PRD: Engine.rs Deduplication — Extract Shared Send/Recv Helpers
+
+## Problem
+
+`desktop/src-tauri/src/engine.rs` is 1,705 lines with two nearly identical `CallEngine::start()` implementations — one for Android (880 lines) and one for desktop (430 lines). ~350 lines are copy-pasted between them. Every change to the encode/decode/adaptive-quality pipeline requires editing both places, and they've already diverged in subtle ways (Android has extensive first-join diagnostics that desktop lacks).
+
+## Scope
+
+Extract the duplicated logic into shared helper functions. The Android and desktop paths should only differ in their audio I/O mechanism (Oboe ring via wzp-native vs CPAL capture_ring/playout_ring).
+
+## What's Duplicated
+
+| Block | Description | Lines (each) |
+|-------|-------------|------|
+| `build_call_config()` | Resolve quality string → CallConfig | 23 |
+| Codec-to-profile match | Map CodecId → QualityProfile for decoder switch | 19 |
+| Adaptive quality switch | Read AtomicU8, index_to_profile, set_profile, update frame_samples + dred_tuner | 15 |
+| DRED tuner poll | Check frame counter, poll quinn stats, apply tuning | 15 |
+| Quality report ingestion | Extract quality_report, feed to AdaptiveQualityController, store to AtomicU8 | 8 |
+| Signal task | Accept signals, handle RoomUpdate/QualityDirective/Hangup | 48 |
+| **Total** | | **~128 lines × 2 = 256 lines eliminated** |
+
+## Implementation
+
+### Phase 1: Top-Level Helper Functions
+
+```rust
+fn build_call_config(quality: &str) -> CallConfig {
+    let profile = resolve_quality(quality);
+    match profile {
+        Some(p) => CallConfig {
+            noise_suppression: false,
+            suppression_enabled: false,
+            ..CallConfig::from_profile(p)
+        },
+        None => CallConfig {
+            noise_suppression: false,
+            suppression_enabled: false,
+            ..CallConfig::default()
+        },
+    }
+}
+
+fn codec_to_profile(codec: CodecId) -> QualityProfile {
+    match codec {
+        CodecId::Opus24k => QualityProfile::GOOD,
+        CodecId::Opus6k => QualityProfile::DEGRADED,
+        CodecId::Opus32k => QualityProfile::STUDIO_32K,
+        CodecId::Opus48k => QualityProfile::STUDIO_48K,
+        CodecId::Opus64k => QualityProfile::STUDIO_64K,
+        CodecId::Codec2_1200 => QualityProfile::CATASTROPHIC,
+        CodecId::Codec2_3200 => QualityProfile {
+            codec: CodecId::Codec2_3200,
+            fec_ratio: 0.5,
+            frame_duration_ms: 20,
+            frames_per_block: 5,
+        },
+        other => QualityProfile { codec: other, ..QualityProfile::GOOD },
+    }
+}
+
+fn check_adaptive_switch(
+    pending: &AtomicU8,
+    encoder: &mut CallEncoder,
+    tuner: &mut wzp_proto::DredTuner,
+    frame_samples: &mut usize,
+    tx_codec: &tokio::sync::Mutex<String>,
+) -> bool {
+    let p = pending.swap(PROFILE_NO_CHANGE, Ordering::Acquire);
+    if p == PROFILE_NO_CHANGE { return false; }
+    if let Some(new_profile) = index_to_profile(p) {
+        let new_fs = (new_profile.frame_duration_ms as usize) * 48;
+        if encoder.set_profile(new_profile).is_ok() {
+            *frame_samples = new_fs;
+            tuner.set_codec(new_profile.codec);
+            // Caller updates tx_codec display string
+            return true;
+        }
+    }
+    false
+}
+```
+
+### Phase 2: Shared Signal Task
+
+Extract the signal task into a standalone async function:
+
+```rust
+async fn run_signal_task(
+    transport: Arc<wzp_transport::QuinnTransport>,
+    running: Arc<AtomicBool>,
+    pending_profile: Arc<AtomicU8>,
+    participants: Arc<Mutex<Vec<ParticipantInfo>>>,
+) {
+    loop {
+        if !running.load(Ordering::Relaxed) { break; }
+        match tokio::time::timeout(
+            Duration::from_millis(SIGNAL_TIMEOUT_MS),
+            transport.recv_signal(),
+        ).await {
+            Ok(Ok(Some(msg))) => {
+                // Handle RoomUpdate, QualityDirective, Hangup...
+            }
+            _ => {}
+        }
+    }
+}
+```
+
+### Phase 3: Shared DRED Poll + Quality Ingestion
+
+These are small blocks but appear in both send and recv tasks. Extract as inline helpers or closures.
+
+## Verification
+
+1. `cargo check --workspace` — must compile
+2. `cargo test -p wzp-proto -p wzp-relay -p wzp-client --lib` — must pass
+3. Manual test: place a call Android↔Desktop, verify audio works in both directions
+4. Verify adaptive quality still switches (set one side to auto, degrade network)
+
+## Effort
+
+- Phase 1: 1 hour (extract 3 functions, update 6 call sites)
+- Phase 2: 30 min (extract signal task, update 2 spawn sites)
+- Phase 3: 30 min (cleanup remaining small duplicates)
+- Total: ~2 hours
+
+## Not In Scope
+
+- Audio I/O trait abstraction (Oboe vs CPAL) — different project, different risk profile
+- Moving Android-specific diagnostics (first-join, PCM recorder) into a feature flag
+- Splitting engine.rs into multiple files