fix(android): release communication route after dictation (#4069)

Stopping capture abandoned audio focus but left Android's communication mode and selected device owned by Paseo, which could keep Bluetooth audio on its narrow-band call route without an active microphone. Release and reacquire the complete route with the audio session, and prevent idle device callbacks from restoring it.

docs/mobile-testing.md

@@ -259,7 +259,9 @@ background music stays paused. On iOS this is not just a "while recording" probl
 `.playAndRecord`/`.voiceChat` category is non-mixing and survives backgrounding, and iOS re-asserts
 it every time the app returns to the foreground — so one dictation turn kills music for the life of
 the process, on every open, until the app is force-quit. Android holds
-`AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE` with the same effect.
+`AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE` with the same effect. It must also reset
+`MODE_IN_COMMUNICATION` and clear the selected communication device; abandoning focus alone can
+leave Bluetooth earbuds on their narrow-band call route without an active microphone indicator.
 
 `createAudioEngine` (`packages/app/src/voice/audio-engine.native.ts`) calls
 `releaseAudioSession()` whenever capture stops and the playback queue drains, and the iOS module
@@ -267,9 +269,9 @@ also releases on `OnAppEntersBackground`. The native side re-guards on `isRecord
 `speechPlayer.isPlaying`, because the native engine is a singleton shared by multiple JS engine
 wrappers (voice provider + dictation) and only it knows the true state.
 
-This cannot be validated by a JS test — verify on a device: play music, open Paseo, use dictation
-once, stop, and confirm the music resumes; then background/foreground the app and confirm it keeps
-playing.
+This cannot be validated by a JS test — verify on a device: play music through Bluetooth earbuds,
+open Paseo, use dictation once, stop, and confirm the music resumes at full quality; then
+background/foreground the app and confirm it keeps playing at full quality.
 
 ## Unistyles + Reanimated
 

packages/expo-two-way-audio/android/src/main/java/expo/modules/twowayaudio/AudioEngine.kt

@@ -35,6 +35,7 @@ class AudioEngine (context: Context) {
     private val executorServiceMicrophone = Executors.newFixedThreadPool(1)
     private val executorServicePlayback = Executors.newFixedThreadPool(1)
     private var speakerDevice: AudioDeviceInfo? = null
+    private var communicationRouteActive = false
     private var bridgeWindowStartedAtMs = System.currentTimeMillis()
     private var micEvents = 0
     private var micBytes = 0L
@@ -82,25 +83,26 @@ class AudioEngine (context: Context) {
     @SuppressLint("NewApi")
     private fun initializeAudio(context:Context) {
         audioManager = context.getSystemService(Context.AUDIO_SERVICE) as AudioManager
-        audioManager.mode = AudioManager.MODE_IN_COMMUNICATION
+        activateCommunicationRoute()
         if (!requestAudioFocus()) {
             handleAudioFocusBlocked()
         }
 
-        // Route audio to external device if connected, otherwise route to speaker
-        updateAudioRouting()
-
         // Listen for changes in audio routing
         audioManager.registerAudioDeviceCallback(object:android.media.AudioDeviceCallback(){
             override fun onAudioDevicesAdded(addedDevices: Array<out AudioDeviceInfo>?) {
                 Log.d("AudioEngine", "onAudioDevicesAdded")
                 super.onAudioDevicesAdded(addedDevices)
-                updateAudioRouting()
+                if (communicationRouteActive) {
+                    updateAudioRouting()
+                }
             }
             override fun onAudioDevicesRemoved(removedDevices: Array<out AudioDeviceInfo>?) {
                 Log.d("AudioEngine", "onAudioDevicesRemoved")
                 super.onAudioDevicesRemoved(removedDevices)
-                updateAudioRouting()
+                if (communicationRouteActive) {
+                    updateAudioRouting()
+                }
             }
         }, null)
 
@@ -169,10 +171,29 @@ class AudioEngine (context: Context) {
         }
     }
 
+    @SuppressLint("NewApi")
+    private fun activateCommunicationRoute() {
+        communicationRouteActive = true
+        audioManager.mode = AudioManager.MODE_IN_COMMUNICATION
+        updateAudioRouting()
+    }
+
+    @SuppressLint("NewApi")
+    private fun releaseCommunicationRoute() {
+        communicationRouteActive = false
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
+            audioManager.clearCommunicationDevice()
+        } else {
+            @Suppress("DEPRECATION")
+            audioManager.isSpeakerphoneOn = false
+        }
+        audioManager.mode = AudioManager.MODE_NORMAL
+    }
+
     /**
-     * Give audio focus back once we are neither recording nor playing. The focus request is
-     * AUDIOFOCUS_GAIN_TRANSIENT_EXCLUSIVE, so holding it after a dictation turn leaves the
-     * user's music paused indefinitely.
+     * Give the complete communication session back once we are neither recording nor playing.
+     * Focus pauses the user's music, while MODE_IN_COMMUNICATION and the selected communication
+     * device can leave Bluetooth earbuds on their narrow-band call route after capture stops.
      */
     @SuppressLint("NewApi")
     fun releaseAudioSession() {
@@ -186,6 +207,7 @@ class AudioEngine (context: Context) {
         if (::audioTrack.isInitialized) {
             audioTrack.pause()
         }
+        releaseCommunicationRoute()
     }
 
     /**
@@ -209,6 +231,7 @@ class AudioEngine (context: Context) {
         if (audioFocusRequest != null) {
             return
         }
+        activateCommunicationRoute()
         requestAudioFocus()
         if (::audioTrack.isInitialized) {
             audioTrack.play()
@@ -273,6 +296,7 @@ class AudioEngine (context: Context) {
         if (::audioTrack.isInitialized) {
             audioTrack.pause()
         }
+        releaseCommunicationRoute()
         audioSampleQueue.clear()
         isPlaying = false
         isRecordingBeforePause = false
@@ -283,6 +307,7 @@ class AudioEngine (context: Context) {
     @RequiresApi(Build.VERSION_CODES.Q)
     @SuppressLint("MissingPermission")
     private fun startRecording(): Boolean {
+        activateCommunicationRoute()
         if (!requestAudioFocus()) {
             handleAudioFocusBlocked()
             return false
@@ -453,6 +478,7 @@ class AudioEngine (context: Context) {
         if (!wasRecordingBeforePause && !isPlaying) {
             return
         }
+        activateCommunicationRoute()
         if (!requestAudioFocus()) {
             handleAudioFocusBlocked()
             return
@@ -489,13 +515,11 @@ class AudioEngine (context: Context) {
     fun tearDown() {
         stopRecording()
         audioTrack.stop()
-        audioManager.mode = AudioManager.MODE_NORMAL
-        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) {
-            audioManager.clearCommunicationDevice()
-        }
+        releaseCommunicationRoute()
         audioFocusRequest?.let { request ->
             audioManager.abandonAudioFocusRequest(request)
         }
+        audioFocusRequest = null
         executorServiceMicrophone.shutdownNow()
     }