Merge pull request 'fix(android): don't flip offline on WAN-validation flicker — trust /healthz' (#85) from dev into main

A self-hosted Minstrel server is usually on the LAN, but ConnectivityObserver
gated 'online' on NET_CAPABILITY_VALIDATED — which tracks whether Android
reached its own WAN internet-validation probe, not whether Minstrel is
reachable. A transient WAN/DNS blip (or Android's periodic re-validation)
momentarily drops VALIDATED while the LAN server stays reachable. That flipped
ServerHealth -> Offline with NO debounce (only the /healthz path got hysteresis),
and OfflineGatedDataSource fast-failed the in-flight stream read with
OfflineException -> ExoPlayer SOURCE error -> the load_failed 'Source error'
event. On-device: 'app said server offline while it wasn't', one track failed,
then recovered when VALIDATED returned.

- ConnectivityObserver: require INTERNET only, not VALIDATED. The /healthz poll
  (VersionCheckController, with its own failure hysteresis) is the authority on
  whether Minstrel is reachable; the device-link signal only answers 'is there a
  network at all' (airplane mode).
- ServerHealthController: add a WARN-tier transition log. The signal had zero
  instrumentation, which is why this was hard to diagnose from logcat.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/test-go.yml

@@ -116,6 +116,27 @@ jobs:
           # Wait for Postgres to accept TCP (no health-check dependency).
           for i in $(seq 1 60); do (echo > "/dev/tcp/${PG_IP}/5432") 2>/dev/null && break; sleep 2; done
 
+          # Relax durability on the throwaway CI Postgres. Our test pattern
+          # is dbtest.ResetDB → TRUNCATE … RESTART IDENTITY CASCADE before
+          # every test, and the per-TRUNCATE commit fsync is the dominant
+          # cost of the integration suite. The CI DB is rebuilt every run so
+          # fsync / full_page_writes / synchronous_commit buy nothing. Apply
+          # via docker exec because:
+          #  - The act_runner `services:` block can't override the container
+          #    command, so `postgres -c fsync=off` at boot isn't an option.
+          #  - ALTER SYSTEM cannot run inside a transaction; psql -c
+          #    auto-commits each statement, which is what we need.
+          #  - fsync / full_page_writes are sighup GUCs and
+          #    synchronous_commit is user-context, so pg_reload_conf() picks
+          #    all three up with no restart.
+          # Non-fatal: a perms surprise degrades to "slower", never red CI.
+          docker exec "$PG_ID" psql -U minstrel -d minstrel_test \
+            -c "ALTER SYSTEM SET fsync = off" \
+            -c "ALTER SYSTEM SET synchronous_commit = off" \
+            -c "ALTER SYSTEM SET full_page_writes = off" \
+            -c "SELECT pg_reload_conf()" \
+            || echo "WARN: durability relax failed; continuing"
+
           # Apply embedded migrations to the fresh test DB, then run the
           # full suite (no -short → integration tests execute). -p 1:
           # every integration package TRUNCATEs the one shared test DB;

android/app/src/main/java/com/fabledsword/minstrel/MainActivity.kt

@@ -21,6 +21,9 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.compose.rememberNavController
 import com.fabledsword.minstrel.auth.ui.AuthGateViewModel
 import com.fabledsword.minstrel.cache.CachedTrackIds
+import com.fabledsword.minstrel.connectivity.LocalServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealthController
 import com.fabledsword.minstrel.nav.DetailSeedCache
 import com.fabledsword.minstrel.nav.LocalDetailSeedCache
 import com.fabledsword.minstrel.nav.MinstrelNavGraph
@@ -38,6 +41,7 @@ import javax.inject.Inject
 class MainActivity : ComponentActivity() {
     @Inject lateinit var seedCache: DetailSeedCache
     @Inject lateinit var cachedTrackIds: CachedTrackIds
+    @Inject lateinit var serverHealth: ServerHealthController
 
     // Flipped to true when the user taps the media notification (or
     // any other entry point that asks for the full player). The App
@@ -54,6 +58,7 @@ class MainActivity : ComponentActivity() {
             App(
                 seedCache = seedCache,
                 cachedTrackIds = cachedTrackIds,
+                serverHealth = serverHealth,
                 pendingOpenNowPlaying = pendingOpenNowPlaying.asStateFlow(),
                 onOpenedNowPlaying = { pendingOpenNowPlaying.value = false },
             )
@@ -86,6 +91,7 @@ class MainActivity : ComponentActivity() {
 private fun App(
     seedCache: DetailSeedCache,
     cachedTrackIds: CachedTrackIds,
+    serverHealth: ServerHealthController,
     pendingOpenNowPlaying: StateFlow<Boolean>,
     onOpenedNowPlaying: () -> Unit,
     themeVm: ThemePreferenceViewModel = hiltViewModel(),
@@ -93,11 +99,13 @@ private fun App(
 ) {
     val theme by themeVm.themeMode.collectAsStateWithLifecycle()
     val cached by cachedTrackIds.ids.collectAsStateWithLifecycle()
+    val health: ServerHealth by serverHealth.state.collectAsStateWithLifecycle()
     val pending by pendingOpenNowPlaying.collectAsStateWithLifecycle()
     MinstrelTheme(darkOverride = theme.toDarkOverride()) {
         CompositionLocalProvider(
             LocalDetailSeedCache provides seedCache,
             LocalCachedTrackIds provides cached,
+            LocalServerHealth provides health,
         ) {
             val startDestination by gate.startDestination.collectAsStateWithLifecycle()
             val resolved = startDestination

android/app/src/main/java/com/fabledsword/minstrel/MinstrelApplication.kt

@@ -19,6 +19,7 @@ import com.fabledsword.minstrel.player.PlayEventsReporter
 import com.fabledsword.minstrel.player.PlaybackErrorReporter
 import com.fabledsword.minstrel.player.ResumeController
 import com.fabledsword.minstrel.update.data.UpdateBannerController
+import com.fabledsword.minstrel.connectivity.ServerHealthController
 import com.fabledsword.minstrel.update.data.VersionCheckController
 import dagger.hilt.android.HiltAndroidApp
 import kotlinx.coroutines.CoroutineScope
@@ -121,6 +122,15 @@ class MinstrelApplication :
      */
     @Suppress("unused") @Inject lateinit var versionCheckController: VersionCheckController
 
+    /**
+     * Same construct-the-singleton trick — ServerHealthController combines
+     * ConnectivityObserver + VersionCheckController.reachable into the
+     * tri-state ServerHealth signal. Its stateIn is `SharingStarted.Eagerly`
+     * so the StateFlow needs an active subscriber from launch onward; the
+     * @Inject keeps the singleton alive and the flow collecting.
+     */
+    @Suppress("unused") @Inject lateinit var serverHealthController: ServerHealthController
+
     /**
      * Same construct-the-singleton trick — UpdateBannerController polls
      * /api/client/version at launch + every 24h and drives the shell's

android/app/src/main/java/com/fabledsword/minstrel/api/endpoints/CastApi.kt

@@ -39,11 +39,18 @@ data class StreamTokenRequest(
 /**
  * Response body. [url] is a fully-formed stream URL with [token] and
  * [exp] already embedded as query params — callers pass it verbatim
- * to `AVTransport.SetAVTransportURI`.
+ * to `AVTransport.SetAVTransportURI`. [mime] + [title] are the bits
+ * the client needs to build DIDL-Lite metadata for that call: Sonos
+ * rejects empty DIDL with vendor error 1023, so the server hands back
+ * the track's MIME (from `tracks.file_format`) and title so the
+ * client can populate `<res protocolInfo>` and `<dc:title>` without
+ * a follow-up round trip.
  */
 @Serializable
 data class StreamTokenResponse(
     val token: String,
     val exp: Long,
     val url: String,
+    val mime: String = "audio/mpeg",
+    val title: String = "",
 )

android/app/src/main/java/com/fabledsword/minstrel/cache/db/dao/CachedAlbumDao.kt

@@ -24,6 +24,14 @@ interface CachedAlbumDao {
     @Query("SELECT * FROM cached_albums WHERE id = :id")
     fun observeById(id: String): Flow<CachedAlbumEntity?>
 
+    @Query(
+        "SELECT * FROM cached_albums " +
+            "WHERE title LIKE '%' || :q || '%' COLLATE NOCASE " +
+            "ORDER BY sortTitle COLLATE NOCASE ASC " +
+            "LIMIT :limit",
+    )
+    suspend fun searchByTitle(q: String, limit: Int): List<CachedAlbumEntity>
+
     @Query("SELECT id FROM cached_albums WHERE fetchedAt < :before LIMIT :limit")
     suspend fun idsStaleBefore(before: Long, limit: Int): List<String>
 

android/app/src/main/java/com/fabledsword/minstrel/cache/db/dao/CachedArtistDao.kt

@@ -18,6 +18,14 @@ interface CachedArtistDao {
     @Query("SELECT * FROM cached_artists WHERE id = :id")
     fun observeById(id: String): Flow<CachedArtistEntity?>
 
+    @Query(
+        "SELECT * FROM cached_artists " +
+            "WHERE name LIKE '%' || :q || '%' COLLATE NOCASE " +
+            "ORDER BY sortName COLLATE NOCASE ASC " +
+            "LIMIT :limit",
+    )
+    suspend fun searchByName(q: String, limit: Int): List<CachedArtistEntity>
+
     @Query("SELECT id FROM cached_artists WHERE fetchedAt < :before LIMIT :limit")
     suspend fun idsStaleBefore(before: Long, limit: Int): List<String>
 

android/app/src/main/java/com/fabledsword/minstrel/cache/db/dao/CachedTrackDao.kt

@@ -24,6 +24,14 @@ interface CachedTrackDao {
     @Query("SELECT * FROM cached_tracks WHERE id IN (:ids)")
     suspend fun getByIds(ids: List<String>): List<CachedTrackEntity>
 
+    @Query(
+        "SELECT * FROM cached_tracks " +
+            "WHERE title LIKE '%' || :q || '%' COLLATE NOCASE " +
+            "ORDER BY title COLLATE NOCASE ASC " +
+            "LIMIT :limit",
+    )
+    suspend fun searchByTitle(q: String, limit: Int): List<CachedTrackEntity>
+
     @Query("SELECT id FROM cached_tracks WHERE fetchedAt < :before LIMIT :limit")
     suspend fun idsStaleBefore(before: Long, limit: Int): List<String>
 

android/app/src/main/java/com/fabledsword/minstrel/cache/mutations/MutationQueue.kt

@@ -2,12 +2,18 @@ package com.fabledsword.minstrel.cache.mutations
 
 import com.fabledsword.minstrel.cache.db.dao.CachedMutationDao
 import com.fabledsword.minstrel.cache.db.entities.CachedMutationEntity
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.SharedFlow
+import kotlinx.coroutines.flow.asSharedFlow
 import kotlinx.serialization.Serializable
 import kotlinx.serialization.encodeToString
 import kotlinx.serialization.json.Json
 import javax.inject.Inject
 import javax.inject.Singleton
 
+private const val QUEUED_MESSAGE = "Saved — will sync when online"
+
 /**
  * Stable mutation kinds the queue knows how to replay. Strings are
  * persisted in `cached_mutations.kind` so renaming a variant breaks
@@ -71,47 +77,59 @@ class MutationQueue @Inject constructor(
     private val dao: CachedMutationDao,
     private val json: Json,
 ) {
+    // capacity=1 DROP_OLDEST so a burst of user enqueues (e.g. liking N
+    // tracks while offline) surfaces as one snackbar rather than queueing
+    // N. replay=0 because a hint observed at enqueue time isn't useful
+    // to a screen that mounts later.
+    private val _userEnqueueHints = MutableSharedFlow<String>(
+        replay = 0,
+        extraBufferCapacity = 1,
+        onBufferOverflow = BufferOverflow.DROP_OLDEST,
+    )
+
+    /**
+     * Hint stream consumed by [com.fabledsword.minstrel.shared.widgets.ShellScaffold]
+     * to surface "Saved — will sync when online" as a snackbar whenever a
+     * user-driven write hits the offline-fallback path. Background-only
+     * enqueues (play-events, playback-error reports) do not emit — those
+     * fire from non-foreground paths where a snackbar would be either
+     * dropped (no shell mounted) or jarring (lock-screen toggle).
+     */
+    val userEnqueueHints: SharedFlow<String> = _userEnqueueHints.asSharedFlow()
+
     suspend fun enqueueLikeToggle(
         entityType: String,
         entityId: String,
         desiredState: Boolean,
-    ): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.LIKE_TOGGLE,
-            payload = json.encodeToString(
-                LikeTogglePayload.serializer(),
-                LikeTogglePayload(entityType, entityId, desiredState),
-            ),
+    ): Long = insertUserDriven(
+        MutationKind.LIKE_TOGGLE,
+        json.encodeToString(
+            LikeTogglePayload.serializer(),
+            LikeTogglePayload(entityType, entityId, desiredState),
         ),
     )
 
-    suspend fun enqueueRequestCreate(payload: RequestCreatePayload): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.REQUEST_CREATE,
-            payload = json.encodeToString(RequestCreatePayload.serializer(), payload),
-        ),
+    suspend fun enqueueRequestCreate(payload: RequestCreatePayload): Long = insertUserDriven(
+        MutationKind.REQUEST_CREATE,
+        json.encodeToString(RequestCreatePayload.serializer(), payload),
     )
 
-    suspend fun enqueueQuarantineUnflag(trackId: String): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.QUARANTINE_UNFLAG,
-            payload = json.encodeToString(
-                QuarantineUnflagPayload.serializer(),
-                QuarantineUnflagPayload(trackId),
-            ),
+    suspend fun enqueueQuarantineUnflag(trackId: String): Long = insertUserDriven(
+        MutationKind.QUARANTINE_UNFLAG,
+        json.encodeToString(
+            QuarantineUnflagPayload.serializer(),
+            QuarantineUnflagPayload(trackId),
         ),
     )
 
     suspend fun enqueuePlaylistAppend(
         playlistId: String,
         trackIds: List<String>,
-    ): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.PLAYLIST_APPEND,
-            payload = json.encodeToString(
-                PlaylistAppendPayload.serializer(),
-                PlaylistAppendPayload(playlistId, trackIds),
-            ),
+    ): Long = insertUserDriven(
+        MutationKind.PLAYLIST_APPEND,
+        json.encodeToString(
+            PlaylistAppendPayload.serializer(),
+            PlaylistAppendPayload(playlistId, trackIds),
         ),
     )
 
@@ -119,13 +137,19 @@ class MutationQueue @Inject constructor(
         trackId: String,
         reason: String,
         notes: String,
-    ): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.QUARANTINE_FLAG,
-            payload = json.encodeToString(
-                QuarantineFlagPayload.serializer(),
-                QuarantineFlagPayload(trackId, reason, notes),
-            ),
+    ): Long = insertUserDriven(
+        MutationKind.QUARANTINE_FLAG,
+        json.encodeToString(
+            QuarantineFlagPayload.serializer(),
+            QuarantineFlagPayload(trackId, reason, notes),
+        ),
+    )
+
+    suspend fun enqueueRequestCancel(requestId: String): Long = insertUserDriven(
+        MutationKind.REQUEST_CANCEL,
+        json.encodeToString(
+            RequestCancelPayload.serializer(),
+            RequestCancelPayload(requestId),
         ),
     )
 
@@ -136,22 +160,18 @@ class MutationQueue @Inject constructor(
         ),
     )
 
-    suspend fun enqueueRequestCancel(requestId: String): Long = dao.insert(
-        CachedMutationEntity(
-            kind = MutationKind.REQUEST_CANCEL,
-            payload = json.encodeToString(
-                RequestCancelPayload.serializer(),
-                RequestCancelPayload(requestId),
-            ),
-        ),
-    )
-
     suspend fun enqueuePlaybackErrorReport(payload: PlaybackErrorReportPayload): Long = dao.insert(
         CachedMutationEntity(
             kind = MutationKind.PLAYBACK_ERROR_REPORT,
             payload = json.encodeToString(PlaybackErrorReportPayload.serializer(), payload),
         ),
     )
+
+    private suspend fun insertUserDriven(kind: String, payload: String): Long {
+        val id = dao.insert(CachedMutationEntity(kind = kind, payload = payload))
+        _userEnqueueHints.tryEmit(QUEUED_MESSAGE)
+        return id
+    }
 }
 
 /**

android/app/src/main/java/com/fabledsword/minstrel/cache/mutations/OfflineWriteHintViewModel.kt

@@ -0,0 +1,20 @@
+package com.fabledsword.minstrel.cache.mutations
+
+import androidx.lifecycle.ViewModel
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.Flow
+import javax.inject.Inject
+
+/**
+ * Hilt-injectable wrapper exposing [MutationQueue.userEnqueueHints] to
+ * ShellScaffold. The queue itself is an app-scoped singleton; this VM
+ * just bridges its SharedFlow into a `hiltViewModel()`-resolvable
+ * surface so ShellScaffold can collect it without an EntryPoint
+ * accessor. Mirrors PlaybackErrorViewModel.
+ */
+@HiltViewModel
+class OfflineWriteHintViewModel @Inject constructor(
+    mutationQueue: MutationQueue,
+) : ViewModel() {
+    val messages: Flow<String> = mutationQueue.userEnqueueHints
+}

android/app/src/main/java/com/fabledsword/minstrel/connectivity/ConnectivityObserver.kt

@@ -14,11 +14,23 @@ import javax.inject.Inject
 import javax.inject.Singleton
 
 /**
- * Single source of truth for the device's "is the internet usable
- * right now" signal — wraps [ConnectivityManager] and exposes a hot
- * cold-startable Flow that emits `false` while the active network
- * lacks INTERNET + VALIDATED capabilities (airplane mode, no carrier,
- * captive portal, etc.) and `true` once a usable network appears.
+ * Single source of truth for "does the device have a network link at
+ * all" — wraps [ConnectivityManager] and exposes a hot cold-startable
+ * Flow that emits `false` only when there is no active INTERNET-capable
+ * network (airplane mode, no carrier/Wi-Fi) and `true` once any network
+ * link appears.
+ *
+ * Deliberately does NOT require `NET_CAPABILITY_VALIDATED`. VALIDATED
+ * tracks whether Android reached its own WAN internet-validation probe
+ * (Google's `generate_204`) — which is the wrong question for a
+ * self-hosted server that is usually on the LAN. A transient WAN/DNS
+ * blip (or Android's periodic re-validation) momentarily drops VALIDATED
+ * while the Minstrel box stays perfectly reachable; gating on it flipped
+ * the app to Offline with no debounce and fast-failed in-flight playback
+ * via [com.fabledsword.minstrel.player.OfflineGatedDataSource]. The
+ * authority on whether *Minstrel* is reachable is the `/healthz` poll
+ * ([com.fabledsword.minstrel.update.data.VersionCheckController], which
+ * has its own failure hysteresis), not this coarse device-link signal.
  *
  * Used by the shell-level ConnectionErrorBanner; downstream
  * repositories can also collect this to gate retry loops.
@@ -35,36 +47,36 @@ class ConnectivityObserver @Inject constructor(
             .build()
         val callback = object : ConnectivityManager.NetworkCallback() {
             override fun onAvailable(network: Network) {
-                trySend(hasUsableInternet())
+                trySend(hasActiveNetwork())
             }
             override fun onLost(network: Network) {
-                trySend(hasUsableInternet())
+                trySend(hasActiveNetwork())
             }
             override fun onCapabilitiesChanged(
                 network: Network,
                 capabilities: NetworkCapabilities,
             ) {
+                // INTERNET only -- NOT VALIDATED. A WAN/validation flicker
+                // must not read as "device offline" when the LAN (and the
+                // Minstrel server on it) is still reachable. /healthz is the
+                // authority on server reachability.
                 trySend(
                     capabilities.hasCapability(
                         NetworkCapabilities.NET_CAPABILITY_INTERNET,
-                    ) &&
-                        capabilities.hasCapability(
-                            NetworkCapabilities.NET_CAPABILITY_VALIDATED,
-                        ),
+                    ),
                 )
             }
         }
         cm.registerNetworkCallback(request, callback)
         // Seed the initial value so the banner doesn't flash before the
         // first capability callback fires.
-        trySend(hasUsableInternet())
+        trySend(hasActiveNetwork())
         awaitClose { cm.unregisterNetworkCallback(callback) }
     }.distinctUntilChanged()
 
-    private fun hasUsableInternet(): Boolean {
+    private fun hasActiveNetwork(): Boolean {
         val caps = cm.activeNetwork?.let { cm.getNetworkCapabilities(it) }
         return caps != null &&
-            caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET) &&
-            caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_VALIDATED)
+            caps.hasCapability(NetworkCapabilities.NET_CAPABILITY_INTERNET)
     }
 }

android/app/src/main/java/com/fabledsword/minstrel/connectivity/ServerHealthController.kt

@@ -0,0 +1,75 @@
+package com.fabledsword.minstrel.connectivity
+
+import androidx.compose.runtime.staticCompositionLocalOf
+import com.fabledsword.minstrel.di.ApplicationScope
+import com.fabledsword.minstrel.update.data.VersionCheckController
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.SharingStarted
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.distinctUntilChanged
+import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.stateIn
+import timber.log.Timber
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Tri-state server-reachability signal that downstream consumers can branch
+ * on to decide whether to hit the network, gate writes, or fall back to
+ * cache-only behavior.
+ *
+ * Composed from two existing signals -- this controller doesn't poll its own
+ * endpoint:
+ *
+ *  - [ConnectivityObserver.online] -- system-level NetworkCallback that
+ *    answers only "is there an active INTERNET-capable network link" (NOT
+ *    VALIDATED -- a WAN-validation flicker must not read as offline when
+ *    the LAN server is reachable).
+ *  - [VersionCheckController.reachable] -- did the last `/healthz` poll
+ *    succeed. This is the authority on whether *Minstrel* is reachable;
+ *    it has its own failure hysteresis. Distinguishes "device has a link
+ *    but our server is down" from "no network at all."
+ *
+ * `version too old` is intentionally *not* folded in here -- it's a separate
+ * UX (the VersionTooOldBanner) and conflating it with offline would mask the
+ * real cause.
+ */
+enum class ServerHealth { Healthy, Offline, ServerDown }
+
+@Singleton
+class ServerHealthController @Inject constructor(
+    @ApplicationScope scope: CoroutineScope,
+    connectivity: ConnectivityObserver,
+    versionCheck: VersionCheckController,
+) {
+    val state: StateFlow<ServerHealth> = combine(
+        connectivity.online,
+        versionCheck.reachable,
+    ) { online, serverReachable ->
+        when {
+            !online -> ServerHealth.Offline
+            !serverReachable -> ServerHealth.ServerDown
+            else -> ServerHealth.Healthy
+        }
+    }
+        // Transition log -- the signal had no instrumentation, which is why a
+        // false-offline (WAN flicker flipping playback to "Source error") was
+        // hard to diagnose from logcat. WARN-tier so ReleaseTree surfaces it.
+        .distinctUntilChanged()
+        .onEach { Timber.w("ServerHealth -> %s", it) }
+        .stateIn(
+            scope = scope,
+            started = SharingStarted.Eagerly,
+            initialValue = ServerHealth.Healthy,
+        )
+}
+
+/**
+ * Reactive [ServerHealth] snapshot provided once at the app root from the
+ * controller's StateFlow. Lets leaf composables (TrackRow gating, write-
+ * affordance disabling) branch on health without each ViewModel re-
+ * injecting the controller. Defaults to Healthy so unwrapped previews
+ * and tests don't crash.
+ */
+val LocalServerHealth = staticCompositionLocalOf { ServerHealth.Healthy }

android/app/src/main/java/com/fabledsword/minstrel/connectivity/ui/ConnectionErrorBanner.kt

@@ -25,45 +25,45 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.viewModelScope
 import com.composables.icons.lucide.CloudOff
 import com.composables.icons.lucide.Lucide
-import com.fabledsword.minstrel.connectivity.ConnectivityObserver
+import com.fabledsword.minstrel.connectivity.ServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealthController
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.stateIn
 import javax.inject.Inject
 
-private const val ONLINE_SHARE_STOP_TIMEOUT_MS = 5_000L
+private const val HEALTH_SHARE_STOP_TIMEOUT_MS = 5_000L
 
 /**
- * Tiny VM that just lifts the [ConnectivityObserver] singleton's
- * Flow into a StateFlow with the standard sharing strategy. Keeps
- * the banner composable pure-presentation.
+ * Lifts [ServerHealthController]'s tri-state into a StateFlow for the banner
+ * composable. Keeps the banner pure-presentation.
  */
 @HiltViewModel
 class ConnectivityBannerViewModel @Inject constructor(
-    observer: ConnectivityObserver,
+    health: ServerHealthController,
     @Suppress("UnusedPrivateProperty") savedStateHandle: SavedStateHandle,
 ) : ViewModel() {
-    val online: StateFlow<Boolean> = observer.online.stateIn(
+    val health: StateFlow<ServerHealth> = health.state.stateIn(
         scope = viewModelScope,
-        started = SharingStarted.WhileSubscribed(ONLINE_SHARE_STOP_TIMEOUT_MS),
-        initialValue = true,
+        started = SharingStarted.WhileSubscribed(HEALTH_SHARE_STOP_TIMEOUT_MS),
+        initialValue = ServerHealth.Healthy,
     )
 }
 
 /**
- * Banner shown at the top of the shell when the device has no usable
- * internet. Mirrors Flutter's ConnectionErrorBanner: red-tinted error
- * surface, CloudOff icon, "No connection — check Wi-Fi or mobile
- * data" copy. Auto-hides via slide+fade when connectivity returns.
+ * Banner shown at the top of the shell when the user can't reach the server.
+ * Tri-state so we tell the user *why*: no device network vs server-down.
+ * Copy choices match the Flutter analogues. Auto-hides via slide+fade when
+ * health returns to [ServerHealth.Healthy].
  */
 @Composable
 fun ConnectionErrorBanner(
     viewModel: ConnectivityBannerViewModel = hiltViewModel(),
 ) {
-    val online by viewModel.online.collectAsStateWithLifecycle()
+    val health by viewModel.health.collectAsStateWithLifecycle()
     AnimatedVisibility(
-        visible = !online,
+        visible = health != ServerHealth.Healthy,
         enter = expandVertically() + fadeIn(),
         exit = shrinkVertically() + fadeOut(),
     ) {
@@ -81,7 +81,13 @@ fun ConnectionErrorBanner(
                 tint = MaterialTheme.colorScheme.onErrorContainer,
             )
             Text(
-                text = "No connection — check Wi-Fi or mobile data.",
+                text = when (health) {
+                    ServerHealth.Offline ->
+                        "No connection — check Wi-Fi or mobile data."
+                    ServerHealth.ServerDown ->
+                        "Server unreachable — your cached content is still available."
+                    ServerHealth.Healthy -> ""
+                },
                 style = MaterialTheme.typography.bodyMedium,
                 color = MaterialTheme.colorScheme.onErrorContainer,
             )

android/app/src/main/java/com/fabledsword/minstrel/home/ui/HomeScreen.kt

@@ -69,7 +69,7 @@ import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.nav.Home
 import com.fabledsword.minstrel.nav.PlaylistDetail
 import com.fabledsword.minstrel.playlists.data.PlaylistsRepository
-import com.fabledsword.minstrel.playlists.data.toPlayableTrackRefs
+import com.fabledsword.minstrel.playlists.data.playPlaylistShuffled
 import com.fabledsword.minstrel.playlists.widgets.OfflinePoolCard
 import com.fabledsword.minstrel.playlists.widgets.PlaylistCard
 import com.fabledsword.minstrel.playlists.widgets.PlaylistPlaceholderCard
@@ -95,11 +95,9 @@ import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.receiveAsFlow
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
-import kotlinx.coroutines.withTimeout
 import javax.inject.Inject
 
 private const val SHARE_STOP_TIMEOUT_MS = 5_000L
-private const val PLAYLIST_FETCH_TIMEOUT_MS = 8_000L
 private const val BOTTOM_PADDING_FOR_MINIPLAYER_DP = 140
 // Recently Added is laid out in a multi-row LazyHorizontalGrid that
 // scrolls as one panel (same pattern as Most Played). Two rows trades
@@ -259,45 +257,9 @@ class HomeViewModel @Inject constructor(
      */
     suspend fun playPlaylist(playlist: PlaylistRef) {
         viewModelScope.launch {
-            val detail = try {
-                withTimeout(PLAYLIST_FETCH_TIMEOUT_MS) {
-                    if (playlist.refreshable && playlist.systemVariant != null) {
-                        playlistsRepository.systemShuffle(playlist.systemVariant)
-                    } else {
-                        playlistsRepository.refreshDetail(playlist.id)
-                    }
-                }
-            } catch (
-                @Suppress("SwallowedException") _: kotlinx.coroutines.TimeoutCancellationException,
-            ) {
-                poolMessages.trySend("Couldn't load playlist - check your connection")
-                return@launch
-            } catch (
-                @Suppress("TooGenericExceptionCaught") e: Throwable,
-            ) {
-                poolMessages.trySend(
-                    "Couldn't load playlist: ${ErrorCopy.fromThrowable(e)}",
-                )
-                return@launch
+            playPlaylistShuffled(playlist, playlistsRepository, player) {
+                poolMessages.trySend(it)
             }
-            // Shared with PlaylistDetailViewModel.play - filters out
-            // unplayable rows (missing trackId or empty streamUrl) so the
-            // queue can't end up with tracks Media3 silently rejects.
-            val tracks = detail.tracks.toPlayableTrackRefs()
-            if (tracks.isEmpty()) {
-                poolMessages.trySend("Mix isn't ready yet - try again in a moment")
-                return@launch
-            }
-            // Drift #564: send the BARE systemVariant string, not
-            // "playlist:<variant>" — the server's rotation matcher
-            // (internal/playevents/writer.go systemPlaylistSources)
-            // keys on the bare variant. Web sends the bare form too
-            // (web/src/lib/components/PlaylistCard.svelte:83), so this
-            // brings Android into alignment. Wrong prefix here meant
-            // system-mix plays from Android Home never advanced the
-            // rotation.
-            val source = if (playlist.refreshable) playlist.systemVariant else null
-            player.setQueue(tracks, initialIndex = 0, source = source)
         }.join()
     }
 

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

@@ -58,59 +58,98 @@ class AudioPrefetcher @Inject constructor(
     private val activeJobs = mutableMapOf<String, Job>()
     private val mutex = Mutex()
 
+    private data class ReconcileInput(
+        val queue: List<Pair<String, String>>,
+        val index: Int,
+        val window: Int,
+        val isPlaying: Boolean,
+    )
+
     init {
         scope.launch {
             combine(
                 playerController.uiState.map { it.queue.map { t -> t.id to t.streamUrl } },
                 playerController.uiState.map { it.queueIndex },
                 authStore.cacheSettings.map { it.prefetchWindow },
-            ) { queue, index, window -> Triple(queue, index, window) }
+                playerController.uiState.map { it.isPlaying },
+            ) { queue, index, window, isPlaying ->
+                ReconcileInput(queue, index, window, isPlaying)
+            }
                 .distinctUntilChanged()
-                .collect { (queue, index, window) -> reconcile(queue, index, window) }
+                .collect { input ->
+                    reconcile(input.queue, input.index, input.window, input.isPlaying)
+                }
         }
     }
 
+    /**
+     * Apply the prefetch window to the current queue.
+     *
+     * Cancellation of out-of-window jobs always runs -- a queue mutation
+     * or skip should free bandwidth from stale prefetches immediately.
+     * Starting new prefetches is gated on [isPlaying]: until the current
+     * track is actually playing, every byte of upstream bandwidth should
+     * land on it, not on upcoming-track prefetches. Without this gate a
+     * cold start fanned out 4-6 concurrent CacheWriter jobs against the
+     * same OkHttp client as the playback DataSource and the user waited
+     * ~25 s for the first audio to start; with the gate the current
+     * track gets the full pipe to its first STATE_READY, then the
+     * prefetcher fills in the next window.
+     */
     private suspend fun reconcile(
         queue: List<Pair<String, String>>,
         index: Int,
         window: Int,
+        isPlaying: Boolean,
     ) {
         mutex.withLock {
-            if (index < 0 || queue.isEmpty() || window <= 0) {
+            val targets = computeTargets(queue, index, window)
+            if (targets.isEmpty()) {
                 cancelAllLocked()
                 return
             }
-            // Exclude the currently-playing track (it's loaded by the
-            // player itself) and walk `window` tracks forward.
-            val firstIdx = (index + 1).coerceAtMost(queue.size)
-            val lastIdx = (index + window).coerceAtMost(queue.size - 1)
-            if (firstIdx > lastIdx) {
-                cancelAllLocked()
-                return
-            }
-            val targets = queue.subList(firstIdx, lastIdx + 1)
             val targetIds = targets.mapTo(mutableSetOf()) { it.first }
+            // Cancellation always runs so a queue mutation or skip frees
+            // the pipe immediately, even while paused.
+            cancelOutOfWindowLocked(targetIds)
+            if (isPlaying) startInWindowLocked(targets)
+        }
+    }
 
-            // Cancel jobs for tracks that have slid out of the window.
-            activeJobs.entries
-                .filter { it.key !in targetIds }
-                .toList()
-                .forEach { (id, job) ->
-                    job.cancel()
-                    activeJobs.remove(id)
-                }
+    private fun computeTargets(
+        queue: List<Pair<String, String>>,
+        index: Int,
+        window: Int,
+    ): List<Pair<String, String>> {
+        // Exclude the currently-playing track (it's loaded by the player
+        // itself) and walk `window` tracks forward.
+        val firstIdx = index + 1
+        val lastIdx = (index + window).coerceAtMost(queue.size - 1)
+        val isValid = index >= 0 && queue.isNotEmpty() && window > 0 && firstIdx <= lastIdx
+        return if (isValid) queue.subList(firstIdx, lastIdx + 1) else emptyList()
+    }
 
-            // Start prefetches for new arrivals. Skip blank URLs (these
-            // come from minimal TrackRefs synthesized from playlist rows
-            // when the upstream track was removed from the library).
-            for ((trackId, streamUrl) in targets) {
-                if (trackId in activeJobs || streamUrl.isBlank()) continue
-                val job = scope.launch(Dispatchers.IO) {
-                    runCatching { prefetchOne(trackId, streamUrl) }
-                    mutex.withLock { activeJobs.remove(trackId) }
-                }
-                activeJobs[trackId] = job
+    private fun cancelOutOfWindowLocked(targetIds: Set<String>) {
+        activeJobs.entries
+            .filter { it.key !in targetIds }
+            .toList()
+            .forEach { (id, job) ->
+                job.cancel()
+                activeJobs.remove(id)
             }
+    }
+
+    private fun startInWindowLocked(targets: List<Pair<String, String>>) {
+        // Skip blank URLs (these come from minimal TrackRefs synthesized
+        // from playlist rows when the upstream track was removed from
+        // the library).
+        for ((trackId, streamUrl) in targets) {
+            if (trackId in activeJobs || streamUrl.isBlank()) continue
+            val job = scope.launch(Dispatchers.IO) {
+                runCatching { prefetchOne(trackId, streamUrl) }
+                mutex.withLock { activeJobs.remove(trackId) }
+            }
+            activeJobs[trackId] = job
         }
     }
 

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

@@ -0,0 +1,517 @@
+@file:Suppress("TooManyFunctions") // Mirrors Player surface: ~16 methods is the API.
+
+package com.fabledsword.minstrel.player
+
+import android.os.Handler
+import android.os.SystemClock
+import androidx.lifecycle.DefaultLifecycleObserver
+import androidx.lifecycle.LifecycleOwner
+import androidx.lifecycle.ProcessLifecycleOwner
+import androidx.media3.common.ForwardingPlayer
+import androidx.media3.common.MediaItem
+import androidx.media3.common.Player
+import com.fabledsword.minstrel.player.output.ActiveUpnp
+import com.fabledsword.minstrel.player.output.ActiveUpnpHolder
+import com.fabledsword.minstrel.player.output.upnp.TransportState
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.selects.onTimeout
+import kotlinx.coroutines.selects.select
+import timber.log.Timber
+
+/**
+ * Integration point for UPnP transport parity. Wraps the local
+ * ExoPlayer; every transport method either forwards (local route
+ * active -- the default) or translates into AVTransport SOAP +
+ * [RemotePlayerState] updates (UPnP route active).
+ *
+ * Created inside [MinstrelPlayerService]; runs on the service's main
+ * looper. Network SOAP calls fire on [Dispatchers.IO]. While UPnP is
+ * active, the MediaSession's reads of [Player.isPlaying] and
+ * [Player.getCurrentPosition] pull from [RemotePlayerState]; the
+ * wrapped ExoPlayer stays paused at the position it had when the
+ * route was selected.
+ *
+ * Drop heuristic: 3 consecutive poll failures fire [onDrop]. The
+ * factory wraps that callback into a SharedFlow consumed by the
+ * NowPlaying surface as a snackbar.
+ *
+ * Queue mode: OutputPickerController loads the full queue into Sonos's
+ * native queue via ClearQueue + AddURIToQueue, then points the
+ * transport at x-rincon-queue:<udn>#0. Skip/prev/seekTo delegate to
+ * AVTransport Next/Previous/SeekToTrack so Sonos manages gap-free
+ * advance natively. PollLoop syncs the local cursor by comparing the
+ * 1-based Track index from GetPositionInfo.
+ */
+class MinstrelForwardingPlayer(
+    private val delegate: Player,
+    private val holder: ActiveUpnpHolder,
+    private val remoteState: RemotePlayerState,
+    private val onDrop: (routeName: String) -> Unit,
+) : ForwardingPlayer(delegate) {
+
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.IO)
+    private val handler = Handler(delegate.applicationLooper)
+    private var pollJob: Job? = null
+
+    // Tracks consecutive non-PLAYING poll observations so a single transient
+    // PAUSED_PLAYBACK / STOPPED tick during a Sonos track transition does not
+    // flip the play/pause button. Manual pause still feels instant because it
+    // bypasses the poll entirely via applyTransportPaused().
+    @Volatile private var nonPlayingPollStreak = 0
+
+    // Wall-clock of the most-recent within-track seek we issued to Sonos.
+    // pollOnce uses this to suppress position overwrites for SEEK_ACK_WINDOW_MS
+    // -- Sonos can take 1-2s to apply a Seek, and a poll landing inside that
+    // window reports the *old* position. Without the lockout the scrubber
+    // visibly jumps backwards immediately after a drag, then forwards again.
+    @Volatile private var lastSeekIssuedAtMs: Long = 0L
+
+    // Wake channel for the poll loop. requestImmediatePoll() trySend's a Unit;
+    // pollLoop's select{} races the delay against this channel so the next
+    // pollOnce can fire immediately instead of waiting up to POLL_INTERVAL_MS.
+    // Used on activity resume (ProcessLifecycleOwner.ON_RESUME) so the UI
+    // catches up to Sonos within RTT rather than the full poll cadence.
+    // CONFLATED so repeated trySend's between polls don't queue up.
+    private val pollTrigger = Channel<Unit>(Channel.CONFLATED)
+
+    // External Player.Listener registry (separate from super.addListener which
+    // forwards to the wrapped ExoPlayer). The wrapped player is paused with
+    // no audio loaded while UPnP is active, so it never fires events for our
+    // synthesized remote state -- the MediaSession's notification card and
+    // lock-screen scrubber stay frozen on whatever state was last captured
+    // before UPnP took over. We dual-register: super.addListener keeps the
+    // listener attached to the delegate (so local-playback events still
+    // reach it), AND we hold a ref here so we can directly invoke listener
+    // callbacks on remote-state changes. The listener's read of isPlaying /
+    // duration / position then routes through our overrides to remoteState.
+    private val externalListeners = mutableListOf<Player.Listener>()
+
+    @Volatile private var lastNotifiedIsPlaying: Boolean = false
+    @Volatile private var lastNotifiedTrackIdx: Int = -1
+
+    private val lifecycleObserver = object : DefaultLifecycleObserver {
+        override fun onResume(owner: LifecycleOwner) {
+            pollTrigger.trySend(Unit)
+        }
+    }
+
+    init {
+        scope.launch {
+            holder.active.collect { active -> onActiveChanged(active) }
+        }
+        // Process lifecycle is observed on the main thread; ProcessLifecycleOwner's
+        // addObserver requires it. The observer just trySend's to the channel.
+        handler.post {
+            ProcessLifecycleOwner.get().lifecycle.addObserver(lifecycleObserver)
+        }
+    }
+
+    private fun isRemote(): Boolean = holder.active.value != null
+
+    /**
+     * Returns true when selectUpnp has marked a UPnP route as the intended
+     * target but loadQueueOnSonos hasn't yet wired ActiveUpnp. During this
+     * window we drop transport commands silently -- they would hit Sonos's
+     * stale state from a prior session and trigger restarts.
+     */
+    private fun isLoadingUpnp(): Boolean =
+        holder.target.value != null && holder.active.value == null
+
+    // ─── setMediaItems intercepts ──────────────────────────────────────
+    // When PlayerController.setQueue replaces the queue while Sonos is the
+    // active route, the wrapped delegate's queue gets the new items but
+    // Sonos's native queue still holds the OLD tracks -- and the play()
+    // that PlayerController fires immediately after setMediaItems would
+    // resume the old Sonos queue (user reported on-device: "player view
+    // updates but Sonos queue does not"). We clear active + set target
+    // synchronously here so the next play() in the same IPC sequence
+    // drops via isLoadingUpnp() = true; the OutputPickerController
+    // observes the uiState.queue change and runs the resync (re-clears
+    // Sonos's native queue + AddURIToQueue the new tracks + Play).
+
+    override fun setMediaItems(mediaItems: List<MediaItem>) {
+        super.setMediaItems(mediaItems)
+        markPendingResyncIfRemote()
+    }
+
+    override fun setMediaItems(mediaItems: List<MediaItem>, resetPosition: Boolean) {
+        super.setMediaItems(mediaItems, resetPosition)
+        markPendingResyncIfRemote()
+    }
+
+    override fun setMediaItems(mediaItems: List<MediaItem>, startIndex: Int, startPositionMs: Long) {
+        super.setMediaItems(mediaItems, startIndex, startPositionMs)
+        markPendingResyncIfRemote()
+    }
+
+    private fun markPendingResyncIfRemote() {
+        val wasActive = holder.active.value ?: return
+        Timber.w(
+            "setMediaItems while UPnP active (%s) -- marking pending resync",
+            wasActive.routeName,
+        )
+        holder.set(null)
+        holder.setTarget(wasActive.routeId)
+    }
+
+    override fun play() {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.play() dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w("ForwardingPlayer.play() active=%s", active?.routeName)
+        if (active == null) {
+            super.play()
+        } else {
+            scope.launch {
+                runCatching { active.avTransport.play() }
+                    .onSuccess {
+                        remoteState.applyTransportPlaying()
+                        notifyRemoteStateChanged()
+                    }
+                    .onFailure { handleSoapFailure(active, it) }
+            }
+        }
+    }
+
+    override fun pause() {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.pause() dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w("ForwardingPlayer.pause() active=%s", active?.routeName)
+        if (active == null) {
+            super.pause()
+        } else {
+            scope.launch {
+                runCatching { active.avTransport.pause() }
+                    .onSuccess {
+                        remoteState.applyTransportPaused()
+                        notifyRemoteStateChanged()
+                    }
+                    .onFailure { handleSoapFailure(active, it) }
+            }
+        }
+    }
+
+    override fun seekTo(positionMs: Long) {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.seekTo(positionMs) dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w("ForwardingPlayer.seekTo(%dms) active=%s", positionMs, active?.routeName)
+        if (active == null) {
+            super.seekTo(positionMs)
+        } else {
+            lastSeekIssuedAtMs = SystemClock.elapsedRealtime()
+            remoteState.applyPositionInfo(
+                positionMs = positionMs,
+                durationMs = remoteState.durationMs,
+                trackUri = remoteState.currentTrackUri,
+                trackNumber = remoteState.trackNumber,
+            )
+            scope.launch {
+                runCatching { active.avTransport.seek(positionMs) }
+                    .onFailure { handleSoapFailure(active, it) }
+            }
+        }
+    }
+
+    /**
+     * Widget-driven track change (user taps a track in the queue widget).
+     * Seeks Sonos to the correct queue slot, then seeks within-track if
+     * [positionMs] is non-zero.
+     */
+    override fun seekTo(mediaItemIndex: Int, positionMs: Long) {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.seekTo(idx, positionMs) dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w(
+            "ForwardingPlayer.seekTo(idx=%d, %dms) active=%s",
+            mediaItemIndex, positionMs, active?.routeName,
+        )
+        if (active == null) {
+            super.seekTo(mediaItemIndex, positionMs)
+            return
+        }
+        super.seekTo(mediaItemIndex, positionMs)
+        remoteState.beginPendingTransport(
+            SystemClock.elapsedRealtime() + PENDING_TRANSPORT_SAFETY_TIMEOUT_MS,
+        )
+        scope.launch {
+            runCatching {
+                active.avTransport.seekToTrack(mediaItemIndex + 1)
+                if (positionMs > 0L) {
+                    active.avTransport.seek(positionMs)
+                }
+            }.onFailure { handleSoapFailure(active, it) }
+        }
+    }
+
+    override fun seekToNextMediaItem() {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.seekToNextMediaItem() dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w("ForwardingPlayer.seekToNextMediaItem() active=%s", active?.routeName)
+        if (active == null) {
+            super.seekToNextMediaItem()
+            return
+        }
+        // Super first for immediate local cursor advance (UI feedback);
+        // then delegate to Sonos Next. PollLoop reconciles cursor via
+        // Track index if they diverge.
+        super.seekToNextMediaItem()
+        remoteState.beginPendingTransport(
+            SystemClock.elapsedRealtime() + PENDING_TRANSPORT_SAFETY_TIMEOUT_MS,
+        )
+        scope.launch {
+            runCatching { active.avTransport.next() }
+                .onFailure { handleSoapFailure(active, it) }
+        }
+    }
+
+    override fun seekToPreviousMediaItem() {
+        if (isLoadingUpnp()) {
+            Timber.w("ForwardingPlayer.seekToPreviousMediaItem() dropped -- UPnP loading")
+            return
+        }
+        val active = holder.active.value
+        Timber.w("ForwardingPlayer.seekToPreviousMediaItem() active=%s", active?.routeName)
+        if (active == null) {
+            super.seekToPreviousMediaItem()
+            return
+        }
+        // Super first for immediate local cursor advance (UI feedback);
+        // then delegate to Sonos Previous. PollLoop reconciles.
+        super.seekToPreviousMediaItem()
+        remoteState.beginPendingTransport(
+            SystemClock.elapsedRealtime() + PENDING_TRANSPORT_SAFETY_TIMEOUT_MS,
+        )
+        scope.launch {
+            runCatching { active.avTransport.previous() }
+                .onFailure { handleSoapFailure(active, it) }
+        }
+    }
+
+    override fun getCurrentPosition(): Long =
+        if (isRemote()) remoteState.positionMs else super.getCurrentPosition()
+
+    override fun getDuration(): Long =
+        if (isRemote()) remoteState.durationMs else super.getDuration()
+
+    override fun isPlaying(): Boolean =
+        if (isRemote()) remoteState.isPlaying else super.isPlaying()
+
+    override fun getPlaybackState(): Int =
+        if (isRemote()) Player.STATE_READY else super.getPlaybackState()
+
+    // Mirror remote state so any consumer that gates on playWhenReady --
+    // notably MediaSessionService's foreground-keepalive checks and our own
+    // onTaskRemoved -- sees the remote renderer as the source of truth.
+    // Without this, swiping the app away with Sonos playing would stop the
+    // service, kill the poll loop, and leave Sonos orphaned.
+    override fun getPlayWhenReady(): Boolean =
+        if (isRemote()) remoteState.isPlaying else super.getPlayWhenReady()
+
+    override fun addListener(listener: Player.Listener) {
+        super.addListener(listener)
+        synchronized(externalListeners) { externalListeners.add(listener) }
+    }
+
+    override fun removeListener(listener: Player.Listener) {
+        super.removeListener(listener)
+        synchronized(externalListeners) { externalListeners.remove(listener) }
+    }
+
+    /**
+     * Direct-invoke the externally-registered Player.Listeners so the
+     * MediaSession's PlaybackState publisher (notification card, lock-screen
+     * scrubber, BT/AVRCP, Auto, Wear OS tile) re-reads our overridden state.
+     * The listeners then query isPlaying / getDuration / getCurrentPosition,
+     * all of which route through to remoteState while UPnP is active.
+     *
+     * Posted to the player's application looper because Player.Listener
+     * callbacks contract on the application thread.
+     */
+    private fun notifyRemoteStateChanged() {
+        if (!isRemote()) return
+        val playing = remoteState.isPlaying
+        val trackIdx = (remoteState.trackNumber - 1).coerceAtLeast(0)
+        val isPlayingChanged = playing != lastNotifiedIsPlaying
+        val trackChanged = trackIdx != lastNotifiedTrackIdx
+        if (!isPlayingChanged && !trackChanged) return
+        lastNotifiedIsPlaying = playing
+        lastNotifiedTrackIdx = trackIdx
+        val snapshot = synchronized(externalListeners) { externalListeners.toList() }
+        handler.post {
+            for (l in snapshot) {
+                if (isPlayingChanged) {
+                    l.onIsPlayingChanged(playing)
+                    l.onPlaybackStateChanged(Player.STATE_READY)
+                }
+                if (trackChanged) {
+                    val item = if (trackIdx < delegate.mediaItemCount) {
+                        delegate.getMediaItemAt(trackIdx)
+                    } else {
+                        null
+                    }
+                    l.onMediaItemTransition(item, Player.MEDIA_ITEM_TRANSITION_REASON_AUTO)
+                }
+            }
+        }
+    }
+
+    override fun release() {
+        pollJob?.cancel()
+        scope.cancel()
+        handler.post {
+            ProcessLifecycleOwner.get().lifecycle.removeObserver(lifecycleObserver)
+        }
+        super.release()
+    }
+
+    private fun handleSoapFailure(active: ActiveUpnp, t: Throwable) {
+        pollJob?.cancel()
+        Timber.w(t, "UPnP transport call failed on %s", active.routeName)
+        remoteState.applyError(t)
+        handler.post { onDrop(active.routeName) }
+    }
+
+    private fun onActiveChanged(active: ActiveUpnp?) {
+        pollJob?.cancel()
+        nonPlayingPollStreak = 0
+        // Reset notify cache so the first poll after a route flip republishes
+        // playing/track state to the MediaSession even if it happens to match
+        // the prior session's values numerically.
+        lastNotifiedIsPlaying = false
+        lastNotifiedTrackIdx = -1
+        if (active != null) {
+            Timber.w("UPnP active: %s -- pollLoop starting", active.routeName)
+            // Pause the wrapped ExoPlayer so we are not playing local audio
+            // simultaneously with the remote renderer. handler.post targets the
+            // application looper, so this runs on the same thread that processes
+            // our override calls -- no race with the pause() override branching
+            // to SOAP (holder.active is already non-null by the time this post
+            // fires, but delegate.pause() bypasses the override entirely).
+            handler.post { delegate.pause() }
+            pollJob = scope.launch { pollLoop(active) }
+        } else {
+            remoteState.reset()
+        }
+    }
+
+    @OptIn(ExperimentalCoroutinesApi::class) // onTimeout / select.onReceive
+    private suspend fun pollLoop(active: ActiveUpnp) {
+        while (scope.isActive && holder.active.value?.routeId == active.routeId) {
+            val outcome = runCatching { pollOnce(active) }
+            if (outcome.isSuccess) {
+                remoteState.recordPollSuccess()
+            } else if (remoteState.recordPollFailure()) {
+                Timber.w("UPnP drop threshold tripped for %s", active.routeName)
+                handler.post { onDrop(active.routeName) }
+                return
+            }
+            // Race the normal cadence against any external wake (activity
+            // resume). Whichever wins continues to the next pollOnce.
+            select<Unit> {
+                onTimeout(POLL_INTERVAL_MS) {}
+                pollTrigger.onReceive {}
+            }
+        }
+    }
+
+    /**
+     * One poll tick: read position + transport state from Sonos, apply to
+     * [remoteState], and forward-sync the local cursor to Sonos's Track
+     * index when not in queue load.
+     *
+     * Cursor sync is gated on `holder.target == null` (= not loading)
+     * because during load Sonos reports Track=1 while we're still
+     * appending, and syncing would race the SetAV+Seek that lands
+     * after. Outside load, forward sync catches Sonos auto-advances
+     * (queue end-of-track), Sonos-app driven Next presses, and any
+     * drift after a brief poll-failure burst that didn't trip the
+     * drop threshold. Forward-only because a Next override we just
+     * issued can race with a poll still reporting the prior Track --
+     * the next poll catches up safely.
+     */
+    private suspend fun pollOnce(active: ActiveUpnp) {
+        val info = active.avTransport.getPositionInfo()
+        val now = SystemClock.elapsedRealtime()
+        val inSeekAckWindow = lastSeekIssuedAtMs > 0L &&
+            (now - lastSeekIssuedAtMs) < SEEK_ACK_WINDOW_MS
+        // Inside the seek-ack window, keep the optimistic position we wrote in
+        // seekTo -- the poll's reported position is stale until Sonos finishes
+        // processing the Seek SOAP. Other fields still refresh from the poll.
+        remoteState.applyPositionInfo(
+            positionMs = if (inSeekAckWindow) remoteState.positionMs else info.relTimeMs,
+            durationMs = info.trackDurationMs,
+            trackUri = info.trackUri,
+            trackNumber = info.track,
+        )
+        maybeSyncLocalCursor(info.track)
+        val transport = active.avTransport.getTransportInfo()
+        when (transport.state) {
+            TransportState.PLAYING -> {
+                nonPlayingPollStreak = 0
+                remoteState.applyTransportPlaying()
+            }
+            TransportState.PAUSED -> {
+                nonPlayingPollStreak += 1
+                if (nonPlayingPollStreak >= NON_PLAYING_CONFIRM) {
+                    remoteState.applyTransportPaused()
+                }
+            }
+            TransportState.STOPPED -> {
+                nonPlayingPollStreak += 1
+                if (nonPlayingPollStreak >= NON_PLAYING_CONFIRM) {
+                    remoteState.applyTransportStopped()
+                }
+            }
+            TransportState.TRANSITIONING, TransportState.UNKNOWN -> Unit
+        }
+        notifyRemoteStateChanged()
+    }
+
+    private fun maybeSyncLocalCursor(sonosTrack: Int) {
+        if (holder.target.value != null) return
+        if (sonosTrack <= 0) return
+        val sonosIdx = sonosTrack - 1
+        handler.post {
+            val localIdx = delegate.currentMediaItemIndex
+            if (sonosIdx > localIdx && sonosIdx < delegate.mediaItemCount) {
+                Timber.w(
+                    "UPnP cursor catch-up: local=%d -> sonos=%d",
+                    localIdx, sonosIdx,
+                )
+                delegate.seekTo(sonosIdx, 0L)
+            }
+        }
+    }
+
+    private companion object {
+        const val POLL_INTERVAL_MS = 1_000L
+        const val NON_PLAYING_CONFIRM = 2
+        const val SEEK_ACK_WINDOW_MS = 2_000L
+        // Safety upper bound on how long the polling tick will wait for
+        // Sonos to ack a user transport. The common case clears event-driven
+        // when Sonos's reported Track matches the wrapped player; this only
+        // kicks in if SOAP fails or Sonos drops the ack entirely.
+        const val PENDING_TRANSPORT_SAFETY_TIMEOUT_MS = 5_000L
+    }
+}

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

@@ -72,11 +72,12 @@ class MinstrelPlayerService : MediaSessionService() {
 
     override fun onCreate() {
         super.onCreate()
-        val player = playerFactory.build()
+        val player: Player = playerFactory.build()
         val callback = LikeMediaCallback(likesRepository, serviceScope)
         val session = MediaSession.Builder(this, player)
             .setSessionActivity(buildNowPlayingPendingIntent())
             .setCallback(callback)
+            .setBitmapLoader(playerFactory.buildBitmapLoader())
             .setMediaButtonPreferences(ImmutableList.of(buildLikeButton(isLiked = false)))
             .build()
         mediaSession = session
@@ -176,7 +177,11 @@ class MinstrelPlayerService : MediaSessionService() {
 
     override fun onTaskRemoved(rootIntent: Intent?) {
         val player = mediaSession?.player ?: return super.onTaskRemoved(rootIntent)
-        val activelyPlaying = player.playWhenReady && player.playbackState != Player.STATE_ENDED
+        // player.isPlaying is overridden on MinstrelForwardingPlayer to return
+        // remoteState.isPlaying while UPnP is active, so a swipe-away with
+        // Sonos playing keeps the service (and its UPnP poll loop) alive.
+        val activelyPlaying = player.isPlaying ||
+            (player.playWhenReady && player.playbackState != Player.STATE_ENDED)
         if (!activelyPlaying) {
             stopSelf()
         }

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

@@ -0,0 +1,65 @@
+package com.fabledsword.minstrel.player
+
+import androidx.media3.datasource.DataSource
+import androidx.media3.datasource.DataSpec
+import androidx.media3.datasource.TransferListener
+import com.fabledsword.minstrel.connectivity.ServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealthController
+import java.io.IOException
+import java.io.InterruptedIOException
+
+/**
+ * DataSource wrapper that fails the network read immediately when
+ * [ServerHealthController] reports a non-Healthy state. CacheDataSource only
+ * calls this upstream factory on cache misses, so playback of cached audio is
+ * unaffected -- only "tap a non-cached track while offline" hits this branch
+ * and gets a fast, meaningful error instead of a multi-second network timeout
+ * (which then surfaced as a silent decode failure to the user).
+ *
+ * Wrapping rather than substituting the OkHttp data source lets the cache
+ * write path remain intact for when health returns and we DO want to fetch:
+ * we keep the same upstream all the time, just gate `open()`.
+ */
+class OfflineGatedDataSource(
+    private val delegate: DataSource,
+    private val health: ServerHealthController,
+) : DataSource {
+
+    override fun open(dataSpec: DataSpec): Long {
+        when (health.state.value) {
+            ServerHealth.Offline -> throw OfflineException(
+                "Track not in the on-device cache and the device is offline.",
+            )
+            ServerHealth.ServerDown -> throw OfflineException(
+                "Track not in the on-device cache and the Minstrel server is unreachable.",
+            )
+            ServerHealth.Healthy -> Unit
+        }
+        return delegate.open(dataSpec)
+    }
+
+    override fun close() = delegate.close()
+    override fun getUri() = delegate.uri
+    override fun read(buffer: ByteArray, offset: Int, length: Int): Int =
+        delegate.read(buffer, offset, length)
+    override fun addTransferListener(transferListener: TransferListener) =
+        delegate.addTransferListener(transferListener)
+    override fun getResponseHeaders() = delegate.responseHeaders
+}
+
+class OfflineGatedDataSourceFactory(
+    private val upstream: DataSource.Factory,
+    private val health: ServerHealthController,
+) : DataSource.Factory {
+    override fun createDataSource(): DataSource =
+        OfflineGatedDataSource(upstream.createDataSource(), health)
+}
+
+/**
+ * Signals the audio-source error path that the request was denied because the
+ * device is offline / the server is unreachable. ExoPlayer's [androidx.media3
+ * .common.PlaybackException] catches it via [InterruptedIOException]'s
+ * `IOException` ancestor and surfaces it as a SOURCE error, which then flows
+ * through the existing [PlaybackErrorReporter] -> snackbar path.
+ */
+class OfflineException(message: String) : IOException(message)

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

@@ -5,6 +5,8 @@ import android.content.Context
 import android.os.Bundle
 import android.os.Handler
 import android.os.Looper
+import android.os.SystemClock
+import androidx.core.net.toUri
 import androidx.media3.common.MediaItem
 import androidx.media3.common.MediaMetadata
 import androidx.media3.common.Player
@@ -20,8 +22,10 @@ import kotlinx.coroutines.channels.Channel
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.receiveAsFlow
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -59,7 +63,17 @@ class PlayerController @Inject constructor(
     @ApplicationContext private val context: Context,
     @ApplicationScope private val scope: CoroutineScope,
     private val radio: RadioController,
+    private val playerFactory: PlayerFactory,
+    private val activeUpnpHolder: com.fabledsword.minstrel.player.output.ActiveUpnpHolder,
+    private val remoteState: RemotePlayerState,
 ) {
+
+    /**
+     * UPnP drop events surfaced from [PlayerFactory.dropEvents]. NowPlaying
+     * collects this into its snackbar host so a transport / poll failure
+     * during UPnP playback shows "Disconnected from <name>" to the user.
+     */
+    val dropEvents: SharedFlow<String> = playerFactory.dropEvents
     private val sessionToken =
         SessionToken(context, ComponentName(context, MinstrelPlayerService::class.java))
 
@@ -130,11 +144,24 @@ class PlayerController @Inject constructor(
 
     // ── Transport (no-op until the controller is connected) ──────────────
 
-    fun play() { mediaController?.play() }
-    fun pause() { mediaController?.pause() }
-    fun seekTo(positionMs: Long) { mediaController?.seekTo(positionMs) }
-    fun skipToNext() { mediaController?.seekToNextMediaItem() }
-    fun skipToPrevious() { mediaController?.seekToPreviousMediaItem() }
+    // Each transport call must run on the MediaController's
+    // applicationLooper; calling from a background coroutine throws
+    // IllegalStateException (see PlayerController.setQueue's note).
+    // UI tap handlers are already on Main so the in-place branch hits;
+    // the background path only fires for cross-thread callers like
+    // OutputPickerController.selectUpnp (which calls pause() after
+    // handing playback off to a UPnP renderer).
+    fun play() { mediaController?.let { runOnControllerThread(it) { it.play() } } }
+    fun pause() { mediaController?.let { runOnControllerThread(it) { it.pause() } } }
+    fun seekTo(positionMs: Long) {
+        mediaController?.let { runOnControllerThread(it) { it.seekTo(positionMs) } }
+    }
+    fun skipToNext() {
+        mediaController?.let { runOnControllerThread(it) { it.seekToNextMediaItem() } }
+    }
+    fun skipToPrevious() {
+        mediaController?.let { runOnControllerThread(it) { it.seekToPreviousMediaItem() } }
+    }
 
     /** Flip shuffle on/off. Media3 emits onEvents → uiState reflects. */
     fun toggleShuffle() {
@@ -299,7 +326,15 @@ class PlayerController @Inject constructor(
      * and advance past the dead track. Otherwise no-op.
      */
     private fun handleZeroDurationIfNeeded(controller: MediaController, idx: Int) {
-        val current = queueRefs.getOrNull(idx) ?: return
+        // Skip during UPnP playback (active) AND during the activation load
+        // window (target set, active not yet wired). ExoPlayer is intentionally
+        // paused throughout both windows so its STATE_READY duration is always
+        // 0 / TIME_UNSET -- without this guard we rapid-advance through the
+        // entire local queue (and spam /api/playback-errors).
+        val current = queueRefs.getOrNull(idx)
+        val upnpEngaged = activeUpnpHolder.active.value != null ||
+            activeUpnpHolder.target.value != null
+        if (current == null || upnpEngaged) return
         val duration = controller.duration
         val isZeroDuration = duration <= 0L || duration == androidx.media3.common.C.TIME_UNSET
         if (!isZeroDuration) return
@@ -341,6 +376,19 @@ class PlayerController @Inject constructor(
         // awaitReady, the Player.Listener is wired too.
         if (!readyDeferred.isCompleted) readyDeferred.complete(Unit)
         startPositionPolling(controller)
+        // Keep isUpnpLoading current between player-event fires: holder state
+        // changes (setTarget / set(active)) are independent of Media3 events, so
+        // onEvents alone would lag behind by up to one event cycle. This collector
+        // runs for the process lifetime alongside the position poller.
+        scope.launch {
+            combine(
+                activeUpnpHolder.target,
+                activeUpnpHolder.active,
+            ) { target, active -> target != null && active == null }
+                .collect { isLoading ->
+                    uiStateInternal.value = uiStateInternal.value.copy(isUpnpLoading = isLoading)
+                }
+        }
         controller.addListener(
             object : Player.Listener {
                 override fun onPlayerError(error: androidx.media3.common.PlaybackException) {
@@ -364,6 +412,11 @@ class PlayerController @Inject constructor(
                     // Reset the per-item evaluation guard so the new
                     // item's STATE_READY transition gets a fresh check.
                     lastEvaluatedItemIndex = -1
+                    // The track flipped -- re-anchor the position interpolator
+                    // so the next polling tick treats the new track's
+                    // remoteState.positionMs as fresh rather than carrying the
+                    // old anchor + elapsed forward.
+                    lastSeenRemotePositionMs = -1L
                 }
 
                 override fun onPlaybackStateChanged(playbackState: Int) {
@@ -381,15 +434,38 @@ class PlayerController @Inject constructor(
                         ?.mediaMetadata
                         ?.extras
                         ?.getString(MINSTREL_SOURCE_KEY)
+                    val isUpnpLoading = activeUpnpHolder.target.value != null &&
+                        activeUpnpHolder.active.value == null
+                    // When UPnP is active, the wrapped ExoPlayer is paused with
+                    // no real audio loaded -- player.duration / isPlaying /
+                    // currentPosition all reflect that. Read from remoteState
+                    // instead so an onEvents fire (e.g. activity resume) doesn't
+                    // clobber the UI with zeros. Duration falls back to the
+                    // wrapped player's value when Sonos hasn't reported one yet
+                    // (pre-first-poll window, or Sonos still buffering) -- the
+                    // wrapped ExoPlayer was prepared with the same MediaItem so
+                    // it knows the real duration before any SOAP poll lands.
+                    val upnpActive = activeUpnpHolder.active.value != null
                     uiStateInternal.value =
                         PlayerUiState(
                             currentTrack = current,
                             queue = queueRefs,
                             queueIndex = idx,
-                            isPlaying = player.isPlaying,
-                            isBuffering = player.playbackState == Player.STATE_BUFFERING,
-                            positionMs = player.currentPosition.coerceAtLeast(0),
-                            durationMs = player.duration.coerceAtLeast(0),
+                            isPlaying = if (upnpActive) remoteState.isPlaying else player.isPlaying,
+                            isBuffering = !upnpActive &&
+                                player.playbackState == Player.STATE_BUFFERING,
+                            positionMs = if (upnpActive) {
+                                remoteState.positionMs
+                            } else {
+                                player.currentPosition
+                            }.coerceAtLeast(0),
+                            durationMs = effectiveDuration(
+                                upnpActive,
+                                remoteState.durationMs,
+                                player.duration,
+                                desiredIdx = idx,
+                                controllerIdx = idx,
+                            ),
                             bufferedPositionMs = player.bufferedPosition.coerceAtLeast(0),
                             playbackError = player.playerError?.message,
                             currentSource = source,
@@ -399,6 +475,7 @@ class PlayerController @Inject constructor(
                                 Player.REPEAT_MODE_ONE -> RepeatMode.ONE
                                 else -> RepeatMode.OFF
                             },
+                            isUpnpLoading = isUpnpLoading,
                         )
                 }
             },
@@ -423,15 +500,138 @@ class PlayerController @Inject constructor(
         scope.launch(Dispatchers.Main.immediate) {
             while (isActive) {
                 delay(POSITION_POLL_INTERVAL_MS)
-                if (!controller.isPlaying) continue
-                uiStateInternal.value = uiStateInternal.value.copy(
-                    positionMs = controller.currentPosition.coerceAtLeast(0),
-                    bufferedPositionMs = controller.bufferedPosition.coerceAtLeast(0),
-                )
+                tickPositionPoll(controller)
             }
         }
     }
 
+    /**
+     * One position-polling tick. Owns track-change detection too: when UPnP
+     * is active and the wrapped ExoPlayer is paused, `delegate.seekTo` from
+     * `maybeSyncLocalCursor` may not fire `onMediaItemTransition`, leaving
+     * uiState.queueIndex stuck on the old track even after Sonos has
+     * advanced. So the tick reads Sonos's reported Track as the source of
+     * truth, rebuilds the index/title fields itself, and force-syncs the
+     * wrapped player as defense in depth.
+     */
+    private fun tickPositionPoll(controller: MediaController) {
+        val upnpActive = activeUpnpHolder.active.value != null
+        resolvePendingTransport(controller, upnpActive)
+        val pendingTransport = upnpActive && remoteState.pendingTransportDeadlineMs > 0L
+        val effectiveIsPlaying =
+            if (upnpActive) remoteState.isPlaying else controller.isPlaying
+        val effectivePosition = if (upnpActive) {
+            interpolatedRemotePosition(effectiveIsPlaying)
+        } else {
+            controller.currentPosition
+        }
+        val desiredIdx = desiredQueueIndex(controller, upnpActive)
+        val current = uiStateInternal.value
+        val newPos = effectivePosition.coerceAtLeast(0)
+        val newDur = effectiveDuration(
+            upnpActive,
+            remoteState.durationMs,
+            controller.duration,
+            desiredIdx = desiredIdx,
+            controllerIdx = controller.currentMediaItemIndex,
+        )
+        val newBuf = controller.bufferedPosition.coerceAtLeast(0)
+        // Track adjustments are forward-only AND suppressed while a user
+        // transport press is pending Sonos confirmation. Together those keep
+        // either direction of user input from being undone by a stale poll.
+        val trackChanged = !pendingTransport &&
+            desiredIdx > current.queueIndex &&
+            desiredIdx in queueRefs.indices
+        publishTickIfChanged(
+            current, trackChanged, desiredIdx,
+            effectiveIsPlaying, newPos, newDur, newBuf,
+        )
+    }
+
+    /**
+     * Event-driven primary path: clear pending the moment Sonos's reported
+     * Track matches the wrapped player's index. Safety fallback: clear on
+     * deadline so we don't ignore Sonos's actual state forever if SOAP fails.
+     */
+    private fun resolvePendingTransport(controller: MediaController, upnpActive: Boolean) {
+        if (!upnpActive || remoteState.pendingTransportDeadlineMs <= 0L) return
+        val sonosIdx = (remoteState.trackNumber - 1).coerceAtLeast(0)
+        val timedOut = SystemClock.elapsedRealtime() > remoteState.pendingTransportDeadlineMs
+        if (sonosIdx == controller.currentMediaItemIndex || timedOut) {
+            remoteState.clearPendingTransport()
+        }
+    }
+
+    @Suppress("LongParameterList") // assembled at one tick call site; refactor would cost clarity
+    private fun publishTickIfChanged(
+        current: PlayerUiState,
+        trackChanged: Boolean,
+        desiredIdx: Int,
+        effectiveIsPlaying: Boolean,
+        newPos: Long,
+        newDur: Long,
+        newBuf: Long,
+    ) {
+        val somethingChanged = trackChanged ||
+            current.isPlaying != effectiveIsPlaying ||
+            current.positionMs != newPos ||
+            current.durationMs != newDur
+        if (!somethingChanged) return
+        val newTrack = if (trackChanged) queueRefs[desiredIdx] else current.currentTrack
+        val newIdx = if (trackChanged) desiredIdx else current.queueIndex
+        uiStateInternal.value = current.copy(
+            currentTrack = newTrack,
+            queueIndex = newIdx,
+            isPlaying = effectiveIsPlaying,
+            positionMs = newPos,
+            durationMs = newDur,
+            bufferedPositionMs = newBuf,
+        )
+        // Intentionally do NOT call controller.seekTo here. That would route
+        // through MinstrelForwardingPlayer's seekTo override and re-issue
+        // AVTransport.SeekToTrack to Sonos -- which seeks Sonos back to the
+        // start of the same track it's already playing, restarting the song.
+        // The wrapped player's index is kept in sync by maybeSyncLocalCursor's
+        // delegate.seekTo (which bypasses the override). If it lags briefly,
+        // the next pollOnce catches up; the uiState above already reflects
+        // Sonos's truth for the user.
+    }
+
+    private fun desiredQueueIndex(controller: MediaController, upnpActive: Boolean): Int =
+        if (upnpActive) {
+            (remoteState.trackNumber - 1).coerceAtLeast(0)
+        } else {
+            controller.currentMediaItemIndex
+        }
+
+    // ── Remote position interpolation state ──────────────────────────────
+    // remoteState.positionMs is only refreshed by ForwardingPlayer's 1Hz
+    // SOAP poll (and only when the round-trip completes -- screen-off WiFi
+    // sleep can stall it for many seconds). To keep the scrubber moving
+    // smoothly we anchor each fresh reading + an elapsed-realtime stamp;
+    // between updates we display anchor + elapsed when Sonos is playing.
+    // A real correction lands as soon as the next poll arrives.
+    @Volatile private var lastSeenRemotePositionMs: Long = -1L
+    @Volatile private var positionAnchorMs: Long = 0L
+    @Volatile private var positionAnchorAtRealtimeMs: Long = 0L
+
+    private fun interpolatedRemotePosition(isPlaying: Boolean): Long {
+        val raw = remoteState.positionMs
+        val now = SystemClock.elapsedRealtime()
+        if (raw != lastSeenRemotePositionMs) {
+            lastSeenRemotePositionMs = raw
+            positionAnchorMs = raw
+            positionAnchorAtRealtimeMs = now
+        }
+        if (!isPlaying) return positionAnchorMs
+        // Cap how far past the last anchor we extrapolate. After
+        // MAX_INTERPOLATION_DRIFT_MS without a poll update, freeze the
+        // displayed position at anchor + cap rather than projecting wildly.
+        // The next successful poll re-anchors and motion resumes.
+        val delta = (now - positionAnchorAtRealtimeMs).coerceAtMost(MAX_INTERPOLATION_DRIFT_MS)
+        return positionAnchorMs + delta
+    }
+
     /**
      * Bridges Media3's `ListenableFuture<MediaController>.buildAsync()`
      * to a suspend function without pulling in `kotlinx-coroutines-guava`
@@ -467,7 +667,23 @@ class PlayerController @Inject constructor(
             .setArtist(artistName)
             .setAlbumTitle(albumTitle)
             .apply {
+                // Server-known duration -- gives the lock-screen / notification
+                // scrubber a real total even when the wrapped ExoPlayer is
+                // paused under UPnP (it never probes a duration in that state).
+                if (durationSec > 0) setDurationMs(durationSec.toLong() * MS_PER_SECOND)
                 if (source != null) setExtras(sourceExtras(source))
+                // Point the notification / lock-screen art at the SAME album
+                // cover the in-app surfaces use (TrackRef.coverUrl ->
+                // /api/albums/{id}/cover). Without this, Media3 falls back to
+                // whatever art is embedded in the stream's tags, which can be a
+                // different image than the server's album cover. Setting
+                // artworkUri here is load-bearing: MediaMetadata.populate()
+                // overwrites artworkUri + artworkData as a pair, so the
+                // MediaItem's URI clears any embedded artworkData ExoPlayer
+                // extracts from the stream -- the cover endpoint wins on both
+                // surfaces. The session's OkHttp-backed BitmapLoader (see
+                // PlayerFactory) is what makes this authed placeholder URL load.
+                if (coverUrl.isNotEmpty()) setArtworkUri(coverUrl.toUri())
             }
             .build()
         // Server's stream_url is a relative path (/api/tracks/{id}/stream);
@@ -489,8 +705,40 @@ class PlayerController @Inject constructor(
     private fun sourceExtras(source: String): Bundle =
         Bundle().apply { putString(MINSTREL_SOURCE_KEY, source) }
 
+    /**
+     * Duration to surface to the UI. Priority: Sonos's reported duration
+     * (only when UPnP active and non-zero) -> wrapped ExoPlayer's value
+     * (only valid once it's probed the stream) -> TrackRef.durationSec
+     * (always known from the server response). The third tier is what
+     * keeps the scrubber populated when the user taps Sonos before the
+     * wrapped player has had time to probe its own duration -- without
+     * it, both top tiers report 0/TIME_UNSET and the field reads empty
+     * until the first SOAP poll lands.
+     */
+    @Suppress("ReturnCount") // 3-tier fallback reads cleanest as a ladder of early returns
+    private fun effectiveDuration(
+        upnpActive: Boolean,
+        remoteMs: Long,
+        localMs: Long,
+        desiredIdx: Int,
+        controllerIdx: Int,
+    ): Long {
+        if (upnpActive && remoteMs > 0) return remoteMs
+        // Tier 2 (wrapped player's probed duration) only valid when the
+        // wrapped player is on the same track we're trying to show. After a
+        // Sonos natural advance the polling tick updates desiredIdx from
+        // Sonos's truth while controllerIdx is briefly stale -- using the
+        // wrapped player's duration here would surface the old track's
+        // length under the new track's title.
+        if (localMs > 0 && controllerIdx == desiredIdx) return localMs
+        val ref = queueRefs.getOrNull(desiredIdx) ?: return 0
+        return ref.durationSec.toLong() * MS_PER_SECOND
+    }
+
     companion object {
         const val MINSTREL_SOURCE_KEY: String = "minstrel_source"
+        private const val MS_PER_SECOND = 1_000L
+        private const val MAX_INTERPOLATION_DRIFT_MS = 5_000L
     }
 }
 

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

@@ -3,7 +3,10 @@ package com.fabledsword.minstrel.player
 import android.content.Context
 import androidx.media3.common.AudioAttributes
 import androidx.media3.common.C
+import androidx.media3.common.Player
+import androidx.media3.common.util.BitmapLoader
 import androidx.media3.database.StandaloneDatabaseProvider
+import androidx.media3.datasource.DataSourceBitmapLoader
 import androidx.media3.datasource.cache.CacheDataSink
 import androidx.media3.datasource.cache.CacheDataSource
 import androidx.media3.datasource.cache.LeastRecentlyUsedCacheEvictor
@@ -11,15 +14,21 @@ import androidx.media3.datasource.cache.SimpleCache
 import androidx.media3.datasource.okhttp.OkHttpDataSource
 import androidx.media3.exoplayer.ExoPlayer
 import androidx.media3.exoplayer.source.DefaultMediaSourceFactory
+import androidx.media3.session.CacheBitmapLoader
 import com.fabledsword.minstrel.cache.audiocache.CacheConfig
+import com.fabledsword.minstrel.player.output.ActiveUpnpHolder
 import dagger.hilt.android.qualifiers.ApplicationContext
+import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.flow.MutableSharedFlow
+import kotlinx.coroutines.flow.SharedFlow
+import kotlinx.coroutines.flow.asSharedFlow
 import okhttp3.OkHttpClient
 import java.io.File
 import javax.inject.Inject
 import javax.inject.Singleton
 
 /**
- * Builds the process-singleton ExoPlayer with our shared OkHttp +
+ * Builds the process-singleton player with our shared OkHttp +
  * SimpleCache chain. The MinstrelPlayerService (Phase 6.2) calls
  * `build()` once during onCreate.
  *
@@ -31,12 +40,22 @@ import javax.inject.Singleton
  * (sizeBytes cap = rollingCap); our policy layer in the worker layers
  * the 2-bucket protection on top by feeding `removeSpan` only for
  * unprotected tracks.
+ *
+ * `build()` returns a [MinstrelForwardingPlayer] wrapping the internal
+ * ExoPlayer. When the UPnP route drops (3 consecutive poll failures or
+ * a SOAP failure), [dropEvents] emits the route name so the NowPlaying
+ * surface can show a snackbar. The MutableSharedFlow uses DROP_OLDEST
+ * with capacity=1 so a burst of failures during a single tear-down
+ * surfaces as one event rather than queueing N.
  */
 @Singleton
 class PlayerFactory @Inject constructor(
     @ApplicationContext private val context: Context,
     private val okHttpClient: OkHttpClient,
     private val cacheConfig: CacheConfig,
+    private val activeUpnpHolder: ActiveUpnpHolder,
+    private val remoteState: RemotePlayerState,
+    private val serverHealth: com.fabledsword.minstrel.connectivity.ServerHealthController,
 ) {
     private val cacheDir: File = File(context.cacheDir, "audio_cache").apply { mkdirs() }
 
@@ -46,11 +65,36 @@ class PlayerFactory @Inject constructor(
         StandaloneDatabaseProvider(context),
     )
 
-    fun build(): ExoPlayer {
+    // MutableSharedFlow with extraBufferCapacity=1 + DROP_OLDEST so a burst
+    // of drop events (rapid SOAP failures during a single tear-down) surfaces
+    // as one snackbar rather than queueing N.
+    private val dropEventsInternal = MutableSharedFlow<String>(
+        replay = 0,
+        extraBufferCapacity = 1,
+        onBufferOverflow = BufferOverflow.DROP_OLDEST,
+    )
+    val dropEvents: SharedFlow<String> = dropEventsInternal.asSharedFlow()
+
+    fun build(): Player {
+        val exo = buildExoPlayer()
+        return MinstrelForwardingPlayer(
+            delegate = exo,
+            holder = activeUpnpHolder,
+            remoteState = remoteState,
+            onDrop = { name -> emitDrop(name) },
+        )
+    }
+
+    private fun buildExoPlayer(): ExoPlayer {
         val httpDataSource = OkHttpDataSource.Factory(okHttpClient)
+        // Gate network reads on ServerHealth so a cache miss while offline
+        // fails fast with an OfflineException instead of hitting an OkHttp
+        // timeout. CacheDataSource only consults the upstream factory on a
+        // cache miss, so playback of cached audio is unaffected.
+        val gatedUpstream = OfflineGatedDataSourceFactory(httpDataSource, serverHealth)
         val cacheDataSource = CacheDataSource.Factory()
             .setCache(simpleCache)
-            .setUpstreamDataSourceFactory(httpDataSource)
+            .setUpstreamDataSourceFactory(gatedUpstream)
             .setCacheWriteDataSinkFactory(
                 CacheDataSink.Factory()
                     .setCache(simpleCache)
@@ -71,4 +115,26 @@ class PlayerFactory @Inject constructor(
             .setHandleAudioBecomingNoisy(true)
             .build()
     }
+
+    /**
+     * BitmapLoader for the MediaSession's notification / lock-screen art.
+     * Backed by the shared [okHttpClient] so it inherits the same
+     * BaseUrlInterceptor placeholder rewrite + auth cookie that Coil uses
+     * for in-app covers — without it the default DefaultHttpDataSource
+     * loader can't resolve `http://placeholder.invalid/...` and would 401
+     * on the cover endpoint. Wrapped in CacheBitmapLoader so a cover the
+     * notification already fetched isn't re-loaded on every metadata
+     * refresh. Lets the album-cover artworkUri set in
+     * [PlayerController.toMediaItem] actually render on the media card.
+     */
+    fun buildBitmapLoader(): BitmapLoader =
+        CacheBitmapLoader(
+            DataSourceBitmapLoader.Builder(context)
+                .setDataSourceFactory(OkHttpDataSource.Factory(okHttpClient))
+                .build(),
+        )
+
+    private fun emitDrop(routeName: String) {
+        dropEventsInternal.tryEmit(routeName)
+    }
 }

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

@@ -28,4 +28,6 @@ data class PlayerUiState(
     val currentSource: String? = null,
     val shuffleEnabled: Boolean = false,
     val repeatMode: RepeatMode = RepeatMode.OFF,
+    /** True while the UPnP initial-batch load is in progress (target set, active not yet wired). */
+    val isUpnpLoading: Boolean = false,
 )

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

@@ -0,0 +1,98 @@
+package com.fabledsword.minstrel.player
+
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Synthesized state for the UPnP route -- what the ForwardingPlayer
+ * exposes via Player.getCurrentPosition / isPlaying / etc. when the
+ * remote leg is active. Not a Player; a container.
+ *
+ * Updates flow in from:
+ *  - 1Hz GetPositionInfo poll -> applyPositionInfo()
+ *  - Transport SOAP calls landing 200 OK -> applyTransport{Playing,Paused,Stopped}()
+ *  - Error paths -> applyError() (drop fallback) or recordPollFailure()
+ *
+ * The poll-failure counter implements the rolling-3 drop heuristic: 3
+ * consecutive poll failures = remote considered dropped (returns true
+ * from recordPollFailure for the caller to surface). Success resets it.
+ */
+@Singleton
+class RemotePlayerState @Inject constructor() {
+
+    @Volatile var positionMs: Long = 0L; private set
+    @Volatile var durationMs: Long = 0L; private set
+    @Volatile var isPlaying: Boolean = false; private set
+    @Volatile var currentTrackUri: String = ""; private set
+    @Volatile var lastError: Throwable? = null; private set
+    @Volatile var trackNumber: Int = 0; private set
+
+    // Pending-transport deadline (SystemClock.elapsedRealtime() at which we
+    // give up waiting). When > 0, a user transport action (next/prev/seekTo
+    // idx) is in flight: ForwardingPlayer has already moved the wrapped
+    // player's index, but Sonos's reported Track hasn't refreshed via a
+    // SOAP poll yet. PlayerController.tickPositionPoll skips track
+    // adjustments while pending is non-zero. Pending clears when:
+    //   (a) [event-driven, primary] a poll lands and Sonos's reported Track
+    //       matches the wrapped player's currentMediaItemIndex; or
+    //   (b) [safety fallback] the deadline expires (covers SOAP-fail cases
+    //       where Sonos never acks).
+    @Volatile var pendingTransportDeadlineMs: Long = 0L; private set
+
+    fun beginPendingTransport(deadlineMs: Long) {
+        pendingTransportDeadlineMs = deadlineMs
+    }
+
+    fun clearPendingTransport() {
+        pendingTransportDeadlineMs = 0L
+    }
+
+    @Volatile private var consecutivePollFailures: Int = 0
+
+    fun applyPositionInfo(positionMs: Long, durationMs: Long, trackUri: String, trackNumber: Int) {
+        this.positionMs = positionMs
+        this.durationMs = durationMs
+        this.currentTrackUri = trackUri
+        this.trackNumber = trackNumber
+    }
+
+    fun applyTransportPlaying() { isPlaying = true }
+    fun applyTransportPaused() { isPlaying = false }
+    fun applyTransportStopped() {
+        isPlaying = false
+        positionMs = 0L
+    }
+
+    fun applyError(t: Throwable) {
+        isPlaying = false
+        lastError = t
+    }
+
+    /** Returns true when the rolling threshold trips this call. */
+    fun recordPollFailure(): Boolean {
+        consecutivePollFailures += 1
+        return consecutivePollFailures >= DROP_THRESHOLD
+    }
+
+    fun recordPollSuccess() { consecutivePollFailures = 0 }
+
+    fun reset() {
+        positionMs = 0L
+        durationMs = 0L
+        isPlaying = false
+        currentTrackUri = ""
+        lastError = null
+        consecutivePollFailures = 0
+        trackNumber = 0
+        pendingTransportDeadlineMs = 0L
+    }
+
+    private companion object {
+        // ~30 seconds of consecutive poll failures before declaring the route
+        // dropped. Bumped from 3 because screen-off WiFi sleep / brief Doze
+        // can stall socket I/O for several seconds without the renderer
+        // actually being unreachable -- a 3-failure drop kicked us back to
+        // local audio every time the phone went into a pocket.
+        const val DROP_THRESHOLD = 30
+    }
+}

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

@@ -0,0 +1,24 @@
+package com.fabledsword.minstrel.player
+
+import com.fabledsword.minstrel.api.endpoints.CastApi
+import com.fabledsword.minstrel.api.endpoints.StreamTokenRequest
+import com.fabledsword.minstrel.api.endpoints.StreamTokenResponse
+import retrofit2.Retrofit
+import retrofit2.create
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Mints stream tokens for a given track id. Pulled into its own Hilt
+ * singleton so [MinstrelForwardingPlayer] (service-side) and
+ * [com.fabledsword.minstrel.player.output.OutputPickerController]
+ * (controller-side) don't each construct their own [CastApi] from
+ * Retrofit. The shared Retrofit instance is unchanged.
+ */
+@Singleton
+class StreamTokenProvider @Inject constructor(retrofit: Retrofit) {
+    private val api: CastApi = retrofit.create()
+
+    suspend fun mint(trackId: String): StreamTokenResponse =
+        api.streamToken(StreamTokenRequest(trackId = trackId))
+}

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

@@ -0,0 +1,43 @@
+package com.fabledsword.minstrel.player.output
+
+import com.fabledsword.minstrel.player.output.upnp.AVTransportClient
+import com.fabledsword.minstrel.player.output.upnp.RenderingControlClient
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import javax.inject.Inject
+import javax.inject.Singleton
+
+/**
+ * Shared singleton handle to the currently-active UPnP route's transport
+ * + rendering clients. Decouples [com.fabledsword.minstrel.player.MinstrelForwardingPlayer]
+ * from [OutputPickerController] -- the picker writes; the forwarding
+ * player reads. Null = no UPnP active (local ExoPlayer path).
+ */
+data class ActiveUpnp(
+    val routeId: String,
+    val routeName: String,
+    val avTransport: AVTransportClient,
+    val rendering: RenderingControlClient?,
+)
+
+@Singleton
+class ActiveUpnpHolder @Inject constructor() {
+
+    private val internal = MutableStateFlow<ActiveUpnp?>(null)
+    val active: StateFlow<ActiveUpnp?> = internal.asStateFlow()
+
+    /**
+     * Pending route id during selectUpnp's queue-load window. Set when
+     * loadQueueOnSonos starts; cleared on completion (success or failure).
+     * ForwardingPlayer overrides treat (target != null && active == null)
+     * as "UPnP intended but SOAP not yet wired" -- drop transport commands
+     * silently rather than send them to a half-loaded queue.
+     */
+    private val targetInternal = MutableStateFlow<String?>(null)
+    val target: StateFlow<String?> = targetInternal.asStateFlow()
+
+    fun set(active: ActiveUpnp?) { internal.value = active }
+
+    fun setTarget(routeId: String?) { targetInternal.value = routeId }
+}

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

@@ -1,24 +1,34 @@
+@file:Suppress("TooManyFunctions") // 5 MediaRouter.Callback overrides inflate the count
 package com.fabledsword.minstrel.player.output
 
 import android.content.Context
 import androidx.mediarouter.media.MediaControlIntent
 import androidx.mediarouter.media.MediaRouteSelector
 import androidx.mediarouter.media.MediaRouter
-import com.fabledsword.minstrel.api.endpoints.CastApi
-import com.fabledsword.minstrel.api.endpoints.StreamTokenRequest
 import com.fabledsword.minstrel.di.ApplicationScope
+import com.fabledsword.minstrel.models.TrackRef
 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.AVTransportClient
+import com.fabledsword.minstrel.player.output.upnp.RenderingControlClient
+import com.fabledsword.minstrel.player.output.upnp.SoapClient
+import com.fabledsword.minstrel.player.output.upnp.SoapFaultException
 import com.fabledsword.minstrel.player.output.upnp.UpnpDiscoveryController
+import com.fabledsword.minstrel.player.output.upnp.bareUdn
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
-import retrofit2.Retrofit
-import retrofit2.create
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
+import okhttp3.OkHttpClient
 import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
@@ -26,9 +36,9 @@ import javax.inject.Singleton
 /**
  * Snapshot of the audio output route state. [current] is the live
  * route audio is being delivered to. [available] is every route the
- * picker knows about — MediaRouter system routes merged with
- * UPnP/DLNA renderers discovered on the LAN — sorted current-first
- * then by [OutputRoute.Kind] (Bluetooth, Wired, BuiltIn, Other).
+ * picker knows about -- MediaRouter system routes merged with
+ * UPnP/DLNA renderers discovered on the LAN -- with the BuiltIn
+ * "Phone speaker" pinned first, everything else alphabetical.
  */
 data class RouteSnapshot(
     val current: OutputRoute,
@@ -48,7 +58,7 @@ data class RouteSnapshot(
  *  - [OutputRoute.Protocol.SYSTEM] — MediaRouter.selectRoute (built-in,
  *    wired, Bluetooth)
  *  - [OutputRoute.Protocol.UPNP] — mint a signed stream token via
- *    [CastApi.streamToken], drive the discovered renderer with
+ *    [StreamTokenProvider.mint], drive the discovered renderer with
  *    AVTransport.SetAVTransportURI + Play, pause local playback so
  *    audio yields to the network speaker
  *  - [OutputRoute.Protocol.CAST] / [OutputRoute.Protocol.SONOS] —
@@ -65,10 +75,12 @@ class OutputPickerController @Inject constructor(
     @ApplicationScope private val scope: CoroutineScope,
     private val upnpDiscovery: UpnpDiscoveryController,
     private val playerController: PlayerController,
-    retrofit: Retrofit,
+    private val playerFactory: PlayerFactory,
+    private val streamTokens: StreamTokenProvider,
+    private val activeUpnpHolder: ActiveUpnpHolder,
+    private val remoteState: RemotePlayerState,
+    private val okHttp: OkHttpClient,
 ) {
-    private val castApi: CastApi = retrofit.create()
-
     private val mediaRouter = MediaRouter.getInstance(context)
 
     private val selector = MediaRouteSelector.Builder()
@@ -82,12 +94,26 @@ class OutputPickerController @Inject constructor(
      */
     private val systemRoutesInternal = MutableStateFlow(snapshotFromRouter())
 
+    private val selectedUpnpRouteIdInternal = MutableStateFlow<String?>(null)
+    private val selectUpnpMutex = Mutex()
+
     val routesState: StateFlow<RouteSnapshot> = combine(
         systemRoutesInternal,
         upnpDiscovery.routes,
-    ) { sys, upnp ->
-        val merged = sys.available + upnp.map { OutputRoute.fromUpnpRoute(it) }
-        RouteSnapshot(current = sys.current, available = sortRoutes(sys.current, merged))
+        upnpDiscovery.sonosTopology,
+        selectedUpnpRouteIdInternal,
+    ) { sys, upnp, _, upnpSelected ->
+        val suppressed = upnpDiscovery.nonCoordinatorMemberUdns()
+        val visibleUpnp = upnp
+            .filter { it.id.bareUdn() !in suppressed } // suppressed set is bare UDNs
+            .map { OutputRoute.fromUpnpRoute(it) }
+        val merged = sys.available + visibleUpnp
+        val current = if (upnpSelected != null) {
+            merged.firstOrNull { it.id == upnpSelected } ?: sys.current
+        } else {
+            sys.current
+        }
+        RouteSnapshot(current = current, available = sortRoutes(merged))
     }.stateIn(scope, SharingStarted.Eagerly, systemRoutesInternal.value)
 
     private val callback = object : MediaRouter.Callback() {
@@ -113,6 +139,14 @@ class OutputPickerController @Inject constructor(
         ) = refresh()
     }
 
+    // Last-synced queue identity. Used by observeQueueChangesForSonosResync
+    // to detect when the user has mutated the queue (full replacement,
+    // playNext insert, or radio-append) while UPnP is active and apply the
+    // minimum-incremental set of Sonos SOAP operations to bring its native
+    // queue back in sync. Stored as the full id list (not a join-key) so we
+    // can run the longest-common-prefix / common-suffix diff.
+    private var lastSyncedQueueIds: List<String>? = null
+
     init {
         // Two-arg addCallback registers with no discovery flag —
         // androidx.mediarouter 1.7.0's default passive behavior:
@@ -120,6 +154,232 @@ 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() }
+        }
+        scope.launch { observeQueueChangesForSonosResync() }
+    }
+
+    /**
+     * When the user plays a different playlist while Sonos is active,
+     * PlayerController.setQueue replaces the local queue but Sonos's
+     * native queue still holds the OLD tracks. MinstrelForwardingPlayer's
+     * setMediaItems override clears holder.active + sets target so the
+     * imminent play() call drops (drops via isLoadingUpnp() = true). Then
+     * this collector observes the uiState.queue change and re-runs
+     * loadQueueOnSonos to push the new tracks to Sonos.
+     *
+     * Discrimination: selectUpnp's initial-load path doesn't change
+     * uiState.queue (the queue was already populated before route
+     * selection), so this collector doesn't fire during that window. Only
+     * a fresh setQueue from PlayerController bumps the joined-ids key.
+     */
+    private suspend fun observeQueueChangesForSonosResync() {
+        playerController.uiState.collect { state ->
+            val newIds = state.queue.map { it.id }
+            val oldIds = lastSyncedQueueIds
+            if (newIds == oldIds) return@collect
+            lastSyncedQueueIds = newIds
+            // Route can be in target (setMediaItems-induced clearing already
+            // ran in ForwardingPlayer) OR in active (queue changed via
+            // addMediaItem / removeMediaItems etc. which don't hit the
+            // markPending hook).
+            val routeId = activeUpnpHolder.target.value
+                ?: activeUpnpHolder.active.value?.routeId
+                ?: return@collect
+            if (state.queue.isEmpty()) {
+                Timber.w("Sonos resync skipped: empty queue (clearing target)")
+                activeUpnpHolder.setTarget(null)
+                return@collect
+            }
+            scope.launch {
+                resyncSonosQueue(routeId, oldIds.orEmpty(), state.queue, state.queueIndex)
+            }
+        }
+    }
+
+    /**
+     * Bring Sonos's native queue back in sync with the local queue after a
+     * mutation. Tries an incremental SOAP diff first (RemoveTrackRangeFromQueue
+     * + AddURIToQueue at the insertion point) so playback continues without
+     * interruption -- that's what playNext / radio-append want. Falls back to
+     * the full removeAllTracks + reload path when the diff implies the current
+     * Sonos track was deleted (e.g. user switched playlists), which is what
+     * the user-reported "Sonos queue does not update" bug needed.
+     */
+    private suspend fun resyncSonosQueue(
+        routeId: String,
+        oldIds: List<String>,
+        newQueue: List<TrackRef>,
+        newCurrentIndex: Int,
+    ) = selectUpnpMutex.withLock {
+        val upnpRoute = upnpDiscovery.routes.value.firstOrNull { it.id == routeId }
+        val transport = upnpDiscovery.transportFor(routeId)
+        if (upnpRoute == null || transport == null) {
+            Timber.w(
+                "Sonos resync: route or transport gone for %s, dropping to local",
+                routeId,
+            )
+            activeUpnpHolder.setTarget(null)
+            selectedUpnpRouteIdInternal.value = null
+            return@withLock
+        }
+        val handledIncrementally = runCatching {
+            tryIncrementalResync(transport, oldIds, newQueue)
+        }.getOrElse { e ->
+            Timber.w(e, "Sonos incremental resync errored; falling back to full reload")
+            false
+        }
+        if (handledIncrementally) {
+            // Active was never cleared on the incremental path; clear any
+            // target that markPendingResyncIfRemote set (it didn't, for
+            // incremental cases that don't go through setMediaItems, but
+            // belt-and-suspenders).
+            activeUpnpHolder.setTarget(null)
+            return@withLock
+        }
+        // Full rebuild: ensure active is cleared so transport calls drop
+        // (markPendingResyncIfRemote may already have done this on the
+        // setMediaItems path).
+        if (activeUpnpHolder.active.value != null) {
+            activeUpnpHolder.set(null)
+            activeUpnpHolder.setTarget(routeId)
+        }
+        val outputRoute = OutputRoute.fromUpnpRoute(upnpRoute)
+        val rendering = renderingClientFor(routeId)
+        Timber.w("Sonos resync: full reload of %d tracks on %s", newQueue.size, outputRoute.name)
+        runCatching {
+            loadQueueOnSonos(transport, outputRoute, newQueue, newCurrentIndex)
+            activeUpnpHolder.set(
+                ActiveUpnp(
+                    routeId = routeId,
+                    routeName = outputRoute.name,
+                    avTransport = transport,
+                    rendering = rendering,
+                ),
+            )
+            activeUpnpHolder.setTarget(null)
+        }.onFailure { e ->
+            Timber.w(e, "Sonos resync (full) failed -- dropping to local")
+            activeUpnpHolder.setTarget(null)
+            selectedUpnpRouteIdInternal.value = null
+        }
+    }
+
+    /**
+     * Diff-based incremental Sonos queue sync. Returns true when the new
+     * queue can be produced from the old one with a remove-then-insert at
+     * the same middle slice -- the common-prefix and common-suffix portions
+     * stay untouched, and the current Sonos track must lie in the preserved
+     * prefix (otherwise the diff would orphan playback). Returns false to
+     * signal the caller to fall back to a full reload.
+     */
+    private suspend fun tryIncrementalResync(
+        transport: AVTransportClient,
+        oldIds: List<String>,
+        newQueue: List<TrackRef>,
+    ): Boolean {
+        val newIds = newQueue.map { it.id }
+        if (oldIds == newIds) return true
+        val prefixLen = commonPrefixLength(oldIds, newIds)
+        val suffixLen = commonSuffixLength(
+            oldIds.subList(prefixLen, oldIds.size),
+            newIds.subList(prefixLen, newIds.size),
+        )
+        val removedCount = oldIds.size - prefixLen - suffixLen
+        val addedCount = newIds.size - prefixLen - suffixLen
+        // Sonos's current track number is 1-based; compare against the
+        // preserved-prefix range as 0-based. If the current track is in
+        // the removed slice, incremental can't preserve playback -- caller
+        // falls back to full rebuild.
+        val currentSonosIdx0 = remoteState.trackNumber - 1
+        val canApply = currentSonosIdx0 in 0 until prefixLen
+        if (canApply) {
+            applyQueueDiff(transport, newQueue, prefixLen, removedCount, addedCount)
+        } else {
+            Timber.w(
+                "Sonos incremental: current track %d not in preserved prefix [0,%d); full rebuild",
+                currentSonosIdx0,
+                prefixLen,
+            )
+        }
+        return canApply
+    }
+
+    private suspend fun applyQueueDiff(
+        transport: AVTransportClient,
+        newQueue: List<TrackRef>,
+        prefixLen: Int,
+        removedCount: Int,
+        addedCount: Int,
+    ) {
+        if (removedCount > 0) {
+            Timber.w(
+                "Sonos incremental: RemoveTrackRangeFromQueue start=%d count=%d",
+                prefixLen + 1,
+                removedCount,
+            )
+            transport.removeTrackRangeFromQueue(
+                startingIndex = prefixLen + 1,
+                numberOfTracks = removedCount,
+            )
+        }
+        if (addedCount == 0) return
+        Timber.w(
+            "Sonos incremental: AddURIToQueue x%d starting at position %d",
+            addedCount,
+            prefixLen + 1,
+        )
+        for (i in 0 until addedCount) {
+            val ref = newQueue[prefixLen + i]
+            val token = streamTokens.mint(ref.id)
+            transport.addURIToQueue(
+                uri = token.url,
+                mime = token.mime,
+                title = token.title,
+                enqueuedURIPosition = prefixLen + i + 1,
+            )
+            if (i > 0) delay(EXTEND_THROTTLE_MS)
+        }
+    }
+
+    private fun commonPrefixLength(a: List<String>, b: List<String>): Int {
+        val limit = minOf(a.size, b.size)
+        for (i in 0 until limit) {
+            if (a[i] != b[i]) return i
+        }
+        return limit
+    }
+
+    private fun commonSuffixLength(a: List<String>, b: List<String>): Int {
+        val limit = minOf(a.size, b.size)
+        for (i in 0 until limit) {
+            if (a[a.size - 1 - i] != b[b.size - 1 - i]) return i
+        }
+        return limit
+    }
+
+    /**
+     * 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)
+        activeUpnpHolder.setTarget(null)
+        selectedUpnpRouteIdInternal.value = null
+        playerController.seekTo(capturedPositionMs)
+        if (wasPlayingRemote) playerController.play()
     }
 
     /**
@@ -163,48 +423,198 @@ class OutputPickerController @Inject constructor(
     }
 
     private fun selectSystem(route: OutputRoute) {
+        val wasUpnp = selectedUpnpRouteIdInternal.value
+        if (wasUpnp != null) {
+            val active = activeUpnpHolder.active.value
+            val capturedPositionMs = remoteState.positionMs
+            val wasPlayingRemote = remoteState.isPlaying
+            scope.launch {
+                runCatching { active?.avTransport?.stop() }
+                    .onFailure { Timber.w(it, "UPnP Stop failed during disconnect") }
+                activeUpnpHolder.set(null)
+                activeUpnpHolder.setTarget(null)
+                selectedUpnpRouteIdInternal.value = null
+                playerController.seekTo(capturedPositionMs)
+                if (wasPlayingRemote) playerController.play()
+            }
+        }
         val target = mediaRouter.routes.firstOrNull { it.id == route.id } ?: return
         mediaRouter.selectRoute(target)
     }
 
     /**
-     * Drive the UPnP renderer: mint a token for the currently playing
-     * track, set the renderer's URI, play, then pause local playback so
-     * audio yields to the speaker. Wrapped in `runCatching` at each
-     * step — token failure, transport-lookup failure, and SOAP failure
-     * each abandon the selection cleanly rather than crashing. Failures
-     * log at warn level via Timber so on-device verification can find
-     * the cause in logcat (OkHttp's logger doesn't cover our own
-     * deserialize / SOAP-parse code paths).
+     * Drive the UPnP renderer using Sonos native queue mode:
+     * clear the device's queue, load every track from our local queue
+     * via AddURIToQueue, point the transport at the queue URI, seek to
+     * the current index, and play. Wrapped in `runCatching` — SOAP
+     * failure abandons the selection cleanly.
+     *
+     * Order of operations is deliberate:
+     *  1. Pause local so the user doesn't keep hearing local audio.
+     *  2. Set target early so ForwardingPlayer drops transport taps
+     *     while the 17-second queue load is in progress.
+     *  3. Wire active LAST (after loadQueueOnSonos) so SOAP commands
+     *     are never routed to a half-loaded Sonos queue.
      */
-    private suspend fun selectUpnp(route: OutputRoute) {
-        val trackId = playerController.uiState.value.currentTrack?.id
-        if (trackId == null) {
+    private suspend fun selectUpnp(route: OutputRoute) = selectUpnpMutex.withLock {
+        val uiState = playerController.uiState.value
+        val currentTrack = uiState.currentTrack
+        if (currentTrack == null) {
             Timber.w("UPnP select skipped: no currentTrack (start playback first)")
-            return
+            return@withLock
         }
-        val transport = upnpDiscovery.transportFor(route.id)
+        // Honor Sonos topology: pick the coordinator's route when the user
+        // tapped a group row. Suppression in routesState already keeps the
+        // visible row at the coordinator's id, so this is identity in the
+        // common case -- defensive for follow-up flows.
+        val effectiveRoute = upnpDiscovery.coordinatorRouteFor(route.id)
+            ?.let { OutputRoute.fromUpnpRoute(it) } ?: route
+        val transport = upnpDiscovery.transportFor(effectiveRoute.id)
         if (transport == null) {
             Timber.w(
-                "UPnP select skipped: no transport for route id=${route.id} " +
+                "UPnP select skipped: no transport for route id=${effectiveRoute.id} " +
                     "(route disappeared or id mismatch with discovery list)",
             )
-            return
+            return@withLock
         }
+        val rendering = renderingClientFor(effectiveRoute.id)
+        // Pause local before flipping UI state -- user shouldn't keep hearing
+        // local audio while we queue up Sonos.
+        playerController.pause()
+        selectedUpnpRouteIdInternal.value = effectiveRoute.id
+        // Mark UPnP loading. ForwardingPlayer overrides drop transport commands
+        // silently while target is set but active is null -- the user's premature
+        // taps don't hit Sonos's stale state from a prior session.
+        activeUpnpHolder.setTarget(effectiveRoute.id)
         runCatching {
-            Timber.i("UPnP select: mint token for track=$trackId, route=${route.name}")
-            val token = castApi.streamToken(StreamTokenRequest(trackId = trackId))
-            Timber.i("UPnP select: SetAVTransportURI to ${token.url}")
-            transport.setAVTransportURI(token.url)
-            Timber.i("UPnP select: Play")
-            transport.play()
-            playerController.pause()
-            Timber.i("UPnP select: done")
+            loadQueueOnSonos(transport, effectiveRoute, uiState.queue, uiState.queueIndex)
+            // Wire active LAST -- SOAP path is now safe to use.
+            activeUpnpHolder.set(
+                ActiveUpnp(
+                    routeId = effectiveRoute.id,
+                    routeName = effectiveRoute.name,
+                    avTransport = transport,
+                    rendering = rendering,
+                ),
+            )
         }.onFailure { e ->
-            Timber.w(e, "UPnP select failed for route ${route.id}")
+            Timber.w(e, "UPnP select failed for route ${effectiveRoute.id}")
+            activeUpnpHolder.set(null)
+            activeUpnpHolder.setTarget(null)
+            selectedUpnpRouteIdInternal.value = null
         }
     }
 
+    private suspend fun loadQueueOnSonos(
+        transport: AVTransportClient,
+        route: OutputRoute,
+        queue: List<TrackRef>,
+        currentIndex: Int,
+    ) {
+        Timber.w("UPnP select: clear queue on %s", route.name)
+        transport.removeAllTracksFromQueue()
+        val initialEnd = (currentIndex + 1).coerceAtMost(queue.size)
+        val initialBatch = queue.subList(0, initialEnd)
+        Timber.w(
+            "UPnP select: add %d initial tracks (currentIndex=%d, totalQueue=%d)",
+            initialBatch.size, currentIndex, queue.size,
+        )
+        initialBatch.forEachIndexed { idx, ref ->
+            val token = streamTokens.mint(ref.id)
+            transport.addURIToQueue(
+                uri = token.url,
+                mime = token.mime,
+                title = token.title,
+                enqueuedURIPosition = idx + 1,
+            )
+        }
+        val coordinatorUdn = route.id.bareUdn()
+        val queueUri = "x-rincon-queue:$coordinatorUdn#0"
+        Timber.w("UPnP select: SetAVTransportURI %s", queueUri)
+        transport.setAVTransportURI(queueUri, "")
+        Timber.w("UPnP select: Seek to track %d", currentIndex + 1)
+        transport.seekToTrack(currentIndex + 1)
+        Timber.w("UPnP select: Play")
+        transport.play()
+        Timber.w("UPnP select: initial done; backgrounding remainder")
+        val remaining = queue.drop(initialEnd)
+        if (remaining.isNotEmpty()) {
+            scope.launch { extendQueueOnSonos(transport, route, remaining, initialEnd) }
+        }
+    }
+
+    /**
+     * Background-append tracks after activation. Runs concurrently with
+     * Sonos playback. Cancels if the user disconnects from this route
+     * (active.routeId changes or becomes null). Tolerates individual
+     * AddURIToQueue failures — log and continue so some tracks loaded
+     * is better than zero tracks loaded.
+     */
+    private suspend fun extendQueueOnSonos(
+        transport: AVTransportClient,
+        route: OutputRoute,
+        tracks: List<TrackRef>,
+        startPosition: Int,
+    ) {
+        Timber.w(
+            "UPnP extend: appending %d tracks starting at position %d",
+            tracks.size, startPosition + 1,
+        )
+        var consecutiveFailures = 0
+        var succeeded = 0
+        var aborted = false
+        for ((i, ref) in tracks.withIndex()) {
+            if (aborted) break
+            if (activeUpnpHolder.active.value?.routeId != route.id) {
+                Timber.w("UPnP extend: cancelled at offset %d (route changed)", i)
+                aborted = true
+            } else {
+                val outcome = runCatching {
+                    val token = streamTokens.mint(ref.id)
+                    transport.addURIToQueue(
+                        uri = token.url,
+                        mime = token.mime,
+                        title = token.title,
+                        enqueuedURIPosition = startPosition + i + 1,
+                    )
+                }
+                if (outcome.isSuccess) {
+                    consecutiveFailures = 0
+                    succeeded += 1
+                    // Throttle the burst so we don't tickle Sonos's burst-add
+                    // rejection -- logcat 2026-06-04 showed 33 consecutive
+                    // failures clustered at ~10ms intervals once offset 39 was
+                    // reached, which looks like a rate-limit kicking in. The
+                    // delay is small enough that extending 100 tracks adds
+                    // only ~5s to background work that's already async.
+                    delay(EXTEND_THROTTLE_MS)
+                } else {
+                    consecutiveFailures += 1
+                    val e = outcome.exceptionOrNull()
+                    val detail = (e as? SoapFaultException)?.let {
+                        "code=${it.code} desc=${it.description}"
+                    } ?: e?.message
+                    Timber.w(e, "UPnP extend: append failed at offset %d -- %s", i, detail)
+                    if (consecutiveFailures >= EXTEND_ABORT_AFTER_FAILURES) {
+                        Timber.w(
+                            "UPnP extend: aborting after %d consecutive failures",
+                            consecutiveFailures,
+                        )
+                        aborted = true
+                    }
+                }
+            }
+        }
+        Timber.w("UPnP extend: done (%d / %d appended)", succeeded, tracks.size)
+    }
+
+    private fun renderingClientFor(routeId: String): RenderingControlClient? {
+        val rcUrl = upnpDiscovery.routes.value
+            .firstOrNull { it.id == routeId }
+            ?.renderingControlUrl ?: return null
+        return RenderingControlClient(SoapClient(okHttp), rcUrl)
+    }
+
     private fun refresh() {
         systemRoutesInternal.value = snapshotFromRouter()
     }
@@ -214,24 +624,21 @@ class OutputPickerController @Inject constructor(
             .filter { it.matchesSelector(selector) }
             .map { OutputRoute.fromRouteInfo(it) }
         val current = OutputRoute.fromRouteInfo(mediaRouter.selectedRoute)
-        return RouteSnapshot(current = current, available = sortRoutes(current, all))
+        return RouteSnapshot(current = current, available = sortRoutes(all))
     }
 
     /**
-     * Selected first, then Bluetooth, then Wired, then BuiltIn, then
-     * Other (UPnP renderers fall in Other). Keeps the active output at
-     * the top + likely-wanted alternatives next + fallback last.
+     * BuiltIn "Phone speaker" pinned first; everything else
+     * alphabetical. Selection state is conveyed by the radio button
+     * indicator in the picker row, not by sort order.
      */
-    private fun sortRoutes(current: OutputRoute, all: List<OutputRoute>): List<OutputRoute> {
-        val rank: (OutputRoute) -> Int = { route ->
-            when {
-                route.id == current.id -> 0
-                route.kind == OutputRoute.Kind.Bluetooth -> 1
-                route.kind == OutputRoute.Kind.Wired -> 2
-                route.kind == OutputRoute.Kind.BuiltIn -> 3
-                else -> 4
-            }
-        }
-        return all.sortedBy(rank)
+    private fun sortRoutes(all: List<OutputRoute>): List<OutputRoute> {
+        val (builtIn, rest) = all.partition { it.kind == OutputRoute.Kind.BuiltIn }
+        return builtIn + rest.sortedBy { it.name.lowercase() }
+    }
+
+    private companion object {
+        const val EXTEND_ABORT_AFTER_FAILURES = 3
+        const val EXTEND_THROTTLE_MS = 50L
     }
 }

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

@@ -4,8 +4,11 @@ import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.heightIn
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.Icon
 import androidx.compose.material3.MaterialTheme
@@ -69,12 +72,19 @@ fun OutputPickerSheet(
                 color = MaterialTheme.colorScheme.onSurface,
                 modifier = Modifier.padding(vertical = 8.dp),
             )
-            snapshot.available.forEach { route ->
-                RouteRow(
-                    route = route,
-                    isSelected = route.id == snapshot.current.id,
-                    onClick = { onRouteSelected(route) },
-                )
+            LazyColumn(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .heightIn(max = ROUTE_LIST_MAX_HEIGHT_DP.dp),
+                verticalArrangement = Arrangement.spacedBy(4.dp),
+            ) {
+                items(items = snapshot.available, key = { it.id }) { route ->
+                    RouteRow(
+                        route = route,
+                        isSelected = route.id == snapshot.current.id,
+                        onClick = { onRouteSelected(route) },
+                    )
+                }
             }
             if (permissionDenied) {
                 PermissionHintRow()
@@ -198,3 +208,4 @@ private fun defaultSubtitle(route: OutputRoute): String = when (route.kind) {
 
 private const val ROW_ICON_DP = 24
 private const val HINT_ICON_DP = 20
+private const val ROUTE_LIST_MAX_HEIGHT_DP = 400

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

@@ -24,6 +24,7 @@ import javax.inject.Inject
 @HiltViewModel
 class OutputPickerViewModel @Inject constructor(
     private val controller: OutputPickerController,
+    private val activeUpnpHolder: ActiveUpnpHolder,
 ) : ViewModel() {
 
     val routes: StateFlow<RouteSnapshot> = controller.routesState
@@ -33,6 +34,9 @@ class OutputPickerViewModel @Inject constructor(
             initialValue = controller.routesState.value,
         )
 
+    val activeUpnp: StateFlow<ActiveUpnp?> = activeUpnpHolder.active
+        .stateIn(viewModelScope, SharingStarted.WhileSubscribed(STOP_TIMEOUT_MS), null)
+
     private val sheetVisibleInternal = MutableStateFlow(false)
     val sheetVisible: StateFlow<Boolean> = sheetVisibleInternal.asStateFlow()
 

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

@@ -3,12 +3,13 @@ package com.fabledsword.minstrel.player.output.upnp
 import okhttp3.HttpUrl
 
 /**
- * High-level wrapper for the UPnP AVTransport service. Three calls
- * for v1: SetAVTransportURI / Play / Stop. Pause + Seek deferred
- * until we have hardware in the loop to verify each device's quirks
- * (Sonos and BubbleUPnP accept the standard shape; some smart TVs
- * reject Pause without DIDL).
+ * High-level wrapper for the UPnP AVTransport service.
+ * Covers SetAVTransportURI / Play / Pause / Stop / Seek /
+ * GetPositionInfo / GetTransportInfo / queue management
+ * (RemoveAllTracksFromQueue, AddURIToQueue, Next, Previous, SeekToTrack).
  */
+// One method per AVTransport SOAP verb; splitting would obscure the 1:1 protocol mapping.
+@Suppress("TooManyFunctions")
 class AVTransportClient(
     private val soap: SoapClient,
     private val controlUrl: HttpUrl,
@@ -26,6 +27,135 @@ class AVTransportClient(
         )
     }
 
+    /**
+     * Convenience overload that builds DIDL-Lite metadata around [uri]
+     * + [mime] + [title] and forwards to [setAVTransportURI]. Sonos
+     * rejects empty DIDL with vendor error 1023; this constructs the
+     * minimal-but-Sonos-acceptable shape:
+     *   <DIDL-Lite>
+     *     <item id="0" parentID="-1" restricted="1">
+     *       <dc:title>...</dc:title>
+     *       <upnp:class>object.item.audioItem.musicTrack</upnp:class>
+     *       <res protocolInfo="http-get:*:<mime>:*">...</res>
+     *     </item>
+     *   </DIDL-Lite>
+     * Generic UPnP renderers tolerate this shape too — there's no
+     * downside to always sending it. Title falls back to "Minstrel"
+     * when the caller doesn't supply one.
+     */
+    suspend fun setAVTransportURIWithMetadata(uri: String, mime: String, title: String) {
+        val safeTitle = title.ifBlank { "Minstrel" }
+        setAVTransportURI(uri, buildDidlLite(uri, mime, safeTitle))
+    }
+
+    /**
+     * Remove all tracks from the renderer's queue. UPnP action name is
+     * `RemoveAllTracksFromQueue`. Used at activation time to clear out any
+     * leftover queue from prior sessions before loading our local queue.
+     */
+    suspend fun removeAllTracksFromQueue() {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "RemoveAllTracksFromQueue",
+            args = mapOf("InstanceID" to "0"),
+        )
+    }
+
+    /**
+     * Remove a contiguous range of tracks from the renderer's native queue.
+     * Sonos-specific extension to AVTransport; `UpdateID=0` skips the queue-
+     * version check so this works without first calling GetQueue to learn
+     * the current update id.
+     *
+     * [startingIndex] is 1-based per Sonos convention; [numberOfTracks] is
+     * the count to remove. Used by OutputPickerController's incremental
+     * queue resync path (radio-append: remove tail, then AddURIToQueue
+     * the new items).
+     */
+    suspend fun removeTrackRangeFromQueue(startingIndex: Int, numberOfTracks: Int) {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "RemoveTrackRangeFromQueue",
+            args = mapOf(
+                "InstanceID" to "0",
+                "UpdateID" to "0",
+                "StartingIndex" to startingIndex.toString(),
+                "NumberOfTracks" to numberOfTracks.toString(),
+            ),
+        )
+    }
+
+    /**
+     * Append a track to the renderer's queue. Sonos returns the assigned
+     * track number + new total queue length in the response, but we don't
+     * read those (we know our intended position). DIDL-Lite metadata is
+     * required; reuses the same shape as [setAVTransportURIWithMetadata].
+     *
+     * [enqueuedURIPosition] is 1-based; 0 means "append to end" per UPnP.
+     * Our caller passes 1, 2, 3, ... to ensure stable order.
+     */
+    suspend fun addURIToQueue(
+        uri: String,
+        mime: String,
+        title: String,
+        enqueuedURIPosition: Int = 0,
+    ) {
+        val safeTitle = title.ifBlank { "Minstrel" }
+        val didl = buildDidlLite(uri, mime, safeTitle)
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "AddURIToQueue",
+            args = mapOf(
+                "InstanceID" to "0",
+                "EnqueuedURI" to uri,
+                "EnqueuedURIMetaData" to didl,
+                "DesiredFirstTrackNumberEnqueued" to enqueuedURIPosition.toString(),
+                "EnqueueAsNext" to "0",
+            ),
+        )
+    }
+
+    /** Skip to the next track in the renderer's queue. */
+    suspend fun next() {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "Next",
+            args = mapOf("InstanceID" to "0"),
+        )
+    }
+
+    /** Skip to the previous track in the renderer's queue. */
+    suspend fun previous() {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "Previous",
+            args = mapOf("InstanceID" to "0"),
+        )
+    }
+
+    /**
+     * Seek to a specific track in the queue. UPnP Seek unit "TRACK_NR";
+     * target is the 1-based track index. Separate from the existing
+     * [seek] which uses unit REL_TIME for position-within-track.
+     */
+    suspend fun seekToTrack(trackNumber: Int) {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "Seek",
+            args = mapOf(
+                "InstanceID" to "0",
+                "Unit" to "TRACK_NR",
+                "Target" to trackNumber.toString(),
+            ),
+        )
+    }
+
     suspend fun play() {
         soap.call(
             controlUrl = controlUrl,
@@ -35,6 +165,15 @@ class AVTransportClient(
         )
     }
 
+    suspend fun pause() {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "Pause",
+            args = mapOf("InstanceID" to "0"),
+        )
+    }
+
     suspend fun stop() {
         soap.call(
             controlUrl = controlUrl,
@@ -44,7 +183,114 @@ class AVTransportClient(
         )
     }
 
+    suspend fun seek(positionMs: Long) {
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "Seek",
+            args = mapOf(
+                "InstanceID" to "0",
+                "Unit" to "REL_TIME",
+                "Target" to formatHhMmSs(positionMs),
+            ),
+        )
+    }
+
+    suspend fun getPositionInfo(): PositionInfo {
+        val result = soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "GetPositionInfo",
+            args = mapOf("InstanceID" to "0"),
+        )
+        return PositionInfo(
+            track = result["Track"]?.toIntOrNull() ?: 0,
+            trackUri = result["TrackURI"].orEmpty(),
+            relTimeMs = parseHhMmSs(result["RelTime"].orEmpty()),
+            trackDurationMs = parseHhMmSs(result["TrackDuration"].orEmpty()),
+        )
+    }
+
+    suspend fun getTransportInfo(): TransportInfo {
+        val result = soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "GetTransportInfo",
+            args = mapOf("InstanceID" to "0"),
+        )
+        val state = when (result["CurrentTransportState"]) {
+            "PLAYING" -> TransportState.PLAYING
+            "PAUSED_PLAYBACK" -> TransportState.PAUSED
+            "STOPPED" -> TransportState.STOPPED
+            "TRANSITIONING" -> TransportState.TRANSITIONING
+            else -> TransportState.UNKNOWN
+        }
+        return TransportInfo(state)
+    }
+
+    private fun buildDidlLite(uri: String, mime: String, title: String): String {
+        // Sonos requires (a) the rinconnetworks namespace declared on
+        // <DIDL-Lite> even if we don't use Rincon elements directly, and
+        // (b) a <desc id="cdudn"> element identifying the URI as an
+        // external (non-Sonos-library) source. Without those, Sonos
+        // discards our metadata content and regenerates its own with
+        // class=object.item and the URL query string as the title
+        // (logcat 2026-06-04 confirmed). Match SoCo's pattern.
+        val safeTitle = title.ifBlank { "Minstrel" }
+        return buildString {
+            append("<DIDL-Lite ")
+            append("xmlns=\"urn:schemas-upnp-org:metadata-1-0/DIDL-Lite/\" ")
+            append("xmlns:dc=\"http://purl.org/dc/elements/1.1/\" ")
+            append("xmlns:upnp=\"urn:schemas-upnp-org:metadata-1-0/upnp/\" ")
+            append("xmlns:r=\"urn:schemas-rinconnetworks-com:metadata-1-0/\">")
+            append("<item id=\"-1\" parentID=\"-1\" restricted=\"true\">")
+            append("<dc:title>").append(xmlEscape(safeTitle)).append("</dc:title>")
+            append("<upnp:class>object.item.audioItem.musicTrack</upnp:class>")
+            append("<res protocolInfo=\"http-get:*:").append(xmlEscape(mime))
+            append(":*\">").append(xmlEscape(uri)).append("</res>")
+            append("<desc id=\"cdudn\" ")
+            append("nameSpace=\"urn:schemas-rinconnetworks-com:metadata-1-0/\">")
+            append("RINCON_AssociatedZPUDN")
+            append("</desc>")
+            append("</item>")
+            append("</DIDL-Lite>")
+        }
+    }
+
+    private fun formatHhMmSs(positionMs: Long): String {
+        val totalSec = (positionMs / MILLIS_PER_SECOND).coerceAtLeast(0)
+        val h = totalSec / SECONDS_PER_HOUR
+        val m = (totalSec % SECONDS_PER_HOUR) / SECONDS_PER_MINUTE
+        val s = totalSec % SECONDS_PER_MINUTE
+        return "%d:%02d:%02d".format(h, m, s)
+    }
+
+    private fun parseHhMmSs(raw: String): Long {
+        val parts = raw.split(':').mapNotNull { it.trim().toLongOrNull() }
+        return if (parts.size == EXPECTED_HMS_PARTS) {
+            val (h, m, s) = parts
+            ((h * SECONDS_PER_HOUR) + (m * SECONDS_PER_MINUTE) + s) * MILLIS_PER_SECOND
+        } else {
+            0L
+        }
+    }
+
     private companion object {
         const val SERVICE_TYPE = "urn:schemas-upnp-org:service:AVTransport:1"
+        const val MILLIS_PER_SECOND = 1000L
+        const val SECONDS_PER_MINUTE = 60L
+        const val SECONDS_PER_HOUR = 3600L
+        const val EXPECTED_HMS_PARTS = 3
     }
 }
+
+data class PositionInfo(
+    val track: Int,
+    val trackUri: String,
+    val relTimeMs: Long,
+    val trackDurationMs: Long,
+)
+
+enum class TransportState { PLAYING, PAUSED, STOPPED, TRANSITIONING, UNKNOWN }
+
+data class TransportInfo(val state: TransportState)

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

@@ -22,10 +22,12 @@ data class DeviceDescription(
     val modelName: String,
     val avTransportControlUrl: HttpUrl,
     val renderingControlUrl: HttpUrl?,
+    val zoneGroupTopologyControlUrl: HttpUrl? = null,
 ) {
     companion object {
         private const val AVT_SERVICE_TYPE = "urn:schemas-upnp-org:service:AVTransport:1"
         private const val RC_SERVICE_TYPE = "urn:schemas-upnp-org:service:RenderingControl:1"
+        private const val ZGT_SERVICE_TYPE = "urn:schemas-upnp-org:service:ZoneGroupTopology:1"
 
         private const val TAG_SERVICE = "service"
         private const val TAG_UDN = "UDN"
@@ -43,6 +45,7 @@ data class DeviceDescription(
          */
         fun parse(xml: String, base: HttpUrl): DeviceDescription? {
             val parser = XmlPullParserFactory.newInstance().newPullParser().apply {
+                setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, true)
                 setInput(xml.reader())
             }
             val acc = ParseState()
@@ -58,6 +61,7 @@ data class DeviceDescription(
                 modelName = acc.modelName,
                 avTransportControlUrl = avt,
                 renderingControlUrl = acc.rcControlUrl,
+                zoneGroupTopologyControlUrl = acc.zgtControlUrl,
             )
         }
 
@@ -91,6 +95,7 @@ data class DeviceDescription(
             when (acc.serviceType) {
                 AVT_SERVICE_TYPE -> acc.avtControlUrl = resolved
                 RC_SERVICE_TYPE -> acc.rcControlUrl = resolved
+                ZGT_SERVICE_TYPE -> acc.zgtControlUrl = resolved
             }
             acc.inService = false
         }
@@ -115,6 +120,7 @@ data class DeviceDescription(
         var modelName: String = ""
         var avtControlUrl: HttpUrl? = null
         var rcControlUrl: HttpUrl? = null
+        var zgtControlUrl: HttpUrl? = null
         var inService: Boolean = false
         var serviceType: String = ""
         var serviceControlUrl: String = ""

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

@@ -0,0 +1,44 @@
+package com.fabledsword.minstrel.player.output.upnp
+
+import okhttp3.HttpUrl
+
+/**
+ * RenderingControl service wrapper for hardware-volume routing while a
+ * UPnP route is active. GetVolume seeds an in-memory cache; SetVolume
+ * is invoked by NowPlayingScreen's volume-key interceptor. Clamps to
+ * the UPnP-standard 0..100 range.
+ */
+class RenderingControlClient(
+    private val soap: SoapClient,
+    private val controlUrl: HttpUrl,
+) {
+    suspend fun getVolume(channel: String = "Master"): Int {
+        val args = soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "GetVolume",
+            args = mapOf("InstanceID" to "0", "Channel" to channel),
+        )
+        return args["CurrentVolume"]?.toIntOrNull() ?: 0
+    }
+
+    suspend fun setVolume(volume: Int, channel: String = "Master") {
+        val clamped = volume.coerceIn(VOLUME_MIN, VOLUME_MAX)
+        soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "SetVolume",
+            args = mapOf(
+                "InstanceID" to "0",
+                "Channel" to channel,
+                "DesiredVolume" to clamped.toString(),
+            ),
+        )
+    }
+
+    private companion object {
+        const val SERVICE_TYPE = "urn:schemas-upnp-org:service:RenderingControl:1"
+        const val VOLUME_MIN = 0
+        const val VOLUME_MAX = 100
+    }
+}

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

@@ -1,5 +1,6 @@
 package com.fabledsword.minstrel.player.output.upnp
 
+import java.util.concurrent.atomic.AtomicInteger
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.withContext
 import okhttp3.HttpUrl
@@ -8,6 +9,7 @@ import okhttp3.Request
 import okhttp3.RequestBody.Companion.toRequestBody
 import org.xmlpull.v1.XmlPullParser
 import org.xmlpull.v1.XmlPullParserFactory
+import timber.log.Timber
 
 /**
  * Minimal SOAP/UPnP envelope builder + POST. Hand-rolled rather than
@@ -25,6 +27,7 @@ import org.xmlpull.v1.XmlPullParserFactory
  */
 class SoapClient(
     private val okHttp: OkHttpClient,
+    private val onRawResponse: ((action: String, body: String) -> Unit)? = null,
 ) {
     suspend fun call(
         controlUrl: HttpUrl,
@@ -41,6 +44,7 @@ class SoapClient(
             .build()
         okHttp.newCall(request).execute().use { response ->
             val body = response.body?.string().orEmpty()
+            onRawResponse?.invoke(action, body)
             if (!response.isSuccessful) {
                 throw SoapFaultException(faultCodeOf(body), faultDescriptionOf(body))
             }
@@ -69,15 +73,9 @@ class SoapClient(
         append("</s:Envelope>")
     }
 
-    private fun xmlEscape(v: String): String = v
-        .replace("&", "&amp;")
-        .replace("<", "&lt;")
-        .replace(">", "&gt;")
-        .replace("\"", "&quot;")
-        .replace("'", "&apos;")
-
     private fun parseResponseArgs(body: String, action: String): Map<String, String> {
         val parser = XmlPullParserFactory.newInstance().newPullParser().apply {
+            setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, true)
             setInput(body.reader())
         }
         val responseTag = "${action}Response"
@@ -102,7 +100,7 @@ class SoapClient(
             } else {
                 if (inResponse) {
                     val name = parser.name
-                    val text = runCatching { parser.nextText() }.getOrDefault("")
+                    val text = readElementContent(parser, name)
                     args[name] = text
                 }
                 inResponse
@@ -112,6 +110,59 @@ class SoapClient(
         else -> inResponse
     }
 
+    /**
+     * Read the content of the currently-started element. Try nextText() first
+     * (works when the content is text -- escaped XML included). If that throws
+     * (because the content is nested elements), manually walk to the matching
+     * END_TAG, accumulating text and re-serializing child elements.
+     *
+     * Some Sonos firmware sends the GetZoneGroupState payload as nested XML
+     * elements without escaping; this fallback recovers that path.
+     */
+    private fun readElementContent(parser: XmlPullParser, tagName: String): String {
+        return runCatching { parser.nextText() }.getOrElse {
+            readUntilEndTag(parser, tagName)
+        }
+    }
+
+    private fun readUntilEndTag(parser: XmlPullParser, tagName: String): String {
+        val sb = StringBuilder()
+        var depth = 1
+        var done = false
+        while (!done && depth > 0) {
+            when (parser.next()) {
+                XmlPullParser.START_TAG -> {
+                    appendStartTag(sb, parser)
+                    depth += 1
+                }
+                XmlPullParser.END_TAG -> {
+                    depth -= 1
+                    if (depth == 0 && parser.name == tagName) {
+                        done = true
+                    } else {
+                        sb.append("</").append(parser.name).append('>')
+                    }
+                }
+                XmlPullParser.TEXT -> sb.append(parser.text.orEmpty())
+                XmlPullParser.END_DOCUMENT -> done = true
+                else -> Unit
+            }
+        }
+        return sb.toString()
+    }
+
+    private fun appendStartTag(sb: StringBuilder, parser: XmlPullParser) {
+        sb.append('<').append(parser.name)
+        for (i in 0 until parser.attributeCount) {
+            sb.append(' ')
+                .append(parser.getAttributeName(i))
+                .append("=\"")
+                .append(parser.getAttributeValue(i))
+                .append('"')
+        }
+        sb.append('>')
+    }
+
     private fun faultCodeOf(body: String): String =
         extractBetween(body, "<errorCode>", "</errorCode>") ?: "unknown"
 
@@ -138,3 +189,42 @@ class SoapClient(
  */
 class SoapFaultException(val code: String, val description: String) :
     Exception("SOAP fault $code: $description")
+
+private const val MAX_DIAGNOSTIC_RESPONSES = 6  // 3 polls x 2 action types
+private const val MAX_BODY_LOG_CHARS = 2048
+
+/**
+ * Returns a [SoapClient] that logs the raw response body for the first
+ * [MAX_DIAGNOSTIC_RESPONSES] calls for actions in [DIAGNOSTIC_ACTIONS]
+ * (GetPositionInfo, GetTransportInfo, GetZoneGroupState). After that the
+ * callback is a no-op so there is no persistent log spam. Logged at WARN
+ * so release builds capture it without a separate log-level override.
+ */
+internal fun loggingSoapClient(okHttp: OkHttpClient, label: String): SoapClient {
+    val counter = AtomicInteger(0)
+    return SoapClient(okHttp) { action, body ->
+        if (action !in DIAGNOSTIC_ACTIONS) return@SoapClient
+        val n = counter.incrementAndGet()
+        if (n <= MAX_DIAGNOSTIC_RESPONSES) {
+            Timber.w(
+                "UPnP %s response #%d (%s): %s",
+                label, n, action,
+                body.take(MAX_BODY_LOG_CHARS),
+            )
+        }
+    }
+}
+
+private val DIAGNOSTIC_ACTIONS = setOf(
+    "GetPositionInfo",
+    "GetTransportInfo",
+    "GetZoneGroupState",
+)
+
+/** XML-escapes a string value for embedding as text content inside a SOAP envelope. */
+internal fun xmlEscape(v: String): String = v
+    .replace("&", "&amp;")
+    .replace("<", "&lt;")
+    .replace(">", "&gt;")
+    .replace("\"", "&quot;")
+    .replace("'", "&apos;")

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

@@ -1,7 +1,10 @@
+@file:Suppress("TooManyFunctions") // discovery + Sonos topology + transport-lookup density
 package com.fabledsword.minstrel.player.output.upnp
 
 import android.content.Context
 import com.fabledsword.minstrel.di.ApplicationScope
+import com.fabledsword.minstrel.player.output.upnp.sonos.SonosZoneGroup
+import com.fabledsword.minstrel.player.output.upnp.sonos.ZoneGroupTopologyClient
 import dagger.hilt.android.qualifiers.ApplicationContext
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -13,6 +16,7 @@ import okhttp3.HttpUrl
 import okhttp3.HttpUrl.Companion.toHttpUrlOrNull
 import okhttp3.OkHttpClient
 import okhttp3.Request
+import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -44,6 +48,9 @@ class UpnpDiscoveryController @Inject constructor(
     private val routesInternal = MutableStateFlow<List<UpnpRoute>>(emptyList())
     val routes: StateFlow<List<UpnpRoute>> = routesInternal.asStateFlow()
 
+    private val sonosTopologyInternal = MutableStateFlow<List<SonosZoneGroup>>(emptyList())
+    val sonosTopology: StateFlow<List<SonosZoneGroup>> = sonosTopologyInternal.asStateFlow()
+
     init {
         ssdp.start(appScope)
         // appScope is process-lifetime (SupervisorJob + Dispatchers.Default),
@@ -83,13 +90,77 @@ class UpnpDiscoveryController @Inject constructor(
      */
     fun transportFor(routeId: String): AVTransportClient? {
         val route = routesInternal.value.firstOrNull { it.id == routeId } ?: return null
-        return AVTransportClient(SoapClient(okHttp), route.avTransportControlUrl)
+        return AVTransportClient(
+            loggingSoapClient(okHttp, route.name),
+            route.avTransportControlUrl,
+        )
     }
 
     private suspend fun handleDiscovery(locationUrl: String) {
         val route = fetchRoute(locationUrl) ?: return
-        routesInternal.value =
-            routesInternal.value.filterNot { it.id == route.id } + route
+        upsertRoute(route)
+        if (route.manufacturer.contains("Sonos", ignoreCase = true)) {
+            refreshSonosTopology(route)
+        }
+    }
+
+    private fun upsertRoute(route: UpnpRoute) {
+        val current = routesInternal.value
+        val idx = current.indexOfFirst { it.id == route.id }
+        routesInternal.value = if (idx < 0) {
+            current + route
+        } else {
+            current.toMutableList().also { it[idx] = route }
+        }
+    }
+
+    private suspend fun refreshSonosTopology(anySonos: UpnpRoute) {
+        val zgtUrl = anySonos.zoneGroupTopologyControlUrl ?: run {
+            Timber.w(
+                "Sonos %s has no ZoneGroupTopology URL -- topology grouping disabled",
+                anySonos.id,
+            )
+            return
+        }
+        val groups = runCatching {
+            ZoneGroupTopologyClient(
+                loggingSoapClient(okHttp, "ZGT-${anySonos.id}"),
+                zgtUrl,
+            ).getZoneGroupState()
+        }
+            .onFailure { Timber.w(it, "refreshSonosTopology failed for %s", anySonos.id) }
+            .getOrNull() ?: return
+        Timber.w(
+            "Sonos topology refreshed for %s: %d group(s)",
+            anySonos.id,
+            groups.size,
+        )
+        sonosTopologyInternal.value = groups
+    }
+
+    /**
+     * Returns the coordinator UDN's full route for the group [udn] belongs
+     * to, or null if topology hasn't loaded / the udn is in no group. UDN
+     * normalization strips the "uuid:" prefix because DeviceDescription's
+     * <UDN> carries it but Sonos's ZoneGroupState Coordinator attr does not.
+     */
+    fun coordinatorRouteFor(udn: String): UpnpRoute? {
+        val bare = udn.bareUdn()
+        val coord = sonosTopologyInternal.value
+            .firstOrNull { g -> g.members.any { it.udn.bareUdn() == bare } }
+            ?.coordinatorUdn ?: return null
+        return routesInternal.value.firstOrNull { it.id.bareUdn() == coord.bareUdn() }
+    }
+
+    /**
+     * UDNs of every NON-coordinator Sonos group member. The picker
+     * controller suppresses these from the visible list.
+     */
+    fun nonCoordinatorMemberUdns(): Set<String> {
+        return sonosTopologyInternal.value.flatMap { g ->
+            g.members.map { it.udn.bareUdn() }
+                .filter { it != g.coordinatorUdn.bareUdn() }
+        }.toSet()
     }
 
     /**
@@ -111,6 +182,7 @@ class UpnpDiscoveryController @Inject constructor(
                     modelName = desc.modelName,
                     avTransportControlUrl = desc.avTransportControlUrl,
                     renderingControlUrl = desc.renderingControlUrl,
+                    zoneGroupTopologyControlUrl = desc.zoneGroupTopologyControlUrl,
                 )
             }
     }
@@ -155,3 +227,20 @@ class UpnpDiscoveryController @Inject constructor(
         val IP_SUFFIX_REGEX = Regex("""\s*\(\d+\.\d+\.\d+\.\d+\)$""")
     }
 }
+
+/**
+ * Normalize a Sonos UDN to its bare RINCON form for cross-comparison.
+ *
+ * Three places use UDN strings with different conventions:
+ *  - DeviceDescription's <UDN> tag carries the `uuid:` prefix.
+ *  - Sonos exposes one UDN per embedded device. The MediaRenderer adds
+ *    a `_MR` suffix and the MediaServer adds `_MS`.
+ *  - The ZGT GetZoneGroupState response uses bare `RINCON_xxx` with
+ *    neither the `uuid:` prefix nor any device suffix.
+ *
+ * To compare any pair of those, strip the prefix and the suffix so
+ * everything reduces to the underlying speaker identity.
+ */
+internal fun String.bareUdn(): String = removePrefix("uuid:")
+    .removeSuffix("_MR")
+    .removeSuffix("_MS")

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

@@ -7,10 +7,10 @@ import okhttp3.HttpUrl
  * Bose SoundTouch, generic DLNA renderers). Lifted out of the SOAP /
  * SSDP details so the picker UI consumes a narrow domain shape.
  *
- * Generic UPnP only for THIS slice — Sonos-specific grouping value-adds
- * (group join/leave, zone topology) live in a separate Sonos extension
- * scoped in
- * docs/superpowers/specs/2026-06-03-android-output-picker-upnp-scope.md.
+ * Sonos devices additionally populate [zoneGroupTopologyControlUrl] from the
+ * ZoneGroupTopology service in their device description; non-Sonos devices
+ * leave it null. The discovery controller uses that URL to aggregate stereo
+ * pairs and multi-speaker groups into single picker rows.
  *
  * [id] is the device UDN (e.g. `uuid:RINCON_ABC...`). [name] is the
  * raw `<friendlyName>` straight from the device description — callers
@@ -24,4 +24,5 @@ data class UpnpRoute(
     val modelName: String,
     val avTransportControlUrl: HttpUrl,
     val renderingControlUrl: HttpUrl?,
+    val zoneGroupTopologyControlUrl: HttpUrl? = null,
 )

android/app/src/main/java/com/fabledsword/minstrel/player/output/upnp/sonos/SonosTopology.kt

@@ -0,0 +1,90 @@
+package com.fabledsword.minstrel.player.output.upnp.sonos
+
+import org.xmlpull.v1.XmlPullParser
+import org.xmlpull.v1.XmlPullParserFactory
+
+/**
+ * One Sonos zone group as exposed by ZoneGroupTopology.GetZoneGroupState.
+ * Stereo pairs and multi-speaker groups all appear as one group with
+ * multiple members; one member is the coordinator we send SOAP to.
+ */
+data class SonosZoneGroup(
+    val coordinatorUdn: String,
+    val name: String,
+    val members: List<SonosZoneMember>,
+)
+
+data class SonosZoneMember(
+    val udn: String,
+    val roomName: String,
+    val location: String?,
+    val channelMapSet: String?,
+)
+
+object SonosTopology {
+
+    fun parse(xml: String): List<SonosZoneGroup> {
+        val effective = if (xml.contains("&lt;ZoneGroup")) {
+            unescapeXmlEntities(xml)
+        } else {
+            xml
+        }
+        return runCatching { parseStrict(effective) }.getOrDefault(emptyList())
+    }
+
+    private fun unescapeXmlEntities(s: String): String = s
+        .replace("&lt;", "<")
+        .replace("&gt;", ">")
+        .replace("&quot;", "\"")
+        .replace("&apos;", "'")
+        .replace("&amp;", "&")  // must be last to avoid double-decoding
+
+    private fun parseStrict(xml: String): List<SonosZoneGroup> {
+        val parser = XmlPullParserFactory.newInstance().newPullParser().apply {
+            setFeature(XmlPullParser.FEATURE_PROCESS_NAMESPACES, true)
+            setInput(xml.reader())
+        }
+        val groups = mutableListOf<SonosZoneGroup>()
+        var currentCoordinator: String? = null
+        var currentMembers: MutableList<SonosZoneMember>? = null
+        while (parser.eventType != XmlPullParser.END_DOCUMENT) {
+            when (parser.eventType) {
+                XmlPullParser.START_TAG -> when (parser.name) {
+                    TAG_ZONE_GROUP -> {
+                        currentCoordinator = parser.getAttributeValue(null, ATTR_COORDINATOR)
+                        currentMembers = mutableListOf()
+                    }
+                    TAG_ZONE_GROUP_MEMBER -> currentMembers?.add(memberOf(parser))
+                }
+                XmlPullParser.END_TAG -> if (parser.name == TAG_ZONE_GROUP) {
+                    val members = currentMembers ?: emptyList()
+                    val coord = currentCoordinator
+                    if (coord != null && members.isNotEmpty()) {
+                        val name = members.firstOrNull { it.udn == coord }?.roomName
+                            ?: members.first().roomName
+                        groups.add(SonosZoneGroup(coord, name, members))
+                    }
+                    currentCoordinator = null
+                    currentMembers = null
+                }
+            }
+            parser.next()
+        }
+        return groups
+    }
+
+    private fun memberOf(parser: XmlPullParser): SonosZoneMember = SonosZoneMember(
+        udn = parser.getAttributeValue(null, ATTR_UUID).orEmpty(),
+        roomName = parser.getAttributeValue(null, ATTR_ZONE_NAME).orEmpty(),
+        location = parser.getAttributeValue(null, ATTR_LOCATION),
+        channelMapSet = parser.getAttributeValue(null, ATTR_CHANNEL_MAP_SET),
+    )
+
+    private const val TAG_ZONE_GROUP = "ZoneGroup"
+    private const val TAG_ZONE_GROUP_MEMBER = "ZoneGroupMember"
+    private const val ATTR_COORDINATOR = "Coordinator"
+    private const val ATTR_UUID = "UUID"
+    private const val ATTR_ZONE_NAME = "ZoneName"
+    private const val ATTR_LOCATION = "Location"
+    private const val ATTR_CHANNEL_MAP_SET = "ChannelMapSet"
+}

android/app/src/main/java/com/fabledsword/minstrel/player/output/upnp/sonos/ZoneGroupTopologyClient.kt

@@ -0,0 +1,37 @@
+package com.fabledsword.minstrel.player.output.upnp.sonos
+
+import com.fabledsword.minstrel.player.output.upnp.SoapClient
+import okhttp3.HttpUrl
+import timber.log.Timber
+
+/**
+ * Sonos's proprietary ZoneGroupTopology service. Same SOAP shape as a
+ * standard UPnP service, exposed on port 1400 at
+ * /ZoneGroupTopology/Control. GetZoneGroupState returns the full
+ * network topology as one XML doc wrapped inside a SOAP arg.
+ */
+class ZoneGroupTopologyClient(
+    private val soap: SoapClient,
+    private val controlUrl: HttpUrl,
+) {
+    suspend fun getZoneGroupState(): List<SonosZoneGroup> {
+        val args = soap.call(
+            controlUrl = controlUrl,
+            serviceType = SERVICE_TYPE,
+            action = "GetZoneGroupState",
+            args = emptyMap(),
+        )
+        val inner = args["ZoneGroupState"].orEmpty()
+        Timber.w(
+            "ZGT extracted ZoneGroupState (%d chars): %s",
+            inner.length,
+            inner.take(ZGT_LOG_TRUNCATE_CHARS),
+        )
+        return SonosTopology.parse(inner)
+    }
+
+    private companion object {
+        const val SERVICE_TYPE = "urn:schemas-upnp-org:service:ZoneGroupTopology:1"
+        const val ZGT_LOG_TRUNCATE_CHARS = 2048
+    }
+}

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

@@ -17,6 +17,7 @@ import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.width
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
@@ -164,6 +165,7 @@ fun MiniPlayer(
             MiniRow(
                 track = track,
                 isPlaying = state.isPlaying,
+                isUpnpLoading = state.isUpnpLoading,
                 isLiked = isLiked,
                 onExpandClick = onExpandClick,
                 onPlayPause = { if (state.isPlaying) viewModel.pause() else viewModel.play() },
@@ -204,6 +206,7 @@ private fun MiniProgressFill(positionMs: Long, durationMs: Long) {
 private fun MiniRow(
     track: TrackRef,
     isPlaying: Boolean,
+    isUpnpLoading: Boolean,
     isLiked: Boolean,
     onExpandClick: () -> Unit,
     onPlayPause: () -> Unit,
@@ -248,15 +251,39 @@ private fun MiniRow(
         }
         LikeButton(liked = isLiked, onToggle = onToggleLike)
         TransportButton(icon = Lucide.SkipBack, description = "Previous", onClick = onPrev)
-        TransportButton(
-            icon = if (isPlaying) Lucide.Pause else Lucide.Play,
-            description = if (isPlaying) "Pause" else "Play",
+        MiniPlayPauseButton(
+            isPlaying = isPlaying,
+            isUpnpLoading = isUpnpLoading,
             onClick = onPlayPause,
         )
         TransportButton(icon = Lucide.SkipForward, description = "Next", onClick = onNext)
     }
 }
 
+@Composable
+private fun MiniPlayPauseButton(
+    isPlaying: Boolean,
+    isUpnpLoading: Boolean,
+    onClick: () -> Unit,
+) {
+    IconButton(onClick = onClick, enabled = !isUpnpLoading) {
+        if (isUpnpLoading) {
+            CircularProgressIndicator(
+                modifier = Modifier.size(MINI_PLAY_PAUSE_SPINNER_DP.dp),
+                strokeWidth = 2.dp,
+            )
+        } else {
+            Icon(
+                imageVector = if (isPlaying) Lucide.Pause else Lucide.Play,
+                contentDescription = if (isPlaying) "Pause" else "Play",
+                tint = MaterialTheme.colorScheme.onSurface,
+            )
+        }
+    }
+}
+
+private const val MINI_PLAY_PAUSE_SPINNER_DP = 24
+
 @Composable
 private fun TransportButton(
     icon: androidx.compose.ui.graphics.vector.ImageVector,

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

@@ -8,6 +8,7 @@ import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.compose.animation.ExperimentalSharedTransitionApi
 import androidx.compose.foundation.background
+import androidx.compose.foundation.focusable
 import androidx.compose.foundation.rememberScrollState
 import androidx.compose.foundation.verticalScroll
 import androidx.compose.foundation.layout.Arrangement
@@ -25,6 +26,7 @@ import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.widthIn
 import androidx.compose.foundation.shape.CircleShape
 import androidx.compose.foundation.shape.RoundedCornerShape
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
@@ -50,10 +52,19 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
+import androidx.compose.ui.focus.FocusRequester
+import androidx.compose.ui.focus.focusRequester
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
+import androidx.compose.ui.input.key.Key
+import androidx.compose.ui.input.key.KeyEvent
+import androidx.compose.ui.input.key.KeyEventType
+import androidx.compose.ui.input.key.key
+import androidx.compose.ui.input.key.onKeyEvent
+import androidx.compose.ui.input.key.type
 import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.text.style.TextOverflow
@@ -74,11 +85,13 @@ import com.composables.icons.lucide.Shuffle
 import com.composables.icons.lucide.SkipBack
 import com.composables.icons.lucide.SkipForward
 import com.fabledsword.minstrel.player.RepeatMode
+import com.fabledsword.minstrel.player.output.ActiveUpnp
 import com.fabledsword.minstrel.player.output.DeviceChip
 import com.fabledsword.minstrel.player.output.OutputPickerSheet
 import com.fabledsword.minstrel.player.output.OutputPickerViewModel
 import com.fabledsword.minstrel.player.output.OutputRoute
 import com.fabledsword.minstrel.player.output.RouteSnapshot
+import kotlinx.coroutines.launch
 import com.fabledsword.minstrel.nav.AlbumDetail
 import com.fabledsword.minstrel.nav.ArtistDetail
 import com.fabledsword.minstrel.nav.HERO_KEY_NOW_PLAYING_COVER
@@ -129,27 +142,30 @@ fun NowPlayingScreen(
             snackbarHostState.showSnackbar(msg)
         }
     }
+    LaunchedEffect(Unit) {
+        viewModel.dropEvents.collect { snackbarHostState.showSnackbar("Disconnected from $it") }
+    }
     val track = state.currentTrack
     if (track == null) {
-        // Session torn down (queue finished + auto-stop, or user cleared
-        // the queue from elsewhere). Pop back to whichever shell screen
-        // launched NowPlaying rather than stranding the user on an
-        // EmptyState with no escape. A short delay swallows the
-        // momentary null during MediaController IPC bind on cold-mount.
-        LaunchedEffect(Unit) {
-            kotlinx.coroutines.delay(POP_GRACE_MS)
-            if (viewModel.uiState.value.currentTrack == null) {
-                navController.popBackStack()
-            }
-        }
+        NowPlayingNullTrackGuard(navController, viewModel)
         return
     }
+    val outputViewModel: OutputPickerViewModel = hiltViewModel()
+    val activeUpnp by outputViewModel.activeUpnp.collectAsStateWithLifecycle()
+    val onKeyEvent = rememberUpnpVolumeKeyHandler(activeUpnp)
+    val focusRequester = remember { FocusRequester() }
+    LaunchedEffect(activeUpnp) { if (activeUpnp != null) focusRequester.requestFocus() }
     val dominant = rememberDominantColor(track.coverUrl)
     val dismissConnection = rememberDragDismissConnection(
         onDismiss = { navController.popBackStack() },
     )
     Scaffold(
-        modifier = Modifier.fillMaxSize().nestedScroll(dismissConnection),
+        modifier = Modifier
+            .fillMaxSize()
+            .nestedScroll(dismissConnection)
+            .focusRequester(focusRequester)
+            .focusable()
+            .onKeyEvent(onKeyEvent),
         topBar = { NowPlayingTopBar(onClose = { navController.popBackStack() }) },
         snackbarHost = { SnackbarHost(snackbarHostState) },
         containerColor = Color.Transparent,
@@ -166,11 +182,32 @@ fun NowPlayingScreen(
                 navController = navController,
                 viewModel = viewModel,
                 trackActionsViewModel = trackActionsViewModel,
+                outputViewModel = outputViewModel,
             )
         }
     }
 }
 
+/**
+ * Null-track guard extracted from [NowPlayingScreen] to keep that
+ * function under detekt's LongMethod ceiling. Session torn down
+ * (queue finished + auto-stop, or user cleared the queue from
+ * elsewhere). Pops back after a short grace delay so a momentary
+ * null during MediaController IPC bind on cold-mount doesn't flash.
+ */
+@Composable
+private fun NowPlayingNullTrackGuard(
+    navController: NavHostController,
+    viewModel: PlayerViewModel,
+) {
+    LaunchedEffect(Unit) {
+        kotlinx.coroutines.delay(POP_GRACE_MS)
+        if (viewModel.uiState.value.currentTrack == null) {
+            navController.popBackStack()
+        }
+    }
+}
+
 @Composable
 private fun dominantGradient(top: Color): Brush {
     val base = MaterialTheme.colorScheme.background
@@ -270,6 +307,7 @@ private fun NowPlayingTopBar(onClose: () -> Unit) {
     )
 }
 
+@Suppress("LongParameterList") // Compose screen wiring — layout args, not logic
 @Composable
 private fun NowPlayingBody(
     inner: androidx.compose.foundation.layout.PaddingValues,
@@ -278,10 +316,10 @@ private fun NowPlayingBody(
     navController: NavHostController,
     viewModel: PlayerViewModel,
     trackActionsViewModel: TrackActionsViewModel,
+    outputViewModel: OutputPickerViewModel,
 ) {
     val isLiked by trackActionsViewModel.isLikedFlow(track.id)
         .collectAsStateWithLifecycle(initialValue = false)
-    val outputViewModel: OutputPickerViewModel = hiltViewModel()
     val routes by outputViewModel.routes.collectAsStateWithLifecycle()
     val sheetVisible by outputViewModel.sheetVisible.collectAsStateWithLifecycle()
     val permissionDenied = rememberBluetoothPermissionState(sheetVisible)
@@ -387,6 +425,7 @@ private fun PlaybackControlsBlock(
     Spacer(Modifier.height(4.dp))
     TransportRow(
         isPlaying = state.isPlaying,
+        isUpnpLoading = state.isUpnpLoading,
         onPrev = viewModel::skipToPrevious,
         onPlayPause = { if (state.isPlaying) viewModel.pause() else viewModel.play() },
         onNext = viewModel::skipToNext,
@@ -667,6 +706,7 @@ private fun ScrubTrack(fraction: Float, accent: Color) {
 @Composable
 private fun TransportRow(
     isPlaying: Boolean,
+    isUpnpLoading: Boolean,
     onPrev: () -> Unit,
     onPlayPause: () -> Unit,
     onNext: () -> Unit,
@@ -685,13 +725,20 @@ private fun TransportRow(
                 modifier = Modifier.size(TRANSPORT_ICON_DP.dp),
             )
         }
-        IconButton(onClick = onPlayPause) {
-            Icon(
-                imageVector = if (isPlaying) Lucide.Pause else Lucide.Play,
-                contentDescription = if (isPlaying) "Pause" else "Play",
-                tint = actionColors.primary,
-                modifier = Modifier.size(PLAY_PAUSE_ICON_DP.dp),
-            )
+        IconButton(onClick = onPlayPause, enabled = !isUpnpLoading) {
+            if (isUpnpLoading) {
+                CircularProgressIndicator(
+                    modifier = Modifier.size(PLAY_PAUSE_ICON_DP.dp),
+                    strokeWidth = 3.dp,
+                )
+            } else {
+                Icon(
+                    imageVector = if (isPlaying) Lucide.Pause else Lucide.Play,
+                    contentDescription = if (isPlaying) "Pause" else "Play",
+                    tint = actionColors.primary,
+                    modifier = Modifier.size(PLAY_PAUSE_ICON_DP.dp),
+                )
+            }
         }
         IconButton(onClick = onNext) {
             Icon(
@@ -703,3 +750,40 @@ private fun TransportRow(
         }
     }
 }
+
+/**
+ * Returns a key-event handler that intercepts volume-up/down when a UPnP
+ * route is active and routes the step through [ActiveUpnp.rendering].
+ * Volume is cached locally so rapid key presses don't each wait on a
+ * getVolume() round-trip. Returns false (not consumed) for every event
+ * when no UPnP route is active so the system handles volume normally.
+ */
+@Composable
+private fun rememberUpnpVolumeKeyHandler(activeUpnp: ActiveUpnp?): (KeyEvent) -> Boolean {
+    val scope = rememberCoroutineScope()
+    val cache = remember(activeUpnp?.routeId) { VolumeCache() }
+    return remember(activeUpnp) {
+        handler@{ event: KeyEvent ->
+            val rc = activeUpnp?.rendering ?: return@handler false
+            if (event.type != KeyEventType.KeyDown) return@handler false
+            val delta = when (event.key) {
+                Key.VolumeUp -> VOLUME_KEY_STEP
+                Key.VolumeDown -> -VOLUME_KEY_STEP
+                else -> return@handler false
+            }
+            scope.launch {
+                val current = cache.value ?: runCatching { rc.getVolume() }.getOrNull() ?: 0
+                val next = (current + delta).coerceIn(VOLUME_MIN_PERCENT, VOLUME_MAX_PERCENT)
+                cache.value = next
+                runCatching { rc.setVolume(next) }
+            }
+            true
+        }
+    }
+}
+
+private class VolumeCache(var value: Int? = null)
+
+private const val VOLUME_KEY_STEP = 5
+private const val VOLUME_MIN_PERCENT = 0
+private const val VOLUME_MAX_PERCENT = 100

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

@@ -4,6 +4,7 @@ import androidx.lifecycle.ViewModel
 import com.fabledsword.minstrel.player.PlayerController
 import com.fabledsword.minstrel.player.PlayerUiState
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.SharedFlow
 import kotlinx.coroutines.flow.StateFlow
 import javax.inject.Inject
 
@@ -24,6 +25,7 @@ class PlayerViewModel @Inject constructor(
 ) : ViewModel() {
 
     val uiState: StateFlow<PlayerUiState> = controller.uiState
+    val dropEvents: SharedFlow<String> = controller.dropEvents
 
     fun play() = controller.play()
     fun pause() = controller.pause()

android/app/src/main/java/com/fabledsword/minstrel/playlists/data/PlaylistPlayback.kt

@@ -0,0 +1,71 @@
+package com.fabledsword.minstrel.playlists.data
+
+import com.fabledsword.minstrel.models.PlaylistRef
+import com.fabledsword.minstrel.player.PlayerController
+import com.fabledsword.minstrel.api.ErrorCopy
+import kotlinx.coroutines.TimeoutCancellationException
+import kotlinx.coroutines.withTimeout
+
+private const val PLAYLIST_FETCH_TIMEOUT_MS = 8_000L
+
+/**
+ * Fetch a playlist and hand it to the player as a shuffled queue.
+ *
+ * Behavior matches the tile play-button contract used on Home and the
+ * Playlists list: refreshable system playlists go through systemShuffle
+ * (server-side rotation-aware order; tagging with the variant advances
+ * rotation), everything else uses refreshDetail. System playlists are
+ * then client-side shuffled so the tile feels random rather than
+ * "start at the rotation head". User playlists keep their authored
+ * order.
+ *
+ * Errors and empty mixes surface through [onMessage] for the caller to
+ * present as a snackbar / toast / etc. Returns when the player has
+ * accepted the queue (or an error path bailed).
+ */
+suspend fun playPlaylistShuffled(
+    playlist: PlaylistRef,
+    repository: PlaylistsRepository,
+    player: PlayerController,
+    onMessage: (String) -> Unit,
+) {
+    val detail = fetchPlaylistDetail(playlist, repository, onMessage) ?: return
+    val tracks = detail.tracks.toPlayableTrackRefs()
+    if (tracks.isEmpty()) {
+        onMessage("Mix isn't ready yet - try again in a moment")
+        return
+    }
+    // Drift #564: bare systemVariant string (not "playlist:<variant>") --
+    // server's rotation matcher keys on the bare variant.
+    val source = if (playlist.refreshable) playlist.systemVariant else null
+    // System playlist tile play button == "pick a random song + shuffle
+    // the rest" UX. Server's rotation-aware order still drives rotation
+    // bookkeeping via `source`; the client shuffle just removes the
+    // deterministic "start at rotation head" feel.
+    val ordered = if (playlist.isSystem) tracks.shuffled() else tracks
+    player.setQueue(ordered, initialIndex = 0, source = source)
+}
+
+private suspend fun fetchPlaylistDetail(
+    playlist: PlaylistRef,
+    repository: PlaylistsRepository,
+    onMessage: (String) -> Unit,
+): PlaylistDetailRef? = try {
+    withTimeout(PLAYLIST_FETCH_TIMEOUT_MS) {
+        if (playlist.refreshable && playlist.systemVariant != null) {
+            repository.systemShuffle(playlist.systemVariant)
+        } else {
+            repository.refreshDetail(playlist.id)
+        }
+    }
+} catch (
+    @Suppress("SwallowedException") _: TimeoutCancellationException,
+) {
+    onMessage("Couldn't load playlist - check your connection")
+    null
+} catch (
+    @Suppress("TooGenericExceptionCaught") e: Throwable,
+) {
+    onMessage("Couldn't load playlist: ${ErrorCopy.fromThrowable(e)}")
+    null
+}

android/app/src/main/java/com/fabledsword/minstrel/playlists/ui/PlaylistsListScreen.kt

@@ -13,9 +13,13 @@ import androidx.compose.foundation.lazy.grid.LazyVerticalGrid
 import androidx.compose.foundation.lazy.grid.items
 import androidx.compose.material3.MaterialTheme
 import androidx.compose.material3.Scaffold
+import androidx.compose.material3.SnackbarHost
+import androidx.compose.material3.SnackbarHostState
 import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
@@ -23,11 +27,14 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.lifecycle.viewModelScope
 import androidx.navigation.NavHostController
+import com.fabledsword.minstrel.connectivity.ConnectivityObserver
 import com.fabledsword.minstrel.events.EventsStream
 import com.fabledsword.minstrel.models.PlaylistRef
 import com.fabledsword.minstrel.nav.PlaylistDetail
 import com.fabledsword.minstrel.nav.Playlists
+import com.fabledsword.minstrel.player.PlayerController
 import com.fabledsword.minstrel.playlists.data.PlaylistsRepository
+import com.fabledsword.minstrel.playlists.data.playPlaylistShuffled
 import com.fabledsword.minstrel.shared.UiState
 import com.fabledsword.minstrel.shared.asCacheFirstStateFlow
 import com.fabledsword.minstrel.playlists.widgets.PlaylistCard
@@ -37,12 +44,19 @@ import com.fabledsword.minstrel.shared.widgets.MinstrelTopAppBar
 import com.fabledsword.minstrel.shared.widgets.PullToRefreshScaffold
 import dagger.hilt.android.lifecycle.HiltViewModel
 import kotlinx.coroutines.Job
+import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.filter
 import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.receiveAsFlow
+import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 import javax.inject.Inject
 
+private const val SHARE_STOP_TIMEOUT_MS = 5_000L
+
 // ─── State ───────────────────────────────────────────────────────────
 
 // ─── ViewModel ───────────────────────────────────────────────────────
@@ -50,9 +64,25 @@ import javax.inject.Inject
 @HiltViewModel
 class PlaylistsListViewModel @Inject constructor(
     private val repository: PlaylistsRepository,
+    private val player: PlayerController,
     private val eventsStream: EventsStream,
+    connectivity: ConnectivityObserver,
 ) : ViewModel() {
 
+    private val poolMessages = Channel<String>(Channel.BUFFERED)
+
+    /** Transient snackbar messages from playlist tile play taps. */
+    val transientMessages: Flow<String> = poolMessages.receiveAsFlow()
+
+    /** True when the device has no usable internet -- gates refreshable system tiles. */
+    val offline: StateFlow<Boolean> = connectivity.online
+        .map { !it }
+        .stateIn(
+            scope = viewModelScope,
+            started = SharingStarted.WhileSubscribed(SHARE_STOP_TIMEOUT_MS),
+            initialValue = false,
+        )
+
     init {
         refresh()
         // Live updates: a playlist created/updated/deleted from another
@@ -69,6 +99,15 @@ class PlaylistsListViewModel @Inject constructor(
         runCatching { repository.refreshList() }
     }
 
+    /** Tile play button: shuffle the playlist's tracks and start at index 0. */
+    suspend fun playPlaylist(playlist: PlaylistRef) {
+        viewModelScope.launch {
+            playPlaylistShuffled(playlist, repository, player) {
+                poolMessages.trySend(it)
+            }
+        }.join()
+    }
+
     val uiState: StateFlow<UiState<List<PlaylistRef>>> =
         repository.observeAll()
             .map { list ->
@@ -88,6 +127,10 @@ fun PlaylistsListScreen(
     navController: NavHostController,
     viewModel: PlaylistsListViewModel = hiltViewModel(),
 ) {
+    val snackbar = remember { SnackbarHostState() }
+    LaunchedEffect(Unit) {
+        viewModel.transientMessages.collect { snackbar.showSnackbar(it) }
+    }
     Scaffold(
         modifier = Modifier.fillMaxSize(),
         topBar = {
@@ -97,8 +140,10 @@ fun PlaylistsListScreen(
                 currentRouteName = Playlists::class.qualifiedName,
             )
         },
+        snackbarHost = { SnackbarHost(snackbar) },
     ) { inner ->
         val state by viewModel.uiState.collectAsStateWithLifecycle()
+        val offline by viewModel.offline.collectAsStateWithLifecycle()
         PullToRefreshScaffold(
             onRefresh = { viewModel.refresh().join() },
             modifier = Modifier.fillMaxSize().padding(inner),
@@ -117,7 +162,9 @@ fun PlaylistsListScreen(
                 )
                 is UiState.Success -> PlaylistsGrid(
                     playlists = s.data,
+                    offline = offline,
                     onPlaylistClick = { id -> navController.navigate(PlaylistDetail(id)) },
+                    onPlay = viewModel::playPlaylist,
                 )
             }
         }
@@ -127,7 +174,9 @@ fun PlaylistsListScreen(
 @Composable
 private fun PlaylistsGrid(
     playlists: List<PlaylistRef>,
+    offline: Boolean,
     onPlaylistClick: (String) -> Unit,
+    onPlay: suspend (PlaylistRef) -> Unit,
 ) {
     val systemPlaylists = playlists.filter { it.isSystem }
     val userPlaylists = playlists.filter { !it.isSystem }
@@ -142,7 +191,15 @@ private fun PlaylistsGrid(
                 SectionHeader("System playlists")
             }
             items(items = systemPlaylists, key = { it.id }) { playlist ->
-                PlaylistCard(playlist = playlist, onClick = { onPlaylistClick(playlist.id) })
+                PlaylistCard(
+                    playlist = playlist,
+                    onClick = { onPlaylistClick(playlist.id) },
+                    onPlay = { onPlay(playlist) },
+                    // Refreshable system tiles need server endpoints (systemShuffle);
+                    // disable when offline. Empty mixes show a snackbar after tap.
+                    playEnabled = playlist.trackCount > 0 &&
+                        !(offline && playlist.refreshable),
+                )
             }
         }
         if (userPlaylists.isNotEmpty()) {
@@ -150,7 +207,12 @@ private fun PlaylistsGrid(
                 SectionHeader("Your playlists")
             }
             items(items = userPlaylists, key = { it.id }) { playlist ->
-                PlaylistCard(playlist = playlist, onClick = { onPlaylistClick(playlist.id) })
+                PlaylistCard(
+                    playlist = playlist,
+                    onClick = { onPlaylistClick(playlist.id) },
+                    onPlay = { onPlay(playlist) },
+                    playEnabled = playlist.trackCount > 0,
+                )
             }
         }
     }

android/app/src/main/java/com/fabledsword/minstrel/search/data/SearchRepository.kt

@@ -1,6 +1,11 @@
 package com.fabledsword.minstrel.search.data
 
 import com.fabledsword.minstrel.api.endpoints.SearchApi
+import com.fabledsword.minstrel.cache.db.dao.CachedAlbumDao
+import com.fabledsword.minstrel.cache.db.dao.CachedArtistDao
+import com.fabledsword.minstrel.cache.db.dao.CachedTrackDao
+import com.fabledsword.minstrel.connectivity.ServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealthController
 import com.fabledsword.minstrel.library.data.toDomain
 import com.fabledsword.minstrel.models.SearchResponseRef
 import retrofit2.Retrofit
@@ -8,17 +13,34 @@ import retrofit2.create
 import javax.inject.Inject
 import javax.inject.Singleton
 
+private const val LOCAL_SEARCH_LIMIT = 20
+
 /**
- * Thin Retrofit wrapper around `/api/search`. Debouncing lives in
- * the ViewModel, not here, so the repository stays trivial.
+ * Cache-first when offline. When [ServerHealthController] is Healthy the
+ * repository hits `/api/search` and returns the server's three-facet
+ * paged response. When health is Offline or ServerDown it falls back to
+ * Room LIKE queries against `cached_*` so the user can still find
+ * something to play from what's already on the device; the outcome's
+ * [SearchOutcome.localOnly] flag lets the screen draw an "offline
+ * results" hint instead of pretending the server answered.
  */
 @Singleton
 class SearchRepository @Inject constructor(
     retrofit: Retrofit,
+    private val serverHealth: ServerHealthController,
+    private val trackDao: CachedTrackDao,
+    private val albumDao: CachedAlbumDao,
+    private val artistDao: CachedArtistDao,
 ) {
     private val api: SearchApi = retrofit.create()
 
-    suspend fun search(query: String): SearchResponseRef {
+    suspend fun search(query: String): SearchOutcome = when (serverHealth.state.value) {
+        ServerHealth.Healthy -> SearchOutcome(remoteSearch(query), localOnly = false)
+        ServerHealth.Offline, ServerHealth.ServerDown ->
+            SearchOutcome(localSearch(query), localOnly = true)
+    }
+
+    private suspend fun remoteSearch(query: String): SearchResponseRef {
         val wire = api.search(query)
         return SearchResponseRef(
             artists = wire.artists.items.map { it.toDomain() },
@@ -26,4 +48,21 @@ class SearchRepository @Inject constructor(
             tracks = wire.tracks.items.map { it.toDomain() },
         )
     }
+
+    private suspend fun localSearch(query: String): SearchResponseRef = SearchResponseRef(
+        artists = artistDao.searchByName(query, LOCAL_SEARCH_LIMIT).map { it.toDomain() },
+        albums = albumDao.searchByTitle(query, LOCAL_SEARCH_LIMIT).map { it.toDomain() },
+        tracks = trackDao.searchByTitle(query, LOCAL_SEARCH_LIMIT).map { it.toDomain() },
+    )
 }
+
+/**
+ * Wraps the search response with the signal of whether the result came
+ * from the server or from the local cached entities. The screen renders
+ * the same SearchResponseRef either way; the flag drives the offline
+ * banner copy.
+ */
+data class SearchOutcome(
+    val response: SearchResponseRef,
+    val localOnly: Boolean,
+)

android/app/src/main/java/com/fabledsword/minstrel/search/ui/SearchScreen.kt

@@ -158,17 +158,28 @@ private fun ResultsPane(
         is SearchResultsState.Error -> CenteredHint("Search failed: ${state.message}")
         is SearchResultsState.Loaded -> {
             if (state.response.isEmpty) {
-                CenteredHint("No matches for that query.")
-            } else {
-                ResultsList(
-                    response = state.response,
-                    playingTrackId = playingTrackId,
-                    onArtistClick = onArtistClick,
-                    onAlbumClick = onAlbumClick,
-                    onTrackPlay = onTrackPlay,
-                    onNavigateToAlbum = onNavigateToAlbum,
-                    onNavigateToArtist = onNavigateToArtist,
+                CenteredHint(
+                    if (state.localOnly) {
+                        "No matches in your on-device library."
+                    } else {
+                        "No matches for that query."
+                    },
                 )
+            } else {
+                Column(modifier = Modifier.fillMaxSize()) {
+                    if (state.localOnly) {
+                        OfflineResultsHint()
+                    }
+                    ResultsList(
+                        response = state.response,
+                        playingTrackId = playingTrackId,
+                        onArtistClick = onArtistClick,
+                        onAlbumClick = onAlbumClick,
+                        onTrackPlay = onTrackPlay,
+                        onNavigateToAlbum = onNavigateToAlbum,
+                        onNavigateToArtist = onNavigateToArtist,
+                    )
+                }
             }
         }
     }
@@ -308,6 +319,18 @@ private fun SectionHeader(label: String, count: Int) {
     }
 }
 
+@Composable
+private fun OfflineResultsHint() {
+    Text(
+        text = "Showing on-device matches only — the server is unreachable.",
+        modifier = Modifier
+            .fillMaxWidth()
+            .padding(horizontal = 16.dp, vertical = 6.dp),
+        style = MaterialTheme.typography.bodySmall,
+        color = MaterialTheme.colorScheme.onSurfaceVariant,
+    )
+}
+
 @Composable
 private fun CenteredHint(text: String) {
     Box(modifier = Modifier.fillMaxSize().padding(24.dp), contentAlignment = Alignment.Center) {

android/app/src/main/java/com/fabledsword/minstrel/search/ui/SearchViewModel.kt

@@ -26,7 +26,10 @@ sealed interface SearchResultsState {
     /** Empty query — screen shows "type to search" hint. */
     data object Idle : SearchResultsState
     data object Loading : SearchResultsState
-    data class Loaded(val response: SearchResponseRef) : SearchResultsState
+    data class Loaded(
+        val response: SearchResponseRef,
+        val localOnly: Boolean = false,
+    ) : SearchResultsState
     data class Error(val message: String) : SearchResultsState
 }
 
@@ -98,8 +101,15 @@ class SearchViewModel @Inject constructor(
     private suspend fun runSearch(q: String) {
         internal.update { it.copy(results = SearchResultsState.Loading) }
         try {
-            val response = repository.search(q)
-            internal.update { it.copy(results = SearchResultsState.Loaded(response)) }
+            val outcome = repository.search(q)
+            internal.update {
+                it.copy(
+                    results = SearchResultsState.Loaded(
+                        response = outcome.response,
+                        localOnly = outcome.localOnly,
+                    ),
+                )
+            }
         } catch (
             @Suppress("TooGenericExceptionCaught") e: Throwable,
         ) {

android/app/src/main/java/com/fabledsword/minstrel/shared/widgets/ShellScaffold.kt

@@ -12,6 +12,7 @@ import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.hilt.navigation.compose.hiltViewModel
+import com.fabledsword.minstrel.cache.mutations.OfflineWriteHintViewModel
 import com.fabledsword.minstrel.connectivity.ui.ConnectionErrorBanner
 import com.fabledsword.minstrel.player.ui.MiniPlayer
 import com.fabledsword.minstrel.player.ui.PlaybackErrorViewModel
@@ -48,6 +49,7 @@ fun ShellScaffold(
     modifier: Modifier = Modifier,
     trackActionsViewModel: TrackActionsViewModel = hiltViewModel(),
     playbackErrorViewModel: PlaybackErrorViewModel = hiltViewModel(),
+    offlineWriteHintViewModel: OfflineWriteHintViewModel = hiltViewModel(),
     content: @Composable () -> Unit,
 ) {
     val snackbarHostState = remember { SnackbarHostState() }
@@ -61,6 +63,11 @@ fun ShellScaffold(
             snackbarHostState.showSnackbar(msg)
         }
     }
+    LaunchedEffect(Unit) {
+        offlineWriteHintViewModel.messages.collect { msg ->
+            snackbarHostState.showSnackbar(msg)
+        }
+    }
     // Consume the status-bar inset once here so the banner stack sits
     // below the status bar (mirrors Flutter's SafeArea(bottom:false)).
     // statusBarsPadding consumes the inset for descendants, so the in-

android/app/src/main/java/com/fabledsword/minstrel/shared/widgets/TrackRow.kt

@@ -1,5 +1,6 @@
 package com.fabledsword.minstrel.shared.widgets
 
+import android.widget.Toast
 import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
@@ -12,8 +13,14 @@ import androidx.compose.material3.Text
 import androidx.compose.runtime.Composable
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
 import androidx.compose.ui.text.style.TextOverflow
 import androidx.compose.ui.unit.dp
+import com.fabledsword.minstrel.connectivity.LocalServerHealth
+import com.fabledsword.minstrel.connectivity.ServerHealth
+
+private const val OFFLINE_UNAVAILABLE_ALPHA = 0.4f
+private const val OFFLINE_TAP_MESSAGE = "Not downloaded — connect to play"
 
 /**
  * Shared track-list row. Replaces the 5 per-screen `TrackRow`s — every
@@ -30,6 +37,14 @@ import androidx.compose.ui.unit.dp
  * for applying its own alpha if it should match (the row doesn't
  * cascade because the trailing slot's content is the caller's, not
  * ours).
+ *
+ * Reads [LocalServerHealth] + [LocalCachedTrackIds] and intercepts taps
+ * on tracks that aren't downloaded when the server is unreachable —
+ * fires a Toast instead of attempting playback. The text dims so the
+ * user can see at a glance which rows in a long list will work offline.
+ * The trailing slot stays interactive so the kebab / like / playlist-
+ * add affordances can still queue mutations for offline replay (Phase
+ * 5 of #618 gates those at the action level).
  */
 @Composable
 fun TrackRow(
@@ -45,15 +60,28 @@ fun TrackRow(
     leading: @Composable () -> Unit = {},
     trailing: @Composable RowScope.() -> Unit = {},
 ) {
+    val context = LocalContext.current
+    val offlineUnavailable = LocalServerHealth.current != ServerHealth.Healthy &&
+        trackId !in LocalCachedTrackIds.current
     val titleColor = if (nowPlaying) {
         MaterialTheme.colorScheme.primary
     } else {
         MaterialTheme.colorScheme.onSurface
     }
+    val effectiveAlpha = if (offlineUnavailable) {
+        minOf(contentAlpha, OFFLINE_UNAVAILABLE_ALPHA)
+    } else {
+        contentAlpha
+    }
+    val effectiveOnClick: () -> Unit = if (offlineUnavailable) {
+        { Toast.makeText(context, OFFLINE_TAP_MESSAGE, Toast.LENGTH_SHORT).show() }
+    } else {
+        onClick
+    }
     Row(
         modifier = modifier
             .fillMaxWidth()
-            .clickable(enabled = enabled, onClick = onClick)
+            .clickable(enabled = enabled, onClick = effectiveOnClick)
             .padding(horizontal = 16.dp, vertical = 8.dp),
         verticalAlignment = Alignment.CenterVertically,
         horizontalArrangement = horizontalArrangement,
@@ -63,7 +91,7 @@ fun TrackRow(
             Text(
                 text = title,
                 style = MaterialTheme.typography.bodyLarge,
-                color = titleColor.copy(alpha = contentAlpha),
+                color = titleColor.copy(alpha = effectiveAlpha),
                 maxLines = 1,
                 overflow = TextOverflow.Ellipsis,
             )
@@ -71,7 +99,7 @@ fun TrackRow(
                 Text(
                     text = artist,
                     style = MaterialTheme.typography.bodySmall,
-                    color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = contentAlpha),
+                    color = MaterialTheme.colorScheme.onSurfaceVariant.copy(alpha = effectiveAlpha),
                     maxLines = 1,
                     overflow = TextOverflow.Ellipsis,
                 )

android/app/src/main/java/com/fabledsword/minstrel/update/data/VersionCheckController.kt

@@ -10,11 +10,25 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.launch
 import retrofit2.Retrofit
+import timber.log.Timber
 import javax.inject.Inject
 import javax.inject.Singleton
 
 private const val POLL_INTERVAL_MS = 5 * 60 * 1000L
 
+// Hysteresis on the reachable signal. Flipping internalReachable to false on
+// the very first /healthz failure produced two false positives:
+//   1. App startup — AuthStore.baseUrl loads from Room asynchronously, so the
+//      first runOnce() can fire against AuthStore.DEFAULT_BASE_URL
+//      ("http://localhost:8080") before the real server URL has hydrated.
+//   2. Deployments whose reverse proxy routes only /api/* to the Go server —
+//      /healthz never reaches the handler, so the user sees a permanent
+//      "Server unreachable" banner even though all real /api/* calls succeed.
+// Requiring 3 consecutive failures (~15 min at the 5-min poll cadence) ensures
+// the banner only fires on sustained, real unreachability — and a single
+// success at any point resets the counter so transient hiccups self-clear.
+private const val REACHABILITY_FAILURE_THRESHOLD = 3
+
 /**
  * Result of the most recent /healthz version-compatibility check.
  * `Skipped` means the server didn't include `min_client_version`
@@ -41,6 +55,18 @@ class VersionCheckController @Inject constructor(
     private val internal = MutableStateFlow(VersionResult.SKIPPED)
     val result: StateFlow<VersionResult> = internal.asStateFlow()
 
+    // Whether the most recent /healthz poll reached the server. Separate from
+    // VersionResult because "unreachable" and "version mismatch" drive
+    // different UX (offline banner vs version-too-old banner). Optimistic
+    // initial value -- the first poll fires within seconds of app launch and
+    // we don't want a "server down" flash before we've actually tried.
+    // Consumed by ServerHealthController to compose with ConnectivityObserver
+    // for the tri-state offline / server-down / healthy signal.
+    private val internalReachable = MutableStateFlow(true)
+    val reachable: StateFlow<Boolean> = internalReachable.asStateFlow()
+
+    private var consecutiveFailures = 0
+
     init {
         scope.launch {
             while (true) {
@@ -56,7 +82,26 @@ class VersionCheckController @Inject constructor(
     }
 
     private suspend fun runOnce() {
-        val response = runCatching { api.check() }.getOrNull() ?: return
+        val outcome = runCatching { api.check() }
+        val response = outcome.getOrNull()
+        if (response == null) {
+            consecutiveFailures++
+            if (consecutiveFailures >= REACHABILITY_FAILURE_THRESHOLD &&
+                internalReachable.value
+            ) {
+                Timber.w(
+                    "/healthz unreachable for %d consecutive polls — flipping reachable=false",
+                    consecutiveFailures,
+                )
+                internalReachable.value = false
+            }
+            return
+        }
+        if (!internalReachable.value) {
+            Timber.i("/healthz recovered after %d failures", consecutiveFailures)
+        }
+        consecutiveFailures = 0
+        internalReachable.value = true
         val min = response.minClientVersion
         internal.value = when {
             min.isEmpty() -> VersionResult.SKIPPED

android/app/src/test/java/com/fabledsword/minstrel/player/RemotePlayerStateTest.kt

@@ -0,0 +1,75 @@
+package com.fabledsword.minstrel.player
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class RemotePlayerStateTest {
+
+    @Test
+    fun `starts in idle state`() {
+        val state = RemotePlayerState()
+        assertFalse(state.isPlaying)
+        assertEquals(0L, state.positionMs)
+        assertEquals(0L, state.durationMs)
+    }
+
+    @Test
+    fun `applyPositionInfo updates position, duration, and trackNumber`() {
+        val state = RemotePlayerState()
+        state.applyPositionInfo(
+            positionMs = 65_000L, durationMs = 210_000L, trackUri = "x", trackNumber = 3,
+        )
+        assertEquals(65_000L, state.positionMs)
+        assertEquals(210_000L, state.durationMs)
+        assertEquals("x", state.currentTrackUri)
+        assertEquals(3, state.trackNumber)
+    }
+
+    @Test
+    fun `applyTransportPlaying flips isPlaying true`() {
+        val state = RemotePlayerState()
+        state.applyTransportPlaying()
+        assertTrue(state.isPlaying)
+    }
+
+    @Test
+    fun `applyTransportPaused flips isPlaying false`() {
+        val state = RemotePlayerState().apply { applyTransportPlaying() }
+        state.applyTransportPaused()
+        assertFalse(state.isPlaying)
+    }
+
+    @Test
+    fun `applyError resets to idle and records error`() {
+        val state = RemotePlayerState().apply { applyTransportPlaying() }
+        val ex = RuntimeException("disconnected")
+        state.applyError(ex)
+        assertFalse(state.isPlaying)
+        assertEquals(ex, state.lastError)
+    }
+
+    @Test
+    fun `recordPollFailure trips after threshold`() {
+        val state = RemotePlayerState()
+        // Threshold is 30 -- tolerate ~30s of screen-off WiFi sleep before
+        // declaring the remote dropped. Pre-threshold calls all return false.
+        repeat(DROP_THRESHOLD - 1) {
+            assertFalse(state.recordPollFailure())
+        }
+        assertTrue(state.recordPollFailure())
+    }
+
+    @Test
+    fun `recordPollSuccess clears the failure counter`() {
+        val state = RemotePlayerState()
+        repeat(DROP_THRESHOLD - 1) { state.recordPollFailure() }
+        state.recordPollSuccess()
+        assertFalse(state.recordPollFailure())
+    }
+
+    private companion object {
+        const val DROP_THRESHOLD = 30
+    }
+}

android/app/src/test/java/com/fabledsword/minstrel/player/output/upnp/AVTransportClientTest.kt

@@ -0,0 +1,194 @@
+package com.fabledsword.minstrel.player.output.upnp
+
+import kotlinx.coroutines.test.runTest
+import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertFalse
+import org.junit.jupiter.api.Assertions.assertTrue
+
+class AVTransportClientTest {
+
+    private lateinit var server: MockWebServer
+    private lateinit var client: AVTransportClient
+
+    @BeforeEach
+    fun setUp() {
+        server = MockWebServer()
+        server.start()
+        val controlUrl = server.url("/MediaRenderer/AVTransport/Control")
+        client = AVTransportClient(SoapClient(OkHttpClient()), controlUrl)
+    }
+
+    @AfterEach
+    fun tearDown() {
+        server.shutdown()
+    }
+
+    @Test
+    fun `seek sends Target in HH MM SS format`() = runTest {
+        server.enqueue(emptyResponse("Seek"))
+        client.seek(positionMs = 65_000L)
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<Target>0:01:05</Target>")) { "body was $body" }
+    }
+
+    @Test
+    fun `getPositionInfo parses Track, RelTime and TrackDuration`() = runTest {
+        server.enqueue(
+            MockResponse().setBody(
+                """<?xml version="1.0"?>
+                   <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                     <s:Body>
+                       <u:GetPositionInfoResponse
+                           xmlns:u="urn:schemas-upnp-org:service:AVTransport:1">
+                         <Track>3</Track>
+                         <TrackDuration>0:03:30</TrackDuration>
+                         <TrackURI>http://x/y.mp3</TrackURI>
+                         <RelTime>0:01:05</RelTime>
+                       </u:GetPositionInfoResponse>
+                     </s:Body>
+                   </s:Envelope>""".trimIndent(),
+            ),
+        )
+        val info = client.getPositionInfo()
+        assertEquals(3, info.track)
+        assertEquals(65_000L, info.relTimeMs)
+        assertEquals(210_000L, info.trackDurationMs)
+        assertEquals("http://x/y.mp3", info.trackUri)
+    }
+
+    @Test
+    fun `getTransportInfo maps PAUSED_PLAYBACK to PAUSED`() = runTest {
+        server.enqueue(
+            MockResponse().setBody(
+                """<?xml version="1.0"?>
+                   <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                     <s:Body>
+                       <u:GetTransportInfoResponse
+                           xmlns:u="urn:schemas-upnp-org:service:AVTransport:1">
+                         <CurrentTransportState>PAUSED_PLAYBACK</CurrentTransportState>
+                         <CurrentTransportStatus>OK</CurrentTransportStatus>
+                         <CurrentSpeed>1</CurrentSpeed>
+                       </u:GetTransportInfoResponse>
+                     </s:Body>
+                   </s:Envelope>""".trimIndent(),
+            ),
+        )
+        val info = client.getTransportInfo()
+        assertEquals(TransportState.PAUSED, info.state)
+    }
+
+    @Test
+    fun `getTransportInfo maps unknown state to UNKNOWN`() = runTest {
+        server.enqueue(
+            MockResponse().setBody(
+                """<?xml version="1.0"?>
+                   <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                     <s:Body>
+                       <u:GetTransportInfoResponse
+                           xmlns:u="urn:schemas-upnp-org:service:AVTransport:1">
+                         <CurrentTransportState>BUFFERING_PLAYBACK</CurrentTransportState>
+                         <CurrentTransportStatus>OK</CurrentTransportStatus>
+                         <CurrentSpeed>1</CurrentSpeed>
+                       </u:GetTransportInfoResponse>
+                     </s:Body>
+                   </s:Envelope>""".trimIndent(),
+            ),
+        )
+        val info = client.getTransportInfo()
+        assertEquals(TransportState.UNKNOWN, info.state)
+    }
+
+    @Test
+    fun `removeAllTracksFromQueue sends correct SOAP action`() = runTest {
+        server.enqueue(emptyResponse("RemoveAllTracksFromQueue"))
+        client.removeAllTracksFromQueue()
+        val request = server.takeRequest()
+        assertTrue(request.getHeader("SOAPACTION").orEmpty().contains("RemoveAllTracksFromQueue")) {
+            "SOAPACTION header missing action: ${request.getHeader("SOAPACTION")}"
+        }
+        val body = request.body.readUtf8()
+        assertTrue(body.contains("RemoveAllTracksFromQueue")) { "body: $body" }
+    }
+
+    @Test
+    fun `addURIToQueue sends EnqueuedURI and DIDL-Lite metadata`() = runTest {
+        server.enqueue(emptyResponse("AddURIToQueue"))
+        client.addURIToQueue(
+            uri = "http://x/y.mp3",
+            mime = "audio/mpeg",
+            title = "Song",
+            enqueuedURIPosition = 2,
+        )
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<EnqueuedURI>http://x/y.mp3</EnqueuedURI>")) {
+            "body missing EnqueuedURI: $body"
+        }
+        val positionTag = "<DesiredFirstTrackNumberEnqueued>2</DesiredFirstTrackNumberEnqueued>"
+        assertTrue(body.contains(positionTag)) { "body missing position: $body" }
+        assertTrue(body.contains("&lt;dc:title&gt;Song&lt;/dc:title&gt;")) {
+            "title missing in DIDL: $body"
+        }
+        assertTrue(body.contains("audio/mpeg")) { "mime missing: $body" }
+    }
+
+    @Test
+    fun `next sends Next SOAP action`() = runTest {
+        server.enqueue(emptyResponse("Next"))
+        client.next()
+        val request = server.takeRequest()
+        assertTrue(request.getHeader("SOAPACTION").orEmpty().endsWith("#Next\"")) {
+            "SOAPACTION: ${request.getHeader("SOAPACTION")}"
+        }
+    }
+
+    @Test
+    fun `previous sends Previous SOAP action`() = runTest {
+        server.enqueue(emptyResponse("Previous"))
+        client.previous()
+        val request = server.takeRequest()
+        assertTrue(request.getHeader("SOAPACTION").orEmpty().endsWith("#Previous\"")) {
+            "SOAPACTION: ${request.getHeader("SOAPACTION")}"
+        }
+    }
+
+    @Test
+    fun `seekToTrack sends TRACK_NR unit with 1-based target`() = runTest {
+        server.enqueue(emptyResponse("Seek"))
+        client.seekToTrack(trackNumber = 4)
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<Unit>TRACK_NR</Unit>")) { "body: $body" }
+        assertTrue(body.contains("<Target>4</Target>")) { "body: $body" }
+    }
+
+    @Test
+    fun `setAVTransportURIWithMetadata sends plain https URI for music track`() = runTest {
+        server.enqueue(emptyResponse("SetAVTransportURI"))
+        client.setAVTransportURIWithMetadata(
+            uri = "https://example.com/track.mp3",
+            mime = "audio/mpeg",
+            title = "Song",
+        )
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<CurrentURI>https://example.com/track.mp3</CurrentURI>")) {
+            "CurrentURI should be sent as plain https: $body"
+        }
+        assertFalse(body.contains("x-rincon-mp3radio")) {
+            "x-rincon-mp3radio scheme should not appear: $body"
+        }
+    }
+
+    private fun emptyResponse(action: String): MockResponse = MockResponse().setBody(
+        """<?xml version="1.0"?>
+           <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+             <s:Body>
+               <u:${action}Response xmlns:u="urn:schemas-upnp-org:service:AVTransport:1"/>
+             </s:Body>
+           </s:Envelope>""".trimIndent(),
+    )
+}

android/app/src/test/java/com/fabledsword/minstrel/player/output/upnp/BareUdnTest.kt

@@ -0,0 +1,44 @@
+package com.fabledsword.minstrel.player.output.upnp
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+class BareUdnTest {
+
+    @Test
+    fun `strips uuid prefix`() {
+        assertEquals("RINCON_ABC", "uuid:RINCON_ABC".bareUdn())
+    }
+
+    @Test
+    fun `strips MR suffix`() {
+        assertEquals("RINCON_ABC", "RINCON_ABC_MR".bareUdn())
+    }
+
+    @Test
+    fun `strips MS suffix`() {
+        assertEquals("RINCON_ABC", "RINCON_ABC_MS".bareUdn())
+    }
+
+    @Test
+    fun `strips both uuid prefix and MR suffix`() {
+        assertEquals("RINCON_ABC", "uuid:RINCON_ABC_MR".bareUdn())
+    }
+
+    @Test
+    fun `strips both uuid prefix and MS suffix`() {
+        assertEquals("RINCON_ABC", "uuid:RINCON_ABC_MS".bareUdn())
+    }
+
+    @Test
+    fun `leaves already bare UDN unchanged`() {
+        assertEquals("RINCON_ABC", "RINCON_ABC".bareUdn())
+    }
+
+    @Test
+    fun `MR suffix comparison crosses MediaRenderer vs ZGT response`() {
+        val routeId = "uuid:RINCON_5CAAFD794B6401400_MR"
+        val zgtMemberUdn = "RINCON_5CAAFD794B6401400"
+        assertEquals(routeId.bareUdn(), zgtMemberUdn.bareUdn())
+    }
+}

android/app/src/test/java/com/fabledsword/minstrel/player/output/upnp/DeviceDescriptionTest.kt

@@ -58,6 +58,7 @@ class DeviceDescriptionTest {
             "http://192.168.1.50:1400/MediaRenderer/RenderingControl/Control",
             desc.renderingControlUrl?.toString(),
         )
+        assertNull(desc.zoneGroupTopologyControlUrl)
     }
 
     @Test
@@ -81,6 +82,37 @@ class DeviceDescriptionTest {
         assertNull(DeviceDescription.parse(xml, base))
     }
 
+    @Test
+    fun `parses ZoneGroupTopology control URL when present`() {
+        val xml = """
+            <?xml version="1.0"?>
+            <root xmlns="urn:schemas-upnp-org:device-1-0">
+              <device>
+                <UDN>uuid:RINCON_XYZ</UDN>
+                <friendlyName>Office</friendlyName>
+                <manufacturer>Sonos, Inc.</manufacturer>
+                <modelName>Sonos One</modelName>
+                <serviceList>
+                  <service>
+                    <serviceType>urn:schemas-upnp-org:service:AVTransport:1</serviceType>
+                    <controlURL>/MediaRenderer/AVTransport/Control</controlURL>
+                  </service>
+                  <service>
+                    <serviceType>urn:schemas-upnp-org:service:ZoneGroupTopology:1</serviceType>
+                    <controlURL>/ZoneGroupTopology/Control</controlURL>
+                  </service>
+                </serviceList>
+              </device>
+            </root>
+        """.trimIndent()
+        val desc = DeviceDescription.parse(xml, base)
+        assertNotNull(desc)
+        assertEquals(
+            "http://192.168.1.50:1400/ZoneGroupTopology/Control",
+            desc.zoneGroupTopologyControlUrl?.toString(),
+        )
+    }
+
     @Test
     fun `handles missing optional fields`() {
         val xml = """

android/app/src/test/java/com/fabledsword/minstrel/player/output/upnp/RenderingControlClientTest.kt

@@ -0,0 +1,78 @@
+package com.fabledsword.minstrel.player.output.upnp
+
+import kotlinx.coroutines.test.runTest
+import okhttp3.OkHttpClient
+import okhttp3.mockwebserver.MockResponse
+import okhttp3.mockwebserver.MockWebServer
+import org.junit.jupiter.api.AfterEach
+import org.junit.jupiter.api.BeforeEach
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertTrue
+
+class RenderingControlClientTest {
+
+    private lateinit var server: MockWebServer
+    private lateinit var client: RenderingControlClient
+
+    @BeforeEach
+    fun setUp() {
+        server = MockWebServer()
+        server.start()
+        client = RenderingControlClient(SoapClient(OkHttpClient()), server.url("/RC"))
+    }
+
+    @AfterEach
+    fun tearDown() { server.shutdown() }
+
+    @Test
+    fun `getVolume parses CurrentVolume`() = runTest {
+        server.enqueue(MockResponse().setBody(
+            """<?xml version="1.0"?>
+               <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                 <s:Body>
+                   <u:GetVolumeResponse xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1">
+                     <CurrentVolume>42</CurrentVolume>
+                   </u:GetVolumeResponse>
+                 </s:Body>
+               </s:Envelope>""".trimIndent()))
+        assertEquals(42, client.getVolume())
+        val request = server.takeRequest()
+        val body = request.body.readUtf8()
+        assertTrue(body.contains("<Channel>Master</Channel>")) { body }
+        assertEquals(
+            "\"urn:schemas-upnp-org:service:RenderingControl:1#GetVolume\"",
+            request.getHeader("SOAPACTION"),
+        )
+    }
+
+    @Test
+    fun `setVolume clamps and sends DesiredVolume`() = runTest {
+        server.enqueue(MockResponse().setBody(
+            """<?xml version="1.0"?>
+               <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                 <s:Body>
+                   <u:SetVolumeResponse
+                       xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"/>
+                 </s:Body>
+               </s:Envelope>""".trimIndent()))
+        client.setVolume(150)
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<DesiredVolume>100</DesiredVolume>")) { body }
+    }
+
+    @Test
+    fun `setVolume clamps below VOLUME_MIN to zero`() = runTest {
+        server.enqueue(MockResponse().setBody(
+            """<?xml version="1.0"?>
+               <s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/">
+                 <s:Body>
+                   <u:SetVolumeResponse
+                       xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"/>
+                 </s:Body>
+               </s:Envelope>""".trimIndent()))
+        client.setVolume(-5)
+        val body = server.takeRequest().body.readUtf8()
+        assertTrue(body.contains("<DesiredVolume>0</DesiredVolume>")) { body }
+    }
+}

android/app/src/test/java/com/fabledsword/minstrel/player/output/upnp/sonos/SonosTopologyTest.kt

@@ -0,0 +1,109 @@
+package com.fabledsword.minstrel.player.output.upnp.sonos
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertNotNull
+
+class SonosTopologyTest {
+
+    @Test
+    fun `single zone group with one member`() {
+        val xml = """
+            <ZoneGroupState>
+              <ZoneGroups>
+                <ZoneGroup Coordinator="RINCON_A" ID="RINCON_A:1">
+                  <ZoneGroupMember UUID="RINCON_A" ZoneName="Kitchen"
+                    Location="http://192.168.1.10:1400/xml/device_description.xml"/>
+                </ZoneGroup>
+              </ZoneGroups>
+            </ZoneGroupState>
+        """.trimIndent()
+        val groups = SonosTopology.parse(xml)
+        assertEquals(1, groups.size)
+        val g = groups.first()
+        assertEquals("RINCON_A", g.coordinatorUdn)
+        assertEquals("Kitchen", g.name)
+        assertEquals(1, g.members.size)
+    }
+
+    @Test
+    fun `stereo pair collapses to one group with two members`() {
+        val xml = """
+            <ZoneGroupState>
+              <ZoneGroups>
+                <ZoneGroup Coordinator="RINCON_L" ID="RINCON_L:2">
+                  <ZoneGroupMember UUID="RINCON_L" ZoneName="Living Room"
+                    Location="http://192.168.1.11:1400/xml/device_description.xml"
+                    ChannelMapSet="RINCON_L:LF,LF;RINCON_R:RF,RF"/>
+                  <ZoneGroupMember UUID="RINCON_R" ZoneName="Living Room"
+                    Location="http://192.168.1.12:1400/xml/device_description.xml"
+                    ChannelMapSet="RINCON_L:LF,LF;RINCON_R:RF,RF"/>
+                </ZoneGroup>
+              </ZoneGroups>
+            </ZoneGroupState>
+        """.trimIndent()
+        val groups = SonosTopology.parse(xml)
+        assertEquals(1, groups.size)
+        val g = groups.first()
+        assertEquals("RINCON_L", g.coordinatorUdn)
+        assertEquals("Living Room", g.name)
+        assertEquals(2, g.members.size)
+        assertNotNull(g.members[0].channelMapSet)
+    }
+
+    @Test
+    fun `multi-speaker group lists coordinator name`() {
+        val xml = """
+            <ZoneGroupState>
+              <ZoneGroups>
+                <ZoneGroup Coordinator="RINCON_X" ID="RINCON_X:3">
+                  <ZoneGroupMember UUID="RINCON_X" ZoneName="Office"/>
+                  <ZoneGroupMember UUID="RINCON_Y" ZoneName="Bedroom"/>
+                </ZoneGroup>
+              </ZoneGroups>
+            </ZoneGroupState>
+        """.trimIndent()
+        val groups = SonosTopology.parse(xml)
+        assertEquals("Office", groups.first().name)
+    }
+
+    @Test
+    fun `malformed xml returns empty list`() {
+        assertEquals(emptyList(), SonosTopology.parse("<garbage"))
+    }
+
+    @Test
+    fun `parses inline non-escaped ZoneGroupState document`() {
+        // Some Sonos firmware sends the topology as nested elements with
+        // no escaping. After SoapClient.readUntilEndTag rebuilds a flat
+        // string, parse should still find the groups.
+        val xml = """
+            <ZoneGroupState>
+              <ZoneGroups>
+                <ZoneGroup Coordinator="RINCON_A" ID="RINCON_A:1">
+                  <ZoneGroupMember UUID="RINCON_A" ZoneName="Kitchen"
+                    Location="http://192.168.1.10:1400/xml/device_description.xml"/>
+                </ZoneGroup>
+              </ZoneGroups>
+            </ZoneGroupState>
+        """.trimIndent()
+        val groups = SonosTopology.parse(xml)
+        assertEquals(1, groups.size)
+    }
+
+    @Test
+    fun `parses escaped ZoneGroupState wrapped in entities`() {
+        val xml = """
+            &lt;ZoneGroupState&gt;
+              &lt;ZoneGroups&gt;
+                &lt;ZoneGroup Coordinator="RINCON_A" ID="RINCON_A:1"&gt;
+                  &lt;ZoneGroupMember UUID="RINCON_A" ZoneName="Kitchen"
+                    Location="http://192.168.1.10:1400/xml/device_description.xml"/&gt;
+                &lt;/ZoneGroup&gt;
+              &lt;/ZoneGroups&gt;
+            &lt;/ZoneGroupState&gt;
+        """.trimIndent()
+        val groups = SonosTopology.parse(xml)
+        assertEquals(1, groups.size)
+    }
+}

internal/api/api.go

@@ -65,6 +65,10 @@ func Mount(r chi.Router, pool *pgxpool.Pool, logger *slog.Logger, events *playev
 		// design at
 		// docs/superpowers/specs/2026-06-03-android-output-picker-upnp-design.md.
 		api.With(auth.OptionalUser(pool, logger)).Get("/tracks/{id}/stream", h.handleGetStream)
+		// Extension-bearing alias so Sonos's URL probe can identify the
+		// audio format from the path. The {ext} param is consumed by chi
+		// and ignored by the handler (which keys off {id}). See task #610.
+		api.With(auth.OptionalUser(pool, logger)).Get("/tracks/{id}/stream.{ext}", h.handleGetStream)
 
 		api.Group(func(authed chi.Router) {
 			authed.Use(auth.RequireUser(pool))

internal/api/cast_token.go

@@ -3,9 +3,11 @@ package api
 import (
 	"net/http"
 	"strconv"
+	"strings"
 	"time"
 
 	"git.fabledsword.com/bvandeusen/minstrel/internal/apierror"
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
 const (
@@ -23,6 +25,53 @@ type castTokenResponse struct {
 	Token string `json:"token"`
 	Exp   int64  `json:"exp"`
 	URL   string `json:"url"`
+	// MIME and Title let the client build proper DIDL-Lite metadata for
+	// SetAVTransportURI. Sonos rejects empty DIDL with vendor error 1023;
+	// passing back the track's MIME + title here lets the client populate
+	// `<res protocolInfo>` and `<dc:title>` without a follow-up round trip.
+	MIME  string `json:"mime"`
+	Title string `json:"title"`
+}
+
+// mimeForFormat returns the audio MIME type for a cast (Sonos/UPnP) URL.
+// Wraps the canonical audioContentType lookup in media.go and overrides
+// the unknown-format fallback to audio/mpeg, because Sonos rejects
+// DIDL-Lite with protocolInfo=application/octet-stream (the browser
+// fallback) -- most Sonos firmware probes the URL anyway and recovers
+// from a small MIME mismatch.
+func mimeForFormat(format string) string {
+	mime := audioContentType(format)
+	if mime == "application/octet-stream" {
+		return "audio/mpeg"
+	}
+	return mime
+}
+
+// extForFormat maps the tracks.file_format column to a path-safe file
+// extension. Sonos firmware gates duration probing on the URL path
+// extension (Content-Type header alone is insufficient) -- without a
+// recognizable extension, Sonos reports TrackDuration=0 and seeks
+// trigger auto-advance because every position past 0 looks past-the-
+// end. Defaults to "mp3" for unknown formats. See task #610.
+func extForFormat(format string) string {
+	switch strings.ToLower(strings.TrimSpace(format)) {
+	case "mp3", "mpeg":
+		return "mp3"
+	case "flac":
+		return "flac"
+	case "aac":
+		return "aac"
+	case "m4a", "mp4":
+		return "m4a"
+	case "ogg", "vorbis":
+		return "ogg"
+	case "opus":
+		return "opus"
+	case "wav", "wave":
+		return "wav"
+	default:
+		return "mp3"
+	}
 }
 
 // handleCastStreamToken issues a short-lived HMAC stream token for the
@@ -52,6 +101,14 @@ func (h *handlers) handleCastStreamToken(w http.ResponseWriter, r *http.Request)
 		writeErr(w, apierror.BadRequest("invalid_track_id", "trackId must be a UUID"))
 		return
 	}
+	// Track lookup for the DIDL-Lite metadata the client builds for
+	// SetAVTransportURI. A missing track is a 404 — there's nothing to
+	// cast in that case.
+	track, err := dbq.New(h.pool).GetTrackByID(r.Context(), trackUUID)
+	if err != nil {
+		writeErr(w, apierror.NotFound("track"))
+		return
+	}
 	expSec := clampExpSeconds(req.ExpSeconds)
 	exp := time.Now().Add(time.Duration(expSec) * time.Second).Unix()
 	token := SignStreamToken(h.streamSecret, req.TrackID, exp)
@@ -74,10 +131,19 @@ func (h *handlers) handleCastStreamToken(w http.ResponseWriter, r *http.Request)
 	if h := r.Header.Get("X-Forwarded-Host"); h != "" {
 		host = h
 	}
-	url := scheme + "://" + host + "/api/tracks/" + req.TrackID +
-		"/stream?token=" + token + "&exp=" + strconv.FormatInt(exp, 10)
+	// Include the file extension in the path so Sonos's URL probe sees a
+	// recognizable audio file. Without it, Sonos reports TrackDuration=0
+	// and seeks past 0s land "after the end" -> early track-skip.
+	url := scheme + "://" + host + streamURLWithExt(trackUUID, extForFormat(track.FileFormat)) +
+		"?token=" + token + "&exp=" + strconv.FormatInt(exp, 10)
 
-	writeJSON(w, http.StatusOK, castTokenResponse{Token: token, Exp: exp, URL: url})
+	writeJSON(w, http.StatusOK, castTokenResponse{
+		Token: token,
+		Exp:   exp,
+		URL:   url,
+		MIME:  mimeForFormat(track.FileFormat),
+		Title: track.Title,
+	})
 }
 
 // clampExpSeconds applies the [60, 86400] window with a 6h default for

internal/api/cast_token_test.go

@@ -10,15 +10,21 @@ import (
 	"time"
 )
 
-const testTrackUUID = "11111111-1111-1111-1111-111111111111"
+// nonExistentTrackUUID is used by tests that exercise paths which don't
+// require the track to actually exist (auth/UUID-shape rejection).
+const nonExistentTrackUUID = "11111111-1111-1111-1111-111111111111"
 
 func TestCastStreamToken_HappyPath(t *testing.T) {
 	h, pool := testHandlers(t)
 	user := seedUser(t, pool, "alice", "hunter2", false)
+	artist := seedArtist(t, pool, "Artist")
+	album := seedAlbum(t, pool, artist.ID, "Album", 0)
+	track := seedTrack(t, pool, album.ID, artist.ID, "Song", 1, 180_000)
+	trackID := uuidToString(track.ID)
 	h.streamSecret = []byte("cast-token-test-secret")
 
 	body, err := json.Marshal(castTokenRequest{
-		TrackID:    testTrackUUID,
+		TrackID:    trackID,
 		ExpSeconds: 3600,
 	})
 	if err != nil {
@@ -44,10 +50,16 @@ func TestCastStreamToken_HappyPath(t *testing.T) {
 	if !strings.Contains(resp.URL, "token="+resp.Token) {
 		t.Fatalf("URL missing token query: %s", resp.URL)
 	}
-	if !strings.Contains(resp.URL, "/api/tracks/"+testTrackUUID+"/stream") {
+	if !strings.Contains(resp.URL, "/api/tracks/"+trackID+"/stream") {
 		t.Fatalf("URL missing stream path: %s", resp.URL)
 	}
-	if !VerifyStreamToken(h.streamSecret, testTrackUUID, resp.Exp, resp.Token) {
+	// Stream URL must carry a file extension so Sonos's URL probe can
+	// identify the audio format (see task #610). Track seeded above is
+	// .flac via seedTrack's default file_format.
+	if !strings.Contains(resp.URL, "/stream.flac?") {
+		t.Fatalf("URL missing file-extension segment: %s", resp.URL)
+	}
+	if !VerifyStreamToken(h.streamSecret, trackID, resp.Exp, resp.Token) {
 		t.Fatal("returned token does not verify")
 	}
 }
@@ -77,7 +89,7 @@ func TestCastStreamToken_RejectsUnauthenticated(t *testing.T) {
 	h, _ := testHandlers(t)
 	h.streamSecret = []byte("cast-token-test-secret")
 
-	body, err := json.Marshal(castTokenRequest{TrackID: testTrackUUID})
+	body, err := json.Marshal(castTokenRequest{TrackID: nonExistentTrackUUID})
 	if err != nil {
 		t.Fatalf("marshal: %v", err)
 	}
@@ -96,11 +108,15 @@ func TestCastStreamToken_RejectsUnauthenticated(t *testing.T) {
 func TestCastStreamToken_ClampsExpSeconds(t *testing.T) {
 	h, pool := testHandlers(t)
 	user := seedUser(t, pool, "alice", "hunter2", false)
+	artist := seedArtist(t, pool, "Artist")
+	album := seedAlbum(t, pool, artist.ID, "Album", 0)
+	track := seedTrack(t, pool, album.ID, artist.ID, "Song", 1, 180_000)
+	trackID := uuidToString(track.ID)
 	h.streamSecret = []byte("cast-token-test-secret")
 
 	// Request 1 second (below min 60), expect clamp to 60s.
 	body, err := json.Marshal(castTokenRequest{
-		TrackID:    testTrackUUID,
+		TrackID:    trackID,
 		ExpSeconds: 1,
 	})
 	if err != nil {

internal/api/convert.go

@@ -75,6 +75,15 @@ func streamURL(trackID pgtype.UUID) string {
 	return "/api/tracks/" + uuidToString(trackID) + "/stream"
 }
 
+// streamURLWithExt returns the extension-bearing stream URL used by UPnP
+// cast tokens. Sonos's URL probe gates duration detection on a recognizable
+// audio file extension; the bare `/stream` shape reports TrackDuration=0
+// and breaks seek/auto-advance. The bare /stream route stays mounted as an
+// alias for legacy / web / Subsonic clients. See task #610.
+func streamURLWithExt(trackID pgtype.UUID, ext string) string {
+	return streamURL(trackID) + "." + ext
+}
+
 // artistRefFrom projects a dbq.Artist into an ArtistRef without cover.
 // albumCount must be pre-computed by the caller. Used by code paths that
 // don't have a representative-album lookup at hand (artist detail, search,

internal/api/media.go

@@ -22,46 +22,42 @@ import (
 	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
-// resolveAlbumCoverPath returns the filesystem path to the album's cover art.
-// It prefers an explicit cover_art_path (set by the scanner in a future
-// milestone) and falls back to a sidecar next to the first track in the
-// album's directory. "" means no art was found.
+// resolveAlbumCoverPath delegates to coverart.ResolveAlbumPath; kept as a
+// local alias so the call sites in this file read naturally.
 func resolveAlbumCoverPath(ctx context.Context, q *dbq.Queries, album dbq.Album) string {
-	if album.CoverArtPath != nil && *album.CoverArtPath != "" {
-		if _, err := os.Stat(*album.CoverArtPath); err == nil {
-			return *album.CoverArtPath
-		}
-	}
-	tracks, err := q.ListTracksByAlbum(ctx, dbq.ListTracksByAlbumParams{AlbumID: album.ID})
-	if err != nil || len(tracks) == 0 {
-		return ""
-	}
-	return coverart.FindSidecar(filepath.Dir(tracks[0].FilePath))
+	return coverart.ResolveAlbumPath(ctx, q, album)
 }
 
 // audioContentType maps the short file_format recorded on tracks (mp3, flac,
 // ogg, opus, m4a, aac, wav) to a MIME type for the Content-Type header.
-// Unknown formats fall back to octet-stream so the browser downloads them
-// rather than attempting to decode.
+// This is the canonical table; both the browser stream endpoint and the
+// UPnP cast token URL builder consult it. Unknown formats fall back to
+// octet-stream so the browser downloads them rather than attempting to
+// decode -- cast_token.go applies its own audio/mpeg fallback for Sonos.
+//
+// Aliases (mpeg/vorbis/wave) cover historical / alternate format spellings
+// that have shown up in track rows. The trim+lowercase normalization makes
+// the lookup permissive to whatever a scanner happened to write.
 //
 // Divergences from internal/subsonic/types.go's contentTypeForFormat are
-// intentional: opus→audio/ogg (library .opus files are Ogg-encapsulated, so
-// this matches real library contents), aac→audio/aac (raw AAC is ADTS, not
-// MP4, so audio/mp4 would mislead codec sniffers), and there is no "oga" case
-// (we don't record that format). Don't "fix" these to match subsonic.
+// intentional: opus/vorbis→audio/ogg (library .opus / .ogg files are
+// Ogg-encapsulated, so this matches real library contents), aac→audio/aac
+// (raw AAC is ADTS, not MP4, so audio/mp4 would mislead codec sniffers),
+// and there is no "oga" case (we don't record that format). Subsonic is a
+// frozen client contract -- don't "fix" these to match it.
 func audioContentType(format string) string {
-	switch strings.ToLower(format) {
-	case "mp3":
+	switch strings.ToLower(strings.TrimSpace(format)) {
+	case "mp3", "mpeg":
 		return "audio/mpeg"
 	case "flac":
 		return "audio/flac"
-	case "ogg", "opus":
+	case "ogg", "opus", "vorbis":
 		return "audio/ogg"
-	case "m4a":
+	case "m4a", "mp4":
 		return "audio/mp4"
 	case "aac":
 		return "audio/aac"
-	case "wav":
+	case "wav", "wave":
 		return "audio/wav"
 	}
 	return "application/octet-stream"

internal/api/playlists.go

@@ -476,8 +476,8 @@ func playlistDetailToView(d *playlists.PlaylistDetail) playlistDetailView {
 		if t.TrackID != nil {
 			s := uuidToString(*t.TrackID)
 			v.TrackID = &s
-			streamURL := "/api/tracks/" + s + "/stream"
-			v.StreamURL = &streamURL
+			url := streamURL(*t.TrackID)
+			v.StreamURL = &url
 		}
 		if t.AlbumID != nil {
 			s := uuidToString(*t.AlbumID)

internal/coverart/sidecar.go

@@ -7,8 +7,11 @@
 package coverart
 
 import (
+	"context"
 	"os"
 	"path/filepath"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
 )
 
 // SidecarNames is the lookup order for cover art living next to audio files.
@@ -33,3 +36,24 @@ func FindSidecar(albumDir string) string {
 	}
 	return ""
 }
+
+// ResolveAlbumPath returns the on-disk path to an album's cover image,
+// preferring the explicit album.cover_art_path when set and the file
+// exists, falling back to a sidecar (cover.jpg / folder.jpg) next to the
+// first track in the album's directory. "" means no art was found.
+//
+// Shared by internal/api/media.go (browser endpoint) and
+// internal/subsonic/stream.go (Subsonic endpoint); they were byte-identical
+// duplicates before extraction.
+func ResolveAlbumPath(ctx context.Context, q *dbq.Queries, album dbq.Album) string {
+	if album.CoverArtPath != nil && *album.CoverArtPath != "" {
+		if _, err := os.Stat(*album.CoverArtPath); err == nil {
+			return *album.CoverArtPath
+		}
+	}
+	tracks, err := q.ListTracksByAlbum(ctx, dbq.ListTracksByAlbumParams{AlbumID: album.ID})
+	if err != nil || len(tracks) == 0 {
+		return ""
+	}
+	return FindSidecar(filepath.Dir(tracks[0].FilePath))
+}

internal/playlists/collage.go

@@ -176,16 +176,43 @@ func fallbackGlyph() image.Image {
 	return img
 }
 
-// drawScaled copies src into dst.Rect, scaling with simple nearest-neighbor.
-// stdlib lacks high-quality scaling; nearest-neighbor is fine for a
-// 600x600 output where each cell is 300x300 — most album covers are
-// already 300-1500 pixels and the visual loss is minor.
+// drawScaled copies src into dst.Rect using a center-cropped "cover" fit
+// (the same model as BoxFit.cover / object-fit: cover in the clients).
+// Non-square sources are scaled so the *smaller* destination dimension is
+// fully filled and the larger axis is center-cropped, preserving aspect
+// ratio. Without this, banner-shaped or LP-shaped album art stretches in
+// the cell -- the album-coherent system playlists (new_for_you,
+// first_listens) make the stretching disproportionately visible because
+// fewer unique covers contribute, so each warped cell is a quarter of
+// the collage rather than diluted.
+//
+// Scaling itself stays nearest-neighbor -- stdlib lacks high-quality
+// scaling and dependency cost is unjustified for this 600x600 output.
 func drawScaled(dst draw.Image, r image.Rectangle, src image.Image) {
 	srcBounds := src.Bounds()
+	srcW := srcBounds.Dx()
+	srcH := srcBounds.Dy()
+	if srcW <= 0 || srcH <= 0 {
+		return
+	}
+	dstW := r.Dx()
+	dstH := r.Dy()
+	// Cover-fit: the side of src that maps to dst at the larger scale
+	// fully fills its axis; the other axis is center-cropped.
+	scaleX := float64(dstW) / float64(srcW)
+	scaleY := float64(dstH) / float64(srcH)
+	scale := scaleX
+	if scaleY > scale {
+		scale = scaleY
+	}
+	cropW := float64(dstW) / scale
+	cropH := float64(dstH) / scale
+	cropOffX := float64(srcBounds.Min.X) + (float64(srcW)-cropW)/2
+	cropOffY := float64(srcBounds.Min.Y) + (float64(srcH)-cropH)/2
 	for y := r.Min.Y; y < r.Max.Y; y++ {
+		sy := int(cropOffY + float64(y-r.Min.Y)*cropH/float64(dstH))
 		for x := r.Min.X; x < r.Max.X; x++ {
-			sx := srcBounds.Min.X + (x-r.Min.X)*srcBounds.Dx()/r.Dx()
-			sy := srcBounds.Min.Y + (y-r.Min.Y)*srcBounds.Dy()/r.Dy()
+			sx := int(cropOffX + float64(x-r.Min.X)*cropW/float64(dstW))
 			dst.Set(x, y, src.At(sx, sy))
 		}
 	}

internal/subsonic/stream.go

@@ -130,21 +130,10 @@ func (m *mediaHandlers) handleGetCoverArt(w http.ResponseWriter, r *http.Request
 	WriteFail(w, r, ErrDataNotFound, "Cover art not found")
 }
 
-// resolveAlbumCoverPath returns the filesystem path to the album's cover art,
-// preferring an explicit cover_art_path (set by the scanner in a future
-// milestone) and falling back to a sidecar image next to any track in the
-// album directory. "" means no art was found.
+// resolveAlbumCoverPath delegates to coverart.ResolveAlbumPath; kept as a
+// local alias so the call sites in this file read naturally.
 func resolveAlbumCoverPath(ctx context.Context, q *dbq.Queries, album dbq.Album) string {
-	if album.CoverArtPath != nil && *album.CoverArtPath != "" {
-		if _, err := os.Stat(*album.CoverArtPath); err == nil {
-			return *album.CoverArtPath
-		}
-	}
-	tracks, err := q.ListTracksByAlbum(ctx, dbq.ListTracksByAlbumParams{AlbumID: album.ID})
-	if err != nil || len(tracks) == 0 {
-		return ""
-	}
-	return coverart.FindSidecar(filepath.Dir(tracks[0].FilePath))
+	return coverart.ResolveAlbumPath(ctx, q, album)
 }
 
 func serveImage(w http.ResponseWriter, r *http.Request, path string) {