abort local sync

wire hash cancellation

await cleanup

remove forced kill

add regression tests

abort sync requests

fix cleanup ordering in teardown

exit isolate

test background sync

test sigabrt crash

cleanup

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/Messages.g.kt

@@ -542,16 +542,17 @@ private open class MessagesPigeonCodec : StandardMessageCodec() {
 
 /** Generated interface from Pigeon that represents a handler of messages from Flutter. */
 interface NativeSyncApi {
-  fun shouldFullSync(): Boolean
-  fun getMediaChanges(): SyncDelta
+  fun shouldFullSync(callback: (Result<Boolean>) -> Unit)
+  fun getMediaChanges(callback: (Result<SyncDelta>) -> Unit)
   fun checkpointSync()
   fun clearSyncCheckpoint()
-  fun getAssetIdsForAlbum(albumId: String): List<String>
-  fun getAlbums(): List<PlatformAlbum>
+  fun getAssetIdsForAlbum(albumId: String, callback: (Result<List<String>>) -> Unit)
+  fun getAlbums(callback: (Result<List<PlatformAlbum>>) -> Unit)
   fun getAssetsCountSince(albumId: String, timestamp: Long): Long
-  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?): List<PlatformAsset>
+  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?, callback: (Result<List<PlatformAsset>>) -> Unit)
   fun hashAssets(assetIds: List<String>, allowNetworkAccess: Boolean, callback: (Result<List<HashResult>>) -> Unit)
   fun cancelHashing()
+  fun cancelSync()
   fun getTrashedAssets(): Map<String, List<PlatformAsset>>
   fun restoreFromTrashById(mediaId: String, type: Long, callback: (Result<Boolean>) -> Unit)
   fun getCloudIdForAssetIds(assetIds: List<String>): List<CloudIdResult>
@@ -570,27 +571,33 @@ interface NativeSyncApi {
         val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.shouldFullSync$separatedMessageChannelSuffix", codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            val wrapped: List<Any?> = try {
-              listOf(api.shouldFullSync())
-            } catch (exception: Throwable) {
-              MessagesPigeonUtils.wrapError(exception)
+            api.shouldFullSync{ result: Result<Boolean> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(MessagesPigeonUtils.wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(MessagesPigeonUtils.wrapResult(data))
+              }
             }
-            reply.reply(wrapped)
           }
         } else {
           channel.setMessageHandler(null)
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges$separatedMessageChannelSuffix", codec, taskQueue)
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges$separatedMessageChannelSuffix", codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            val wrapped: List<Any?> = try {
-              listOf(api.getMediaChanges())
-            } catch (exception: Throwable) {
-              MessagesPigeonUtils.wrapError(exception)
+            api.getMediaChanges{ result: Result<SyncDelta> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(MessagesPigeonUtils.wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(MessagesPigeonUtils.wrapResult(data))
+              }
             }
-            reply.reply(wrapped)
           }
         } else {
           channel.setMessageHandler(null)
@@ -629,32 +636,38 @@ interface NativeSyncApi {
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum$separatedMessageChannelSuffix", codec, taskQueue)
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum$separatedMessageChannelSuffix", codec)
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
             val albumIdArg = args[0] as String
-            val wrapped: List<Any?> = try {
-              listOf(api.getAssetIdsForAlbum(albumIdArg))
-            } catch (exception: Throwable) {
-              MessagesPigeonUtils.wrapError(exception)
+            api.getAssetIdsForAlbum(albumIdArg) { result: Result<List<String>> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(MessagesPigeonUtils.wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(MessagesPigeonUtils.wrapResult(data))
+              }
             }
-            reply.reply(wrapped)
           }
         } else {
           channel.setMessageHandler(null)
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums$separatedMessageChannelSuffix", codec, taskQueue)
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums$separatedMessageChannelSuffix", codec)
         if (api != null) {
           channel.setMessageHandler { _, reply ->
-            val wrapped: List<Any?> = try {
-              listOf(api.getAlbums())
-            } catch (exception: Throwable) {
-              MessagesPigeonUtils.wrapError(exception)
+            api.getAlbums{ result: Result<List<PlatformAlbum>> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(MessagesPigeonUtils.wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(MessagesPigeonUtils.wrapResult(data))
+              }
             }
-            reply.reply(wrapped)
           }
         } else {
           channel.setMessageHandler(null)
@@ -679,18 +692,21 @@ interface NativeSyncApi {
         }
       }
       run {
-        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum$separatedMessageChannelSuffix", codec, taskQueue)
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum$separatedMessageChannelSuffix", codec)
         if (api != null) {
           channel.setMessageHandler { message, reply ->
             val args = message as List<Any?>
             val albumIdArg = args[0] as String
             val updatedTimeCondArg = args[1] as Long?
-            val wrapped: List<Any?> = try {
-              listOf(api.getAssetsForAlbum(albumIdArg, updatedTimeCondArg))
-            } catch (exception: Throwable) {
-              MessagesPigeonUtils.wrapError(exception)
+            api.getAssetsForAlbum(albumIdArg, updatedTimeCondArg) { result: Result<List<PlatformAsset>> ->
+              val error = result.exceptionOrNull()
+              if (error != null) {
+                reply.reply(MessagesPigeonUtils.wrapError(error))
+              } else {
+                val data = result.getOrNull()
+                reply.reply(MessagesPigeonUtils.wrapResult(data))
+              }
             }
-            reply.reply(wrapped)
           }
         } else {
           channel.setMessageHandler(null)
@@ -733,6 +749,22 @@ interface NativeSyncApi {
           channel.setMessageHandler(null)
         }
       }
+      run {
+        val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.cancelSync$separatedMessageChannelSuffix", codec)
+        if (api != null) {
+          channel.setMessageHandler { _, reply ->
+            val wrapped: List<Any?> = try {
+              api.cancelSync()
+              listOf(null)
+            } catch (exception: Throwable) {
+              MessagesPigeonUtils.wrapError(exception)
+            }
+            reply.reply(wrapped)
+          }
+        } else {
+          channel.setMessageHandler(null)
+        }
+      }
       run {
         val channel = BasicMessageChannel<Any?>(binaryMessenger, "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getTrashedAssets$separatedMessageChannelSuffix", codec, taskQueue)
         if (api != null) {

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImpl26.kt

@@ -4,7 +4,11 @@ import android.content.Context
 
 
 class NativeSyncApiImpl26(context: Context) : NativeSyncApiImplBase(context), NativeSyncApi {
-  override fun shouldFullSync(): Boolean {
+  override fun shouldFullSync(callback: (Result<Boolean>) -> Unit) {
+    runSync(callback) { shouldFullSync() }
+  }
+
+  private fun shouldFullSync(): Boolean {
     return true
   }
 
@@ -18,7 +22,11 @@ class NativeSyncApiImpl26(context: Context) : NativeSyncApiImplBase(context), Na
     // No-op for Android 10 and below
   }
 
-  override fun getMediaChanges(): SyncDelta {
+  override fun getMediaChanges(callback: (Result<SyncDelta>) -> Unit) {
+    runSync(callback) { getMediaChanges() }
+  }
+
+  private fun getMediaChanges(): SyncDelta {
     throw IllegalStateException("Method not supported on this Android version.")
   }
 

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImpl30.kt

@@ -7,6 +7,8 @@ import android.os.Bundle
 import android.provider.MediaStore
 import androidx.annotation.RequiresApi
 import androidx.annotation.RequiresExtension
+import kotlinx.coroutines.currentCoroutineContext
+import kotlinx.coroutines.ensureActive
 import kotlinx.serialization.json.Json
 
 @RequiresApi(Build.VERSION_CODES.Q)
@@ -35,7 +37,11 @@ class NativeSyncApiImpl30(context: Context) : NativeSyncApiImplBase(context), Na
     }
   }
 
-  override fun shouldFullSync(): Boolean =
+  override fun shouldFullSync(callback: (Result<Boolean>) -> Unit) {
+    runSync(callback) { shouldFullSync() }
+  }
+
+  private fun shouldFullSync(): Boolean =
     MediaStore.getVersion(ctx) != prefs.getString(SHARED_PREF_MEDIA_STORE_VERSION_KEY, null)
 
   override fun checkpointSync() {
@@ -49,7 +55,11 @@ class NativeSyncApiImpl30(context: Context) : NativeSyncApiImplBase(context), Na
     }
   }
 
-  override fun getMediaChanges(): SyncDelta {
+  override fun getMediaChanges(callback: (Result<SyncDelta>) -> Unit) {
+    runSync(callback) { getMediaChanges() }
+  }
+
+  private suspend fun getMediaChanges(): SyncDelta {
     val genMap = getSavedGenerationMap()
     val currentVolumes = MediaStore.getExternalVolumeNames(ctx)
     val changed = mutableListOf<PlatformAsset>()
@@ -58,6 +68,7 @@ class NativeSyncApiImpl30(context: Context) : NativeSyncApiImplBase(context), Na
     var hasChanges = genMap.keys != currentVolumes
 
     for (volume in currentVolumes) {
+      currentCoroutineContext().ensureActive()
       val currentGen = MediaStore.getGeneration(ctx, volume)
       val storedGen = genMap[volume] ?: 0
       if (currentGen <= storedGen) {

mobile/android/app/src/main/kotlin/app/alextran/immich/sync/MessagesImplBase.kt

@@ -45,12 +45,14 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
   private val ctx: Context = context.applicationContext
 
   private var hashTask: Job? = null
+  private var syncJob: Job? = null
   private val mediaTrashDelegate = MediaTrashDelegate(ctx)
 
   companion object {
     private const val MAX_CONCURRENT_HASH_OPERATIONS = 16
     private val hashSemaphore = Semaphore(MAX_CONCURRENT_HASH_OPERATIONS)
     private const val HASHING_CANCELLED_CODE = "HASH_CANCELLED"
+    private const val SYNC_CANCELLED_CODE = "SYNC_CANCELLED"
 
     // MediaStore.Files.FileColumns.SPECIAL_FORMAT — S Extensions 21+
     // https://developer.android.com/reference/android/provider/MediaStore.Files.FileColumns#SPECIAL_FORMAT
@@ -295,7 +297,11 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
     return PlatformAssetPlaybackStyle.IMAGE
   }
 
-  fun getAlbums(): List<PlatformAlbum> {
+  fun getAlbums(callback: (Result<List<PlatformAlbum>>) -> Unit) {
+    runSync(callback) { getAlbums() }
+  }
+
+  private suspend fun getAlbums(): List<PlatformAlbum> {
     val albums = mutableListOf<PlatformAlbum>()
     val albumsCount = mutableMapOf<String, Int>()
 
@@ -322,6 +328,7 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
         cursor.getColumnIndexOrThrow(MediaStore.Files.FileColumns.DATE_MODIFIED)
 
       while (cursor.moveToNext()) {
+        currentCoroutineContext().ensureActive()
         val id = cursor.getString(bucketIdColumn)
 
         val count = albumsCount.getOrDefault(id, 0)
@@ -342,7 +349,11 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
       .sortedBy { it.id }
   }
 
-  fun getAssetIdsForAlbum(albumId: String): List<String> {
+  fun getAssetIdsForAlbum(albumId: String, callback: (Result<List<String>>) -> Unit) {
+    runSync(callback) { getAssetIdsForAlbum(albumId) }
+  }
+
+  private fun getAssetIdsForAlbum(albumId: String): List<String> {
     val projection = arrayOf(MediaStore.MediaColumns._ID)
 
     return getCursor(
@@ -366,7 +377,11 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
     )?.use { cursor -> cursor.count.toLong() } ?: 0L
 
 
-  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?): List<PlatformAsset> {
+  fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?, callback: (Result<List<PlatformAsset>>) -> Unit) {
+    runSync(callback) { getAssetsForAlbum(albumId, updatedTimeCond) }
+  }
+
+  private fun getAssetsForAlbum(albumId: String, updatedTimeCond: Long?): List<PlatformAsset> {
     var selection = "$BUCKET_SELECTION AND $MEDIA_SELECTION"
     val selectionArgs = mutableListOf(albumId, *MEDIA_SELECTION_ARGS)
 
@@ -451,6 +466,24 @@ open class NativeSyncApiImplBase(context: Context) : ImmichPlugin(), ActivityAwa
     hashTask = null
   }
 
+  fun cancelSync() {
+    syncJob?.cancel()
+    syncJob = null
+  }
+
+  protected fun <T> runSync(callback: (Result<T>) -> Unit, work: suspend () -> T) {
+    syncJob?.cancel()
+    syncJob = CoroutineScope(Dispatchers.IO).launch {
+      try {
+        completeWhenActive(callback, Result.success(work()))
+      } catch (e: CancellationException) {
+        completeWhenActive(callback, Result.failure(FlutterError(SYNC_CANCELLED_CODE, "Sync cancelled", null)))
+      } catch (e: Exception) {
+        completeWhenActive(callback, Result.failure(e))
+      }
+    }
+  }
+
   fun restoreFromTrashById(mediaId: String, type: Long, callback: (Result<Boolean>) -> Unit) {
     mediaTrashDelegate.restoreFromTrashById(mediaId, type) { completeWhenActive(callback, it) }
   }

mobile/integration_test/background_sync_teardown_test.dart

@@ -0,0 +1,154 @@
+import 'dart:async';
+
+import 'package:drift/drift.dart' show Value;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/domain/models/store.model.dart';
+import 'package:immich_mobile/domain/utils/background_sync.dart';
+import 'package:immich_mobile/entities/store.entity.dart';
+import 'package:immich_mobile/infrastructure/entities/user.entity.drift.dart';
+import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
+import 'package:immich_mobile/main.dart' as app;
+import 'package:immich_mobile/services/api.service.dart';
+import 'package:immich_mobile/utils/bootstrap.dart';
+import 'package:immich_mobile/wm_executor.dart';
+import 'package:integration_test/integration_test.dart';
+import 'package:openapi/api.dart';
+
+import 'test_utils/fake_immich_server.dart';
+
+void main() {
+  final binding = IntegrationTestWidgetsFlutterBinding.ensureInitialized();
+  // These tests do real I/O without pumping a widget tree, so disable the fake async clock
+  binding.framePolicy = LiveTestWidgetsFlutterBindingFramePolicy.fullyLive;
+
+  late Drift drift;
+  late FakeImmichServer server;
+
+  setUpAll(() async {
+    await app.initApp();
+    (drift, _) = await Bootstrap.initDomain();
+  });
+
+  setUp(() async {
+    await workerManagerPatch.init(dynamicSpawning: true);
+    server = await FakeImmichServer.start();
+    await ApiService().resolveAndSetEndpoint(server.endpoint);
+    await drift.delete(drift.userEntity).go();
+    await Store.delete(StoreKey.syncMigrationStatus);
+  });
+
+  tearDown(() async {
+    await workerManagerPatch.dispose();
+    await server.close();
+    await Store.delete(StoreKey.serverEndpoint);
+    await Store.delete(StoreKey.syncMigrationStatus);
+  });
+
+  void sendUser(SyncStream stream, String id, String name) {
+    stream.send(
+      type: SyncEntityType.userV1.value,
+      data: SyncUserV1(
+        id: id,
+        name: name,
+        email: '$id@test.com',
+        hasProfileImage: false,
+        deletedAt: null,
+        profileChangedAt: DateTime.utc(2025),
+      ).toJson(),
+      ack: id,
+    );
+  }
+
+  Future<bool> dbReadable() async {
+    try {
+      await drift.customSelect('SELECT 1').get().timeout(const Duration(seconds: 5));
+      return true;
+    } catch (_) {
+      return false;
+    }
+  }
+
+  Future<int> userCount() async => (await drift.select(drift.userEntity).get()).length;
+
+  // Starts a remote sync and resolves once its /sync/stream request is open.
+  Future<(Future<bool>, SyncStream)> startSync() async {
+    final sync = BackgroundSyncManager().syncRemote();
+    final stream = await server.streamOpened.timeout(
+      const Duration(seconds: 30),
+      onTimeout: () => fail('sync isolate never opened /sync/stream'),
+    );
+    return (sync, stream);
+  }
+
+  testWidgets('a full sync ingests streamed events into the shared DB', (tester) async {
+    expect(await userCount(), 0);
+
+    final (sync, stream) = await startSync();
+
+    sendUser(stream, 'u1', 'Alice');
+    sendUser(stream, 'u2', 'Bob');
+    await stream.close();
+
+    final result = await sync.timeout(
+      const Duration(seconds: 30),
+      onTimeout: () => fail('sync did not complete after the stream ended'),
+    );
+    expect(result, isTrue);
+    expect(await userCount(), 2);
+    expect(server.ackRequests, greaterThan(0));
+  });
+
+  testWidgets('disposing the pool during an in-flight sync drains promptly', (tester) async {
+    final (sync, _) = await startSync();
+
+    final sw = Stopwatch()..start();
+    await workerManagerPatch.dispose().timeout(
+      const Duration(seconds: 15),
+      onTimeout: () => fail('dispose() hung — worker did not drain and exit'),
+    );
+    expect(sw.elapsed, lessThan(const Duration(seconds: 10)), reason: 'abort-driven, not socket-timeout bound');
+
+    expect(await sync.timeout(const Duration(seconds: 5), onTimeout: () => false), isFalse);
+  });
+
+  testWidgets('tearing down a worker blocked mid-write leaves the DB usable', (tester) async {
+    final (sync, stream) = await startSync();
+
+    // Hold an exclusive write transaction so the worker's write is blocked. The lock is taken only
+    // after the stream opens to avoid blocking the worker's own startup DB reads.
+    final releaseTxn = Completer<void>();
+    final txnHeld = Completer<void>();
+    final txn = drift.transaction(() async {
+      await drift.into(drift.userEntity).insert(
+            UserEntityCompanion.insert(
+              id: 'holder',
+              name: 'holder',
+              email: 'holder@test.com',
+              hasProfileImage: const Value(false),
+              profileChangedAt: Value(DateTime.utc(2025)),
+            ),
+          );
+      txnHeld.complete();
+      await releaseTxn.future;
+    });
+    await txnHeld.future;
+
+    sendUser(stream, 'u1', 'Alice');
+    await stream.close();
+
+    // dispose() can only finish once the worker unwinds, which is blocked on the
+    // lock — so start it, release the lock, then await completion.
+    final disposed = workerManagerPatch.dispose();
+    releaseTxn.complete();
+    await txn;
+    await disposed.timeout(
+      const Duration(seconds: 15),
+      onTimeout: () => fail('dispose() hung after releasing the write lock'),
+    );
+    await sync.timeout(const Duration(seconds: 5), onTimeout: () => false);
+
+    expect(await dbReadable(), isTrue);
+    final users = await drift.select(drift.userEntity).get();
+    expect(users.map((u) => u.id), contains('holder'));
+  });
+}

mobile/integration_test/test_utils/fake_immich_server.dart

@@ -0,0 +1,115 @@
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+/// A dummy localhost server that implements only the endpoints that remote-sync touches.
+class FakeImmichServer {
+  FakeImmichServer._(this._server, this.version);
+
+  final HttpServer _server;
+  final (int, int, int) version;
+
+  final Completer<SyncStream> _streamOpened = Completer<SyncStream>();
+
+  int ackRequests = 0;
+
+  String get endpoint => 'http://${_server.address.host}:${_server.port}/api';
+
+  /// Resolves when the sync isolate opens `POST /sync/stream`.
+  Future<SyncStream> get streamOpened => _streamOpened.future;
+
+  static Future<FakeImmichServer> start({(int, int, int) version = (3, 0, 0)}) async {
+    final server = await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
+    final fake = FakeImmichServer._(server, version);
+    fake._listen();
+    return fake;
+  }
+
+  void _listen() {
+    // A connection torn down mid-write during teardown is expected
+    _server.listen((request) => unawaited(_route(request).catchError((_) {})));
+  }
+
+  Future<void> _route(HttpRequest request) async {
+    final method = request.method;
+    final path = request.uri.path;
+
+    if (method == 'GET' && path == '/api/server/ping') {
+      return _respondJson(request, {'res': 'pong'});
+    }
+    if (method == 'GET' && path == '/api/server/version') {
+      final (major, minor, patch) = version;
+      return _respondJson(request, {'major': major, 'minor': minor, 'patch': patch});
+    }
+    if (path == '/api/sync/ack') {
+      if (method != 'DELETE') {
+        ackRequests++;
+      }
+      return _respondEmpty(request);
+    }
+    if (method == 'POST' && path == '/api/sync/stream') {
+      return _openSyncStream(request);
+    }
+    return _respondEmpty(request, status: HttpStatus.notFound);
+  }
+
+  Future<void> _openSyncStream(HttpRequest request) async {
+    await request.drain<void>();
+    request.response
+      ..statusCode = HttpStatus.ok
+      ..headers.contentType = ContentType('application', 'jsonlines+json')
+      ..contentLength = -1 // chunked: stays open to stream incrementally
+      ..bufferOutput = false;
+    // Flush headers so the client's send() resolves and enters its read loop.
+    await request.response.flush();
+    if (!_streamOpened.isCompleted) {
+      _streamOpened.complete(SyncStream._(request.response));
+    }
+  }
+
+  Future<void> _respondJson(HttpRequest request, Object body) async {
+    await request.drain<void>();
+    request.response
+      ..statusCode = HttpStatus.ok
+      ..headers.contentType = ContentType.json
+      ..write(jsonEncode(body));
+    await request.response.close();
+  }
+
+  Future<void> _respondEmpty(HttpRequest request, {int status = HttpStatus.ok}) async {
+    await request.drain<void>();
+    request.response.statusCode = status;
+    await request.response.close();
+  }
+
+  Future<void> close() async {
+    if (_streamOpened.isCompleted) {
+      await (await _streamOpened.future).close();
+    }
+    await _server.close(force: true);
+  }
+}
+
+/// Handle to the open `/sync/stream` response: push jsonlines events, then end.
+class SyncStream {
+  SyncStream._(this._response);
+
+  final HttpResponse _response;
+  bool _closed = false;
+
+  /// [data] should be a Sync*V1 DTO's `toJson()` so the parser's `fromJson` round-trips it.
+  void send({required String type, required Object data, required String ack}) {
+    if (_closed) {
+      return;
+    }
+    _response.write('${jsonEncode({'type': type, 'data': data, 'ack': ack})}\n');
+  }
+
+  Future<void> close() async {
+    if (_closed) {
+      return;
+    }
+    _closed = true;
+    await _response.close();
+  }
+}

mobile/ios/Runner/Background/BackgroundWorker.swift

@@ -121,8 +121,8 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
   
   /**
    * Cancels the currently running background task, either due to timeout or external request.
-   * Sends a cancel signal to the Flutter side and sets up a fallback timer to ensure
-   * the completion handler is eventually called even if Flutter doesn't respond.
+   * Only tears down the engine after Dart confirms it's drained. If Dart overruns iOS's grace window,
+   * the expiration handler still calls setTaskCompleted and iOS suspends us.
    */
   func close() {
     if isComplete {
@@ -132,12 +132,6 @@ class BackgroundWorker: BackgroundWorkerBgHostApi {
     flutterApi?.cancel { result in
       self.complete(success: false)
     }
-
-    // Fallback safety mechanism: ensure completion is called within 2 seconds
-    // This prevents the background task from hanging indefinitely if Flutter doesn't respond
-    Timer.scheduledTimer(withTimeInterval: 2, repeats: false) { _ in
-      self.complete(success: false)
-    }
   }
 
   

mobile/ios/Runner/Sync/Messages.g.swift

@@ -526,16 +526,17 @@ class MessagesPigeonCodec: FlutterStandardMessageCodec, @unchecked Sendable {
 
 /// Generated protocol from Pigeon that represents a handler of messages from Flutter.
 protocol NativeSyncApi {
-  func shouldFullSync() throws -> Bool
-  func getMediaChanges() throws -> SyncDelta
+  func shouldFullSync(completion: @escaping (Result<Bool, Error>) -> Void)
+  func getMediaChanges(completion: @escaping (Result<SyncDelta, Error>) -> Void)
   func checkpointSync() throws
   func clearSyncCheckpoint() throws
-  func getAssetIdsForAlbum(albumId: String) throws -> [String]
-  func getAlbums() throws -> [PlatformAlbum]
+  func getAssetIdsForAlbum(albumId: String, completion: @escaping (Result<[String], Error>) -> Void)
+  func getAlbums(completion: @escaping (Result<[PlatformAlbum], Error>) -> Void)
   func getAssetsCountSince(albumId: String, timestamp: Int64) throws -> Int64
-  func getAssetsForAlbum(albumId: String, updatedTimeCond: Int64?) throws -> [PlatformAsset]
+  func getAssetsForAlbum(albumId: String, updatedTimeCond: Int64?, completion: @escaping (Result<[PlatformAsset], Error>) -> Void)
   func hashAssets(assetIds: [String], allowNetworkAccess: Bool, completion: @escaping (Result<[HashResult], Error>) -> Void)
   func cancelHashing() throws
+  func cancelSync() throws
   func getTrashedAssets() throws -> [String: [PlatformAsset]]
   func restoreFromTrashById(mediaId: String, type: Int64, completion: @escaping (Result<Bool, Error>) -> Void)
   func getCloudIdForAssetIds(assetIds: [String]) throws -> [CloudIdResult]
@@ -555,26 +556,28 @@ class NativeSyncApiSetup {
     let shouldFullSyncChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.shouldFullSync\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       shouldFullSyncChannel.setMessageHandler { _, reply in
-        do {
-          let result = try api.shouldFullSync()
-          reply(wrapResult(result))
-        } catch {
-          reply(wrapError(error))
+        api.shouldFullSync { result in
+          switch result {
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
+          }
         }
       }
     } else {
       shouldFullSyncChannel.setMessageHandler(nil)
     }
-    let getMediaChangesChannel = taskQueue == nil
-      ? FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
-      : FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec, taskQueue: taskQueue)
+    let getMediaChangesChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getMediaChanges\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       getMediaChangesChannel.setMessageHandler { _, reply in
-        do {
-          let result = try api.getMediaChanges()
-          reply(wrapResult(result))
-        } catch {
-          reply(wrapError(error))
+        api.getMediaChanges { result in
+          switch result {
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
+          }
         }
       }
     } else {
@@ -606,33 +609,33 @@ class NativeSyncApiSetup {
     } else {
       clearSyncCheckpointChannel.setMessageHandler(nil)
     }
-    let getAssetIdsForAlbumChannel = taskQueue == nil
-      ? FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
-      : FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec, taskQueue: taskQueue)
+    let getAssetIdsForAlbumChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetIdsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       getAssetIdsForAlbumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
         let albumIdArg = args[0] as! String
-        do {
-          let result = try api.getAssetIdsForAlbum(albumId: albumIdArg)
-          reply(wrapResult(result))
-        } catch {
-          reply(wrapError(error))
+        api.getAssetIdsForAlbum(albumId: albumIdArg) { result in
+          switch result {
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
+          }
         }
       }
     } else {
       getAssetIdsForAlbumChannel.setMessageHandler(nil)
     }
-    let getAlbumsChannel = taskQueue == nil
-      ? FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
-      : FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec, taskQueue: taskQueue)
+    let getAlbumsChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAlbums\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       getAlbumsChannel.setMessageHandler { _, reply in
-        do {
-          let result = try api.getAlbums()
-          reply(wrapResult(result))
-        } catch {
-          reply(wrapError(error))
+        api.getAlbums { result in
+          switch result {
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
+          }
         }
       }
     } else {
@@ -656,19 +659,19 @@ class NativeSyncApiSetup {
     } else {
       getAssetsCountSinceChannel.setMessageHandler(nil)
     }
-    let getAssetsForAlbumChannel = taskQueue == nil
-      ? FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
-      : FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec, taskQueue: taskQueue)
+    let getAssetsForAlbumChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getAssetsForAlbum\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
     if let api = api {
       getAssetsForAlbumChannel.setMessageHandler { message, reply in
         let args = message as! [Any?]
         let albumIdArg = args[0] as! String
         let updatedTimeCondArg: Int64? = nilOrValue(args[1])
-        do {
-          let result = try api.getAssetsForAlbum(albumId: albumIdArg, updatedTimeCond: updatedTimeCondArg)
-          reply(wrapResult(result))
-        } catch {
-          reply(wrapError(error))
+        api.getAssetsForAlbum(albumId: albumIdArg, updatedTimeCond: updatedTimeCondArg) { result in
+          switch result {
+          case .success(let res):
+            reply(wrapResult(res))
+          case .failure(let error):
+            reply(wrapError(error))
+          }
         }
       }
     } else {
@@ -707,6 +710,19 @@ class NativeSyncApiSetup {
     } else {
       cancelHashingChannel.setMessageHandler(nil)
     }
+    let cancelSyncChannel = FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.cancelSync\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
+    if let api = api {
+      cancelSyncChannel.setMessageHandler { _, reply in
+        do {
+          try api.cancelSync()
+          reply(wrapResult(nil))
+        } catch {
+          reply(wrapError(error))
+        }
+      }
+    } else {
+      cancelSyncChannel.setMessageHandler(nil)
+    }
     let getTrashedAssetsChannel = taskQueue == nil
       ? FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getTrashedAssets\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec)
       : FlutterBasicMessageChannel(name: "dev.flutter.pigeon.immich_mobile.NativeSyncApi.getTrashedAssets\(channelSuffix)", binaryMessenger: binaryMessenger, codec: codec, taskQueue: taskQueue)

mobile/ios/Runner/Sync/MessagesImpl.swift

@@ -39,6 +39,9 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
   private static let hashCancelledCode = "HASH_CANCELLED"
   private static let hashCancelled = Result<[HashResult], Error>.failure(PigeonError(code: hashCancelledCode, message: "Hashing cancelled", details: nil))
   
+  private var syncTask: Task<Void?, Error>?
+  private static let syncCancelledCode = "SYNC_CANCELLED"
+  private static let syncCancelled = PigeonError(code: syncCancelledCode, message: "Sync cancelled", details: nil)
   
   init(with defaults: UserDefaults = .standard) {
     self.defaults = defaults
@@ -71,7 +74,11 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     saveChangeToken(token: PHPhotoLibrary.shared().currentChangeToken)
   }
   
-  func shouldFullSync() -> Bool {
+  func shouldFullSync(completion: @escaping (Result<Bool, Error>) -> Void) {
+    runSync(completion) { $0.shouldFullSync() }
+  }
+  
+  private func shouldFullSync() -> Bool {
     guard #available(iOS 16, *),
           PHPhotoLibrary.authorizationStatus(for: .readWrite) == .authorized,
           let storedToken = getChangeToken() else {
@@ -87,12 +94,17 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     return false
   }
   
-  func getAlbums() throws -> [PlatformAlbum] {
+  func getAlbums(completion: @escaping (Result<[PlatformAlbum], Error>) -> Void) {
+    runSync(completion) { try $0.getAlbums() }
+  }
+  
+  private func getAlbums() throws -> [PlatformAlbum] {
     var albums: [PlatformAlbum] = []
     
-    albumTypes.forEach { type in
+    for type in albumTypes {
       let collections = PHAssetCollection.fetchAssetCollections(with: type, subtype: .any, options: nil)
       for i in 0..<collections.count {
+        try Task.checkCancellation()
         let album = collections.object(at: i)
         
         // Ignore recovered album
@@ -126,7 +138,11 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     return albums.sorted { $0.id < $1.id }
   }
   
-  func getMediaChanges() throws -> SyncDelta {
+  func getMediaChanges(completion: @escaping (Result<SyncDelta, Error>) -> Void) {
+    runSync(completion) { try $0.getMediaChanges() }
+  }
+  
+  private func getMediaChanges() throws -> SyncDelta {
     guard #available(iOS 16, *) else {
       throw PigeonError(code: "UNSUPPORTED_OS", message: "This feature requires iOS 16 or later.", details: nil)
     }
@@ -146,51 +162,49 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
       return SyncDelta(hasChanges: false, updates: [], deletes: [], assetAlbums: [:])
     }
     
-    do {
-      let changes = try PHPhotoLibrary.shared().fetchPersistentChanges(since: storedToken)
+    let changes = try PHPhotoLibrary.shared().fetchPersistentChanges(since: storedToken)
+    
+    var updatedAssets: Set<AssetWrapper> = []
+    var deletedAssets: Set<String> = []
+    
+    for change in changes {
+      try Task.checkCancellation()
+      guard let details = try? change.changeDetails(for: PHObjectType.asset) else { continue }
       
-      var updatedAssets: Set<AssetWrapper> = []
-      var deletedAssets: Set<String> = []
+      let updated = details.updatedLocalIdentifiers.union(details.insertedLocalIdentifiers)
+      deletedAssets.formUnion(details.deletedLocalIdentifiers)
       
-      for change in changes {
-        guard let details = try? change.changeDetails(for: PHObjectType.asset) else { continue }
+      if (updated.isEmpty) { continue }
+      
+      let options = PHFetchOptions()
+      options.includeHiddenAssets = false
+      let result = PHAsset.fetchAssets(withLocalIdentifiers: Array(updated), options: options)
+      for i in 0..<result.count {
+        let asset = result.object(at: i)
         
-        let updated = details.updatedLocalIdentifiers.union(details.insertedLocalIdentifiers)
-        deletedAssets.formUnion(details.deletedLocalIdentifiers)
-        
-        if (updated.isEmpty) { continue }
-        
-        let options = PHFetchOptions()
-        options.includeHiddenAssets = false
-        let result = PHAsset.fetchAssets(withLocalIdentifiers: Array(updated), options: options)
-        for i in 0..<result.count {
-          let asset = result.object(at: i)
-          
-          // Asset wrapper only uses the id for comparison. Multiple change can contain the same asset, skip duplicate changes
-          let predicate = PlatformAsset(
-            id: asset.localIdentifier,
-            name: "",
-            type: 0,
-            durationMs: 0,
-            orientation: 0,
-            isFavorite: false,
-            playbackStyle: .unknown
-          )
-          if (updatedAssets.contains(AssetWrapper(with: predicate))) {
-            continue
-          }
-          
-          let domainAsset = AssetWrapper(with: asset.toPlatformAsset())
-          updatedAssets.insert(domainAsset)
+        // Asset wrapper only uses the id for comparison. Multiple change can contain the same asset, skip duplicate changes
+        let predicate = PlatformAsset(
+          id: asset.localIdentifier,
+          name: "",
+          type: 0,
+          durationMs: 0,
+          orientation: 0,
+          isFavorite: false,
+          playbackStyle: .unknown
+        )
+        if (updatedAssets.contains(AssetWrapper(with: predicate))) {
+          continue
         }
+        
+        let domainAsset = AssetWrapper(with: asset.toPlatformAsset())
+        updatedAssets.insert(domainAsset)
       }
-      
-      let updates = Array(updatedAssets.map { $0.asset })
-      return SyncDelta(hasChanges: true, updates: updates, deletes: Array(deletedAssets), assetAlbums: buildAssetAlbumsMap(assets: updates))
     }
+    
+    let updates = Array(updatedAssets.map { $0.asset })
+    return SyncDelta(hasChanges: true, updates: updates, deletes: Array(deletedAssets), assetAlbums: buildAssetAlbumsMap(assets: updates))
   }
   
-  
   private func buildAssetAlbumsMap(assets: Array<PlatformAsset>) -> [String: [String]] {
     guard !assets.isEmpty else {
       return [:]
@@ -213,7 +227,11 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     return albumAssets
   }
   
-  func getAssetIdsForAlbum(albumId: String) throws -> [String] {
+  func getAssetIdsForAlbum(albumId: String, completion: @escaping (Result<[String], Error>) -> Void) {
+    runSync(completion) { try $0.getAssetIdsForAlbum(albumId: albumId) }
+  }
+  
+  private func getAssetIdsForAlbum(albumId: String) throws -> [String] {
     let collections = PHAssetCollection.fetchAssetCollections(withLocalIdentifiers: [albumId], options: nil)
     guard let album = collections.firstObject else {
       return []
@@ -223,9 +241,14 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     let options = PHFetchOptions()
     options.includeHiddenAssets = false
     let assets = getAssetsFromAlbum(in: album, options: options)
-    assets.enumerateObjects { (asset, _, _) in
+    assets.enumerateObjects { (asset, _, stop) in
+      if Task.isCancelled {
+        stop.pointee = true
+        return 
+      }
       ids.append(asset.localIdentifier)
     }
+    try Task.checkCancellation()
     return ids
   }
   
@@ -243,7 +266,11 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     return Int64(assets.count)
   }
   
-  func getAssetsForAlbum(albumId: String, updatedTimeCond: Int64?) throws -> [PlatformAsset] {
+  func getAssetsForAlbum(albumId: String, updatedTimeCond: Int64?, completion: @escaping (Result<[PlatformAsset], Error>) -> Void) {
+    runSync(completion) { try $0.getAssetsForAlbum(albumId: albumId, updatedTimeCond: updatedTimeCond) }
+  }
+  
+  private func getAssetsForAlbum(albumId: String, updatedTimeCond: Int64?) throws -> [PlatformAsset] {
     let collections = PHAssetCollection.fetchAssetCollections(withLocalIdentifiers: [albumId], options: nil)
     guard let album = collections.firstObject else {
       return []
@@ -262,9 +289,14 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     }
     
     var assets: [PlatformAsset] = []
-    result.enumerateObjects { (asset, _, _) in
+    result.enumerateObjects { (asset, _, stop) in
+      if Task.isCancelled {
+        stop.pointee = true
+        return 
+      }
       assets.append(asset.toPlatformAsset())
     }
+    try Task.checkCancellation()
     return assets
   }
   
@@ -324,6 +356,31 @@ class NativeSyncApiImpl: ImmichPlugin, NativeSyncApi, FlutterPlugin {
     hashTask = nil
   }
   
+  func cancelSync() {
+    syncTask?.cancel()
+    syncTask = nil
+  }
+  
+  private func runSync<T>(
+    _ completion: @escaping (Result<T, Error>) -> Void,
+    _ work: @escaping (NativeSyncApiImpl) throws -> T
+  ) {
+    syncTask?.cancel()
+    syncTask = Task { [weak self] in
+      guard let self else { return nil }
+      let result: Result<T, Error>
+      do {
+        result = .success(try work(self))
+      } catch is CancellationError {
+        result = .failure(Self.syncCancelled)
+      } catch {
+        result = .failure(error)
+      }
+      self.completeWhenActive(for: completion, with: result)
+      return nil
+    }
+  }
+  
   private func hashAsset(_ asset: PHAsset, allowNetworkAccess: Bool) async -> HashResult? {
     class RequestRef {
       var id: PHAssetResourceDataRequestID?

mobile/lib/domain/services/background_worker.service.dart

@@ -188,20 +188,14 @@ class BackgroundWorkerBgService extends BackgroundWorkerFlutterApi {
       if (!_cancellationToken.isCompleted) {
         _cancellationToken.complete();
       }
-      final cleanupFutures = [
-        nativeSyncApi?.cancelHashing(),
-        workerManagerPatch.dispose().catchError((_) async {
-          // Discard any errors on the dispose call
-          return;
-        }),
-        LogService.I.dispose(),
-        Store.dispose(),
 
-        backgroundSyncManager?.cancel(),
-        _drift.optimize(allTables: true),
-      ];
-
-      await Future.wait(cleanupFutures.nonNulls);
+      // Workers share one sqlite connection, so DB teardown must wait until every worker has stopped using it.
+      await Future.wait([
+        if (backgroundSyncManager != null) backgroundSyncManager.cancel(),
+        if (nativeSyncApi != null) nativeSyncApi.cancelHashing(),
+      ]);
+      await workerManagerPatch.dispose().catchError((_) async {});
+      await Future.wait([LogService.I.dispose(), Store.dispose(), _drift.optimize(allTables: true)]);
       await _drift.close();
       await _driftLogger.close();
 

mobile/lib/domain/services/hash.service.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:flutter/services.dart';
 import 'package:immich_mobile/constants/constants.dart';
 import 'package:immich_mobile/domain/models/album/local_album.model.dart';
@@ -17,7 +19,7 @@ class HashService {
   final DriftLocalAssetRepository _localAssetRepository;
   final DriftTrashedLocalAssetRepository _trashedLocalAssetRepository;
   final NativeSyncApi _nativeSyncApi;
-  final bool Function()? _cancelChecker;
+  final Completer<void>? _cancellation;
   final _log = Logger('HashService');
 
   HashService({
@@ -25,11 +27,15 @@ class HashService {
     required this._localAssetRepository,
     required this._trashedLocalAssetRepository,
     required this._nativeSyncApi,
-    this._cancelChecker,
+    this._cancellation,
     int? batchSize,
-  }) : _batchSize = batchSize ?? kBatchHashFileLimit;
+  }) : _batchSize = batchSize ?? kBatchHashFileLimit {
+    // Stop the in-flight native hash call promptly on cancellation; the loops
+    // below also observe [isCancelled] to bail between batches.
+    _cancellation?.future.then((_) => _nativeSyncApi.cancelHashing().onError(_log.warning));
+  }
 
-  bool get isCancelled => _cancelChecker?.call() ?? false;
+  bool get isCancelled => _cancellation?.isCompleted ?? false;
 
   Future<void> hashAssets() async {
     _log.info("Starting hashing of assets");

mobile/lib/domain/services/local_sync.service.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 
 import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
 import 'package:immich_mobile/domain/models/album/local_album.model.dart';
 import 'package:immich_mobile/domain/models/asset/base_asset.model.dart';
 import 'package:immich_mobile/domain/models/store.model.dart';
@@ -17,6 +18,8 @@ import 'package:immich_mobile/utils/datetime_helpers.dart';
 import 'package:immich_mobile/utils/diff.dart';
 import 'package:logging/logging.dart';
 
+const String _kSyncCancelledCode = "SYNC_CANCELLED";
+
 class LocalSyncService {
   final DriftLocalAlbumRepository _localAlbumRepository;
   // ignore: unused_field
@@ -25,6 +28,7 @@ class LocalSyncService {
   final DriftTrashedLocalAssetRepository _trashedLocalAssetRepository;
   final AssetMediaRepository _assetMediaRepository;
   final IPermissionRepository _permissionRepository;
+  final Completer<void>? _cancellation;
   final Logger _log = Logger("DeviceSyncService");
 
   LocalSyncService({
@@ -34,7 +38,12 @@ class LocalSyncService {
     required this._trashedLocalAssetRepository,
     required this._assetMediaRepository,
     required this._permissionRepository,
-  });
+    this._cancellation,
+  }) {
+    _cancellation?.future.then((_) => _nativeSyncApi.cancelSync().onError(_log.warning));
+  }
+
+  bool get _isCancelled => _cancellation?.isCompleted ?? false;
 
   Future<void> sync({bool full = false}) async {
     final Stopwatch stopwatch = Stopwatch()..start();
@@ -81,6 +90,10 @@ class LocalSyncService {
       // detect album deletions from the native side
       if (CurrentPlatform.isAndroid) {
         for (final album in dbAlbums) {
+          if (_isCancelled) {
+            _log.warning("Local sync cancelled. Stopped processing albums.");
+            return;
+          }
           final deviceIds = await _nativeSyncApi.getAssetIdsForAlbum(album.id);
           await _localAlbumRepository.syncDeletes(album.id, deviceIds);
         }
@@ -91,6 +104,10 @@ class LocalSyncService {
         // does not include changes for cloud albums.
         final cloudAlbums = deviceAlbums.where((a) => a.isCloud).toLocalAlbums();
         for (final album in cloudAlbums) {
+          if (_isCancelled) {
+            _log.warning("Local sync cancelled. Stopped processing cloud albums.");
+            return;
+          }
           final dbAlbum = dbAlbums.firstWhereOrNull((a) => a.id == album.id);
           if (dbAlbum == null) {
             _log.warning("Cloud album ${album.name} not found in local database. Skipping sync.");
@@ -102,6 +119,12 @@ class LocalSyncService {
         await _mapIosCloudIds(newAssets);
       }
       await _nativeSyncApi.checkpointSync();
+    } on PlatformException catch (e, s) {
+      if (e.code == _kSyncCancelledCode) {
+        _log.warning("Local sync cancelled");
+      } else {
+        _log.severe("Error performing device sync", e, s);
+      }
     } catch (e, s) {
       _log.severe("Error performing device sync", e, s);
     } finally {
@@ -129,12 +152,21 @@ class LocalSyncService {
       await _nativeSyncApi.checkpointSync();
       stopwatch.stop();
       _log.info("Full device sync took - ${stopwatch.elapsedMilliseconds}ms");
+    } on PlatformException catch (e, s) {
+      if (e.code == _kSyncCancelledCode) {
+        _log.warning("Full device sync cancelled");
+      } else {
+        _log.severe("Error performing full device sync", e, s);
+      }
     } catch (e, s) {
       _log.severe("Error performing full device sync", e, s);
     }
   }
 
   Future<void> addAlbum(LocalAlbum album) async {
+    if (_isCancelled) {
+      return;
+    }
     try {
       _log.fine("Adding device album ${album.name}");
 
@@ -162,6 +194,9 @@ class LocalSyncService {
 
   // The deviceAlbum is ignored since we are going to refresh it anyways
   FutureOr<bool> updateAlbum(LocalAlbum dbAlbum, LocalAlbum deviceAlbum) async {
+    if (_isCancelled) {
+      return false;
+    }
     try {
       _log.fine("Syncing device album ${dbAlbum.name}");
 

mobile/lib/domain/services/log.service.dart

@@ -112,10 +112,16 @@ class LogService {
     return _flushBuffer();
   }
 
-  Future<void> dispose() {
+  Future<void> dispose() async {
     _flushTimer?.cancel();
-    _logSubscription.cancel();
-    return _flushBuffer();
+    _flushTimer = null;
+    await _logSubscription.cancel();
+    await _flushBuffer();
+    // Allow a subsequent init() (e.g. when a worker isolate is reused) to
+    // create a fresh instance instead of returning this disposed one.
+    if (identical(_instance, this)) {
+      _instance = null;
+    }
   }
 
   Future<void> _flushBuffer() async {

mobile/lib/domain/services/store.service.dart

@@ -54,7 +54,13 @@ class StoreService {
   /// Disposes the store and cancels the subscription. To reuse the store call init() again
   Future<void> dispose() async {
     await _storeUpdateSubscription?.cancel();
+    _storeUpdateSubscription = null;
     _cache.clear();
+    // Allow a subsequent init() (e.g. when a worker isolate is reused) to
+    // create a fresh instance instead of returning this disposed one.
+    if (identical(_instance, this)) {
+      _instance = null;
+    }
   }
 
   /// Returns the cached value for [key], or `null`

mobile/lib/domain/services/sync_linked_album.service.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/domain/models/album/local_album.model.dart';
 import 'package:immich_mobile/domain/models/store.model.dart';
@@ -5,6 +7,7 @@ import 'package:immich_mobile/domain/services/store.service.dart';
 import 'package:immich_mobile/infrastructure/repositories/local_album.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/remote_album.repository.dart';
 import 'package:immich_mobile/providers/infrastructure/album.provider.dart';
+import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/store.provider.dart';
 import 'package:immich_mobile/repositories/drift_album_api_repository.dart';
 import 'package:immich_mobile/utils/debug_print.dart';
@@ -16,6 +19,7 @@ final syncLinkedAlbumServiceProvider = Provider(
     ref.watch(remoteAlbumRepository),
     ref.watch(driftAlbumApiRepositoryProvider),
     ref.watch(storeServiceProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -24,13 +28,15 @@ class SyncLinkedAlbumService {
   final DriftRemoteAlbumRepository _remoteAlbumRepository;
   final DriftAlbumApiRepository _albumApiRepository;
   final StoreService _storeService;
+  final Completer<void>? _cancellation;
 
   SyncLinkedAlbumService(
     this._localAlbumRepository,
     this._remoteAlbumRepository,
     this._albumApiRepository,
-    this._storeService,
-  );
+    this._storeService, {
+    this._cancellation,
+  });
 
   final _log = Logger("SyncLinkedAlbumService");
 
@@ -55,7 +61,11 @@ class SyncLinkedAlbumService {
         final assetIds = await _remoteAlbumRepository.getLinkedAssetIds(userId, localAlbum.id, linkedRemoteAlbumId);
         _log.fine("Syncing ${assetIds.length} assets to remote album: ${remoteAlbum.name}");
         if (assetIds.isNotEmpty) {
-          final album = await _albumApiRepository.addAssets(remoteAlbum.id, assetIds);
+          final album = await _albumApiRepository.addAssets(
+            remoteAlbum.id,
+            assetIds,
+            abortTrigger: _cancellation?.future,
+          );
           await _remoteAlbumRepository.addAssets(remoteAlbum.id, album.added);
         }
       }),

mobile/lib/domain/services/sync_stream.service.dart

@@ -38,7 +38,7 @@ class SyncStreamService {
   final IPermissionRepository _permissionRepository;
   final SyncMigrationRepository _syncMigrationRepository;
   final ApiService _api;
-  final bool Function()? _cancelChecker;
+  final Completer<void>? _cancellation;
 
   SyncStreamService({
     required this._syncApiRepository,
@@ -49,10 +49,10 @@ class SyncStreamService {
     required this._permissionRepository,
     required this._syncMigrationRepository,
     required this._api,
-    this._cancelChecker,
+    this._cancellation,
   });
 
-  bool get isCancelled => _cancelChecker?.call() ?? false;
+  bool get isCancelled => _cancellation?.isCompleted ?? false;
 
   Future<bool> sync() async {
     _logger.info("Remote sync request for user");
@@ -80,10 +80,15 @@ class SyncStreamService {
       _handleEvents,
       serverVersion: serverSemVer,
       onReset: () => shouldReset = true,
+      abortSignal: _cancellation?.future,
     );
     if (shouldReset) {
       _logger.info("Resetting sync state as requested by server");
-      await _syncApiRepository.streamChanges(_handleEvents, serverVersion: serverSemVer);
+      await _syncApiRepository.streamChanges(
+        _handleEvents,
+        serverVersion: serverSemVer,
+        abortSignal: _cancellation?.future,
+      );
     }
 
     previousLength = migrations.length;
@@ -318,7 +323,7 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetUploadReadyV1Batch(List<dynamic> batchData) async {
-    if (batchData.isEmpty) {
+    if (batchData.isEmpty || isCancelled) {
       return;
     }
 
@@ -361,7 +366,7 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetUploadReadyV2Batch(List<dynamic> batchData) async {
-    if (batchData.isEmpty) {
+    if (batchData.isEmpty || isCancelled) {
       return;
     }
 
@@ -404,6 +409,9 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetEditReadyV1(dynamic data) async {
+    if (isCancelled) {
+      return;
+    }
     _logger.info('Processing AssetEditReadyV1 event');
 
     try {
@@ -444,6 +452,9 @@ class SyncStreamService {
   }
 
   Future<void> handleWsAssetEditReadyV2(dynamic data) async {
+    if (isCancelled) {
+      return;
+    }
     _logger.info('Processing AssetEditReadyV2 event');
 
     try {

mobile/lib/domain/utils/background_sync.dart

@@ -50,53 +50,27 @@ class BackgroundSyncManager {
   });
 
   Future<void> cancel() async {
-    final futures = <Future>[];
-
-    if (_syncTask != null) {
-      futures.add(_syncTask!.future);
+    final tasks = [
+      _syncTask,
+      _syncWebsocketTask,
+      _cloudIdSyncTask,
+      _linkedAlbumSyncTask,
+      _deviceAlbumSyncTask,
+      _hashTask,
+    ];
+    final futures = [
+      for (final task in tasks)
+        if (task != null) task.future,
+    ];
+    for (final task in tasks) {
+      task?.cancel();
     }
-    _syncTask?.cancel();
     _syncTask = null;
-
-    if (_syncWebsocketTask != null) {
-      futures.add(_syncWebsocketTask!.future);
-    }
-    _syncWebsocketTask?.cancel();
     _syncWebsocketTask = null;
-
-    if (_cloudIdSyncTask != null) {
-      futures.add(_cloudIdSyncTask!.future);
-    }
-    _cloudIdSyncTask?.cancel();
     _cloudIdSyncTask = null;
-
-    if (_linkedAlbumSyncTask != null) {
-      futures.add(_linkedAlbumSyncTask!.future);
-    }
-    _linkedAlbumSyncTask?.cancel();
     _linkedAlbumSyncTask = null;
-
-    try {
-      await Future.wait(futures);
-    } on CanceledError {
-      // Ignore cancellation errors
-    }
-  }
-
-  Future<void> cancelLocal() async {
-    final futures = <Future>[];
-
-    if (_hashTask != null) {
-      futures.add(_hashTask!.future);
-    }
-    _hashTask?.cancel();
-    _hashTask = null;
-
-    if (_deviceAlbumSyncTask != null) {
-      futures.add(_deviceAlbumSyncTask!.future);
-    }
-    _deviceAlbumSyncTask?.cancel();
     _deviceAlbumSyncTask = null;
+    _hashTask = null;
 
     try {
       await Future.wait(futures);

mobile/lib/domain/utils/migrate_cloud_ids.dart

@@ -1,3 +1,5 @@
+import 'dart:async';
+
 import 'package:drift/drift.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:immich_mobile/constants/constants.dart';
@@ -9,6 +11,7 @@ import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/local_album.repository.dart';
 import 'package:immich_mobile/platform/native_sync_api.g.dart';
 import 'package:immich_mobile/providers/api.provider.dart';
+import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/sync.provider.dart';
 import 'package:immich_mobile/providers/server_info.provider.dart';
@@ -51,9 +54,10 @@ Future<void> syncCloudIds(ProviderContainer ref) async {
   }
 
   final assetApi = ref.read(apiServiceProvider).assetsApi;
+  final cancellation = ref.read(cancellationProvider);
 
   // Process cloud IDs in paginated batches
-  await _processCloudIdMappingsInBatches(db, currentUser.id, assetApi, canBulkUpdateMetadata, logger);
+  await _processCloudIdMappingsInBatches(db, currentUser.id, assetApi, canBulkUpdateMetadata, logger, cancellation);
 }
 
 Future<void> _processCloudIdMappingsInBatches(
@@ -62,12 +66,17 @@ Future<void> _processCloudIdMappingsInBatches(
   AssetsApi assetsApi,
   bool canBulkUpdate,
   Logger logger,
+  Completer<void> cancellation,
 ) async {
   const pageSize = 20000;
   String? lastLocalId;
   final seenRemoteAssetIds = <String>{};
 
   while (true) {
+    if (cancellation.isCompleted) {
+      logger.warning('Cloud ID migration cancelled. Stopping batch processing.');
+      break;
+    }
     final mappings = await _fetchCloudIdMappings(drift, userId, pageSize, lastLocalId);
     if (mappings.isEmpty) {
       break;
@@ -98,9 +107,9 @@ Future<void> _processCloudIdMappingsInBatches(
 
     if (items.isNotEmpty) {
       if (canBulkUpdate) {
-        await _bulkUpdateCloudIds(assetsApi, items);
+        await _bulkUpdateCloudIds(assetsApi, items, cancellation.future);
       } else {
-        await _sequentialUpdateCloudIds(assetsApi, items);
+        await _sequentialUpdateCloudIds(assetsApi, items, cancellation);
       }
     }
 
@@ -111,20 +120,35 @@ Future<void> _processCloudIdMappingsInBatches(
   }
 }
 
-Future<void> _sequentialUpdateCloudIds(AssetsApi assetsApi, List<AssetMetadataBulkUpsertItemDto> items) async {
+Future<void> _sequentialUpdateCloudIds(
+  AssetsApi assetsApi,
+  List<AssetMetadataBulkUpsertItemDto> items,
+  Completer<void> cancellation,
+) async {
   for (final item in items) {
+    if (cancellation.isCompleted) {
+      break;
+    }
     final upsertItem = AssetMetadataUpsertItemDto(key: item.key, value: item.value);
     try {
-      await assetsApi.updateAssetMetadata(item.assetId, AssetMetadataUpsertDto(items: [upsertItem]));
+      await assetsApi.updateAssetMetadata(
+        item.assetId,
+        AssetMetadataUpsertDto(items: [upsertItem]),
+        abortTrigger: cancellation.future,
+      );
     } catch (error, stack) {
       Logger('migrateCloudIds').warning('Failed to update metadata for asset ${item.assetId}', error, stack);
     }
   }
 }
 
-Future<void> _bulkUpdateCloudIds(AssetsApi assetsApi, List<AssetMetadataBulkUpsertItemDto> items) async {
+Future<void> _bulkUpdateCloudIds(
+  AssetsApi assetsApi,
+  List<AssetMetadataBulkUpsertItemDto> items,
+  Future<void> abortTrigger,
+) async {
   try {
-    await assetsApi.updateBulkAssetMetadata(AssetMetadataBulkUpsertDto(items: items));
+    await assetsApi.updateBulkAssetMetadata(AssetMetadataBulkUpsertDto(items: items), abortTrigger: abortTrigger);
   } catch (error, stack) {
     Logger('migrateCloudIds').warning('Failed to bulk update metadata', error, stack);
   }

mobile/lib/infrastructure/repositories/sync_api.repository.dart

@@ -29,6 +29,7 @@ class SyncApiRepository {
     Function()? onReset,
     int batchSize = kSyncEventBatchSize,
     http.Client? httpClient,
+    Future<void>? abortSignal,
   }) async {
     final stopwatch = Stopwatch()..start();
     final client = httpClient ?? NetworkRepository.client;
@@ -36,7 +37,7 @@ class SyncApiRepository {
 
     final headers = {'Content-Type': 'application/json', 'Accept': 'application/jsonlines+json'};
 
-    final request = http.Request('POST', Uri.parse(endpoint));
+    final request = http.AbortableRequest('POST', Uri.parse(endpoint), abortTrigger: abortSignal);
     request.headers.addAll(headers);
     request.body = jsonEncode(
       SyncStreamDto(

mobile/lib/platform/native_sync_api.g.dart

@@ -635,6 +635,20 @@ class NativeSyncApi {
     _extractReplyValueOrThrow(pigeonVar_replyList, pigeonVar_channelName, isNullValid: true);
   }
 
+  Future<void> cancelSync() async {
+    final pigeonVar_channelName =
+        'dev.flutter.pigeon.immich_mobile.NativeSyncApi.cancelSync$pigeonVar_messageChannelSuffix';
+    final pigeonVar_channel = BasicMessageChannel<Object?>(
+      pigeonVar_channelName,
+      pigeonChannelCodec,
+      binaryMessenger: pigeonVar_binaryMessenger,
+    );
+    final Future<Object?> pigeonVar_sendFuture = pigeonVar_channel.send(null);
+    final pigeonVar_replyList = await pigeonVar_sendFuture as List<Object?>?;
+
+    _extractReplyValueOrThrow(pigeonVar_replyList, pigeonVar_channelName, isNullValid: true);
+  }
+
   Future<Map<String, List<PlatformAsset>>> getTrashedAssets() async {
     final pigeonVar_channelName =
         'dev.flutter.pigeon.immich_mobile.NativeSyncApi.getTrashedAssets$pigeonVar_messageChannelSuffix';

mobile/lib/providers/infrastructure/cancel.provider.dart

@@ -1,8 +1,9 @@
+import 'dart:async';
+
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 
-/// Provider holding a boolean function that returns true when cancellation is requested.
-/// A computation running in the isolate uses the function to implement cooperative cancellation.
-final cancellationProvider = Provider<bool Function()>(
+/// Holds the isolate's cancellation signal.
+final cancellationProvider = Provider<Completer<void>>(
   // This will be overridden in the isolate's container.
   // Throwing ensures it's not used without an override.
   (ref) => throw UnimplementedError(

mobile/lib/providers/infrastructure/sync.provider.dart

@@ -26,7 +26,7 @@ final syncStreamServiceProvider = Provider(
     permissionRepository: ref.watch(permissionRepositoryProvider),
     syncMigrationRepository: ref.watch(syncMigrationRepositoryProvider),
     api: ref.watch(apiServiceProvider),
-    cancelChecker: ref.watch(cancellationProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -42,6 +42,7 @@ final localSyncServiceProvider = Provider(
     assetMediaRepository: ref.watch(assetMediaRepositoryProvider),
     permissionRepository: ref.watch(permissionRepositoryProvider),
     nativeSyncApi: ref.watch(nativeSyncApiProvider),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );
 
@@ -51,5 +52,6 @@ final hashServiceProvider = Provider(
     localAssetRepository: ref.watch(localAssetRepository),
     nativeSyncApi: ref.watch(nativeSyncApiProvider),
     trashedLocalAssetRepository: ref.watch(trashedLocalAssetRepository),
+    cancellation: ref.watch(cancellationProvider),
   ),
 );

mobile/lib/repositories/auth.repository.dart

@@ -1,40 +1,38 @@
 import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:immich_mobile/domain/models/config/app_config.dart';
 import 'package:immich_mobile/infrastructure/repositories/db.repository.dart';
-import 'package:immich_mobile/infrastructure/repositories/settings.repository.dart';
 import 'package:immich_mobile/infrastructure/repositories/sync_stream.repository.dart';
 import 'package:immich_mobile/models/auth/auxilary_endpoint.model.dart';
 import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/settings.provider.dart';
 
 final authRepositoryProvider = Provider<AuthRepository>(
-  (ref) => AuthRepository(ref.watch(driftProvider), ref.watch(settingsProvider)),
+  (ref) => AuthRepository(ref.watch(driftProvider), ref.watch(appConfigProvider)),
 );
 
 class AuthRepository {
   final Drift _drift;
-  final SettingsRepository _settings;
+  final AppConfig _config;
 
-  const AuthRepository(this._drift, this._settings);
+  const AuthRepository(this._drift, this._config);
 
   Future<void> clearLocalData() async {
     await SyncStreamRepository(_drift).reset();
   }
 
   bool getEndpointSwitchingFeature() {
-    return _settings.appConfig.network.autoEndpointSwitching;
+    return _config.network.autoEndpointSwitching;
   }
 
   String? getPreferredWifiName() {
-    return _settings.appConfig.network.preferredWifiName;
+    return _config.network.preferredWifiName;
   }
 
   String? getLocalEndpoint() {
-    return _settings.appConfig.network.localEndpoint;
+    return _config.network.localEndpoint;
   }
 
   List<AuxilaryEndpoint> getExternalEndpointList() {
-    return _settings.appConfig.network.externalEndpointList
-        .map((url) => AuxilaryEndpoint(url: url, status: .valid))
-        .toList();
+    return _config.network.externalEndpointList.map((url) => AuxilaryEndpoint(url: url, status: .valid)).toList();
   }
 }

mobile/lib/repositories/drift_album_api_repository.dart

@@ -41,8 +41,14 @@ class DriftAlbumApiRepository extends ApiRepository {
     return (removed: removed, failed: failed);
   }
 
-  Future<({List<String> added, List<String> failed})> addAssets(String albumId, Iterable<String> assetIds) async {
-    final response = await checkNull(_api.addAssetsToAlbum(albumId, BulkIdsDto(ids: assetIds.toList())));
+  Future<({List<String> added, List<String> failed})> addAssets(
+    String albumId,
+    Iterable<String> assetIds, {
+    Future<void>? abortTrigger,
+  }) async {
+    final response = await checkNull(
+      _api.addAssetsToAlbum(albumId, BulkIdsDto(ids: assetIds.toList()), abortTrigger: abortTrigger),
+    );
     final List<String> added = [], failed = [];
     for (final dto in response) {
       if (dto.success) {

mobile/lib/utils/isolate.dart

@@ -8,10 +8,9 @@ import 'package:immich_mobile/entities/store.entity.dart';
 import 'package:immich_mobile/providers/infrastructure/cancel.provider.dart';
 import 'package:immich_mobile/providers/infrastructure/db.provider.dart';
 import 'package:immich_mobile/utils/bootstrap.dart';
-import 'package:immich_mobile/utils/debug_print.dart';
 import 'package:immich_mobile/wm_executor.dart';
 import 'package:logging/logging.dart';
-import 'package:worker_manager/worker_manager.dart';
+import 'package:worker_manager/worker_manager.dart' show Cancelable;
 
 class InvalidIsolateUsageException implements Exception {
   const InvalidIsolateUsageException();
@@ -30,50 +29,27 @@ Cancelable<T?> runInIsolateGentle<T>({
     throw const InvalidIsolateUsageException();
   }
 
-  return workerManagerPatch.executeGentle((cancelledChecker) async {
-    T? result;
-    await runZonedGuarded(
-      () async {
-        BackgroundIsolateBinaryMessenger.ensureInitialized(token);
-        DartPluginRegistrant.ensureInitialized();
+  return workerManagerPatch.executeGentle((onCancel) async {
+    BackgroundIsolateBinaryMessenger.ensureInitialized(token);
+    DartPluginRegistrant.ensureInitialized();
 
-        final (drift, logDb) = await Bootstrap.initDomain(shouldBufferLogs: false, listenStoreUpdates: false);
-        final ref = ProviderContainer(
-          overrides: [
-            cancellationProvider.overrideWithValue(cancelledChecker),
-            driftProvider.overrideWith(driftOverride(drift)),
-          ],
-        );
-
-        Logger log = Logger("IsolateLogger");
-
-        try {
-          result = await computation(ref);
-        } on CanceledError {
-          log.warning("Computation cancelled ${debugLabel == null ? '' : ' for $debugLabel'}");
-        } catch (error, stack) {
-          log.severe("Error in runInIsolateGentle ${debugLabel == null ? '' : ' for $debugLabel'}", error, stack);
-        } finally {
-          try {
-            ref.dispose();
-
-            await Store.dispose();
-            await LogService.I.dispose();
-            await logDb.close();
-            await drift.close();
-          } catch (error, stack) {
-            dPrint(() => "Error closing resources in isolate: $error, $stack");
-          } finally {
-            ref.dispose();
-            // Delay to ensure all resources are released
-            await Future.delayed(const Duration(seconds: 2));
-          }
-        }
-      },
-      (error, stack) {
-        dPrint(() => "Error in isolate $debugLabel zone: $error, $stack");
-      },
+    final log = Logger("IsolateLogger");
+    final (drift, logDb) = await Bootstrap.initDomain(shouldBufferLogs: false, listenStoreUpdates: false);
+    final ref = ProviderContainer(
+      overrides: [cancellationProvider.overrideWithValue(onCancel), driftProvider.overrideWith(driftOverride(drift))],
     );
-    return result;
+
+    try {
+      return await computation(ref);
+    } catch (error, stack) {
+      log.severe("Error in runInIsolateGentle${debugLabel == null ? '' : ' for $debugLabel'}", error, stack);
+      return null;
+    } finally {
+      ref.dispose();
+      await Store.dispose();
+      await LogService.I.dispose();
+      await logDb.close();
+      await drift.close();
+    }
   });
 }

mobile/lib/utils/isolate_worker.dart

@@ -0,0 +1,163 @@
+// Forked from worker_manager's `WorkerImpl` (src/worker/worker_io.dart): a
+// `CancelRequest` completes the computation's [Completer] (so it can await
+// cancellation and unwind) instead of flipping a polled flag, and [shutdown]
+// lets the isolate drain and exit on its own rather than force-killing it. Only
+// the gentle-with-cancellation path immich uses is kept.
+//
+// ignore_for_file: implementation_imports
+
+import 'dart:async';
+import 'dart:isolate';
+
+import 'package:worker_manager/src/scheduling/task.dart';
+import 'package:worker_manager/src/worker/cancel_request.dart';
+import 'package:worker_manager/src/worker/result.dart';
+
+/// A worker computation that receives a [Completer] which completes on
+/// cancellation: await its future to react promptly, or read `isCompleted`.
+typedef GentleExecution<R> = FutureOr<R> Function(Completer<void> onCancel);
+
+class _Shutdown {
+  const _Shutdown();
+}
+
+class IsolateWorker {
+  IsolateWorker();
+
+  Isolate? _isolate;
+  RawReceivePort? _receivePort;
+  SendPort? _sendPort;
+  Completer<void>? _sendPortReceived;
+  Completer? _result;
+
+  String? taskId;
+
+  bool get initialized => _sendPortReceived?.isCompleted ?? false;
+
+  bool get initializing {
+    final sendPortReceived = _sendPortReceived;
+    return sendPortReceived != null && !sendPortReceived.isCompleted;
+  }
+
+  Future<void> initialize() async {
+    final sendPortReceived = _sendPortReceived = Completer<void>();
+    final receivePort = _receivePort = RawReceivePort();
+    receivePort.handler = (Object message) {
+      if (message is SendPort) {
+        _sendPort = message;
+        sendPortReceived.complete();
+      } else if (message is ResultSuccess) {
+        _result?.complete(message.value);
+        _afterTask();
+      } else if (message is ResultError) {
+        _result?.completeError(message.error, message.stackTrace);
+        _afterTask();
+      }
+    };
+    _isolate = await Isolate.spawn(_isolateEntry, receivePort.sendPort, errorsAreFatal: false);
+    await sendPortReceived.future;
+  }
+
+  Future<R> work<R>(Task<R> task) async {
+    taskId = task.id;
+    final result = _result = Completer();
+    _sendPort!.send(task.execution);
+    return await (result.future as Future<R>);
+  }
+
+  /// Cancels the current task without retiring the worker.
+  void cancelGentle() => _sendPort?.send(CancelRequest());
+
+  /// Cancels any in-flight task and awaits the isolate exiting on its own — no
+  /// force-kill, so `finally` blocks and native cleanup always run.
+  ///
+  /// Detaches the slot up front so a concurrent [initialize] can revive it
+  /// without colliding (revival installs fresh ports while this drains the ones
+  /// it captured locally). A revived worker is always idle, so the still-live
+  /// receive-port handler can't misroute a result.
+  Future<void> shutdown() async {
+    final sendPortReceived = _sendPortReceived;
+    if (sendPortReceived != null && !sendPortReceived.isCompleted) {
+      await sendPortReceived.future;
+    }
+
+    final isolate = _isolate;
+    final receivePort = _receivePort;
+    final sendPort = _sendPort;
+    if (isolate == null || receivePort == null || sendPort == null) {
+      return;
+    }
+    _isolate = null;
+    _sendPort = null;
+    _sendPortReceived = null;
+    // Not _result: an in-flight task still delivers it before exiting; nulling
+    // here would drop that and hang work()'s caller.
+
+    final exited = Completer<void>();
+    final exitPort = RawReceivePort();
+    exitPort.handler = (_) {
+      if (!exited.isCompleted) {
+        exited.complete();
+      }
+      exitPort.close();
+    };
+    isolate.addOnExitListener(exitPort.sendPort);
+    sendPort.send(const _Shutdown());
+    await exited.future;
+    receivePort.close();
+  }
+
+  void _afterTask() {
+    taskId = null;
+    _result = null;
+  }
+
+  static void _isolateEntry(SendPort sendPort) {
+    final receivePort = RawReceivePort();
+    sendPort.send(receivePort.sendPort);
+    // One task at a time, so a single completer suffices; null between tasks.
+    Completer<void>? onCancel;
+    void cancel() {
+      if (onCancel?.isCompleted == false) {
+        onCancel!.complete();
+      }
+    }
+
+    var shuttingDown = false;
+    var running = false;
+    receivePort.handler = (message) async {
+      if (message is _Shutdown) {
+        shuttingDown = true;
+        cancel();
+        if (!running) {
+          Isolate.exit();
+        }
+        return;
+      }
+      if (message is CancelRequest) {
+        cancel();
+        return;
+      }
+      final execution = message as GentleExecution;
+      onCancel = Completer<void>();
+      running = true;
+      Result result;
+      try {
+        result = ResultSuccess(await execution(onCancel!));
+      } catch (error, stackTrace) {
+        result = ResultError(error, stackTrace);
+      } finally {
+        onCancel = null;
+        running = false;
+      }
+      if (shuttingDown) {
+        // An isolate that has used platform channels can't exit on its own (Flutter's BackgroundIsolateBinaryMessenger
+        // opens an undisposable port), so closing our ports isn't enough. Isolate.exit delivers the result as its final
+        // message and terminates. It's abrupt (skips pending finally/microtasks) but safe here: the computation and its
+        // `finally` are already done and there's no await before this, so nothing pending is skipped.
+        Isolate.exit(sendPort, result);
+      }
+      sendPort.send(result);
+    };
+  }
+}

mobile/lib/wm_executor.dart

@@ -6,8 +6,8 @@ import 'dart:math';
 
 import 'package:collection/collection.dart';
 import 'package:flutter/foundation.dart';
+import 'package:immich_mobile/utils/isolate_worker.dart';
 import 'package:worker_manager/src/number_of_processors/processors_io.dart';
-import 'package:worker_manager/src/worker/worker.dart';
 import 'package:worker_manager/worker_manager.dart';
 
 final workerManagerPatch = _Executor();
@@ -16,6 +16,13 @@ final workerManagerPatch = _Executor();
 const _minId = -9007199254740992;
 const _maxId = 9007199254740992;
 
+class _GentleTask<R> extends Task<R> implements Gentle {
+  @override
+  final GentleExecution<R> execution;
+
+  _GentleTask({required super.id, required super.completer, required super.workPriority, required this.execution});
+}
+
 class Mixinable<T> {
   late final itSelf = this as T;
 }
@@ -51,13 +58,13 @@ mixin _ExecutorLogger on Mixinable<_Executor> {
 
 class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   final _queue = PriorityQueue<Task>();
-  final _pool = <Worker>[];
+  final _pool = <IsolateWorker>[];
   var _nextTaskId = _minId;
   var _dynamicSpawning = false;
   var _isolatesCount = numberOfProcessors;
 
   @visibleForTesting
-  UnmodifiableListView<Worker> get pool => UnmodifiableListView(_pool);
+  UnmodifiableListView<IsolateWorker> get pool => UnmodifiableListView(_pool);
 
   @override
   Future<void> init({int? isolatesCount, bool? dynamicSpawning}) async {
@@ -80,117 +87,37 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   @override
   Future<void> dispose() async {
     _queue.clear();
-    for (final worker in _pool) {
-      if (worker.initialized || worker.initializing) {
-        worker.kill();
-      }
-    }
+    final shutdown = _pool.map((worker) => worker.shutdown()).toList(growable: false);
     _pool.clear();
+    await Future.wait(shutdown);
     super.dispose();
   }
 
-  Cancelable<R> execute<R>(Execute<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
-    return _createCancelable<R>(execution: execution, priority: priority);
-  }
-
-  Cancelable<R> executeNow<R>(ExecuteGentle<R> execution) {
-    final task = TaskGentle<R>(
-      id: "",
-      workPriority: WorkPriority.immediately,
-      execution: execution,
-      completer: Completer<R>(),
-    );
-
-    Future<void> run() async {
-      try {
-        final result = await execution(() => task.canceled);
-        task.complete(result, null, null);
-      } catch (error, st) {
-        task.complete(null, error, st);
-      }
-    }
-
-    run();
-    return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
-  }
-
-  Cancelable<R> executeWithPort<R, T>(
-    ExecuteWithPort<R> execution, {
-    WorkPriority priority = WorkPriority.immediately,
-    required void Function(T value) onMessage,
-  }) {
-    return _createCancelable<R>(
-      execution: execution,
-      priority: priority,
-      onMessage: (message) => onMessage(message as T),
-    );
-  }
-
-  Cancelable<R> executeGentle<R>(ExecuteGentle<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
-    return _createCancelable<R>(execution: execution, priority: priority);
-  }
-
-  Cancelable<R> executeGentleWithPort<R, T>(
-    ExecuteGentleWithPort<R> execution, {
-    WorkPriority priority = WorkPriority.immediately,
-    required void Function(T value) onMessage,
-  }) {
-    return _createCancelable<R>(
-      execution: execution,
-      priority: priority,
-      onMessage: (message) => onMessage(message as T),
-    );
-  }
-
-  void _createWorkers() {
-    for (var i = 0; i < _isolatesCount; i++) {
-      _pool.add(Worker());
-    }
-  }
-
-  Future<void> _initializeWorkers() async {
-    await Future.wait(_pool.map((e) => e.initialize()));
-  }
-
-  Cancelable<R> _createCancelable<R>({
-    required Function execution,
-    WorkPriority priority = WorkPriority.immediately,
-    void Function(Object value)? onMessage,
-  }) {
+  /// Runs [execution] on a worker isolate; its [Completer] completes when the
+  /// returned [Cancelable] is cancelled.
+  Cancelable<R> executeGentle<R>(GentleExecution<R> execution, {WorkPriority priority = WorkPriority.immediately}) {
     if (_nextTaskId + 1 == _maxId) {
       _nextTaskId = _minId;
     }
     final id = _nextTaskId.toString();
     _nextTaskId++;
-    late final Task<R> task;
-    final completer = Completer<R>();
-    if (execution is ExecuteWithPort<R>) {
-      task = TaskWithPort<R>(
-        id: id,
-        workPriority: priority,
-        execution: execution,
-        completer: completer,
-        onMessage: onMessage!,
-      );
-    } else if (execution is ExecuteGentle<R>) {
-      task = TaskGentle<R>(id: id, workPriority: priority, execution: execution, completer: completer);
-    } else if (execution is ExecuteGentleWithPort<R>) {
-      task = TaskGentleWithPort<R>(
-        id: id,
-        workPriority: priority,
-        execution: execution,
-        completer: completer,
-        onMessage: onMessage!,
-      );
-    } else if (execution is Execute<R>) {
-      task = TaskRegular<R>(id: id, workPriority: priority, execution: execution, completer: completer);
-    }
+    final task = _GentleTask<R>(id: id, workPriority: priority, execution: execution, completer: Completer<R>());
     _queue.add(task);
     _schedule();
     logTaskAdded(task.id);
     return Cancelable(completer: task.completer, onCancel: () => _cancel(task));
   }
 
+  void _createWorkers() {
+    for (var i = 0; i < _isolatesCount; i++) {
+      _pool.add(IsolateWorker());
+    }
+  }
+
+  Future<void> _initializeWorkers() async {
+    await Future.wait(_pool.map((e) => e.initialize()));
+  }
+
   Future<void> _ensureWorkersInitialized() async {
     if (_pool.isEmpty) {
       _createWorkers();
@@ -240,7 +167,9 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
         )
         .whenComplete(() {
           if (_dynamicSpawning && _queue.isEmpty) {
-            availableWorker.kill();
+            // Retire the idle worker; shutdown() nulls its fields so the husk
+            // stays pooled and is revived by initialize() if work arrives.
+            unawaited(availableWorker.shutdown());
           }
           _schedule();
         });
@@ -250,15 +179,8 @@ class _Executor extends Mixinable<_Executor> with _ExecutorLogger {
   void _cancel(Task task) {
     task.cancel();
     _queue.remove(task);
-    final targetWorker = _pool.firstWhereOrNull((worker) => worker.taskId == task.id);
-    if (task is Gentle) {
-      targetWorker?.cancelGentle();
-    } else {
-      targetWorker?.kill();
-      if (!_dynamicSpawning) {
-        targetWorker?.initialize();
-      }
-    }
+    // All tasks are gentle: signal cancellation; the worker unwinds on its own.
+    _pool.firstWhereOrNull((worker) => worker.taskId == task.id)?.cancelGentle();
     super._cancel(task);
   }
 }

mobile/pigeon/native_sync_api.dart

@@ -105,25 +105,26 @@ class CloudIdResult {
 
 @HostApi()
 abstract class NativeSyncApi {
+  @async
   bool shouldFullSync();
 
-  @TaskQueue(type: TaskQueueType.serialBackgroundThread)
+  @async
   SyncDelta getMediaChanges();
 
   void checkpointSync();
 
   void clearSyncCheckpoint();
 
-  @TaskQueue(type: TaskQueueType.serialBackgroundThread)
+  @async
   List<String> getAssetIdsForAlbum(String albumId);
 
-  @TaskQueue(type: TaskQueueType.serialBackgroundThread)
+  @async
   List<PlatformAlbum> getAlbums();
 
   @TaskQueue(type: TaskQueueType.serialBackgroundThread)
   int getAssetsCountSince(String albumId, int timestamp);
 
-  @TaskQueue(type: TaskQueueType.serialBackgroundThread)
+  @async
   List<PlatformAsset> getAssetsForAlbum(String albumId, {int? updatedTimeCond});
 
   @async
@@ -132,6 +133,8 @@ abstract class NativeSyncApi {
 
   void cancelHashing();
 
+  void cancelSync();
+
   @TaskQueue(type: TaskQueueType.serialBackgroundThread)
   Map<String, List<PlatformAsset>> getTrashedAssets();
 

mobile/test/domain/services/sync_stream_service_test.dart

@@ -36,13 +36,6 @@ class _AbortCallbackWrapper {
 
 class _MockAbortCallbackWrapper extends Mock implements _AbortCallbackWrapper {}
 
-class _CancellationWrapper {
-  const _CancellationWrapper();
-
-  bool call() => false;
-}
-
-class _MockCancellationWrapper extends Mock implements _CancellationWrapper {}
 
 void main() {
   late SyncStreamService sut;
@@ -94,9 +87,13 @@ void main() {
 
     when(() => mockAbortCallbackWrapper()).thenReturn(false);
 
-    when(() => mockSyncApiRepo.streamChanges(any(), serverVersion: any(named: 'serverVersion'))).thenAnswer((
-      invocation,
-    ) async {
+    when(
+      () => mockSyncApiRepo.streamChanges(
+        any(),
+        serverVersion: any(named: 'serverVersion'),
+        abortSignal: any(named: 'abortSignal'),
+      ),
+    ).thenAnswer((invocation) async {
       handleEventsCallback = invocation.positionalArguments.first;
     });
 
@@ -105,6 +102,7 @@ void main() {
         any(),
         onReset: any(named: 'onReset'),
         serverVersion: any(named: 'serverVersion'),
+        abortSignal: any(named: 'abortSignal'),
       ),
     ).thenAnswer((invocation) async {
       handleEventsCallback = invocation.positionalArguments.first;
@@ -233,8 +231,7 @@ void main() {
     });
 
     test("aborts and stops processing if cancelled during iteration", () async {
-      final cancellationChecker = _MockCancellationWrapper();
-      when(() => cancellationChecker()).thenReturn(false);
+      final cancellation = Completer<void>();
 
       sut = SyncStreamService(
         syncApiRepository: mockSyncApiRepo,
@@ -243,7 +240,7 @@ void main() {
         trashedLocalAssetRepository: mockTrashedLocalAssetRepo,
         assetMediaRepository: mockAssetMediaRepo,
         permissionRepository: mockPermissionRepo,
-        cancelChecker: cancellationChecker.call,
+        cancellation: cancellation,
         api: mockApi,
         syncMigrationRepository: mockSyncMigrationRepo,
       );
@@ -252,7 +249,7 @@ void main() {
       final events = [SyncStreamStub.userDeleteV1, SyncStreamStub.userV1Admin, SyncStreamStub.partnerDeleteV1];
 
       when(() => mockSyncStreamRepo.deleteUsersV1(any())).thenAnswer((_) async {
-        when(() => cancellationChecker()).thenReturn(true);
+        cancellation.complete();
       });
 
       await handleEventsCallback(events, mockAbortCallbackWrapper.call, mockResetCallbackWrapper.call);
@@ -267,8 +264,7 @@ void main() {
     });
 
     test("aborts and stops processing if cancelled before processing batch", () async {
-      final cancellationChecker = _MockCancellationWrapper();
-      when(() => cancellationChecker()).thenReturn(false);
+      final cancellation = Completer<void>();
 
       final processingCompleter = Completer<void>();
       bool handler1Started = false;
@@ -284,7 +280,7 @@ void main() {
         trashedLocalAssetRepository: mockTrashedLocalAssetRepo,
         assetMediaRepository: mockAssetMediaRepo,
         permissionRepository: mockPermissionRepo,
-        cancelChecker: cancellationChecker.call,
+        cancellation: cancellation,
         api: mockApi,
         syncMigrationRepository: mockSyncMigrationRepo,
       );
@@ -303,7 +299,7 @@ void main() {
       expect(handler1Started, isTrue);
 
       // Signal cancellation while handler 1 is waiting
-      when(() => cancellationChecker()).thenReturn(true);
+      cancellation.complete();
       await pumpEventQueue();
 
       processingCompleter.complete();

mobile/test/unit/utils/isolate_worker_test.dart

@@ -0,0 +1,23 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:immich_mobile/wm_executor.dart';
+
+void main() {
+  tearDown(workerManagerPatch.dispose);
+
+  test('dispose() drains a cancelled task and delivers its result', () async {
+    await workerManagerPatch.init(isolatesCount: 1, dynamicSpawning: false);
+
+    final task = workerManagerPatch.executeGentle((onCancel) async {
+      await onCancel.future;
+      return 'drained';
+    });
+
+    await workerManagerPatch.dispose();
+
+    expect(
+      await task.timeout(const Duration(seconds: 5)),
+      'drained',
+      reason: 'the worker must finish and return its result, not be killed mid-task',
+    );
+  });
+}