fix: handle audio track recreation to prevent microphone failures

When browsers recreate audio tracks during long sessions, the backend
now properly handles the new track instead of ignoring it. Old track
handlers detect when they've been superseded and exit cleanly to
prevent goroutine leaks.

audio.go

@@ -21,7 +21,7 @@ var (
 	activeConnections  atomic.Int32
 	audioLogger        zerolog.Logger
 	currentAudioTrack  *webrtc.TrackLocalStaticSample
-	inputTrackHandling atomic.Bool
+	currentInputTrack  atomic.Pointer[string]
 	audioOutputEnabled atomic.Bool
 	audioInputEnabled  atomic.Bool
 )
@@ -152,14 +152,10 @@ func setAudioTrack(audioTrack *webrtc.TrackLocalStaticSample) {
 }
 
 func setPendingInputTrack(track *webrtc.TrackRemote) {
-	audioMutex.Lock()
+	trackID := track.ID()
-	defer audioMutex.Unlock()
+	currentInputTrack.Store(&trackID)
-
-	// Start input track handler only once per WebRTC session
-	if inputTrackHandling.CompareAndSwap(false, true) {
 	go handleInputTrackForSession(track)
 }
-}
 
 // SetAudioOutputEnabled enables or disables audio output
 func SetAudioOutputEnabled(enabled bool) error {
@@ -202,22 +198,32 @@ func SetAudioInputEnabled(enabled bool) error {
 // handleInputTrackForSession runs for the entire WebRTC session lifetime
 // It continuously reads from the track and sends to whatever relay is currently active
 func handleInputTrackForSession(track *webrtc.TrackRemote) {
-	defer inputTrackHandling.Store(false)
+	myTrackID := track.ID()
 
 	audioLogger.Debug().
 		Str("codec", track.Codec().MimeType).
-		Str("track_id", track.ID()).
+		Str("track_id", myTrackID).
 		Msg("starting session-lifetime track handler")
 
 	for {
+		// Check if we've been superseded by a new track
+		currentTrackID := currentInputTrack.Load()
+		if currentTrackID != nil && *currentTrackID != myTrackID {
+			audioLogger.Debug().
+				Str("my_track_id", myTrackID).
+				Str("current_track_id", *currentTrackID).
+				Msg("audio track handler exiting - superseded by new track")
+			return
+		}
+
 		// Read RTP packet (must always read to keep track alive)
 		rtpPacket, _, err := track.ReadRTP()
 		if err != nil {
 			if err == io.EOF {
-				audioLogger.Debug().Msg("audio track ended")
+				audioLogger.Debug().Str("track_id", myTrackID).Msg("audio track ended")
 				return
 			}
-			audioLogger.Warn().Err(err).Msg("failed to read RTP packet")
+			audioLogger.Warn().Err(err).Str("track_id", myTrackID).Msg("failed to read RTP packet")
 			continue
 		}