feat(todo): a task done ticks on phones and chimes on desktops

The developer's request of 10 Nov 2026: completing a task should feel like
something. `CompletionFeedback`, held by `TodoDevice` and handed to each
person's `TodoPerson`, gives a light haptic tick on Android and iOS and, on
desktops, a short quiet chime of our own: two soft bell tones a fifth apart,
synthesized by `apps/todo/tool/completion_sound.dart` into
`assets/sounds/task_done.wav`, so it needs no one's licence. A task's check
and the selection's Complete call it once, however many tasks are done;
an undo is silent.

Settings' Tasks turns the chime off on a desktop, kept per device in
`<app support>/completion_feedback.json`; a phone is offered no switch. A
device that can't play loses only the sound. The player is `audioplayers`,
as Learn's sounds: on Linux it links GStreamer, so Todo's snap gains the
`audio-playback` plug and GStreamer's headers to build, as Learn's recipe has.

Whats-New: Completing a task now gives a light tap on phones and a short chime on computers, which Settings › Tasks turns off.
Whats-New-De: Eine erledigte Aufgabe gibt jetzt auf dem Handy ein leichtes Tippen und am Computer einen kurzen Klang, den du unter Einstellungen › Aufgaben ausschaltest.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_flutter/lib/l10n/app_de.arb

@@ -340,6 +340,8 @@
   "weekStartLanguage": "Wie in der Sprache",
   "resetSubTasksTitle": "Unteraufgaben zurücksetzen",
   "resetSubTasksHint": "Wieder öffnen, wenn eine wiederkehrende Aufgabe erledigt ist",
+  "completionSoundTitle": "Ton beim Erledigen",
+  "completionSoundHint": "Ein kurzer Klang, wenn du eine Aufgabe erledigst",
   "automaticReminderTitle": "Automatische Erinnerung",
   "automaticReminderHint": "Für eine Aufgabe mit Uhrzeit, wenn sie keine eigene Erinnerung hat",
   "automaticReminderNone": "Keine",

apps/todo/halkyon_todo_flutter/lib/l10n/app_en.arb

@@ -961,6 +961,14 @@
   "@resetSubTasksHint": {
     "description": "Settings of tasks and reminders (ADR 0033, D4)."
   },
+  "completionSoundTitle": "Sound when done",
+  "@completionSoundTitle": {
+    "description": "Settings of tasks, on a desktop alone: whether a short chime plays as a task is marked done (decided 10 Nov 2026)."
+  },
+  "completionSoundHint": "A short chime as a task is marked done",
+  "@completionSoundHint": {
+    "description": "Explains completionSoundTitle."
+  },
   "automaticReminderTitle": "Automatic reminder",
   "@automaticReminderTitle": {
     "description": "Settings of tasks and reminders (ADR 0033, D4)."

apps/todo/halkyon_todo_flutter/lib/l10n/app_localizations.dart

@@ -2140,6 +2140,18 @@ abstract class AppLocalizations {
   /// **'Open them again when a recurring task is done'**
   String get resetSubTasksHint;
 
+  /// Settings of tasks, on a desktop alone: whether a short chime plays as a task is marked done (decided 10 Nov 2026).
+  ///
+  /// In en, this message translates to:
+  /// **'Sound when done'**
+  String get completionSoundTitle;
+
+  /// Explains completionSoundTitle.
+  ///
+  /// In en, this message translates to:
+  /// **'A short chime as a task is marked done'**
+  String get completionSoundHint;
+
   /// Settings of tasks and reminders (ADR 0033, D4).
   ///
   /// In en, this message translates to:

apps/todo/halkyon_todo_flutter/lib/l10n/app_localizations_de.dart

@@ -1306,6 +1306,13 @@ class AppLocalizationsDe extends AppLocalizations {
   String get resetSubTasksHint =>
       'Wieder öffnen, wenn eine wiederkehrende Aufgabe erledigt ist';
 
+  @override
+  String get completionSoundTitle => 'Ton beim Erledigen';
+
+  @override
+  String get completionSoundHint =>
+      'Ein kurzer Klang, wenn du eine Aufgabe erledigst';
+
   @override
   String get automaticReminderTitle => 'Automatische Erinnerung';
 

apps/todo/halkyon_todo_flutter/lib/l10n/app_localizations_en.dart

@@ -1305,6 +1305,12 @@ class AppLocalizationsEn extends AppLocalizations {
   String get resetSubTasksHint =>
       'Open them again when a recurring task is done';
 
+  @override
+  String get completionSoundTitle => 'Sound when done';
+
+  @override
+  String get completionSoundHint => 'A short chime as a task is marked done';
+
   @override
   String get automaticReminderTitle => 'Automatic reminder';
 

apps/todo/halkyon_todo_flutter/lib/src/app/todo_dependencies.dart

@@ -33,6 +33,7 @@ import 'package:halkyon_todo_flutter/src/feature/section/data/section_repository
 import 'package:halkyon_todo_flutter/src/feature/section/data/sync_section_gateway.dart';
 import 'package:halkyon_todo_flutter/src/feature/settings/data/settings_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/settings/data/sync_settings_gateway.dart';
+import 'package:halkyon_todo_flutter/src/feature/task/data/completion_feedback.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/data/sync_task_gateway.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/data/task_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/weather/data/weather_gateway.dart';
@@ -98,6 +99,10 @@ class TodoPerson(
   /// given; else for this session.
   final PaneWidths? _paneWidths,
 
+  /// What a task done feels like: the device's, where it is given; else
+  /// nothing.
+  final CompletionFeedback? _completionFeedback,
+
   /// The projects whose sub-projects are folded away (decided 10 Nov
   /// 2026): the person's folder's, where it is given; else for this session.
   final FoldedProjects? _foldedProjects,
@@ -118,6 +123,10 @@ class TodoPerson(
   /// How wide the device keeps its side panes (ADR 0033, D33).
   late final PaneWidths paneWidths = _paneWidths ?? PaneWidths();
 
+  /// A tick or a chime as a task is done (decided 10 Nov 2026).
+  late final CompletionFeedback completionFeedback =
+      _completionFeedback ?? CompletionFeedback();
+
   /// The projects folded in Browse and the sidebar, kept on the device.
   late final FoldedProjects foldedProjects =
       _foldedProjects ?? FoldedProjects();
@@ -364,6 +373,7 @@ class TodoDependencies({
             locationReminders: device.locationReminders,
             locationAccess: device.locationAccess,
             paneWidths: device.paneWidths,
+            completionFeedback: device.completionFeedback,
             onClosed: closed.complete,
           );
         } on Object {
@@ -405,6 +415,7 @@ Future<TodoPerson> _openPersonData(
   required LocationReminderGateway locationReminders,
   required LocationReminderAccess locationAccess,
   required PaneWidths paneWidths,
+  required CompletionFeedback completionFeedback,
   required void Function() onClosed,
 }) async {
   final db = await client.createSyncSession(
@@ -471,6 +482,7 @@ Future<TodoPerson> _openPersonData(
     locationReminders: locationReminders,
     locationAccess: locationAccess,
     paneWidths: paneWidths,
+    completionFeedback: completionFeedback,
     foldedProjects: await FoldedProjects.open(
       File(p.join(folder.path, 'folded_projects.json')),
     ),
@@ -522,6 +534,9 @@ class TodoDevice({
 
   /// How wide it keeps its side panes (D33).
   required final PaneWidths paneWidths,
+
+  /// What a task done feels like, the sound turned off or not.
+  required final CompletionFeedback completionFeedback,
 }) {
   /// Whether the device may show reminders, asked once an app start,
   /// whoever is signed in (D31).
@@ -542,6 +557,9 @@ class TodoDevice({
       appBuild: int.tryParse(package.buildNumber),
       appVersion: package.version,
       paneWidths: await PaneWidths.open(File(p.join(support, 'panes.json'))),
+      completionFeedback: await CompletionFeedback.forDevice(
+        File(p.join(support, 'completion_feedback.json')),
+      ),
       reminders: await _reminders(),
       locationReminders: Platform.isAndroid
           ? const AndroidLocationReminders()

apps/todo/halkyon_todo_flutter/lib/src/feature/task/data/completion_feedback.dart

@@ -0,0 +1,112 @@
+import 'dart:convert';
+import 'dart:developer';
+import 'dart:io';
+
+import 'package:audioplayers/audioplayers.dart';
+import 'package:flutter/foundation.dart';
+import 'package:flutter/services.dart';
+
+/// What a task done feels like (decided by the developer, 10 Nov 2026): a
+/// light haptic tick on a phone, a short quiet chime of Todo's own on a
+/// desktop ([sounds]), which Settings turns off there. The device's matter,
+/// whoever is signed in, kept in [_file] where there is one; neither sealed
+/// nor synced.
+class CompletionFeedback({
+  final File? _file,
+
+  /// Whether this device chimes rather than ticks: a desktop's.
+  final bool sounds = false,
+
+  /// The tick; nothing in tests that don't say.
+  final Future<void> Function() _tick = _nothing,
+
+  /// The chime; nothing in tests that don't say.
+  final Future<void> Function() _chime = _nothing,
+}) extends ChangeNotifier {
+  var _soundOn = true;
+
+  /// Opens what [file] holds; the sound on where it can't be read.
+  static Future<CompletionFeedback> open(
+    File file, {
+    required bool sounds,
+    Future<void> Function() tick = _nothing,
+    Future<void> Function() chime = _nothing,
+  }) async {
+    final feedback = CompletionFeedback(
+      file: file,
+      sounds: sounds,
+      tick: tick,
+      chime: chime,
+    );
+    try {
+      if (file.existsSync()) {
+        final json = jsonDecode(await file.readAsString());
+        if (json is Map<String, Object?> && json['sound'] is bool) {
+          feedback._soundOn = json['sound']! as bool;
+        }
+      }
+    } on Object catch (error) {
+      log('Completion sound not read: ${error.runtimeType}', name: 'Tasks');
+    }
+    return feedback;
+  }
+
+  /// The device's own: a tick on Android and iOS, else the chime from
+  /// `assets/sounds/task_done.wav`.
+  static Future<CompletionFeedback> forDevice(File file) {
+    final phone = Platform.isAndroid || Platform.isIOS;
+    return open(
+      file,
+      sounds: !phone,
+      tick: HapticFeedback.lightImpact,
+      chime: phone ? _nothing : _AssetChime().play,
+    );
+  }
+
+  /// Whether Settings offers turning the sound off: on a desktop alone.
+  bool get offersSound => sounds;
+
+  /// Whether a desktop chimes; on at first.
+  bool get soundOn => _soundOn;
+
+  /// Turns the chime [on] or off, and keeps it.
+  Future<void> setSoundOn({required bool on}) async {
+    if (_soundOn == on) {
+      return;
+    }
+    _soundOn = on;
+    notifyListeners();
+    try {
+      await _file?.writeAsString(jsonEncode({'sound': on}));
+    } on Object catch (error) {
+      log('Completion sound not kept: ${error.runtimeType}', name: 'Tasks');
+    }
+  }
+
+  /// A task, or several at once, was just marked done: once whatever their
+  /// number. Never throws: a device that can't play loses only the sound.
+  Future<void> completed() async {
+    try {
+      if (!sounds) {
+        await _tick();
+      } else if (_soundOn) {
+        await _chime();
+      }
+    } on Object catch (error) {
+      log('No completion feedback: ${error.runtimeType}', name: 'Tasks');
+    }
+  }
+}
+
+Future<void> _nothing() async {}
+
+/// The chime on `audioplayers`, one player made at the first, kept for the
+/// app's life.
+class _AssetChime() {
+  late final _player = AudioPlayer();
+
+  Future<void> play() async {
+    await _player.stop();
+    await _player.play(AssetSource('sounds/task_done.wav'));
+  }
+}

apps/todo/halkyon_todo_flutter/lib/src/feature/task/widget/task_selection.dart

@@ -355,6 +355,12 @@ class _SelectionActions(
     final context = _context;
     final tasks = _tasks;
     final chosen = _chosen.where((task) => !task.content.completed).toList();
+    if (chosen.isNotEmpty) {
+      // Once for them all.
+      unawaited(
+        PersonScope.of<TodoPerson>(context).completionFeedback.completed(),
+      );
+    }
     final reopen = context.read<TodoCubit>().state.settings.tasks.resetSubTasks;
     final now = clock.now();
     final before = await _write(

apps/todo/halkyon_todo_flutter/lib/src/feature/task/widget/task_tile.dart

@@ -386,9 +386,14 @@ class const TaskCheck({required final OpenTask task, super.key})
         color: color,
       ),
       onPressed: () async {
-        final tasks = PersonScope.of<TodoPerson>(context).tasks;
+        final person = PersonScope.of<TodoPerson>(context);
+        final tasks = person.tasks;
         final stored = StoredTask(task.id, content);
         final done = !content.completed;
+        if (done) {
+          // Felt as the tap lands, not once it is written.
+          unawaited(person.completionFeedback.completed());
+        }
         final reopen = context
             .read<TodoCubit>()
             .state

apps/todo/halkyon_todo_flutter/lib/src/settings/todo_settings_cards.dart

@@ -75,11 +75,37 @@ class const TaskSettingsCard({super.key}) extends StatelessWidget {
             settings.copyWith(tasks: tasks.copyWith(resetSubTasks: on)),
           ),
         ),
+        const _CompletionSound(),
       ],
     );
   }
 }
 
+/// Whether a desktop chimes as a task is done (decided 10 Nov 2026): the
+/// device's, whoever is signed in; nothing on a phone, which ticks.
+class const _CompletionSound() extends StatelessWidget {
+  @override
+  Widget build(BuildContext context) {
+    final l10n = AppLocalizations.of(context);
+    final feedback = PersonScope.of<TodoPerson>(context).completionFeedback;
+    if (!feedback.offersSound) {
+      return const SizedBox.shrink();
+    }
+    return ListenableBuilder(
+      listenable: feedback,
+      builder: (context, _) => SwitchListTile(
+        secondary: const Icon(LucideIcons.volume2),
+        title: ExplainedTitle(
+          l10n.completionSoundTitle,
+          help: l10n.completionSoundHint,
+        ),
+        value: feedback.soundOn,
+        onChanged: (on) => feedback.setSoundOn(on: on),
+      ),
+    );
+  }
+}
+
 /// Settings' *Reminders* (D4): the automatic reminder a task given a time
 /// gets where it has none of its own (none at first), and how long a
 /// reminder is snoozed for from its notification; above them, while

apps/todo/halkyon_todo_flutter/linux/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,7 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <audioplayers_linux/audioplayers_linux_plugin.h>
 #include <desktop_webview_window/desktop_webview_window_plugin.h>
 #include <emoji_picker_flutter/emoji_picker_flutter_plugin.h>
 #include <file_selector_linux/file_selector_plugin.h>
@@ -14,6 +15,9 @@
 #include <window_to_front/window_to_front_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
+  g_autoptr(FlPluginRegistrar) audioplayers_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "AudioplayersLinuxPlugin");
+  audioplayers_linux_plugin_register_with_registrar(audioplayers_linux_registrar);
   g_autoptr(FlPluginRegistrar) desktop_webview_window_registrar =
       fl_plugin_registry_get_registrar_for_plugin(registry, "DesktopWebviewWindowPlugin");
   desktop_webview_window_plugin_register_with_registrar(desktop_webview_window_registrar);

apps/todo/halkyon_todo_flutter/linux/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  audioplayers_linux
   desktop_webview_window
   emoji_picker_flutter
   file_selector_linux

apps/todo/halkyon_todo_flutter/macos/Flutter/GeneratedPluginRegistrant.swift

@@ -5,6 +5,7 @@
 import FlutterMacOS
 import Foundation
 
+import audioplayers_darwin
 import connectivity_plus
 import desktop_webview_window
 import device_info_plus
@@ -23,6 +24,7 @@ import url_launcher_macos
 import window_to_front
 
 func RegisterGeneratedPlugins(registry: FlutterPluginRegistry) {
+  AudioplayersDarwinPlugin.register(with: registry.registrar(forPlugin: "AudioplayersDarwinPlugin"))
   ConnectivityPlusPlugin.register(with: registry.registrar(forPlugin: "ConnectivityPlusPlugin"))
   DesktopWebviewWindowPlugin.register(with: registry.registrar(forPlugin: "DesktopWebviewWindowPlugin"))
   DeviceInfoPlusMacosPlugin.register(with: registry.registrar(forPlugin: "DeviceInfoPlusMacosPlugin"))

apps/todo/halkyon_todo_flutter/pubspec.yaml

@@ -13,6 +13,9 @@ environment:
 resolution: workspace
 
 dependencies:
+  # The chime of a task done on a desktop (decided 10 Nov 2026), as Learn's
+  # sounds: GStreamer on Linux.
+  audioplayers: ^6.8.1
   clock: ^1.1.3
   # Reactions on comments (ADR 0033, D36): every emoji, searched, recents on
   # the device.
@@ -101,6 +104,9 @@ flutter:
     # (<version>.<language>.txt), drafted by tool/release.dart and edited
     # (Train's ADR 0030, D61): halkyon_app's What's new shows them.
     - assets/whats_new/
+    # The chime of a task done on a desktop, Todo's own, synthesized by
+    # ../tool/completion_sound.dart.
+    - assets/sounds/task_done.wav
     # The app's icon, Lucide's list-todo (ADR 0031), and Lucide's licence for the
     # licence list (the repository's tool/app_icons.py writes both).
     - assets/icon/halkyon_todo_icon.png

apps/todo/halkyon_todo_flutter/test/app/todo_app_test.dart

@@ -42,6 +42,7 @@ import 'package:halkyon_todo_flutter/src/feature/section/data/section_repository
 import 'package:halkyon_todo_flutter/src/feature/section/model/section.dart';
 import 'package:halkyon_todo_flutter/src/feature/settings/data/settings_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/settings/model/todo_settings.dart';
+import 'package:halkyon_todo_flutter/src/feature/task/data/completion_feedback.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/data/task_repository.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/model/repeat.dart';
 import 'package:halkyon_todo_flutter/src/feature/task/model/task.dart';
@@ -99,6 +100,12 @@ void main() {
   /// The projects folded in Browse and the sidebar.
   late FoldedProjects folded;
 
+  /// What the device did as tasks were done: `tick` or `chime`, in order.
+  late List<String> felt;
+
+  /// What a task done feels like: a phone's unless a test says.
+  late CompletionFeedback completion;
+
   /// How many syncs ran.
   late int syncs;
 
@@ -133,6 +140,11 @@ void main() {
     locationGateway = MemoryLocationGateway();
     speech = FakeSpeechInput();
     folded = FoldedProjects();
+    felt = [];
+    completion = CompletionFeedback(
+      tick: () async => felt.add('tick'),
+      chime: () async => felt.add('chime'),
+    );
     store = MemoryInstanceStore();
     looks = MemoryLookStore();
     gateway = FakeAuthGateway();
@@ -239,6 +251,7 @@ void main() {
               locationReminders: locationGateway,
               calendarFeeds: calendarFeeds,
               foldedProjects: folded,
+              completionFeedback: completion,
             );
           },
         ),
@@ -3917,13 +3930,16 @@ void main() {
       await tester.pumpAndSettle();
       expect(find.text('Water plants'), findsNothing);
       expect(find.text('Task done'), findsOneWidget);
+      expect(felt, ['tick'], reason: "a phone's tick");
 
       await tester.tap(find.text('Undo'));
       await tester.pumpAndSettle();
       expect(find.text('Water plants'), findsOneWidget);
+      expect(felt, ['tick'], reason: 'nothing on an undo');
 
       await tester.tap(find.byTooltip('Mark as done'));
       await tester.pumpAndSettle();
+      expect(felt, ['tick', 'tick']);
       await tester.tap(find.byTooltip('Display'));
       await tester.pumpAndSettle();
       await tester.tap(find.text('Completed tasks'));
@@ -6023,6 +6039,7 @@ void main() {
         await tester.pumpAndSettle();
         expect(find.text('Water plants'), findsNothing);
         expect(find.text('2 tasks done'), findsOneWidget);
+        expect(felt, ['tick'], reason: 'once for both');
         await tester.tap(find.text('Undo'));
         await tester.pumpAndSettle();
         expect(find.text('Water plants'), findsOneWidget);
@@ -6708,6 +6725,58 @@ void main() {
         );
       });
 
+      testWidgets("a desktop's chime of a task done is turned off in Tasks, "
+          'for the device; a phone, which ticks, is offered none', (
+        tester,
+      ) async {
+        await start(tester, usedBefore: true);
+        await openSettings(tester);
+        expect(find.text('Sound when done'), findsNothing);
+
+        await tester.pumpWidget(const SizedBox());
+        completion = CompletionFeedback(
+          sounds: true,
+          tick: () async => felt.add('tick'),
+          chime: () async => felt.add('chime'),
+        );
+        await start(tester, usedBefore: true);
+        await seed(
+          tester,
+          TaskContent(title: 'Water plants', projectId: inbox()),
+        );
+        await goTab(tester, 'Inbox');
+        await tester.tap(find.byTooltip('Mark as done'));
+        await tester.pumpAndSettle();
+        expect(felt, ['chime']);
+        // The undo's snack bar gone first, as it would be by the time.
+        ScaffoldMessenger.of(
+          tester.element(find.byType(SnackBar)),
+        ).removeCurrentSnackBar();
+        await tester.pumpAndSettle();
+
+        await openSettings(tester);
+        await tapInSettings(tester, 'Sound when done');
+        expect(completion.soundOn, isFalse);
+        expect(
+          tester
+              .widget<SwitchListTile>(
+                find.widgetWithText(SwitchListTile, 'Sound when done'),
+              )
+              .value,
+          isFalse,
+        );
+        await tester.pageBack();
+        await tester.pumpAndSettle();
+        await seed(
+          tester,
+          TaskContent(title: 'Post letter', projectId: inbox()),
+        );
+        await goTab(tester, 'Inbox');
+        await tester.tap(find.byTooltip('Mark as done'));
+        await tester.pumpAndSettle();
+        expect(felt, ['chime'], reason: 'quiet now');
+      });
+
       testWidgets('a task added with a time gets the automatic reminder; '
           'reminders are snoozed for as long as set', (tester) async {
         await start(tester, usedBefore: true);

apps/todo/halkyon_todo_flutter/test/feature/task/completion_feedback_test.dart

@@ -0,0 +1,83 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+import 'package:halkyon_todo_flutter/src/feature/task/data/completion_feedback.dart';
+import 'package:path/path.dart' as p;
+
+void main() {
+  late int ticks;
+  late int chimes;
+
+  setUp(() {
+    ticks = 0;
+    chimes = 0;
+  });
+
+  Future<void> tick() async => ticks++;
+  Future<void> chime() async => chimes++;
+
+  test('a phone ticks once a task is done, and offers no sound', () async {
+    final feedback = CompletionFeedback(tick: tick, chime: chime);
+
+    await feedback.completed();
+
+    expect(feedback.offersSound, isFalse);
+    expect((ticks, chimes), (1, 0));
+  });
+
+  test('a desktop chimes, while its sound is on, and never ticks', () async {
+    final feedback = CompletionFeedback(
+      sounds: true,
+      tick: tick,
+      chime: chime,
+    );
+    expect(feedback.offersSound, isTrue);
+    expect(feedback.soundOn, isTrue, reason: 'on at first');
+
+    await feedback.completed();
+    expect((ticks, chimes), (0, 1));
+
+    await feedback.setSoundOn(on: false);
+    await feedback.completed();
+    expect((ticks, chimes), (0, 1));
+  });
+
+  test("a sound that can't play takes nothing with it", () async {
+    final feedback = CompletionFeedback(
+      sounds: true,
+      chime: () async => throw StateError('no GStreamer'),
+    );
+
+    await expectLater(feedback.completed(), completes);
+  });
+
+  group('kept on the device', () {
+    late Directory folder;
+
+    setUp(() async {
+      folder = await Directory.systemTemp.createTemp('completion');
+      addTearDown(() => folder.delete(recursive: true));
+    });
+
+    test('the sound turned off stays off when the app opens again', () async {
+      final file = File(p.join(folder.path, 'completion_feedback.json'));
+      final feedback = await CompletionFeedback.open(file, sounds: true);
+      var changes = 0;
+      feedback.addListener(() => changes++);
+
+      await feedback.setSoundOn(on: false);
+      expect(changes, 1);
+
+      final again = await CompletionFeedback.open(file, sounds: true);
+      expect(again.soundOn, isFalse);
+    });
+
+    test('a file that is no setting leaves the sound on', () async {
+      final file = File(p.join(folder.path, 'completion_feedback.json'));
+      await file.writeAsString('not json');
+      expect((await CompletionFeedback.open(file, sounds: true)).soundOn, true);
+      await file.writeAsString('[1]');
+      expect((await CompletionFeedback.open(file, sounds: true)).soundOn, true);
+    });
+  });
+}

apps/todo/halkyon_todo_flutter/windows/flutter/generated_plugin_registrant.cc

@@ -6,6 +6,7 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <audioplayers_windows/audioplayers_windows_plugin.h>
 #include <connectivity_plus/connectivity_plus_windows_plugin.h>
 #include <desktop_webview_window/desktop_webview_window_plugin.h>
 #include <emoji_picker_flutter/emoji_picker_flutter_plugin_c_api.h>
@@ -16,6 +17,8 @@
 #include <window_to_front/window_to_front_plugin.h>
 
 void RegisterPlugins(flutter::PluginRegistry* registry) {
+  AudioplayersWindowsPluginRegisterWithRegistrar(
+      registry->GetRegistrarForPlugin("AudioplayersWindowsPlugin"));
   ConnectivityPlusWindowsPluginRegisterWithRegistrar(
       registry->GetRegistrarForPlugin("ConnectivityPlusWindowsPlugin"));
   DesktopWebviewWindowPluginRegisterWithRegistrar(

apps/todo/halkyon_todo_flutter/windows/flutter/generated_plugins.cmake

@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  audioplayers_windows
   connectivity_plus
   desktop_webview_window
   emoji_picker_flutter