feat: auto-sync the library on a timer while the app is open

While the app is in the foreground a timer checks the auto-sync setting and
syncs when due (default every 24h; the interval is selectable from 15 minutes
to 24 hours). It stops when the app is backgrounded. "Sync automatically"
is one setting: Off, Wi-Fi only (default) or Always.

A running sync is shown by a silent, dismissible notification and a small
spinner on the library tab bar's settings button. A manual pull-to-refresh
still holds the pull spinner; only an automatic sync does not. The library
and Home sync actions no-op while a sync is running, and SyncManager
coalesces a request that arrives mid-run into a single follow-up, so repeated
pull-to-refresh cannot pile up runs while adding a server still syncs it.

The time of the last sync attempt is recorded, so a failing server is retried
once per interval rather than every poll. The sync consumer and the auto-sync
loop both survive an unexpected failure instead of silently disabling syncing
for the rest of the process.

The poll sleeps for the interval (capped at 15 minutes) instead of a fixed
minute, the network mode is collected once rather than re-registering a
connectivity callback each poll, and the decision is logged at DEBUG (visible
with Verbose logging) rather than writing to the log file every poll.

AGENTS.md

@@ -48,6 +48,7 @@ Everything comes from the Nix flake devshell; do not install toolchains by hand.
 - Networking uses OkHttp and DOM XML parsing; auth uses the Subsonic token scheme by default.
 - Use coroutines and `Flow`; library reads are exposed as `Flow` from Room. Large lists page with Paging 3 over Room `PagingSource` rather than loading the whole table.
 - The library is mirrored in full at sync and must work offline. Never fetch library metadata on demand for browsing, filtering or sorting; only media bytes (streams, downloads) and images are on-demand. A server-derived sort key must be synced into a local column, not requested lazily when the sort is selected.
+- Auto-sync is a foreground-only, in-process timer (`AutoSync`, driven by the Activity lifecycle), not a background worker: do not move it to WorkManager or an alarm. `SyncManager` coalesces a request that arrives while a sync is running into a single follow-up; the library and Home sync actions no-op while one is running.
 - Playback is Media3: `PlaybackService` is a `MediaSessionService` owning an `ExoPlayer`, and `PlaybackController` (app-scoped Koin singleton) is the only thing the UI talks to. The queue is a `queue_entries` list of references with optional ranges plus a `playback_cursor` row; keep only a bounded window in memory (never the whole queue, and never load a whole table to build one). Stream URLs are freshly salted per request, so attach artwork by `CoverArtRef` cache key, not by URL.
 - UI state lives in `androidx.lifecycle.ViewModel`, wired with Koin (`koinViewModel()`); screens split into a stateful `*Route` and a stateless `*Screen` for screenshot tests.
 - UI and playback preferences go in DataStore (`UserPreferences`), not Room.

app/src/main/kotlin/com/subtracks/MainActivity.kt

@@ -11,6 +11,7 @@ import androidx.activity.enableEdgeToEdge
 import androidx.activity.result.contract.ActivityResultContracts
 import androidx.activity.viewModels
 import androidx.core.content.ContextCompat
+import com.subtracks.data.sync.AutoSync
 import com.subtracks.ui.NowPlayingLauncher
 import com.subtracks.ui.SubtracksRoot
 import com.subtracks.ui.theme.SubtracksTheme
@@ -19,10 +20,21 @@ import org.koin.core.context.GlobalContext
 class MainActivity : ComponentActivity() {
     private val launchViewModel: NowPlayingLaunchViewModel by viewModels()
     private val nowPlayingLauncher: NowPlayingLauncher by lazy { GlobalContext.get().get() }
+    private val autoSync: AutoSync by lazy { GlobalContext.get().get() }
 
     private val requestNotifications =
         registerForActivityResult(ActivityResultContracts.RequestPermission()) { }
 
+    override fun onStart() {
+        super.onStart()
+        autoSync.setForeground(true)
+    }
+
+    override fun onStop() {
+        super.onStop()
+        autoSync.setForeground(false)
+    }
+
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
         requestNotificationPermission()

app/src/main/kotlin/com/subtracks/data/prefs/UserPreferences.kt

@@ -6,6 +6,7 @@ import androidx.datastore.preferences.core.Preferences
 import androidx.datastore.preferences.core.booleanPreferencesKey
 import androidx.datastore.preferences.core.edit
 import androidx.datastore.preferences.core.intPreferencesKey
+import androidx.datastore.preferences.core.longPreferencesKey
 import androidx.datastore.preferences.core.stringPreferencesKey
 import androidx.datastore.preferences.preferencesDataStore
 import com.subtracks.data.net.NetworkMode
@@ -48,6 +49,10 @@ data class StreamQuality(
 
 private val Context.preferences: DataStore<Preferences> by preferencesDataStore("user_prefs")
 
+const val DEFAULT_SYNC_INTERVAL_MINUTES = 24 * 60
+
+enum class SyncMode { Off, WifiOnly, Always }
+
 data class ArtworkSeedValue(
     val cacheKey: String,
     val primary: Int,
@@ -105,6 +110,34 @@ class UserPreferences(
 
     private val syncConcurrencyKey = intPreferencesKey("sync_concurrency")
 
+    fun syncMode(): Flow<SyncMode> =
+        store.data.map { prefs ->
+            prefs[syncModeKey]?.let { stored -> SyncMode.entries.firstOrNull { it.name == stored } } ?: SyncMode.WifiOnly
+        }
+
+    suspend fun setSyncMode(mode: SyncMode) {
+        store.edit { prefs -> prefs[syncModeKey] = mode.name }
+    }
+
+    private val syncModeKey = stringPreferencesKey("sync_mode")
+
+    fun lastSyncAt(): Flow<Long> = store.data.map { prefs -> prefs[lastSyncAtKey] ?: 0L }
+
+    suspend fun setLastSyncAt(value: Long) {
+        store.edit { prefs -> prefs[lastSyncAtKey] = value }
+    }
+
+    private val lastSyncAtKey = longPreferencesKey("last_sync_at")
+
+    fun syncIntervalMinutes(): Flow<Int> =
+        store.data.map { prefs -> (prefs[syncIntervalKey] ?: DEFAULT_SYNC_INTERVAL_MINUTES).coerceAtLeast(1) }
+
+    suspend fun setSyncIntervalMinutes(value: Int) {
+        store.edit { prefs -> prefs[syncIntervalKey] = value.coerceAtLeast(1) }
+    }
+
+    private val syncIntervalKey = intPreferencesKey("sync_interval_minutes")
+
     fun scrobbling(): Flow<Boolean> = store.data.map { prefs -> prefs[scrobblingKey] ?: true }
 
     suspend fun setScrobbling(enabled: Boolean) {

app/src/main/kotlin/com/subtracks/data/sync/AutoSync.kt

@@ -0,0 +1,108 @@
+package com.subtracks.data.sync
+
+import com.subtracks.data.net.NetworkMode
+import com.subtracks.data.prefs.SyncMode
+import com.subtracks.data.prefs.UserPreferences
+import com.subtracks.log.Log
+import kotlinx.coroutines.CancellationException
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.currentCoroutineContext
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.isActive
+import kotlinx.coroutines.launch
+
+internal const val AUTO_SYNC_MAX_POLL_MS = 15L * 60 * 1000
+
+internal fun shouldAutoSync(
+    mode: SyncMode,
+    network: NetworkMode,
+    offline: Boolean,
+    hasSource: Boolean,
+    lastSyncAt: Long,
+    now: Long,
+    intervalMs: Long,
+): Boolean {
+    val allowed =
+        when (mode) {
+            SyncMode.Off -> false
+            SyncMode.WifiOnly -> network == NetworkMode.Wifi
+            SyncMode.Always -> true
+        }
+    return allowed && !offline && hasSource && (lastSyncAt > now || now - lastSyncAt >= intervalMs)
+}
+
+class AutoSync(
+    private val preferences: UserPreferences,
+    private val networkMode: Flow<NetworkMode>,
+    private val hasSource: suspend () -> Boolean,
+    private val requestSync: () -> Unit,
+    private val scope: CoroutineScope,
+    private val now: () -> Long = System::currentTimeMillis,
+    private val maxPollMs: Long = AUTO_SYNC_MAX_POLL_MS,
+) {
+    @Volatile
+    private var lastNetwork: NetworkMode? = null
+    private var loop: Job? = null
+
+    init {
+        scope.launch { networkMode.collect { lastNetwork = it } }
+    }
+
+    fun setForeground(active: Boolean) {
+        if (active) start() else stop()
+    }
+
+    private fun start() {
+        if (loop?.isActive == true) return
+        loop =
+            scope.launch {
+                while (isActive) {
+                    val intervalMs =
+                        try {
+                            checkAndRequest()
+                        } catch (cancellation: CancellationException) {
+                            throw cancellation
+                        } catch (failure: Exception) {
+                            Log.w("sync", "auto-sync check failed", failure)
+                            maxPollMs
+                        }
+                    delay(intervalMs.coerceAtMost(maxPollMs))
+                }
+            }
+    }
+
+    private fun stop() {
+        loop?.cancel()
+        loop = null
+    }
+
+    private suspend fun checkAndRequest(): Long {
+        val mode = preferences.syncMode().first()
+        val network = lastNetwork ?: networkMode.first()
+        val offline = preferences.offlineMode().first()
+        val hasSource = hasSource()
+        val lastSyncAt = preferences.lastSyncAt().first()
+        val intervalMs = preferences.syncIntervalMinutes().first() * 60_000L
+        val time = now()
+        val due =
+            shouldAutoSync(
+                mode = mode,
+                network = network,
+                offline = offline,
+                hasSource = hasSource,
+                lastSyncAt = lastSyncAt,
+                now = time,
+                intervalMs = intervalMs,
+            )
+        Log.d(
+            "sync",
+            "auto-sync due=$due (mode=$mode, network=$network, offline=$offline, hasSource=$hasSource, " +
+                "sinceLast=${time - lastSyncAt}ms, interval=${intervalMs}ms)",
+        )
+        if (due && currentCoroutineContext().isActive) requestSync()
+        return intervalMs
+    }
+}

app/src/main/kotlin/com/subtracks/data/sync/SyncManager.kt

@@ -3,6 +3,7 @@ package com.subtracks.data.sync
 import com.subtracks.R
 import com.subtracks.UiMessage
 import com.subtracks.data.db.SubtracksDatabase
+import com.subtracks.data.prefs.UserPreferences
 import com.subtracks.data.repo.QueueRepository
 import com.subtracks.data.repo.SourceRepository
 import com.subtracks.data.source.ServerActionSink
@@ -13,14 +14,18 @@ import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.SupervisorJob
 import kotlinx.coroutines.channels.Channel
+import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 
 sealed interface SyncStatus {
     data object Idle : SyncStatus
 
-    data object Running : SyncStatus
+    data class Running(
+        val silent: Boolean,
+    ) : SyncStatus
 
     data object Success : SyncStatus
 
@@ -34,31 +39,47 @@ class SyncManager(
     private val sourceRepository: SourceRepository,
     private val queueRepository: QueueRepository,
     private val serverActions: ServerActionSink,
+    private val preferences: UserPreferences,
     private val showMessage: (UiMessage) -> Unit = {},
     private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.Default),
 ) {
-    private val requests = Channel<Unit>(Channel.CONFLATED)
+    private val requests = Channel<Boolean>(Channel.CONFLATED)
     private val _status = MutableStateFlow<SyncStatus>(SyncStatus.Idle)
     val status: StateFlow<SyncStatus> = _status
 
     init {
         scope.launch {
-            for (ignored in requests) runSync()
+            for (silent in requests) {
+                try {
+                    runSync(silent)
+                } catch (cancellation: CancellationException) {
+                    if (!currentCoroutineContext().isActive) throw cancellation
+                    _status.value = SyncStatus.Idle
+                    Log.w("sync", "sync interrupted", cancellation)
+                } catch (failure: Throwable) {
+                    _status.value = SyncStatus.Idle
+                    Log.w("sync", "unexpected failure", failure)
+                }
+            }
         }
     }
 
-    fun requestSync() {
+    fun requestSync(silent: Boolean = false) {
-        requests.trySend(Unit)
+        requests.trySend(silent)
     }
 
-    private suspend fun runSync() {
+    private suspend fun runSync(silent: Boolean) {
         if (sourceRepository.offline.value) {
-            val offline = UiMessage(R.string.sync_offline)
+            if (!silent) {
-            showMessage(offline)
+                val offline = UiMessage(R.string.sync_offline)
-            _status.value = SyncStatus.Failed(offline)
+                showMessage(offline)
+                _status.value = SyncStatus.Failed(offline)
+            }
             return
         }
-        _status.value = SyncStatus.Running
+        _status.value = SyncStatus.Running(silent)
+        runCatching { preferences.setLastSyncAt(System.currentTimeMillis()) }
+            .onFailure { Log.w("sync", "could not record the sync attempt", it) }
         val startedAt = System.nanoTime()
         val result =
             try {
@@ -88,7 +109,7 @@ class SyncManager(
                                 ?: UiMessage(R.string.sync_failed_detail, listOf(failure.message ?: ""))
                         }
                     }
-                showMessage(message)
+                if (!silent) showMessage(message)
                 SyncStatus.Failed(message)
             }
         queueRepository.invalidateLibraryCache()

app/src/main/kotlin/com/subtracks/data/sync/SyncNotifier.kt

@@ -0,0 +1,72 @@
+package com.subtracks.data.sync
+
+import android.app.Notification
+import android.app.NotificationChannel
+import android.app.NotificationManager
+import android.app.PendingIntent
+import android.content.Context
+import android.os.Build
+import androidx.core.app.NotificationCompat
+import androidx.core.app.NotificationManagerCompat
+import com.subtracks.R
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.launch
+
+class SyncNotifier(
+    private val context: Context,
+    private val status: Flow<SyncStatus>,
+    private val scope: CoroutineScope = CoroutineScope(SupervisorJob() + Dispatchers.Default),
+) {
+    private val manager = NotificationManagerCompat.from(context)
+
+    fun start() {
+        createChannel()
+        scope.launch {
+            status.collect { syncStatus ->
+                if (syncStatus is SyncStatus.Running && manager.areNotificationsEnabled()) {
+                    manager.notify(ID, build())
+                } else {
+                    manager.cancel(ID)
+                }
+            }
+        }
+    }
+
+    private fun build(): Notification =
+        NotificationCompat
+            .Builder(context, CHANNEL_ID)
+            .setSmallIcon(R.drawable.ic_stat_name)
+            .setContentTitle(context.getString(R.string.sync_notification_title))
+            .setContentText(context.getString(R.string.sync_notification_text))
+            .setOnlyAlertOnce(true)
+            .setSilent(true)
+            .setProgress(0, 0, true)
+            .setContentIntent(launchIntent())
+            .build()
+
+    private fun launchIntent(): PendingIntent? =
+        context.packageManager
+            .getLaunchIntentForPackage(context.packageName)
+            ?.let { PendingIntent.getActivity(context, 0, it, PendingIntent.FLAG_IMMUTABLE) }
+
+    private fun createChannel() {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.O) return
+        val manager = context.getSystemService(NotificationManager::class.java) ?: return
+        if (manager.getNotificationChannel(CHANNEL_ID) != null) return
+        manager.createNotificationChannel(
+            NotificationChannel(
+                CHANNEL_ID,
+                context.getString(R.string.sync_notification_channel),
+                NotificationManager.IMPORTANCE_LOW,
+            ).apply { setShowBadge(false) },
+        )
+    }
+
+    companion object {
+        private const val ID = 2
+        private const val CHANNEL_ID = "sync"
+    }
+}

app/src/main/kotlin/com/subtracks/di/AppModule.kt

@@ -27,7 +27,9 @@ import com.subtracks.data.repo.PendingServerActionSink
 import com.subtracks.data.repo.QueueRepository
 import com.subtracks.data.repo.SourceRepository
 import com.subtracks.data.source.ServerActionSink
+import com.subtracks.data.sync.AutoSync
 import com.subtracks.data.sync.SyncManager
+import com.subtracks.data.sync.SyncNotifier
 import com.subtracks.log.Log
 import com.subtracks.playback.MediaSessionConnection
 import com.subtracks.playback.PlaybackController
@@ -96,7 +98,16 @@ fun appModule(
     }
     single { LibraryRepository(get(), get(), get(), toast, scope = get(named("io"))) }
     single<ArtworkSeedStore> { ArtworkSeedRepository(get()) }
-    single { SyncManager(get(), get(), get(), get(), showMessage = toast, scope = get()) }
+    single { SyncManager(get(), get(), get(), get(), preferences = get(), showMessage = toast, scope = get()) }
+    single {
+        AutoSync(
+            preferences = get(),
+            networkMode = networkMode(context.applicationContext),
+            hasSource = { get<SourceRepository>().activeSourceIdOnce() != null },
+            requestSync = { get<SyncManager>().requestSync(silent = true) },
+            scope = get(),
+        )
+    }
     single { QueueRepository(get()) }
     single { ArtworkStore(downloadsRoot(context)) }
     single<ArtworkFetcher> { OkHttpArtworkFetcher(get()) }
@@ -115,6 +126,7 @@ fun appModule(
         ).also { it.start() }
     }
     single(createdAtStart = true) { DownloadNotifier(context.applicationContext, get(), scope = get()).also { it.start() } }
+    single(createdAtStart = true) { SyncNotifier(context.applicationContext, get<SyncManager>().status, scope = get()).also { it.start() } }
     single<PlayerConnection> { MediaSessionConnection(context.applicationContext, get(), get()) }
     single { PlaybackController(get(), get(), get(), get(), showMessage = toast, scope = get(named("playback"))) }
     single(createdAtStart = true) {

app/src/main/kotlin/com/subtracks/ui/home/HomeViewModel.kt

@@ -25,7 +25,6 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.filterNotNull
 import kotlinx.coroutines.flow.flatMapLatest
-import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
 
@@ -53,11 +52,6 @@ class HomeViewModel(
     private val syncManager: SyncManager,
     private val playbackController: PlaybackController,
 ) : ViewModel() {
-    val syncing: StateFlow<Boolean> =
-        syncManager.status
-            .map { it == SyncStatus.Running }
-            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
-
     val offline: StateFlow<Boolean> =
         sourceRepository.offline.stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
 
@@ -141,7 +135,9 @@ class HomeViewModel(
         viewModelScope.playDownloadedList(libraryRepository, playbackController, song)
     }
 
-    fun sync() = syncManager.requestSync()
+    fun sync() {
+        if (syncManager.status.value !is SyncStatus.Running) syncManager.requestSync()
+    }
 
     private data class PlayRows(
         val recentAlbums: List<Album>,

app/src/main/kotlin/com/subtracks/ui/library/LibraryScreen.kt

@@ -40,6 +40,7 @@ import androidx.compose.material.icons.rounded.Person
 import androidx.compose.material.icons.rounded.Remove
 import androidx.compose.material.icons.rounded.Search
 import androidx.compose.material.icons.rounded.Settings
+import androidx.compose.material3.CircularProgressIndicator
 import androidx.compose.material3.ExperimentalMaterial3Api
 import androidx.compose.material3.FilterChip
 import androidx.compose.material3.FilterChipDefaults
@@ -243,6 +244,7 @@ fun LibraryRoute(
     var previousTabName by remember { mutableStateOf(selectedTab.name) }
     val previousTab = LibraryTab.entries.firstOrNull { it.name == previousTabName } ?: LibraryTab.Albums
     val syncing by viewModel.syncing.collectAsStateWithLifecycle()
+    val refreshing by viewModel.refreshing.collectAsStateWithLifecycle()
     val listTab = selectedTab.listTab()
     LaunchedEffect(selectedTab) {
         if (previousTab != selectedTab) {
@@ -296,6 +298,7 @@ fun LibraryRoute(
         selectedTab = selectedTab,
         onTabSelected = { tab -> if (viewModel.selectedTab.value != tab) viewModel.selectTab(tab) },
         syncing = syncing,
+        refreshing = refreshing,
         bottomInset = bottomInset,
         artwork = artwork,
         albums = viewModel.albums,
@@ -392,6 +395,7 @@ fun LibraryScreen(
     onExitOffline: () -> Unit = {},
     onItemLongClick: (MenuTarget) -> Unit = {},
     syncing: Boolean = false,
+    refreshing: Boolean = false,
     bottomInset: Dp = 0.dp,
     listQuery: ListQuery = ListQuery(""),
     resetKeys: Map<LibraryTab, Any?> = emptyMap(),
@@ -474,13 +478,13 @@ fun LibraryScreen(
             val scrollToTopKey = if (pageTab == selectedTab) topRequest else null
             val pullToRefreshState = rememberPullToRefreshState()
             PullToRefreshBox(
-                isRefreshing = syncing,
+                isRefreshing = refreshing,
                 onRefresh = onSync,
                 state = pullToRefreshState,
                 indicator = {
                     PullToRefreshDefaults.Indicator(
                         state = pullToRefreshState,
-                        isRefreshing = syncing,
+                        isRefreshing = refreshing,
                         modifier = Modifier.align(Alignment.TopCenter).statusBarsPadding(),
                         containerColor = headerColor,
                         color = artwork?.scheme?.primary ?: MaterialTheme.colorScheme.primary,
@@ -582,6 +586,7 @@ fun LibraryScreen(
                     offline = offline,
                     onExitOffline = onExitOffline,
                     artwork = artwork,
+                    syncing = syncing,
                 )
             }
         }
@@ -848,6 +853,7 @@ internal fun LibraryTabs(
     offline: Boolean = false,
     onExitOffline: () -> Unit = {},
     artwork: ArtworkColors?,
+    syncing: Boolean = false,
 ) {
     val indicatorStretch = 18.dp
     val density = LocalDensity.current
@@ -939,11 +945,20 @@ internal fun LibraryTabs(
                         }
                     }
                     IconButton(onClick = onOpenSettings) {
-                        Icon(
+                        Box(contentAlignment = Alignment.Center) {
-                            imageVector = Icons.Rounded.Settings,
+                            Icon(
-                            contentDescription = stringResource(R.string.navigation_tabs_settings),
+                                imageVector = Icons.Rounded.Settings,
-                            tint = MaterialTheme.colorScheme.onBackground,
+                                contentDescription = stringResource(R.string.navigation_tabs_settings),
-                        )
+                                tint = MaterialTheme.colorScheme.onBackground,
+                            )
+                            if (syncing) {
+                                CircularProgressIndicator(
+                                    modifier = Modifier.size(32.dp),
+                                    strokeWidth = 2.dp,
+                                    color = MaterialTheme.colorScheme.primary,
+                                )
+                            }
+                        }
                     }
                 }
             }

app/src/main/kotlin/com/subtracks/ui/library/LibraryViewModel.kt

@@ -117,7 +117,12 @@ class LibraryViewModel(
 
     val syncing: StateFlow<Boolean> =
         syncManager.status
-            .map { it == SyncStatus.Running }
+            .map { it is SyncStatus.Running }
+            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
+
+    val refreshing: StateFlow<Boolean> =
+        syncManager.status
+            .map { it is SyncStatus.Running && !it.silent }
             .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), false)
 
     private val activeSourceId = libraryRepository.activeSourceId.filterNotNull()
@@ -206,7 +211,9 @@ class LibraryViewModel(
         thumbnail: Boolean,
     ): CoverArtRef? = sourceRepository.coverArt(coverArt, thumbnail)
 
-    fun sync() = syncManager.requestSync()
+    fun sync() {
+        if (syncManager.status.value !is SyncStatus.Running) syncManager.requestSync()
+    }
 }
 
 internal fun ListQuery.albumSort(): AlbumSort = AlbumSort.entries.firstOrNull { it.name == sort } ?: AlbumSort.Name

app/src/main/kotlin/com/subtracks/ui/playback/QueueScreen.kt

@@ -113,6 +113,8 @@ class QueueViewModel(
     var generation by mutableIntStateOf(0)
         private set
 
+    private var reorderPending = false
+
     private var nextId = 0L
     private val mutex = Mutex()
 
@@ -249,12 +251,19 @@ class QueueViewModel(
     fun move(
         from: Long,
         to: Long,
-    ) {
+    ): Boolean {
-        if (from == to) return
+        if (from == to) return false
+        if (reorderPending) return false
+        reorderPending = true
         viewModelScope.launch {
-            playbackController.move(from, to)
+            try {
-            mutex.withLock { reconcileLocked() }
+                playbackController.move(from, to)
+                mutex.withLock { reconcileLocked() }
+            } finally {
+                reorderPending = false
+            }
         }
+        return true
     }
 
     fun remove(position: Long) {
@@ -331,7 +340,7 @@ fun QueueScreen(
     onPlay: (Long) -> Unit,
     onRemove: (Long) -> Unit,
     onReorder: (Int, Int) -> Unit,
-    onMove: (Long, Long) -> Unit,
+    onMove: (Long, Long) -> Boolean,
     onLoadOlder: () -> Unit,
     onLoadNewer: () -> Unit,
     onUndo: () -> Unit,
@@ -347,7 +356,6 @@ fun QueueScreen(
     val snackbarHostState = remember { SnackbarHostState() }
     val scope = rememberCoroutineScope()
     var dragId by remember { mutableStateOf<Long?>(null) }
-    var dragFrom by remember { mutableStateOf<Long?>(null) }
     val undoLabel = stringResource(R.string.undo)
     val queueReordered = stringResource(R.string.queue_reordered)
     val queueRemoved = stringResource(R.string.queue_removed)
@@ -470,28 +478,14 @@ fun QueueScreen(
                                             null
                                         } else {
                                             Modifier.draggableHandle(
-                                                onDragStarted = {
+                                                onDragStarted = { dragId = row.id },
-                                                    dragId = row.id
-                                                    dragFrom = row.position
-                                                },
                                                 onDragStopped = {
-                                                    val id = dragId
+                                                    dragId?.let { id ->
-                                                    val from = dragFrom
+                                                        rows.dropMoveFor(id)?.let { move ->
-                                                    if (id != null && from != null) {
+                                                            if (onMove(move.from, move.to)) showUndo(queueReordered)
-                                                        val draggedIndex = rows.indexOfFirst { it.id == id }
-                                                        val to =
-                                                            if (draggedIndex < 0) {
-                                                                from
-                                                            } else {
-                                                                dropTarget(rows, draggedIndex, from)
-                                                            }
-                                                        if (to != from) {
-                                                            onMove(from, to)
-                                                            showUndo(queueReordered)
                                                         }
                                                     }
                                                     dragId = null
-                                                    dragFrom = null
                                                 },
                                             )
                                         },
@@ -563,6 +557,19 @@ internal fun dropTarget(
     return (before - if (before > from) 1 else 0) + 1
 }
 
+internal data class QueueMove(
+    val from: Long,
+    val to: Long,
+)
+
+internal fun List<QueueRow>.dropMoveFor(draggedId: Long): QueueMove? {
+    val index = indexOfFirst { it.id == draggedId }
+    if (index < 0) return null
+    val from = this[index].position
+    val to = dropTarget(this, index, from)
+    return if (to == from) null else QueueMove(from, to)
+}
+
 @Suppress("ModifierParameter")
 @Composable
 private fun QueueRowItem(

app/src/main/kotlin/com/subtracks/ui/settings/SettingsScreen.kt

@@ -65,7 +65,9 @@ import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import com.subtracks.BuildConfig
 import com.subtracks.R
 import com.subtracks.data.model.Source
+import com.subtracks.data.prefs.DEFAULT_SYNC_INTERVAL_MINUTES
 import com.subtracks.data.prefs.StreamQuality
+import com.subtracks.data.prefs.SyncMode
 import com.subtracks.log.Log
 import com.subtracks.ui.components.DismissOnRequest
 import com.subtracks.ui.components.rememberViewportFill
@@ -82,7 +84,7 @@ private val streamFormats = listOf(null, "mp3", "opus", "ogg", "webm", "aac", "f
 private const val PROJECT_HOMEPAGE = "https://github.com/austinried/subtracks"
 private const val SUPPORT_URL = "https://ko-fi.com/austinried"
 
-private enum class SettingsDialog { WifiQuality, MobileQuality, DownloadQuality, SyncConcurrency }
+private enum class SettingsDialog { WifiQuality, MobileQuality, DownloadQuality, SyncConcurrency, SyncInterval, SyncMode }
 
 @Composable
 fun SettingsRoute(
@@ -99,6 +101,8 @@ fun SettingsRoute(
     val wifiQuality by viewModel.wifiQuality.collectAsStateWithLifecycle()
     val mobileQuality by viewModel.mobileQuality.collectAsStateWithLifecycle()
     val syncConcurrency by viewModel.syncConcurrency.collectAsStateWithLifecycle()
+    val syncMode by viewModel.syncMode.collectAsStateWithLifecycle()
+    val syncIntervalMinutes by viewModel.syncIntervalMinutes.collectAsStateWithLifecycle()
     val downloadQuality by viewModel.downloadQuality.collectAsStateWithLifecycle()
     val downloadOverMetered by viewModel.downloadOverMetered.collectAsStateWithLifecycle()
     val scrobbling by viewModel.scrobbling.collectAsStateWithLifecycle()
@@ -112,6 +116,8 @@ fun SettingsRoute(
         wifiQuality = wifiQuality,
         mobileQuality = mobileQuality,
         syncConcurrency = syncConcurrency,
+        syncMode = syncMode,
+        syncInterval = syncIntervalMinutes,
         downloadQuality = downloadQuality,
         downloadOverMetered = downloadOverMetered,
         scrobbling = scrobbling,
@@ -122,6 +128,8 @@ fun SettingsRoute(
         onWifiQualityChange = viewModel::setWifiQuality,
         onMobileQualityChange = viewModel::setMobileQuality,
         onSyncConcurrencyChange = viewModel::setSyncConcurrency,
+        onSyncModeChange = viewModel::setSyncMode,
+        onSyncIntervalChange = viewModel::setSyncIntervalMinutes,
         onDownloadQualityChange = viewModel::setDownloadQuality,
         onDownloadOverMeteredChange = viewModel::setDownloadOverMetered,
         onScrobblingChange = viewModel::setScrobbling,
@@ -166,11 +174,15 @@ fun SettingsScreen(
     modifier: Modifier = Modifier,
     offline: Boolean = false,
     verboseLogging: Boolean = false,
+    syncMode: SyncMode = SyncMode.WifiOnly,
+    syncInterval: Int = DEFAULT_SYNC_INTERVAL_MINUTES,
     onSelectSource: (Long) -> Unit,
     onEditServer: (Long) -> Unit,
     onWifiQualityChange: (StreamQuality) -> Unit,
     onMobileQualityChange: (StreamQuality) -> Unit,
     onSyncConcurrencyChange: (Int) -> Unit,
+    onSyncModeChange: (SyncMode) -> Unit = {},
+    onSyncIntervalChange: (Int) -> Unit = {},
     onDownloadQualityChange: (StreamQuality) -> Unit,
     onDownloadOverMeteredChange: (Boolean) -> Unit,
     onScrobblingChange: (Boolean) -> Unit,
@@ -288,6 +300,22 @@ fun SettingsScreen(
                     colors = ListItemDefaults.colors(containerColor = Color.Transparent),
                 )
             }
+            item {
+                ListItem(
+                    headlineContent = { Text(stringResource(R.string.settings_sync_auto_title)) },
+                    supportingContent = { Text(syncModeLabel(LocalResources.current, syncMode)) },
+                    modifier = Modifier.clickable { dialog = SettingsDialog.SyncMode },
+                    colors = ListItemDefaults.colors(containerColor = Color.Transparent),
+                )
+            }
+            item {
+                ListItem(
+                    headlineContent = { Text(stringResource(R.string.sync_interval)) },
+                    supportingContent = { Text(syncIntervalLabel(LocalResources.current, syncInterval)) },
+                    modifier = Modifier.clickable { dialog = SettingsDialog.SyncInterval },
+                    colors = ListItemDefaults.colors(containerColor = Color.Transparent),
+                )
+            }
             item { SectionHeader(stringResource(R.string.settings_music_name)) }
             item {
                 ListItem(
@@ -475,6 +503,22 @@ fun SettingsScreen(
             )
         }
 
+        SettingsDialog.SyncInterval -> {
+            SyncIntervalDialog(
+                selected = syncInterval,
+                onSelect = onSyncIntervalChange,
+                onDismiss = { dialog = null },
+            )
+        }
+
+        SettingsDialog.SyncMode -> {
+            SyncModeDialog(
+                selected = syncMode,
+                onSelect = onSyncModeChange,
+                onDismiss = { dialog = null },
+            )
+        }
+
         null -> {
             Unit
         }
@@ -500,11 +544,56 @@ private fun bitrateLabel(
 
 private val syncConcurrencyOptions = listOf(1, 2, 4, 8, 16)
 
+private val syncIntervalOptions = listOf(15, 60, 360, 720, DEFAULT_SYNC_INTERVAL_MINUTES)
+
 private fun concurrencyLabel(
     resources: Resources,
     value: Int,
 ): String = if (value <= 1) resources.getString(R.string.sync_concurrency_sequential) else value.toString()
 
+private fun syncIntervalLabel(
+    resources: Resources,
+    minutes: Int,
+): String =
+    if (minutes >= 60 && minutes % 60 == 0) {
+        resources.getQuantityString(R.plurals.sync_interval_hours, minutes / 60, minutes / 60)
+    } else {
+        resources.getQuantityString(R.plurals.sync_interval_minutes, minutes, minutes)
+    }
+
+@Composable
+private fun SyncIntervalDialog(
+    selected: Int,
+    onSelect: (Int) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    val resources = LocalResources.current
+    var draft by remember(selected) { mutableIntStateOf(selected) }
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.sync_interval)) },
+        text = {
+            ChoiceGroup(
+                header = stringResource(R.string.sync_interval_prompt),
+                options = syncIntervalOptions.map { it to syncIntervalLabel(resources, it) },
+                selected = draft,
+                onSelect = { draft = it },
+            )
+        },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    onSelect(draft)
+                    onDismiss()
+                },
+            ) { Text(stringResource(R.string.action_done)) }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.actions_cancel)) }
+        },
+    )
+}
+
 @Composable
 private fun ConcurrencyDialog(
     selected: Int,
@@ -538,6 +627,51 @@ private fun ConcurrencyDialog(
     )
 }
 
+private val syncModeOptions = SyncMode.entries
+
+private fun syncModeLabel(
+    resources: Resources,
+    mode: SyncMode,
+): String =
+    when (mode) {
+        SyncMode.Off -> resources.getString(R.string.sync_mode_off)
+        SyncMode.WifiOnly -> resources.getString(R.string.sync_mode_wifi)
+        SyncMode.Always -> resources.getString(R.string.sync_mode_always)
+    }
+
+@Composable
+private fun SyncModeDialog(
+    selected: SyncMode,
+    onSelect: (SyncMode) -> Unit,
+    onDismiss: () -> Unit,
+) {
+    val resources = LocalResources.current
+    var draft by remember(selected) { mutableStateOf(selected) }
+    AlertDialog(
+        onDismissRequest = onDismiss,
+        title = { Text(stringResource(R.string.settings_sync_auto_title)) },
+        text = {
+            ChoiceGroup(
+                header = stringResource(R.string.sync_mode_prompt),
+                options = syncModeOptions.map { it to syncModeLabel(resources, it) },
+                selected = draft,
+                onSelect = { draft = it },
+            )
+        },
+        confirmButton = {
+            TextButton(
+                onClick = {
+                    onSelect(draft)
+                    onDismiss()
+                },
+            ) { Text(stringResource(R.string.action_done)) }
+        },
+        dismissButton = {
+            TextButton(onClick = onDismiss) { Text(stringResource(R.string.actions_cancel)) }
+        },
+    )
+}
+
 @Composable
 private fun QualityDialog(
     title: String,

app/src/main/kotlin/com/subtracks/ui/settings/SettingsViewModel.kt

@@ -4,7 +4,9 @@ import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import com.subtracks.data.model.Source
 import com.subtracks.data.net.NetworkMode
+import com.subtracks.data.prefs.DEFAULT_SYNC_INTERVAL_MINUTES
 import com.subtracks.data.prefs.StreamQuality
+import com.subtracks.data.prefs.SyncMode
 import com.subtracks.data.prefs.UserPreferences
 import com.subtracks.data.repo.SourceRepository
 import com.subtracks.data.source.DEFAULT_FETCH_CONCURRENCY
@@ -48,6 +50,16 @@ class SettingsViewModel(
             .syncConcurrency()
             .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), DEFAULT_FETCH_CONCURRENCY)
 
+    val syncMode: StateFlow<SyncMode> =
+        userPreferences
+            .syncMode()
+            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), SyncMode.WifiOnly)
+
+    val syncIntervalMinutes: StateFlow<Int> =
+        userPreferences
+            .syncIntervalMinutes()
+            .stateIn(viewModelScope, SharingStarted.WhileSubscribed(5_000), DEFAULT_SYNC_INTERVAL_MINUTES)
+
     val scrobbling: StateFlow<Boolean> =
         userPreferences
             .scrobbling()
@@ -92,6 +104,14 @@ class SettingsViewModel(
         viewModelScope.launch { userPreferences.setSyncConcurrency(value) }
     }
 
+    fun setSyncMode(mode: SyncMode) {
+        viewModelScope.launch { userPreferences.setSyncMode(mode) }
+    }
+
+    fun setSyncIntervalMinutes(value: Int) {
+        viewModelScope.launch { userPreferences.setSyncIntervalMinutes(value) }
+    }
+
     fun setScrobbling(enabled: Boolean) {
         viewModelScope.launch { userPreferences.setScrobbling(enabled) }
     }

app/src/main/res/values/strings.xml

@@ -2,6 +2,9 @@
 <resources xmlns:tools="http://schemas.android.com/tools">
     <string name="app_name">subtracks</string>
     <string name="download_channel_description">Progress while songs download</string>
+    <string name="sync_notification_channel">Sync</string>
+    <string name="sync_notification_title">Syncing library</string>
+    <string name="sync_notification_text">Keeping your library up to date</string>
 
     <string name="actions_cancel">Cancel</string>
     <string name="actions_delete">Delete</string>
@@ -201,6 +204,21 @@
     <string name="sync_concurrency">Sync concurrency</string>
     <string name="sync_concurrency_parallel">Parallel server requests while syncing</string>
     <string name="sync_concurrency_sequential">1 (sequential)</string>
+    <string name="settings_sync_auto_title">Sync automatically</string>
+    <string name="sync_mode_off">Off</string>
+    <string name="sync_mode_wifi">Wi-Fi only</string>
+    <string name="sync_mode_always">Always</string>
+    <string name="sync_mode_prompt">When to sync automatically</string>
+    <string name="sync_interval">Automatic sync interval</string>
+    <string name="sync_interval_prompt">How often to sync automatically</string>
+    <plurals name="sync_interval_minutes">
+        <item quantity="one">%1$d minute</item>
+        <item quantity="other">%1$d minutes</item>
+    </plurals>
+    <plurals name="sync_interval_hours">
+        <item quantity="one">%1$d hour</item>
+        <item quantity="other">%1$d hours</item>
+    </plurals>
     <string name="download_quality">Download quality</string>
     <string name="download_over_mobile">Download over mobile data</string>
     <string name="download_network_wifi_and_mobile">Wi-Fi and mobile</string>

app/src/test/kotlin/com/subtracks/data/sync/AutoSyncTest.kt

@@ -0,0 +1,146 @@
+package com.subtracks.data.sync
+
+import com.subtracks.awaitUntil
+import com.subtracks.cancelAndJoinBlocking
+import com.subtracks.data.net.NetworkMode
+import com.subtracks.data.prefs.DEFAULT_SYNC_INTERVAL_MINUTES
+import com.subtracks.data.prefs.SyncMode
+import com.subtracks.data.prefs.UserPreferences
+import com.subtracks.data.prefs.fakeUserPreferences
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.delay
+import kotlinx.coroutines.flow.flowOf
+import kotlinx.coroutines.runBlocking
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+import java.util.concurrent.atomic.AtomicBoolean
+import java.util.concurrent.atomic.AtomicInteger
+
+class AutoSyncTest {
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Default)
+
+    @After
+    fun tearDown() {
+        cancelAndJoinBlocking(scope)
+    }
+
+    @Test
+    fun decidesWhetherASyncIsDue() {
+        assertTrue(shouldSync())
+        assertTrue(shouldSync(mode = SyncMode.WifiOnly))
+        assertTrue(shouldSync(mode = SyncMode.Always, network = NetworkMode.Mobile))
+        assertTrue(shouldSync(lastSyncAt = INTERVAL_MS * 2, now = INTERVAL_MS))
+
+        assertFalse(shouldSync(mode = SyncMode.Off))
+        assertFalse(shouldSync(mode = SyncMode.WifiOnly, network = NetworkMode.Mobile))
+        assertFalse(shouldSync(lastSyncAt = INTERVAL_MS - 1, now = INTERVAL_MS))
+        assertFalse(shouldSync(offline = true))
+        assertFalse(shouldSync(hasSource = false))
+    }
+
+    @Test
+    fun syncsWhenTheAppIsActiveAndDue() {
+        val preferences = fakeUserPreferences()
+        runBlocking {
+            preferences.setSyncMode(SyncMode.WifiOnly)
+            preferences.setLastSyncAt(0L)
+        }
+        val requested = AtomicBoolean(false)
+        val autoSync = autoSync(preferences, requestSync = { requested.set(true) })
+
+        autoSync.setForeground(true)
+
+        awaitUntil("auto sync requested") { requested.get() }
+        autoSync.setForeground(false)
+    }
+
+    @Test
+    fun doesNotSyncWhenOff() {
+        val preferences = fakeUserPreferences()
+        runBlocking {
+            preferences.setSyncMode(SyncMode.Off)
+            preferences.setLastSyncAt(0L)
+        }
+        val requested = AtomicBoolean(false)
+        val autoSync = autoSync(preferences, requestSync = { requested.set(true) })
+
+        autoSync.setForeground(true)
+        runBlocking { delay(300) }
+        autoSync.setForeground(false)
+
+        assertFalse(requested.get())
+    }
+
+    @Test
+    fun stopsSyncingWhenBackgrounded() {
+        val preferences = fakeUserPreferences()
+        runBlocking {
+            preferences.setSyncMode(SyncMode.Always)
+            preferences.setLastSyncAt(0L)
+        }
+        val count = AtomicInteger(0)
+        val autoSync =
+            AutoSync(
+                preferences = preferences,
+                networkMode = flowOf(NetworkMode.Wifi),
+                hasSource = { true },
+                requestSync = { count.incrementAndGet() },
+                scope = scope,
+                now = { INTERVAL_MS + 1 },
+                maxPollMs = 50L,
+            )
+
+        autoSync.setForeground(true)
+        awaitUntil("first sync") { count.get() >= 1 }
+        autoSync.setForeground(false)
+
+        runBlocking { delay(200) }
+        val afterStop = count.get()
+        runBlocking { delay(300) }
+
+        assertEquals(afterStop, count.get())
+    }
+
+    private fun autoSync(
+        preferences: UserPreferences,
+        requestSync: () -> Unit,
+        now: () -> Long = { INTERVAL_MS + 1 },
+    ): AutoSync =
+        AutoSync(
+            preferences = preferences,
+            networkMode = flowOf(NetworkMode.Wifi),
+            hasSource = { true },
+            requestSync = requestSync,
+            scope = scope,
+            now = now,
+            maxPollMs = 10_000L,
+        )
+
+    private fun shouldSync(
+        mode: SyncMode = SyncMode.WifiOnly,
+        network: NetworkMode = NetworkMode.Wifi,
+        offline: Boolean = false,
+        hasSource: Boolean = true,
+        lastSyncAt: Long = 0L,
+        now: Long = INTERVAL_MS,
+        intervalMs: Long = INTERVAL_MS,
+    ): Boolean =
+        shouldAutoSync(
+            mode = mode,
+            network = network,
+            offline = offline,
+            hasSource = hasSource,
+            lastSyncAt = lastSyncAt,
+            now = now,
+            intervalMs = intervalMs,
+        )
+
+    private companion object {
+        val INTERVAL_MS = DEFAULT_SYNC_INTERVAL_MINUTES * 60_000L
+    }
+}

app/src/test/kotlin/com/subtracks/data/sync/SyncManagerTest.kt

@@ -10,6 +10,7 @@ import com.subtracks.TEST_TIMEOUT_MS
 import com.subtracks.cancelAndJoinBlocking
 import com.subtracks.data.db.SubtracksDatabase
 import com.subtracks.data.download.ArtworkStore
+import com.subtracks.data.prefs.UserPreferences
 import com.subtracks.data.prefs.fakeUserPreferences
 import com.subtracks.data.repo.NetworkServerActionSink
 import com.subtracks.data.repo.QueueRepository
@@ -44,6 +45,7 @@ class SyncManagerTest {
     private lateinit var sourceRepository: SourceRepository
     private lateinit var queueRepository: QueueRepository
     private lateinit var manager: SyncManager
+    private lateinit var preferences: UserPreferences
     private lateinit var scope: CoroutineScope
     private val messages = CopyOnWriteArrayList<String>()
     private lateinit var server: MockWebServer
@@ -62,12 +64,14 @@ class SyncManagerTest {
         sourceRepository =
             SourceRepository(db, OkHttpClient(), fakeUserPreferences(), ArtworkStore(File(context.cacheDir, "art")), scope = scope)
         queueRepository = QueueRepository(db)
+        preferences = fakeUserPreferences()
         manager =
             SyncManager(
                 db,
                 sourceRepository,
                 queueRepository,
                 NetworkServerActionSink(sourceRepository),
+                preferences = preferences,
                 showMessage = { messages += it.resolve(resources) },
                 scope = scope,
             )
@@ -89,6 +93,16 @@ class SyncManagerTest {
             withTimeout(TEST_TIMEOUT_MS) { manager.status.first { it is SyncStatus.Failed } }
 
             assertEquals(listOf("No server configured"), messages)
+            assertTrue(preferences.lastSyncAt().first() > 0)
+        }
+
+    @Test
+    fun aSilentSyncDoesNotTellTheUser() =
+        runBlocking {
+            manager.requestSync(silent = true)
+            withTimeout(TEST_TIMEOUT_MS) { manager.status.first { it is SyncStatus.Failed } }
+
+            assertTrue(messages.isEmpty())
         }
 
     @Test
@@ -114,6 +128,7 @@ class SyncManagerTest {
 
             assertEquals(listOf("ar1"), db.libraryDao().artistIds(1))
             assertEquals(listOf("al1"), db.libraryDao().albumIds(1))
+            assertTrue(preferences.lastSyncAt().first() > 0)
         }
 
     @Test

app/src/test/kotlin/com/subtracks/ui/AppScreenshotTest.kt

@@ -506,7 +506,7 @@ class AppScreenshotTest {
                     onPlay = {},
                     onRemove = {},
                     onReorder = { _, _ -> },
-                    onMove = { _, _ -> },
+                    onMove = { _, _ -> true },
                     onLoadOlder = {},
                     onLoadNewer = {},
                     onUndo = {},

app/src/test/kotlin/com/subtracks/ui/playback/QueueViewModelTest.kt

@@ -325,6 +325,42 @@ class QueueViewModelTest {
         assertEquals((220L..399L).toList(), rowsSnapshot().map { it.position })
     }
 
+    @Test
+    fun ignoringASecondMoveWhileTheFirstIsStillCommitting() {
+        runBlocking { seedSongs(10) }
+        controller.playAlbum(1, "al1", 0)
+        await { controller.state.value.position == 0L }
+
+        viewModel.open()
+        await { viewModel.ready }
+        val before = rowsSnapshot().map { it.song.song.id }
+        val from = rowsSnapshot().first().position
+
+        runOnMain {
+            assertTrue(viewModel.move(from, from + 3))
+            assertFalse(viewModel.move(from, from + 1))
+        }
+
+        val expected = before.toMutableList().also { it.add(3, it.removeAt(0)) }
+        await { rowsSnapshot().map { it.song.song.id } == expected }
+        assertEquals(expected, rowsSnapshot().map { it.song.song.id })
+    }
+
+    @Test
+    fun dropMoveTakesTheDraggedRowsCurrentPosition() {
+        val rows =
+            listOf(
+                row(10).copy(id = 2L),
+                row(11).copy(id = 3L),
+                row(9).copy(id = 1L),
+            )
+
+        val move = rows.dropMoveFor(1L)!!
+
+        assertEquals(9L, move.from)
+        assertEquals(11L, move.to)
+    }
+
     @Test
     fun removingATrackUnderTheBlockReloadsRows() {
         runBlocking { seedSongs(10) }

app/src/test/kotlin/com/subtracks/ui/settings/AddSourceViewModelTest.kt

@@ -156,7 +156,14 @@ class AddSourceViewModelTest {
 
     private fun viewModel(sourceId: Long? = null): AddSourceViewModel {
         val syncManager =
-            SyncManager(db, sourceRepository, QueueRepository(db), NetworkServerActionSink(sourceRepository), scope = repoScope)
+            SyncManager(
+                db,
+                sourceRepository,
+                QueueRepository(db),
+                NetworkServerActionSink(sourceRepository),
+                preferences = fakeUserPreferences(),
+                scope = repoScope,
+            )
         val resources = ApplicationProvider.getApplicationContext<Context>().resources
         return AddSourceViewModel(sourceRepository, syncManager, downloadRepository, sourceId, resources).also { createdViewModels += it }
     }

docs/architecture.md

@@ -52,7 +52,7 @@ app/src/main/kotlin/com/subtracks
     repo/                            SourceRepository, LibraryRepository
     source/                          MusicSource abstraction
       subsonic/                      SubsonicClient, SubsonicXml, SubsonicSource
-    sync/                            SyncService (stream + per-batch writes + prune), SyncManager (status)
+    sync/                            SyncService (stream + per-batch writes + prune), SyncManager (status), AutoSync (foreground timer), SyncNotifier
 ```
 
 ## Layers
@@ -65,12 +65,12 @@ Compose UI  ->  ViewModel  ->  Repository  ->  MusicSource (remote, Subsonic)
 - The remote side sits behind `MusicSource` so additional backends can be added later.
 - `SourceRepository` owns the configured servers and builds a `SubsonicSource` from the active one; it also serves cover-art URLs. `LibraryRepository` reads the local mirror.
 - The local side is Room; reads are `Flow`s, so the UI updates as sync writes.
-- `SyncManager` triggers syncs off the UI (its own scope) and exposes a `StateFlow<SyncStatus>`; `SyncService` does the actual work.
+- `SyncManager` triggers syncs off the UI (its own scope) and exposes a `StateFlow<SyncStatus>`; `SyncService` does the actual work. `AutoSync` runs a foreground-only timer that asks `SyncManager` for a silent sync once the configured interval has elapsed.
 - ViewModels are wired with Koin; screens are split into a stateful `*Route` (default `koinViewModel()`) and a stateless `*Screen` so the latter can be screenshot-tested directly.
 
 ## UI shell
 
-The library is one `LibraryScreen` with a pinned top bar: the current section as the title, a custom row of icon buttons (Albums, Artists, Playlists) on the left, and Sync and Settings icon actions on the right. The selected section is drawn as a filled box in the content colour with the icon inverted, like the Flutter app — this is a hand-rolled row, not Material `TabRow` (no underline indicator). Icons use the Material rounded variants. Tabs switch the content in place; album and playlist rows push a detail screen, and Settings is pushed from the top bar. The sync action doubles as the progress indicator while a sync runs. There is no bottom navigation. A mini player sits above the navigation bar across every screen whenever a track is loaded. It is a permanent part of the app shell (the screens above it consume the navigation-bar inset so nothing is padded twice); the Now Playing screen slides up over the whole shell as an overlay rather than being a nav destination, so the mini player never re-lays out during the transition.
+The library is one `LibraryScreen` with a pinned top bar: the current section as the title, a custom row of icon buttons (Albums, Artists, Playlists) on the left, and Sync and Settings icon actions on the right. The selected section is drawn as a filled box in the content colour with the icon inverted, like the Flutter app — this is a hand-rolled row, not Material `TabRow` (no underline indicator). Icons use the Material rounded variants. Tabs switch the content in place; album and playlist rows push a detail screen, and Settings is pushed from the top bar. The library syncs on pull-to-refresh; the pull indicator holds only while a manual sync runs, and a spinner rings the Settings action whenever any sync is running (an automatic sync shows only the spinner, plus a notification). There is no bottom navigation. A mini player sits above the navigation bar across every screen whenever a track is loaded. It is a permanent part of the app shell (the screens above it consume the navigation-bar inset so nothing is padded twice); the Now Playing screen slides up over the whole shell as an overlay rather than being a nav destination, so the mini player never re-lays out during the transition.
 
 The Albums tab is a three-column grid of covers only. Sorting and filtering hang off a FAB, and Settings holds the server list and the network, playback, download and about sections rather than list sort or sync.
 
@@ -116,7 +116,9 @@ Images: grids and lists request a 256 px `getCoverArt` thumbnail; the 120 dp det
 
 ## Sync
 
-`SyncService.sync()` is serialized by `SyncManager`, which coalesces duplicate requests. It walks five entities in sequence — artists, albums, songs, playlists and playlist songs — and each one is a cold `Flow` from `MusicSource` that the service collects: it remembers the IDs already in the local mirror, upserts every batch as it arrives (one `immediateTransaction` per ~500-row batch), crosses those IDs off, and after that entity's stream ends deletes whatever is left, i.e. the rows the server no longer lists. The parser reads the HTTP response stream directly, so the fetched library is streamed page by page rather than materialised wholesale, though the prune still holds the existing ID set to diff against.
+`SyncService.sync()` is serialized by `SyncManager`, which coalesces a request that arrives while one is already running into a single follow-up. The library and Home sync actions are no-ops while a sync runs (so repeated pull-to-refresh cannot pile up runs), while a programmatic request such as adding a server still gets its follow-up. It walks five entities in sequence — artists, albums, songs, playlists and playlist songs — and each one is a cold `Flow` from `MusicSource` that the service collects: it remembers the IDs already in the local mirror, upserts every batch as it arrives (one `immediateTransaction` per ~500-row batch), crosses those IDs off, and after that entity's stream ends deletes whatever is left, i.e. the rows the server no longer lists. The parser reads the HTTP response stream directly, so the fetched library is streamed page by page rather than materialised wholesale, though the prune still holds the existing ID set to diff against.
+
+A run is triggered by the user (pull-to-refresh or a Sync action) or by `AutoSync`, a foreground-only timer. While the app has a visible Activity `AutoSync` re-checks at most every 15 minutes (the configured interval, capped) whether `syncIntervalMinutes` has elapsed since the last attempt and, if the mode allows (`Off`, `Wi-Fi only` or `Always`, default `Wi-Fi only`), the app is online and a server is configured, it asks `SyncManager` for a silent sync; nothing runs while the app is backgrounded, and a missed interval catches up on the next open. Only the time of the last attempt is persisted, so a server that keeps failing is retried once per interval rather than on every poll. A silent sync still shows the progress notification and the Settings spinner, but never a toast.
 
 Songs have a primary and a fallback fetch. The primary probes `search3` with an empty query once (memoized per source); if the server supports it, the library is paged through `search3` 500 songs at a time. Otherwise the fallback pages `getAlbumList2` and then issues one `getAlbum` per album — it works everywhere but costs a request per album instead of per 500 songs. Every paged loop stops on a short page and is capped at 1000 pages. Playlists are fetched whole, and their songs are stored by position so a playlist that got shorter (or was emptied) is trimmed at the end.