fix(android): UPnP drop falls back to local; pollLoop detects natural advance

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/player/MinstrelForwardingPlayer.kt

@@ -207,6 +207,10 @@ class MinstrelForwardingPlayer(
         pollJob?.cancel()
         if (active != null) {
             pollJob = scope.launch { pollLoop(active) }
+            // Pre-queue the next track immediately so Sonos can advance
+            // gap-free into the second track without waiting for the first
+            // onMediaItemTransition event (which only fires on user skips).
+            scope.launch { preQueueNext(active) }
         } else {
             remoteState.reset()
         }
@@ -215,6 +219,10 @@ class MinstrelForwardingPlayer(
     private suspend fun pollLoop(active: ActiveUpnp) {
         while (scope.isActive && holder.active.value?.routeId == active.routeId) {
             val outcome = runCatching {
+                // Capture before applyPositionInfo so we can detect a URI
+                // change that Sonos made via the pre-queued SetNextAVTransportURI
+                // (natural auto-advance without any user skip action).
+                val previousTrackUri = remoteState.currentTrackUri
                 val info = active.avTransport.getPositionInfo()
                 remoteState.applyPositionInfo(
                     positionMs = info.relTimeMs,
@@ -228,6 +236,25 @@ class MinstrelForwardingPlayer(
                     TransportState.STOPPED -> remoteState.applyTransportStopped()
                     TransportState.TRANSITIONING, TransportState.UNKNOWN -> Unit
                 }
+                // Detect remote-side natural advance: Sonos auto-advanced
+                // through SetNextAVTransportURI so the URI changed without
+                // any local user action. Advance the local queue cursor so
+                // the onMediaItemTransition listener fires preQueueNext to
+                // set up the next-next URI on Sonos, keeping the chain going.
+                // Both guards must be non-blank: previousTrackUri="" on the
+                // very first poll (before any state arrives) and we must not
+                // treat that initial empty-to-URI transition as an advance.
+                if (info.trackUri.isNotBlank() &&
+                    previousTrackUri.isNotBlank() &&
+                    info.trackUri != previousTrackUri
+                ) {
+                    // Run on the application looper. ExoPlayer is paused
+                    // while UPnP is active (playWhenReady=false invariant) so
+                    // the cursor advances without producing local audio. The
+                    // delegate's onMediaItemTransition listener (wired in init)
+                    // then calls preQueueNext to load the next-next track.
+                    handler.post { delegate.seekToNextMediaItem() }
+                }
             }
             if (outcome.isSuccess) {
                 remoteState.recordPollSuccess()

android/app/src/main/java/com/fabledsword/minstrel/player/output/OutputPickerController.kt

@@ -7,6 +7,7 @@ import androidx.mediarouter.media.MediaRouteSelector
 import androidx.mediarouter.media.MediaRouter
 import com.fabledsword.minstrel.di.ApplicationScope
 import com.fabledsword.minstrel.player.PlayerController
+import com.fabledsword.minstrel.player.PlayerFactory
 import com.fabledsword.minstrel.player.RemotePlayerState
 import com.fabledsword.minstrel.player.StreamTokenProvider
 import com.fabledsword.minstrel.player.output.upnp.RenderingControlClient
@@ -69,6 +70,7 @@ class OutputPickerController @Inject constructor(
     @ApplicationScope private val scope: CoroutineScope,
     private val upnpDiscovery: UpnpDiscoveryController,
     private val playerController: PlayerController,
+    private val playerFactory: PlayerFactory,
     private val streamTokens: StreamTokenProvider,
     private val activeUpnpHolder: ActiveUpnpHolder,
     private val remoteState: RemotePlayerState,
@@ -139,6 +141,31 @@ class OutputPickerController @Inject constructor(
         // without forcing Bluetooth scans. (There is no
         // CALLBACK_FLAG_PASSIVE_DISCOVERY constant; absent flag = passive.)
         mediaRouter.addCallback(selector, callback)
+        // When MinstrelForwardingPlayer reports the active UPnP route has
+        // dropped (3+ consecutive poll failures or a transport SOAP exception),
+        // clear the UPnP selection state and fall back to local ExoPlayer at
+        // the last-known remote position. This mirrors selectSystem's disconnect
+        // path but skips the Stop SOAP since the device is already unreachable.
+        scope.launch {
+            playerFactory.dropEvents.collect { handleRemoteDrop() }
+        }
+    }
+
+    /**
+     * Called when the active UPnP route drops unexpectedly (poll-failure
+     * threshold or SOAP exception). Captures the last remote position +
+     * play state, clears UPnP selection, and resumes local ExoPlayer at
+     * the same point. Skips the Stop SOAP (device already unreachable).
+     * The snackbar is handled independently by the NowPlaying surface
+     * collecting the same [PlayerFactory.dropEvents] via PlayerController.
+     */
+    private fun handleRemoteDrop() {
+        val capturedPositionMs = remoteState.positionMs
+        val wasPlayingRemote = remoteState.isPlaying
+        activeUpnpHolder.set(null)
+        selectedUpnpRouteIdInternal.value = null
+        playerController.seekTo(capturedPositionMs)
+        if (wasPlayingRemote) playerController.play()
     }
 
     /**