feat(agent): add full-duplex LiveAudioSession and AndroidLiveAudioSession

agent/app/src/main/java/com/example/appfunctions/agent/data/GeminiLiveProviderImpl.kt

@@ -18,6 +18,7 @@ package com.example.appfunctions.agent.data
 import android.util.Log
 import androidx.annotation.VisibleForTesting
 import androidx.appfunctions.metadata.AppFunctionMetadata
+import com.example.appfunctions.agent.domain.LiveAudioConfig
 import com.example.appfunctions.agent.domain.LiveLlmEvent
 import com.example.appfunctions.agent.domain.LiveLlmProvider
 import com.example.appfunctions.agent.domain.LiveLlmSession
@@ -130,6 +131,12 @@ class GeminiLiveProviderImpl
             tools: List<AppFunctionMetadata>,
         ): LiveLlmSession =
             object : LiveLlmSession {
+                override val audioConfig: LiveAudioConfig =
+                    LiveAudioConfig(
+                        inputSampleRateHz = DEFAULT_INPUT_SAMPLE_RATE_HZ,
+                        outputSampleRateHz = DEFAULT_OUTPUT_SAMPLE_RATE_HZ,
+                    )
+
                 override val events: Flow<LiveLlmEvent> =
                     flow {
                         while (currentCoroutineContext().isActive && webSocketSession.isActive) {

agent/app/src/main/java/com/example/appfunctions/agent/di/DataModule.kt

@@ -16,10 +16,12 @@
 package com.example.appfunctions.agent.di
 
 import android.content.Context
+import android.media.AudioManager
 import androidx.datastore.core.DataStore
 import androidx.datastore.preferences.core.Preferences
 import androidx.datastore.preferences.preferencesDataStore
 import androidx.room.Room
+import com.example.appfunctions.agent.data.AndroidLiveAudioSession
 import com.example.appfunctions.agent.data.ChatRepository
 import com.example.appfunctions.agent.data.DataStoreSettingsRepository
 import com.example.appfunctions.agent.data.FileDownloadHelper
@@ -31,6 +33,7 @@ import com.example.appfunctions.agent.data.RoomChatRepository
 import com.example.appfunctions.agent.data.SettingsRepository
 import com.example.appfunctions.agent.data.db.AppDatabase
 import com.example.appfunctions.agent.data.db.dao.ChatDao
+import com.example.appfunctions.agent.domain.LiveAudioSessionFactory
 import com.example.appfunctions.agent.domain.LlmProviderFactory
 import dagger.Binds
 import dagger.Module
@@ -120,6 +123,19 @@ abstract class DataModule {
             }
         }
 
+        @Provides
+        @Singleton
+        fun provideLiveAudioSessionFactory(
+            @ApplicationContext context: Context,
+        ): LiveAudioSessionFactory {
+            return LiveAudioSessionFactory { config ->
+                AndroidLiveAudioSession(
+                    config = config,
+                    audioManager = context.getSystemService(AudioManager::class.java),
+                )
+            }
+        }
+
         private const val SOCKET_TIMEOUT_MS = 30_000L
         private const val WEBSOCKET_PING_INTERVAL_MS = 20_000L
     }

agent/app/src/main/java/com/example/appfunctions/agent/domain/LiveAudioSession.kt

@@ -0,0 +1,77 @@
+/*
+ * Copyright 2026 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.example.appfunctions.agent.domain
+
+import android.Manifest
+import androidx.annotation.RequiresPermission
+import kotlinx.coroutines.flow.Flow
+
+/**
+ * Provider-supplied PCM audio sample rate configuration for a [LiveAudioSession].
+ *
+ * @property inputSampleRateHz Microphone recording sample rate in Hz.
+ * @property outputSampleRateHz Default assistant playback sample rate in Hz.
+ */
+data class LiveAudioConfig(
+    val inputSampleRateHz: Int,
+    val outputSampleRateHz: Int,
+) {
+    init {
+        require(inputSampleRateHz > 0) { "inputSampleRateHz must be positive: $inputSampleRateHz" }
+        require(outputSampleRateHz > 0) { "outputSampleRateHz must be positive: $outputSampleRateHz" }
+    }
+}
+
+/** Abstraction over full-duplex audio recording and playback for a live voice session. */
+interface LiveAudioSession {
+    /** PCM microphone capture sample rate in Hz emitted by [listenToRecording]. */
+    val inputSampleRateHz: Int
+
+    /** Acquires audio focus/routing and starts microphone capture and audio playback resources. */
+    @RequiresPermission(Manifest.permission.RECORD_AUDIO)
+    fun start()
+
+    /** Streams captured PCM microphone audio chunks while recording is active and unpaused. */
+    fun listenToRecording(): Flow<ByteArray>
+
+    /** Temporarily suppresses microphone emissions (e.g. while executing tools). */
+    fun pauseRecording()
+
+    /** Resumes microphone emissions after [pauseRecording]. */
+    fun resumeRecording()
+
+    /**
+     * Enqueues a PCM audio chunk from the assistant for speaker/headset playback.
+     *
+     * @param pcmBytes Raw 16-bit little-endian mono PCM audio bytes.
+     * @param sampleRateHz Playback sample rate in Hz.
+     */
+    fun queueAudio(
+        pcmBytes: ByteArray,
+        sampleRateHz: Int,
+    )
+
+    /** Immediately clears queued assistant audio and flushes active playback on interruption. */
+    fun stopAudio()
+
+    /** Releases all underlying audio recording, playback, and audio-focus resources. */
+    fun release()
+}
+
+/** Factory for creating a new [LiveAudioSession] configured with [LiveAudioConfig] per voice session. */
+fun interface LiveAudioSessionFactory {
+    fun create(config: LiveAudioConfig): LiveAudioSession
+}

agent/app/src/main/java/com/example/appfunctions/agent/domain/LiveLlmProvider.kt

@@ -57,6 +57,9 @@ suspend inline fun LiveLlmProvider.withSession(
 
 /** Represents an active bidirectional voice and tool session with an LLM provider. */
 interface LiveLlmSession {
+    /** Audio capture and playback sample rate configuration required by this session's provider. */
+    val audioConfig: LiveAudioConfig
+
     /** Sequential stream of server-originated events for this live session. */
     val events: Flow<LiveLlmEvent>