feat(android): Bluetooth audio routing + network change detection + per-arch APK builds

Bluetooth: wire existing AudioRouteManager SCO support through both app
variants. Replace binary speaker toggle with 3-way route cycling
(Earpiece → Speaker → Bluetooth). Tauri side adds JNI bridge functions
(start/stop/query SCO, device availability) and Oboe stream restart.

Network awareness: integrate Android ConnectivityManager to detect
WiFi/cellular transitions and feed them to AdaptiveQualityController
via lock-free AtomicU8 signaling. Enables proactive quality downgrade
and FEC boost on network handoffs.

Build: add --arch flag to build-tauri-android.sh supporting arm64,
armv7, or all (separate per-arch APKs for smaller tester binaries).

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

android/app/src/main/java/com/wzp/engine/WzpEngine.kt

@@ -96,6 +96,17 @@ class WzpEngine(private val callback: WzpCallback) {
         if (nativeHandle != 0L) nativeForceProfile(nativeHandle, profile)
     }
 
+    /**
+     * Signal a network transport change (e.g. WiFi → LTE handoff).
+     *
+     * @param networkType matches Rust `NetworkContext` ordinals:
+     *   0=WiFi, 1=LTE, 2=5G, 3=3G, 4=Unknown, 5=None
+     * @param bandwidthKbps reported downstream bandwidth in kbps
+     */
+    fun onNetworkChanged(networkType: Int, bandwidthKbps: Int) {
+        if (nativeHandle != 0L) nativeOnNetworkChanged(nativeHandle, networkType, bandwidthKbps)
+    }
+
     /** Destroy the native engine and free all resources. The instance must not be reused. */
     @Synchronized
     fun destroy() {
@@ -163,6 +174,7 @@ class WzpEngine(private val callback: WzpCallback) {
     private external fun nativeStartSignaling(handle: Long, relay: String, seed: String, token: String, alias: String): Int
     private external fun nativePlaceCall(handle: Long, targetFp: String): Int
     private external fun nativeAnswerCall(handle: Long, callId: String, mode: Int): Int
+    private external fun nativeOnNetworkChanged(handle: Long, networkType: Int, bandwidthKbps: Int)
 
     /**
      * Ping a relay server. Requires engine to be initialized.

android/app/src/main/java/com/wzp/net/NetworkMonitor.kt

@@ -0,0 +1,141 @@
+package com.wzp.net
+
+import android.content.Context
+import android.net.ConnectivityManager
+import android.net.Network
+import android.net.NetworkCapabilities
+import android.net.NetworkRequest
+import android.os.Handler
+import android.os.Looper
+
+/**
+ * Monitors network connectivity changes via [ConnectivityManager.NetworkCallback]
+ * and classifies the active transport (WiFi, LTE, 5G, 3G).
+ *
+ * Callbacks fire on the main looper so callers can safely update UI state or
+ * dispatch to a native engine from any callback.
+ *
+ * Usage:
+ * 1. Set [onNetworkChanged] to receive `(type: Int, downlinkKbps: Int)` events
+ * 2. Optionally set [onIpChanged] for IP address change events (mid-call ICE refresh)
+ * 3. Call [register] when the call starts
+ * 4. Call [unregister] when the call ends
+ */
+class NetworkMonitor(context: Context) {
+
+    private val cm = context.getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
+    private val mainHandler = Handler(Looper.getMainLooper())
+
+    /**
+     * Called when the network transport type or bandwidth changes.
+     * `type` constants match the Rust `NetworkContext` enum ordinals.
+     */
+    var onNetworkChanged: ((type: Int, downlinkKbps: Int) -> Unit)? = null
+
+    /**
+     * Called when the device's IP address changes (link properties changed).
+     * Useful for triggering mid-call ICE candidate re-gathering.
+     */
+    var onIpChanged: (() -> Unit)? = null
+
+    // Track the last emitted type to avoid redundant callbacks
+    @Volatile
+    private var lastEmittedType: Int = TYPE_UNKNOWN
+
+    private val callback = object : ConnectivityManager.NetworkCallback() {
+        override fun onAvailable(network: Network) {
+            classifyAndEmit(network)
+        }
+
+        override fun onCapabilitiesChanged(network: Network, caps: NetworkCapabilities) {
+            classifyFromCaps(caps)
+        }
+
+        override fun onLinkPropertiesChanged(
+            network: Network,
+            linkProperties: android.net.LinkProperties
+        ) {
+            // IP address may have changed — notify for ICE refresh
+            onIpChanged?.invoke()
+            // Also re-classify in case the transport changed simultaneously
+            classifyAndEmit(network)
+        }
+
+        override fun onLost(network: Network) {
+            lastEmittedType = TYPE_NONE
+            onNetworkChanged?.invoke(TYPE_NONE, 0)
+        }
+    }
+
+    // -- Public API -----------------------------------------------------------
+
+    /** Register the network callback. Call when a call starts. */
+    fun register() {
+        val request = NetworkRequest.Builder()
+            .addCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
+            .build()
+        cm.registerNetworkCallback(request, callback, mainHandler)
+    }
+
+    /** Unregister the network callback. Call when the call ends. */
+    fun unregister() {
+        try {
+            cm.unregisterNetworkCallback(callback)
+        } catch (_: IllegalArgumentException) {
+            // Already unregistered — safe to ignore
+        }
+    }
+
+    // -- Classification -------------------------------------------------------
+
+    private fun classifyAndEmit(network: Network) {
+        val caps = cm.getNetworkCapabilities(network) ?: return
+        classifyFromCaps(caps)
+    }
+
+    private fun classifyFromCaps(caps: NetworkCapabilities) {
+        val type = when {
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_WIFI) -> TYPE_WIFI
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_ETHERNET) -> TYPE_WIFI // treat as WiFi
+            caps.hasTransport(NetworkCapabilities.TRANSPORT_CELLULAR) -> classifyCellular(caps)
+            else -> TYPE_UNKNOWN
+        }
+        val bw = caps.getLinkDownstreamBandwidthKbps()
+
+        // Deduplicate: only emit when the transport type actually changes
+        if (type != lastEmittedType) {
+            lastEmittedType = type
+            onNetworkChanged?.invoke(type, bw)
+        }
+    }
+
+    /**
+     * Approximate cellular generation from reported downstream bandwidth.
+     * This avoids requiring READ_PHONE_STATE permission (needed for
+     * TelephonyManager.getNetworkType on API 30+).
+     *
+     * Thresholds are conservative — carriers over-report bandwidth, so we
+     * classify based on what's actually usable for VoIP:
+     * - >= 100 Mbps → 5G NR
+     * - >= 10 Mbps  → LTE
+     * - < 10 Mbps   → 3G or worse
+     */
+    private fun classifyCellular(caps: NetworkCapabilities): Int {
+        val bw = caps.getLinkDownstreamBandwidthKbps()
+        return when {
+            bw >= 100_000 -> TYPE_CELLULAR_5G
+            bw >= 10_000 -> TYPE_CELLULAR_LTE
+            else -> TYPE_CELLULAR_3G
+        }
+    }
+
+    companion object {
+        /** Constants matching Rust `NetworkContext` enum ordinals. */
+        const val TYPE_WIFI = 0
+        const val TYPE_CELLULAR_LTE = 1
+        const val TYPE_CELLULAR_5G = 2
+        const val TYPE_CELLULAR_3G = 3
+        const val TYPE_UNKNOWN = 4
+        const val TYPE_NONE = 5
+    }
+}

android/app/src/main/java/com/wzp/ui/call/CallViewModel.kt

@@ -5,6 +5,7 @@ import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.wzp.audio.AudioPipeline
+import com.wzp.audio.AudioRoute
 import com.wzp.audio.AudioRouteManager
 import com.wzp.data.SettingsRepository
 import com.wzp.debug.DebugReporter
@@ -12,6 +13,7 @@ import com.wzp.engine.CallStats
 import com.wzp.service.CallService
 import com.wzp.engine.WzpCallback
 import com.wzp.engine.WzpEngine
+import com.wzp.net.NetworkMonitor
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.delay
@@ -43,6 +45,7 @@ class CallViewModel : ViewModel(), WzpCallback {
     private var engineInitialized = false
     private var audioPipeline: AudioPipeline? = null
     private var audioRouteManager: AudioRouteManager? = null
+    private var networkMonitor: NetworkMonitor? = null
     private var audioStarted = false
     private var appContext: Context? = null
     private var settings: SettingsRepository? = null
@@ -60,6 +63,9 @@ class CallViewModel : ViewModel(), WzpCallback {
     private val _isSpeaker = MutableStateFlow(false)
     val isSpeaker: StateFlow<Boolean> = _isSpeaker.asStateFlow()
 
+    private val _audioRoute = MutableStateFlow(AudioRoute.EARPIECE)
+    val audioRoute: StateFlow<AudioRoute> = _audioRoute.asStateFlow()
+
     private val _stats = MutableStateFlow(CallStats())
     val stats: StateFlow<CallStats> = _stats.asStateFlow()
 
@@ -226,7 +232,19 @@ class CallViewModel : ViewModel(), WzpCallback {
             audioPipeline = AudioPipeline(appCtx)
         }
         if (audioRouteManager == null) {
-            audioRouteManager = AudioRouteManager(appCtx)
+            audioRouteManager = AudioRouteManager(appCtx).also { arm ->
+                arm.onRouteChanged = { route ->
+                    _audioRoute.value = route
+                    _isSpeaker.value = (route == AudioRoute.SPEAKER)
+                }
+            }
+        }
+        if (networkMonitor == null) {
+            networkMonitor = NetworkMonitor(appCtx).also { nm ->
+                nm.onNetworkChanged = { type, bw ->
+                    engine?.onNetworkChanged(type, bw)
+                }
+            }
         }
         if (debugReporter == null) {
             debugReporter = DebugReporter(appCtx)
@@ -607,6 +625,27 @@ class CallViewModel : ViewModel(), WzpCallback {
         audioRouteManager?.setSpeaker(newSpeaker)
     }
 
+    /** Cycle audio output: Earpiece → Speaker → Bluetooth (if available) → Earpiece. */
+    fun cycleAudioRoute() {
+        val routes = audioRouteManager?.availableRoutes() ?: return
+        val currentIdx = routes.indexOf(_audioRoute.value)
+        val next = routes[(currentIdx + 1) % routes.size]
+        when (next) {
+            AudioRoute.EARPIECE -> {
+                audioRouteManager?.setBluetoothSco(false)
+                audioRouteManager?.setSpeaker(false)
+            }
+            AudioRoute.SPEAKER -> {
+                audioRouteManager?.setSpeaker(true)
+            }
+            AudioRoute.BLUETOOTH -> {
+                audioRouteManager?.setBluetoothSco(true)
+            }
+        }
+        _audioRoute.value = next
+        _isSpeaker.value = (next == AudioRoute.SPEAKER)
+    }
+
     fun clearError() { _errorMessage.value = null }
 
     fun sendDebugReport() {
@@ -661,6 +700,7 @@ class CallViewModel : ViewModel(), WzpCallback {
             it.start(e)
         }
         audioRouteManager?.register()
+        networkMonitor?.register()
         audioStarted = true
     }
 
@@ -668,8 +708,10 @@ class CallViewModel : ViewModel(), WzpCallback {
         if (!audioStarted) return
         audioPipeline?.stop()    // sets running=false; DON'T null — teardown needs awaitDrain()
         audioRouteManager?.unregister()
+        networkMonitor?.unregister()
         audioRouteManager?.setSpeaker(false)
         _isSpeaker.value = false
+        _audioRoute.value = AudioRoute.EARPIECE
         audioStarted = false
     }
 

android/app/src/main/java/com/wzp/ui/call/InCallScreen.kt

@@ -49,6 +49,7 @@ import androidx.compose.ui.text.font.FontWeight
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import com.wzp.audio.AudioRoute
 import com.wzp.engine.CallStats
 import com.wzp.ui.components.CopyableFingerprint
 import com.wzp.ui.components.Identicon
@@ -74,6 +75,7 @@ fun InCallScreen(
     val callState by viewModel.callState.collectAsState()
     val isMuted by viewModel.isMuted.collectAsState()
     val isSpeaker by viewModel.isSpeaker.collectAsState()
+    val audioRoute by viewModel.audioRoute.collectAsState()
     val stats by viewModel.stats.collectAsState()
     val qualityTier by viewModel.qualityTier.collectAsState()
     val errorMessage by viewModel.errorMessage.collectAsState()
@@ -621,12 +623,12 @@ fun InCallScreen(
 
                 Spacer(modifier = Modifier.height(16.dp))
 
-                // Controls: Mic / End / Spk
+                // Controls: Mic / End / Route (Ear/Spk/BT)
                 ControlRow(
                     isMuted = isMuted,
-                    isSpeaker = isSpeaker,
+                    audioRoute = audioRoute,
                     onToggleMute = viewModel::toggleMute,
-                    onToggleSpeaker = viewModel::toggleSpeaker,
+                    onCycleRoute = viewModel::cycleAudioRoute,
                     onHangUp = { viewModel.stopCall() }
                 )
 
@@ -915,9 +917,9 @@ private fun AudioLevelBar(audioLevel: Int) {
 @Composable
 private fun ControlRow(
     isMuted: Boolean,
-    isSpeaker: Boolean,
+    audioRoute: AudioRoute,
     onToggleMute: () -> Unit,
-    onToggleSpeaker: () -> Unit,
+    onCycleRoute: () -> Unit,
     onHangUp: () -> Unit
 ) {
     Row(
@@ -959,22 +961,28 @@ private fun ControlRow(
             Text("End", style = MaterialTheme.typography.titleMedium.copy(fontWeight = FontWeight.Bold))
         }
 
-        // Speaker
+        // Audio route: cycles Earpiece → Speaker → Bluetooth (when available)
         FilledTonalIconButton(
-            onClick = onToggleSpeaker,
+            onClick = onCycleRoute,
             modifier = Modifier.size(56.dp),
-            colors = if (isSpeaker) {
-                IconButtonDefaults.filledTonalIconButtonColors(
+            colors = when (audioRoute) {
+                AudioRoute.SPEAKER -> IconButtonDefaults.filledTonalIconButtonColors(
                     containerColor = Color(0xFF0F3460), contentColor = Color.White
                 )
-            } else {
-                IconButtonDefaults.filledTonalIconButtonColors(
+                AudioRoute.BLUETOOTH -> IconButtonDefaults.filledTonalIconButtonColors(
+                    containerColor = Color(0xFF2563EB), contentColor = Color.White
+                )
+                else -> IconButtonDefaults.filledTonalIconButtonColors(
                     containerColor = DarkSurface2, contentColor = Color.White
                 )
             }
         ) {
             Text(
-                text = if (isSpeaker) "Spk\nOn" else "Spk",
+                text = when (audioRoute) {
+                    AudioRoute.EARPIECE -> "Ear"
+                    AudioRoute.SPEAKER -> "Spk"
+                    AudioRoute.BLUETOOTH -> "BT"
+                },
                 textAlign = TextAlign.Center,
                 style = MaterialTheme.typography.labelSmall,
                 lineHeight = 12.sp