Add sync queue orchestration and local mutation envelopes

docs/progress.md

@@ -2,6 +2,34 @@
 
 Updated: 2026-02-15
 
+## Latest Milestone (2026-02-15): Sync Queue + Orchestrator
+
+Implemented the next sync phase so local mutations are now queued and synced through a real coordinator flow:
+
+- Added persisted sync queue state:
+  - `lib/features/sync/sync_state.dart`
+  - `lib/features/sync/sync_queue_repository.dart`
+  - stores pending `ChangeEnvelope`s, cursor, last attempt/sync, and rejection info
+- Added sync orchestration service:
+  - `lib/features/sync/sync_coordinator.dart`
+  - supports `pushPending`, `pullRemote`, and `syncNow`
+  - keeps offline-first behavior by recording failures without blocking local usage
+- Wired local CRUD to sync envelopes:
+  - `lib/features/local/local_repository.dart`
+  - all person/moment/idea/reminder mutations now enqueue typed change envelopes
+  - added `applyRemoteChanges(...)` to apply pulled backend envelopes into local state
+- Upgraded Sync UI:
+  - `lib/features/sync/sync_view.dart`
+  - now shows queue/cursor/error status and provides real sync actions (sync/push/pull/clear)
+- Added sync tests:
+  - `test/features/sync/sync_queue_repository_test.dart`
+  - `test/features/sync/sync_coordinator_test.dart`
+
+Validation for this milestone:
+
+- `flutter analyze` -> pass
+- `flutter test` -> pass
+
 ## Latest Milestone (2026-02-15): Auth Session UX
 
 Implemented app-level authentication/session flow so navigation is now session-aware:
@@ -149,7 +177,7 @@ Validation status after UI milestone:
 - Local database persistence and repository wiring (currently demo in-memory data).
 - Full CRUD flows (create/edit/delete) for people, captures, reminder rules, gift/event ideas.
 - Auth UX flows (sign-in, session-expired recovery, sign-out confirmation).
-- Real sync orchestration layer (queue, cursor lifecycle, conflict policy UI).
+- Conflict policy UI and merge/resolution UX for rejected remote/local mutations.
 - Notifications/reminders delivery and scheduling integration.
 - End-to-end and integration tests for app flows beyond unit/widget basics.
 
@@ -169,9 +197,9 @@ Validation status after UI milestone:
 
 ### Phase 3: Sync + Auth UX
 
-1. Add sync queue service and cursor management use cases.
+1. Add background sync scheduling/triggers (app start, manual retry, connectivity hooks).
-2. Add conflict handling strategy and UI states.
+2. Add conflict handling strategy and user-facing UI states for rejected mutations.
-3. Implement sign-in/session lifecycle screens and provider state.
+3. Add session-expired recovery UX and guarded routes for protected actions.
 
 ### Phase 4: Quality + Release Readiness
 

lib/features/local/local_repository.dart

@@ -2,6 +2,8 @@ import 'dart:convert';
 
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:relationship_saver/features/local/local_models.dart';
+import 'package:relationship_saver/features/sync/sync_queue_repository.dart';
+import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
 import 'package:shared_preferences/shared_preferences.dart';
 import 'package:uuid/uuid.dart';
 
@@ -10,6 +12,7 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
   static const String _storageKey = 'local_data_state_v1';
   static const String _schemaVersionKey = 'local_data_schema_version';
   static const int _schemaVersion = 2;
+  static const int _syncSchemaVersion = 1;
 
   static const Uuid _uuid = Uuid();
 
@@ -64,6 +67,14 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
       ...current.people,
     ];
     await _setState(current.copyWith(people: people));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'person',
+        entityId: person.id,
+        op: ChangeOperation.upsert,
+        payload: _personPayload(person),
+      ),
+    );
   }
 
   Future<void> updatePerson(PersonProfile person) async {
@@ -76,10 +87,28 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .map((PersonProfile item) => item.id == person.id ? person : item)
         .toList(growable: false);
     await _setState(current.copyWith(people: updated));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'person',
+        entityId: person.id,
+        op: ChangeOperation.upsert,
+        payload: _personPayload(person),
+      ),
+    );
   }
 
   Future<void> deletePerson(String personId) async {
     final LocalDataState current = _requireState();
+    final List<RelationshipMoment> removedMoments = current.moments
+        .where((RelationshipMoment moment) => moment.personId == personId)
+        .toList(growable: false);
+    final List<RelationshipIdea> removedIdeas = current.ideas
+        .where((RelationshipIdea idea) => idea.personId == personId)
+        .toList(growable: false);
+    final List<ReminderRule> removedReminders = current.reminders
+        .where((ReminderRule reminder) => reminder.personId == personId)
+        .toList(growable: false);
+
     final List<PersonProfile> people = current.people
         .where((PersonProfile person) => person.id != personId)
         .toList(growable: false);
@@ -101,6 +130,35 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         reminders: reminders,
       ),
     );
+
+    await _enqueueChanges(<ChangeEnvelope>[
+      _buildEnvelope(
+        entityType: 'person',
+        entityId: personId,
+        op: ChangeOperation.delete,
+      ),
+      ...removedMoments.map(
+        (RelationshipMoment moment) => _buildEnvelope(
+          entityType: 'capture',
+          entityId: moment.id,
+          op: ChangeOperation.delete,
+        ),
+      ),
+      ...removedIdeas.map(
+        (RelationshipIdea idea) => _buildEnvelope(
+          entityType: _ideaEntityType(idea.type),
+          entityId: idea.id,
+          op: ChangeOperation.delete,
+        ),
+      ),
+      ...removedReminders.map(
+        (ReminderRule reminder) => _buildEnvelope(
+          entityType: 'reminderRule',
+          entityId: reminder.id,
+          op: ChangeOperation.delete,
+        ),
+      ),
+    ]);
   }
 
   Future<void> addMoment({
@@ -132,6 +190,14 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
       ...current.moments,
     ];
     await _setState(current.copyWith(moments: moments));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'capture',
+        entityId: moment.id,
+        op: ChangeOperation.upsert,
+        payload: _momentPayload(moment),
+      ),
+    );
   }
 
   Future<void> updateMoment(RelationshipMoment moment) async {
@@ -144,6 +210,14 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .map((RelationshipMoment item) => item.id == moment.id ? moment : item)
         .toList(growable: false);
     await _setState(current.copyWith(moments: updated));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'capture',
+        entityId: moment.id,
+        op: ChangeOperation.upsert,
+        payload: _momentPayload(moment),
+      ),
+    );
   }
 
   Future<void> deleteMoment(String momentId) async {
@@ -152,6 +226,13 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .where((RelationshipMoment moment) => moment.id != momentId)
         .toList(growable: false);
     await _setState(current.copyWith(moments: moments));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'capture',
+        entityId: momentId,
+        op: ChangeOperation.delete,
+      ),
+    );
   }
 
   Future<void> addIdea({
@@ -180,6 +261,14 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
       ...current.ideas,
     ];
     await _setState(current.copyWith(ideas: ideas));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: _ideaEntityType(idea.type),
+        entityId: idea.id,
+        op: ChangeOperation.upsert,
+        payload: _ideaPayload(idea),
+      ),
+    );
   }
 
   Future<void> updateIdea(RelationshipIdea idea) async {
@@ -192,18 +281,42 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .map((RelationshipIdea item) => item.id == idea.id ? idea : item)
         .toList(growable: false);
     await _setState(current.copyWith(ideas: ideas));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: _ideaEntityType(idea.type),
+        entityId: idea.id,
+        op: ChangeOperation.upsert,
+        payload: _ideaPayload(idea),
+      ),
+    );
   }
 
   Future<void> toggleIdeaArchived(String ideaId) async {
     final LocalDataState current = _requireState();
+    RelationshipIdea? updatedIdea;
     final List<RelationshipIdea> ideas = current.ideas
-        .map(
+        .map((RelationshipIdea item) {
-          (RelationshipIdea item) => item.id == ideaId
+          if (item.id != ideaId) {
-              ? item.copyWith(isArchived: !item.isArchived)
+            return item;
-              : item,
+          }
-        )
+          final RelationshipIdea toggled = item.copyWith(
+            isArchived: !item.isArchived,
+          );
+          updatedIdea = toggled;
+          return toggled;
+        })
         .toList(growable: false);
     await _setState(current.copyWith(ideas: ideas));
+    if (updatedIdea != null) {
+      await _enqueueChange(
+        _buildEnvelope(
+          entityType: _ideaEntityType(updatedIdea!.type),
+          entityId: updatedIdea!.id,
+          op: ChangeOperation.upsert,
+          payload: _ideaPayload(updatedIdea!),
+        ),
+      );
+    }
   }
 
   Future<void> deleteIdea(String ideaId) async {
@@ -212,6 +325,13 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .where((RelationshipIdea idea) => idea.id != ideaId)
         .toList(growable: false);
     await _setState(current.copyWith(ideas: ideas));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: _ideaEntityTypeFromId(current.ideas, ideaId),
+        entityId: ideaId,
+        op: ChangeOperation.delete,
+      ),
+    );
   }
 
   Future<void> addReminder({
@@ -240,6 +360,14 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
       ...current.reminders,
     ];
     await _setState(current.copyWith(reminders: reminders));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'reminderRule',
+        entityId: reminder.id,
+        op: ChangeOperation.upsert,
+        payload: _reminderPayload(reminder),
+      ),
+    );
   }
 
   Future<void> updateReminder(ReminderRule reminder) async {
@@ -252,18 +380,40 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .map((ReminderRule item) => item.id == reminder.id ? reminder : item)
         .toList(growable: false);
     await _setState(current.copyWith(reminders: reminders));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'reminderRule',
+        entityId: reminder.id,
+        op: ChangeOperation.upsert,
+        payload: _reminderPayload(reminder),
+      ),
+    );
   }
 
   Future<void> toggleReminderEnabled(String reminderId) async {
     final LocalDataState current = _requireState();
+    ReminderRule? updatedReminder;
     final List<ReminderRule> reminders = current.reminders
-        .map(
+        .map((ReminderRule item) {
-          (ReminderRule item) => item.id == reminderId
+          if (item.id != reminderId) {
-              ? item.copyWith(enabled: !item.enabled)
+            return item;
-              : item,
+          }
-        )
+          final ReminderRule toggled = item.copyWith(enabled: !item.enabled);
+          updatedReminder = toggled;
+          return toggled;
+        })
         .toList(growable: false);
     await _setState(current.copyWith(reminders: reminders));
+    if (updatedReminder != null) {
+      await _enqueueChange(
+        _buildEnvelope(
+          entityType: 'reminderRule',
+          entityId: updatedReminder!.id,
+          op: ChangeOperation.upsert,
+          payload: _reminderPayload(updatedReminder!),
+        ),
+      );
+    }
   }
 
   Future<void> deleteReminder(String reminderId) async {
@@ -272,6 +422,13 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
         .where((ReminderRule reminder) => reminder.id != reminderId)
         .toList(growable: false);
     await _setState(current.copyWith(reminders: reminders));
+    await _enqueueChange(
+      _buildEnvelope(
+        entityType: 'reminderRule',
+        entityId: reminderId,
+        op: ChangeOperation.delete,
+      ),
+    );
   }
 
   Future<void> toggleTaskDone(String taskId) async {
@@ -286,6 +443,431 @@ class LocalRepository extends AsyncNotifier<LocalDataState> {
     await _setState(current.copyWith(tasks: tasks));
   }
 
+  Future<void> applyRemoteChanges(List<ChangeEnvelope> changes) async {
+    if (changes.isEmpty) {
+      return;
+    }
+
+    LocalDataState next = _requireState();
+    for (final ChangeEnvelope change in changes) {
+      next = _applyRemoteChange(next, change);
+    }
+    await _setState(next);
+  }
+
+  LocalDataState _applyRemoteChange(
+    LocalDataState current,
+    ChangeEnvelope change,
+  ) {
+    switch (change.entityType) {
+      case 'person':
+        return _applyPersonChange(current, change);
+      case 'capture':
+        return _applyMomentChange(current, change);
+      case 'giftIdea':
+      case 'eventIdea':
+        return _applyIdeaChange(current, change);
+      case 'reminderRule':
+        return _applyReminderChange(current, change);
+      default:
+        return current;
+    }
+  }
+
+  LocalDataState _applyPersonChange(
+    LocalDataState current,
+    ChangeEnvelope change,
+  ) {
+    if (change.op == ChangeOperation.delete) {
+      final String personId = change.entityId;
+      return current.copyWith(
+        people: current.people
+            .where((PersonProfile person) => person.id != personId)
+            .toList(growable: false),
+        moments: current.moments
+            .where((RelationshipMoment moment) => moment.personId != personId)
+            .toList(growable: false),
+        ideas: current.ideas
+            .where((RelationshipIdea idea) => idea.personId != personId)
+            .toList(growable: false),
+        reminders: current.reminders
+            .where((ReminderRule reminder) => reminder.personId != personId)
+            .toList(growable: false),
+      );
+    }
+
+    final int existingIndex = current.people.indexWhere(
+      (PersonProfile person) => person.id == change.entityId,
+    );
+    final PersonProfile? existing = existingIndex >= 0
+        ? current.people[existingIndex]
+        : null;
+    final Map<String, dynamic> payload = change.payload ?? <String, dynamic>{};
+    final PersonProfile next = PersonProfile(
+      id: change.entityId,
+      name: _stringField(payload, 'name', existing?.name ?? 'Unknown'),
+      relationship: _stringField(
+        payload,
+        'relationship',
+        existing?.relationship ?? 'Relationship',
+      ),
+      affinityScore: _intField(
+        payload,
+        'affinityScore',
+        existing?.affinityScore ?? 70,
+      ),
+      nextMoment: _dateField(
+        payload,
+        'nextMoment',
+        existing?.nextMoment ?? DateTime.now().add(const Duration(days: 3)),
+      ),
+      tags: _stringListField(payload, 'tags', existing?.tags ?? <String>[]),
+      notes: _stringField(payload, 'notes', existing?.notes ?? ''),
+    );
+    final List<PersonProfile> people = _upsertItem(
+      items: current.people,
+      item: next,
+      idOf: (PersonProfile person) => person.id,
+    );
+    return current.copyWith(people: people);
+  }
+
+  LocalDataState _applyMomentChange(
+    LocalDataState current,
+    ChangeEnvelope change,
+  ) {
+    if (change.op == ChangeOperation.delete) {
+      return current.copyWith(
+        moments: current.moments
+            .where((RelationshipMoment moment) => moment.id != change.entityId)
+            .toList(growable: false),
+      );
+    }
+
+    final int existingIndex = current.moments.indexWhere(
+      (RelationshipMoment moment) => moment.id == change.entityId,
+    );
+    final RelationshipMoment? existing = existingIndex >= 0
+        ? current.moments[existingIndex]
+        : null;
+    final Map<String, dynamic> payload = change.payload ?? <String, dynamic>{};
+    final String summary = _stringField(
+      payload,
+      'summary',
+      existing?.summary ?? '',
+    );
+    final RelationshipMoment next = RelationshipMoment(
+      id: change.entityId,
+      personId: _stringField(
+        payload,
+        'personId',
+        existing?.personId ??
+            (current.people.isEmpty
+                ? 'person-unknown'
+                : current.people.first.id),
+      ),
+      title: _stringField(
+        payload,
+        'title',
+        existing?.title ?? _titleFromSummary(summary),
+      ),
+      summary: summary,
+      at: _dateField(payload, 'at', existing?.at ?? DateTime.now()),
+      type: _stringField(payload, 'type', existing?.type ?? 'capture'),
+    );
+    final List<RelationshipMoment> moments = _upsertItem(
+      items: current.moments,
+      item: next,
+      idOf: (RelationshipMoment moment) => moment.id,
+    );
+    return current.copyWith(moments: moments);
+  }
+
+  LocalDataState _applyIdeaChange(
+    LocalDataState current,
+    ChangeEnvelope change,
+  ) {
+    if (change.op == ChangeOperation.delete) {
+      return current.copyWith(
+        ideas: current.ideas
+            .where((RelationshipIdea idea) => idea.id != change.entityId)
+            .toList(growable: false),
+      );
+    }
+
+    final int existingIndex = current.ideas.indexWhere(
+      (RelationshipIdea idea) => idea.id == change.entityId,
+    );
+    final RelationshipIdea? existing = existingIndex >= 0
+        ? current.ideas[existingIndex]
+        : null;
+    final Map<String, dynamic> payload = change.payload ?? <String, dynamic>{};
+    final IdeaType fallbackType = _ideaTypeFromEntityType(
+      change.entityType,
+      fallback: existing?.type ?? IdeaType.gift,
+    );
+    final IdeaType type = _ideaTypeFromRaw(
+      payload['type'],
+      fallback: fallbackType,
+    );
+    final RelationshipIdea next = RelationshipIdea(
+      id: change.entityId,
+      personId: payload['personId'] as String? ?? existing?.personId,
+      type: type,
+      title: _stringField(payload, 'title', existing?.title ?? 'Untitled idea'),
+      details: _stringField(payload, 'details', existing?.details ?? ''),
+      createdAt: _dateField(
+        payload,
+        'createdAt',
+        existing?.createdAt ?? DateTime.now(),
+      ),
+      isArchived: _boolField(
+        payload,
+        'isArchived',
+        existing?.isArchived ?? false,
+      ),
+    );
+    final List<RelationshipIdea> ideas = _upsertItem(
+      items: current.ideas,
+      item: next,
+      idOf: (RelationshipIdea idea) => idea.id,
+    );
+    return current.copyWith(ideas: ideas);
+  }
+
+  LocalDataState _applyReminderChange(
+    LocalDataState current,
+    ChangeEnvelope change,
+  ) {
+    if (change.op == ChangeOperation.delete) {
+      return current.copyWith(
+        reminders: current.reminders
+            .where((ReminderRule reminder) => reminder.id != change.entityId)
+            .toList(growable: false),
+      );
+    }
+
+    final int existingIndex = current.reminders.indexWhere(
+      (ReminderRule reminder) => reminder.id == change.entityId,
+    );
+    final ReminderRule? existing = existingIndex >= 0
+        ? current.reminders[existingIndex]
+        : null;
+    final Map<String, dynamic> payload = change.payload ?? <String, dynamic>{};
+    final ReminderRule next = ReminderRule(
+      id: change.entityId,
+      personId: payload['personId'] as String? ?? existing?.personId,
+      title: _stringField(payload, 'title', existing?.title ?? 'Reminder'),
+      cadence: _cadenceFromRaw(
+        payload['cadence'],
+        fallback: existing?.cadence ?? ReminderCadence.weekly,
+      ),
+      nextAt: _dateField(payload, 'nextAt', existing?.nextAt ?? DateTime.now()),
+      enabled: _boolField(payload, 'enabled', existing?.enabled ?? true),
+    );
+    final List<ReminderRule> reminders = _upsertItem(
+      items: current.reminders,
+      item: next,
+      idOf: (ReminderRule reminder) => reminder.id,
+    );
+    return current.copyWith(reminders: reminders);
+  }
+
+  Future<void> _enqueueChange(ChangeEnvelope change) async {
+    await ref.read(syncQueueRepositoryProvider.notifier).enqueue(change);
+  }
+
+  Future<void> _enqueueChanges(List<ChangeEnvelope> changes) async {
+    await ref.read(syncQueueRepositoryProvider.notifier).enqueueAll(changes);
+  }
+
+  ChangeEnvelope _buildEnvelope({
+    required String entityType,
+    required String entityId,
+    required ChangeOperation op,
+    Map<String, dynamic>? payload,
+  }) {
+    return ChangeEnvelope(
+      schemaVersion: _syncSchemaVersion,
+      entityType: entityType,
+      entityId: entityId,
+      op: op,
+      modifiedAt: DateTime.now().toUtc(),
+      clientMutationId: _uuid.v4(),
+      payload: payload,
+    );
+  }
+
+  Map<String, dynamic> _personPayload(PersonProfile person) {
+    return <String, dynamic>{
+      'name': person.name,
+      'relationship': person.relationship,
+      'affinityScore': person.affinityScore,
+      'nextMoment': person.nextMoment.toUtc().toIso8601String(),
+      'tags': person.tags,
+      'notes': person.notes,
+    };
+  }
+
+  Map<String, dynamic> _momentPayload(RelationshipMoment moment) {
+    return <String, dynamic>{
+      'personId': moment.personId,
+      'title': moment.title,
+      'summary': moment.summary,
+      'at': moment.at.toUtc().toIso8601String(),
+      'type': moment.type,
+    };
+  }
+
+  Map<String, dynamic> _ideaPayload(RelationshipIdea idea) {
+    return <String, dynamic>{
+      'personId': idea.personId,
+      'type': idea.type.name,
+      'title': idea.title,
+      'details': idea.details,
+      'createdAt': idea.createdAt.toUtc().toIso8601String(),
+      'isArchived': idea.isArchived,
+    };
+  }
+
+  Map<String, dynamic> _reminderPayload(ReminderRule reminder) {
+    return <String, dynamic>{
+      'personId': reminder.personId,
+      'title': reminder.title,
+      'cadence': reminder.cadence.name,
+      'nextAt': reminder.nextAt.toUtc().toIso8601String(),
+      'enabled': reminder.enabled,
+    };
+  }
+
+  String _ideaEntityType(IdeaType type) {
+    return type == IdeaType.event ? 'eventIdea' : 'giftIdea';
+  }
+
+  String _ideaEntityTypeFromId(List<RelationshipIdea> ideas, String ideaId) {
+    final int index = ideas.indexWhere(
+      (RelationshipIdea idea) => idea.id == ideaId,
+    );
+    final RelationshipIdea? existing = index >= 0 ? ideas[index] : null;
+    if (existing == null) {
+      return 'giftIdea';
+    }
+    return _ideaEntityType(existing.type);
+  }
+
+  IdeaType _ideaTypeFromEntityType(
+    String entityType, {
+    required IdeaType fallback,
+  }) {
+    switch (entityType) {
+      case 'eventIdea':
+        return IdeaType.event;
+      case 'giftIdea':
+        return IdeaType.gift;
+      default:
+        return fallback;
+    }
+  }
+
+  IdeaType _ideaTypeFromRaw(dynamic value, {required IdeaType fallback}) {
+    if (value is! String || value.isEmpty) {
+      return fallback;
+    }
+
+    return IdeaType.values.firstWhere(
+      (IdeaType type) => type.name == value,
+      orElse: () => fallback,
+    );
+  }
+
+  ReminderCadence _cadenceFromRaw(
+    dynamic value, {
+    required ReminderCadence fallback,
+  }) {
+    if (value is! String || value.isEmpty) {
+      return fallback;
+    }
+
+    return ReminderCadence.values.firstWhere(
+      (ReminderCadence cadence) => cadence.name == value,
+      orElse: () => fallback,
+    );
+  }
+
+  List<T> _upsertItem<T>({
+    required List<T> items,
+    required T item,
+    required String Function(T value) idOf,
+  }) {
+    final int index = items.indexWhere((T value) => idOf(value) == idOf(item));
+    if (index < 0) {
+      return <T>[item, ...items];
+    }
+
+    final List<T> copy = items.toList();
+    copy[index] = item;
+    return copy;
+  }
+
+  String _stringField(
+    Map<String, dynamic> payload,
+    String key,
+    String fallback,
+  ) {
+    final dynamic value = payload[key];
+    if (value is String && value.trim().isNotEmpty) {
+      return value.trim();
+    }
+    return fallback;
+  }
+
+  int _intField(Map<String, dynamic> payload, String key, int fallback) {
+    final dynamic value = payload[key];
+    if (value is int) {
+      return value;
+    }
+    if (value is num) {
+      return value.toInt();
+    }
+    return fallback;
+  }
+
+  bool _boolField(Map<String, dynamic> payload, String key, bool fallback) {
+    final dynamic value = payload[key];
+    if (value is bool) {
+      return value;
+    }
+    return fallback;
+  }
+
+  List<String> _stringListField(
+    Map<String, dynamic> payload,
+    String key,
+    List<String> fallback,
+  ) {
+    final dynamic value = payload[key];
+    if (value is! List<dynamic>) {
+      return fallback;
+    }
+
+    return value.map((dynamic item) => '$item').toList(growable: false);
+  }
+
+  DateTime _dateField(
+    Map<String, dynamic> payload,
+    String key,
+    DateTime fallback,
+  ) {
+    final dynamic value = payload[key];
+    if (value is String) {
+      final DateTime? parsed = DateTime.tryParse(value);
+      if (parsed != null) {
+        return parsed.toLocal();
+      }
+    }
+    return fallback;
+  }
+
   Future<void> _setState(LocalDataState next) async {
     state = AsyncData<LocalDataState>(next);
     await _persist(next);

lib/features/sync/sync_coordinator.dart

@@ -0,0 +1,179 @@
+import 'package:flutter/foundation.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:relationship_saver/features/local/local_repository.dart';
+import 'package:relationship_saver/features/sync/sync_queue_repository.dart';
+import 'package:relationship_saver/features/sync/sync_state.dart';
+import 'package:relationship_saver/integrations/backend/backend_gateway_provider.dart';
+
+/// Result details for one sync action.
+@immutable
+class SyncRunResult {
+  const SyncRunResult({
+    required this.success,
+    required this.operation,
+    required this.message,
+    required this.pendingAfter,
+    this.cursor,
+    this.accepted = 0,
+    this.rejected = 0,
+    this.pulled = 0,
+    this.error,
+  });
+
+  final bool success;
+  final String operation;
+  final String message;
+  final int pendingAfter;
+  final String? cursor;
+  final int accepted;
+  final int rejected;
+  final int pulled;
+  final Object? error;
+}
+
+/// Coordinates push/pull sync operations across queue, gateway, and local store.
+class SyncCoordinator {
+  const SyncCoordinator(this._ref);
+
+  final Ref _ref;
+
+  Future<SyncRunResult> pushPending() async {
+    final SyncState queueState = await _ref.read(
+      syncQueueRepositoryProvider.future,
+    );
+    if (queueState.pendingChanges.isEmpty) {
+      return SyncRunResult(
+        success: true,
+        operation: 'push',
+        message: 'No pending local changes to push.',
+        pendingAfter: 0,
+        cursor: queueState.cursor,
+      );
+    }
+
+    final DateTime now = DateTime.now();
+    final syncQueue = _ref.read(syncQueueRepositoryProvider.notifier);
+    try {
+      final result = await _ref
+          .read(backendGatewayProvider)
+          .pushChanges(
+            changes: queueState.pendingChanges,
+            cursor: queueState.cursor,
+          );
+      await syncQueue.applyPushResult(result, at: now);
+      final SyncState after = await _ref.read(
+        syncQueueRepositoryProvider.future,
+      );
+      return SyncRunResult(
+        success: true,
+        operation: 'push',
+        message:
+            'Push complete. accepted=${result.accepted.length}, rejected=${result.rejected.length}.',
+        accepted: result.accepted.length,
+        rejected: result.rejected.length,
+        pendingAfter: after.pendingChanges.length,
+        cursor: after.cursor,
+      );
+    } catch (error) {
+      await syncQueue.markFailure(error, at: now);
+      final SyncState after = await _ref.read(
+        syncQueueRepositoryProvider.future,
+      );
+      return SyncRunResult(
+        success: false,
+        operation: 'push',
+        message: 'Push failed. Local changes stay queued.',
+        pendingAfter: after.pendingChanges.length,
+        cursor: after.cursor,
+        error: error,
+      );
+    }
+  }
+
+  Future<SyncRunResult> pullRemote() async {
+    final SyncState queueState = await _ref.read(
+      syncQueueRepositoryProvider.future,
+    );
+    final DateTime now = DateTime.now();
+    final syncQueue = _ref.read(syncQueueRepositoryProvider.notifier);
+
+    try {
+      final result = await _ref
+          .read(backendGatewayProvider)
+          .pullChanges(cursor: queueState.cursor);
+      await _ref
+          .read(localRepositoryProvider.notifier)
+          .applyRemoteChanges(result.changes);
+      await syncQueue.applyPullResult(result, at: now);
+      final SyncState after = await _ref.read(
+        syncQueueRepositoryProvider.future,
+      );
+      return SyncRunResult(
+        success: true,
+        operation: 'pull',
+        message: 'Pulled ${result.changes.length} change(s) from backend.',
+        pulled: result.changes.length,
+        pendingAfter: after.pendingChanges.length,
+        cursor: after.cursor,
+      );
+    } catch (error) {
+      await syncQueue.markFailure(error, at: now);
+      final SyncState after = await _ref.read(
+        syncQueueRepositoryProvider.future,
+      );
+      return SyncRunResult(
+        success: false,
+        operation: 'pull',
+        message: 'Pull failed. Staying in local-first mode.',
+        pendingAfter: after.pendingChanges.length,
+        cursor: after.cursor,
+        error: error,
+      );
+    }
+  }
+
+  Future<SyncRunResult> syncNow() async {
+    final SyncRunResult pushResult = await pushPending();
+    if (!pushResult.success) {
+      return SyncRunResult(
+        success: false,
+        operation: 'sync',
+        message: 'Sync paused at push step. ${pushResult.message}',
+        pendingAfter: pushResult.pendingAfter,
+        cursor: pushResult.cursor,
+        accepted: pushResult.accepted,
+        rejected: pushResult.rejected,
+        error: pushResult.error,
+      );
+    }
+
+    final SyncRunResult pullResult = await pullRemote();
+    if (!pullResult.success) {
+      return SyncRunResult(
+        success: false,
+        operation: 'sync',
+        message: 'Sync paused at pull step. ${pullResult.message}',
+        pendingAfter: pullResult.pendingAfter,
+        cursor: pullResult.cursor,
+        accepted: pushResult.accepted,
+        rejected: pushResult.rejected,
+        error: pullResult.error,
+      );
+    }
+
+    return SyncRunResult(
+      success: true,
+      operation: 'sync',
+      message:
+          'Sync complete. accepted=${pushResult.accepted}, rejected=${pushResult.rejected}, pulled=${pullResult.pulled}.',
+      pendingAfter: pullResult.pendingAfter,
+      cursor: pullResult.cursor,
+      accepted: pushResult.accepted,
+      rejected: pushResult.rejected,
+      pulled: pullResult.pulled,
+    );
+  }
+}
+
+final Provider<SyncCoordinator> syncCoordinatorProvider =
+    Provider<SyncCoordinator>(SyncCoordinator.new);

lib/features/sync/sync_queue_repository.dart

@@ -0,0 +1,133 @@
+import 'dart:convert';
+
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:relationship_saver/features/sync/sync_state.dart';
+import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+/// Persists queued local mutations and sync cursor metadata.
+class SyncQueueRepository extends AsyncNotifier<SyncState> {
+  static const String _storageKey = 'sync_queue_state_v1';
+
+  @override
+  Future<SyncState> build() async {
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    final String? raw = prefs.getString(_storageKey);
+    if (raw == null || raw.isEmpty) {
+      return SyncState.empty;
+    }
+
+    try {
+      final Map<String, dynamic> json = jsonDecode(raw) as Map<String, dynamic>;
+      return SyncState.fromJson(json);
+    } on FormatException {
+      await prefs.remove(_storageKey);
+      return SyncState.empty;
+    }
+  }
+
+  Future<void> enqueue(ChangeEnvelope change) async {
+    final SyncState current = await _currentState();
+    final List<ChangeEnvelope> pending = <ChangeEnvelope>[
+      change,
+      ...current.pendingChanges,
+    ];
+    await _setState(current.copyWith(pendingChanges: pending));
+  }
+
+  Future<void> enqueueAll(Iterable<ChangeEnvelope> changes) async {
+    final List<ChangeEnvelope> values = changes.toList(growable: false);
+    if (values.isEmpty) {
+      return;
+    }
+
+    final SyncState current = await _currentState();
+    final List<ChangeEnvelope> pending = <ChangeEnvelope>[
+      ...values,
+      ...current.pendingChanges,
+    ];
+    await _setState(current.copyWith(pendingChanges: pending));
+  }
+
+  Future<void> applyPushResult(SyncPushResult result, {DateTime? at}) async {
+    final SyncState current = await _currentState();
+    final DateTime now = at ?? DateTime.now();
+    final Set<String> completedMutationIds = <String>{
+      ...result.accepted.map((MutationAck ack) => ack.clientMutationId),
+      ...result.rejected.map(
+        (MutationRejection rejection) => rejection.clientMutationId,
+      ),
+    };
+    final List<ChangeEnvelope> pending = current.pendingChanges
+        .where(
+          (ChangeEnvelope change) =>
+              !completedMutationIds.contains(change.clientMutationId),
+        )
+        .toList(growable: false);
+
+    final String? rejectionMessage = result.rejected.isEmpty
+        ? null
+        : 'Push rejected ${result.rejected.length} change(s).';
+
+    await _setState(
+      current.copyWith(
+        cursor: result.cursor,
+        pendingChanges: pending,
+        lastAttemptAt: now,
+        lastSyncAt: now,
+        lastError: rejectionMessage,
+        lastRejected: result.rejected,
+      ),
+    );
+  }
+
+  Future<void> applyPullResult(SyncPullResult result, {DateTime? at}) async {
+    final SyncState current = await _currentState();
+    final DateTime now = at ?? DateTime.now();
+    await _setState(
+      current.copyWith(
+        cursor: result.cursor,
+        lastAttemptAt: now,
+        lastSyncAt: now,
+        lastError: null,
+        lastRejected: const <MutationRejection>[],
+      ),
+    );
+  }
+
+  Future<void> markFailure(Object error, {DateTime? at}) async {
+    final SyncState current = await _currentState();
+    final DateTime now = at ?? DateTime.now();
+    await _setState(current.copyWith(lastAttemptAt: now, lastError: '$error'));
+  }
+
+  Future<void> clearQueue() async {
+    final SyncState current = await _currentState();
+    await _setState(
+      current.copyWith(
+        pendingChanges: const <ChangeEnvelope>[],
+        lastRejected: const <MutationRejection>[],
+      ),
+    );
+  }
+
+  Future<SyncState> _currentState() async {
+    final SyncState? value = state.asData?.value;
+    if (value != null) {
+      return value;
+    }
+    return future;
+  }
+
+  Future<void> _setState(SyncState next) async {
+    state = AsyncData<SyncState>(next);
+    final SharedPreferences prefs = await SharedPreferences.getInstance();
+    await prefs.setString(_storageKey, jsonEncode(next.toJson()));
+  }
+}
+
+final AsyncNotifierProvider<SyncQueueRepository, SyncState>
+syncQueueRepositoryProvider =
+    AsyncNotifierProvider<SyncQueueRepository, SyncState>(
+      SyncQueueRepository.new,
+    );

lib/features/sync/sync_state.dart

@@ -0,0 +1,98 @@
+import 'package:flutter/foundation.dart';
+import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
+
+/// Persisted state for sync queue and cursor progression.
+@immutable
+class SyncState {
+  const SyncState({
+    this.cursor,
+    required this.pendingChanges,
+    this.lastSyncAt,
+    this.lastAttemptAt,
+    this.lastError,
+    this.lastRejected = const <MutationRejection>[],
+  });
+
+  factory SyncState.fromJson(Map<String, dynamic> json) {
+    return SyncState(
+      cursor: json['cursor'] as String?,
+      pendingChanges: (json['pendingChanges'] as List<dynamic>? ?? <dynamic>[])
+          .map(
+            (dynamic item) =>
+                ChangeEnvelope.fromJson(item as Map<String, dynamic>),
+          )
+          .toList(growable: false),
+      lastSyncAt: _tryParseDate(json['lastSyncAt'] as String?),
+      lastAttemptAt: _tryParseDate(json['lastAttemptAt'] as String?),
+      lastError: json['lastError'] as String?,
+      lastRejected: (json['lastRejected'] as List<dynamic>? ?? <dynamic>[])
+          .map(
+            (dynamic item) =>
+                MutationRejection.fromJson(item as Map<String, dynamic>),
+          )
+          .toList(growable: false),
+    );
+  }
+
+  final String? cursor;
+  final List<ChangeEnvelope> pendingChanges;
+  final DateTime? lastSyncAt;
+  final DateTime? lastAttemptAt;
+  final String? lastError;
+  final List<MutationRejection> lastRejected;
+
+  static const Object _unset = Object();
+
+  static const SyncState empty = SyncState(
+    pendingChanges: <ChangeEnvelope>[],
+    lastRejected: <MutationRejection>[],
+  );
+
+  SyncState copyWith({
+    Object? cursor = _unset,
+    List<ChangeEnvelope>? pendingChanges,
+    Object? lastSyncAt = _unset,
+    Object? lastAttemptAt = _unset,
+    Object? lastError = _unset,
+    List<MutationRejection>? lastRejected,
+  }) {
+    return SyncState(
+      cursor: identical(cursor, _unset) ? this.cursor : cursor as String?,
+      pendingChanges: pendingChanges ?? this.pendingChanges,
+      lastSyncAt: identical(lastSyncAt, _unset)
+          ? this.lastSyncAt
+          : lastSyncAt as DateTime?,
+      lastAttemptAt: identical(lastAttemptAt, _unset)
+          ? this.lastAttemptAt
+          : lastAttemptAt as DateTime?,
+      lastError: identical(lastError, _unset)
+          ? this.lastError
+          : lastError as String?,
+      lastRejected: lastRejected ?? this.lastRejected,
+    );
+  }
+
+  Map<String, dynamic> toJson() {
+    return <String, dynamic>{
+      'cursor': cursor,
+      'pendingChanges': pendingChanges
+          .map((ChangeEnvelope change) => change.toJson())
+          .toList(growable: false),
+      'lastSyncAt': lastSyncAt?.toUtc().toIso8601String(),
+      'lastAttemptAt': lastAttemptAt?.toUtc().toIso8601String(),
+      'lastError': lastError,
+      'lastRejected': lastRejected
+          .map((MutationRejection rejection) => rejection.toJson())
+          .toList(growable: false),
+    };
+  }
+
+  static DateTime? _tryParseDate(String? raw) {
+    if (raw == null || raw.isEmpty) {
+      return null;
+    }
+
+    final DateTime? parsed = DateTime.tryParse(raw);
+    return parsed?.toLocal();
+  }
+}

lib/features/sync/sync_view.dart

@@ -2,9 +2,9 @@ import 'package:flutter/material.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
 import 'package:relationship_saver/core/config/app_theme.dart';
 import 'package:relationship_saver/features/shared/frosted_card.dart';
-import 'package:relationship_saver/integrations/backend/backend_gateway_provider.dart';
+import 'package:relationship_saver/features/sync/sync_coordinator.dart';
-import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
+import 'package:relationship_saver/features/sync/sync_queue_repository.dart';
-import 'package:uuid/uuid.dart';
+import 'package:relationship_saver/features/sync/sync_state.dart';
 
 class SyncView extends ConsumerStatefulWidget {
   const SyncView({super.key});
@@ -14,14 +14,15 @@ class SyncView extends ConsumerStatefulWidget {
 }
 
 class _SyncViewState extends ConsumerState<SyncView> {
-  static const Uuid _uuid = Uuid();
-
   bool _busy = false;
   String _status = 'Ready. Local-first mode keeps app usable without sync.';
-  String? _cursor;
 
   @override
   Widget build(BuildContext context) {
+    final AsyncValue<SyncState> syncState = ref.watch(
+      syncQueueRepositoryProvider,
+    );
+
     return Padding(
       padding: const EdgeInsets.fromLTRB(28, 24, 28, 28),
       child: Column(
@@ -30,12 +31,36 @@ class _SyncViewState extends ConsumerState<SyncView> {
           Text('Sync', style: Theme.of(context).textTheme.headlineMedium),
           const SizedBox(height: 6),
           Text(
-            'Push local changes and pull remote updates when connectivity is available.',
+            'Queue local changes, then push and pull when network is available.',
             style: Theme.of(
               context,
             ).textTheme.bodyLarge?.copyWith(color: AppTheme.textSecondary),
           ),
           const SizedBox(height: 16),
+          Expanded(
+            child: syncState.when(
+              data: (SyncState state) => _buildBody(context, state),
+              loading: () => const Center(child: CircularProgressIndicator()),
+              error: (Object error, StackTrace stackTrace) {
+                return Center(
+                  child: Text(
+                    'Unable to load sync state. $error',
+                    style: Theme.of(context).textTheme.bodyMedium?.copyWith(
+                      color: AppTheme.textSecondary,
+                    ),
+                  ),
+                );
+              },
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+
+  Widget _buildBody(BuildContext context, SyncState state) {
+    return ListView(
+      children: <Widget>[
         FrostedCard(
           child: Column(
             crossAxisAlignment: CrossAxisAlignment.start,
@@ -45,109 +70,156 @@ class _SyncViewState extends ConsumerState<SyncView> {
                 runSpacing: 10,
                 children: <Widget>[
                   FilledButton.icon(
-                      onPressed: _busy ? null : _pushSample,
+                    onPressed: _busy ? null : _syncNow,
+                    icon: const Icon(Icons.sync_rounded),
+                    label: const Text('Sync Now'),
+                  ),
+                  OutlinedButton.icon(
+                    onPressed: _busy ? null : _pushPending,
                     icon: const Icon(Icons.upload_rounded),
-                      label: const Text('Push Sample Changes'),
+                    label: const Text('Push Pending'),
                   ),
                   OutlinedButton.icon(
                     onPressed: _busy ? null : _pullChanges,
                     icon: const Icon(Icons.download_rounded),
                     label: const Text('Pull Changes'),
                   ),
+                  TextButton.icon(
+                    onPressed: _busy ? null : _clearQueue,
+                    icon: const Icon(Icons.clear_all_rounded),
+                    label: const Text('Clear Queue'),
+                  ),
                 ],
               ),
               const SizedBox(height: 16),
-                Text(
-                  'Cursor: ${_cursor ?? 'not set'}',
-                  style: Theme.of(context).textTheme.bodyMedium,
-                ),
-                const SizedBox(height: 8),
               Text(
                 _status,
-                  style: Theme.of(context).textTheme.bodyLarge?.copyWith(
+                style: Theme.of(
-                    color: AppTheme.textSecondary,
+                  context,
-                  ),
+                ).textTheme.bodyLarge?.copyWith(color: AppTheme.textSecondary),
               ),
             ],
           ),
         ),
         const SizedBox(height: 16),
+        FrostedCard(
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            children: <Widget>[
+              Text(
+                'Queue Status',
+                style: Theme.of(context).textTheme.titleMedium,
+              ),
+              const SizedBox(height: 10),
+              _infoRow('Pending changes', '${state.pendingChanges.length}'),
+              _infoRow('Cursor', state.cursor ?? 'not set'),
+              _infoRow('Last sync', _formatDateTime(state.lastSyncAt)),
+              _infoRow('Last attempt', _formatDateTime(state.lastAttemptAt)),
+              _infoRow('Last rejected count', '${state.lastRejected.length}'),
+              _infoRow('Last error', state.lastError ?? 'none'),
+            ],
+          ),
+        ),
+        const SizedBox(height: 16),
         FrostedCard(
           child: Text(
-              'Sync policy\n• Core usage never blocks on backend\n• Retries only for transient failures\n• Non-idempotent requests require idempotency key',
+            'Sync policy\n• Core usage never blocks on backend\n• Local changes queue first and remain safe offline\n• Pull applies backend envelopes into local state',
             style: Theme.of(context).textTheme.bodyLarge,
           ),
         ),
       ],
+    );
+  }
+
+  Widget _infoRow(String label, String value) {
+    return Padding(
+      padding: const EdgeInsets.symmetric(vertical: 2),
+      child: Row(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: <Widget>[
+          SizedBox(width: 150, child: Text(label)),
+          Expanded(
+            child: Text(
+              value,
+              style: Theme.of(
+                context,
+              ).textTheme.bodyMedium?.copyWith(color: AppTheme.textSecondary),
+            ),
+          ),
+        ],
       ),
     );
   }
 
+  String _formatDateTime(DateTime? value) {
+    if (value == null) {
+      return 'never';
+    }
+
+    final DateTime local = value.toLocal();
+    final String month = local.month.toString().padLeft(2, '0');
+    final String day = local.day.toString().padLeft(2, '0');
+    final String hour = local.hour.toString().padLeft(2, '0');
+    final String minute = local.minute.toString().padLeft(2, '0');
+    return '${local.year}-$month-$day $hour:$minute';
+  }
+
+  Future<void> _syncNow() async {
+    await _run((SyncCoordinator coordinator) => coordinator.syncNow());
+  }
+
+  Future<void> _pushPending() async {
+    await _run((SyncCoordinator coordinator) => coordinator.pushPending());
+  }
+
   Future<void> _pullChanges() async {
+    await _run((SyncCoordinator coordinator) => coordinator.pullRemote());
+  }
+
+  Future<void> _clearQueue() async {
     setState(() {
       _busy = true;
-      _status = 'Pulling changes...';
     });
 
     try {
-      final SyncPullResult result = await ref
+      await ref.read(syncQueueRepositoryProvider.notifier).clearQueue();
-          .read(backendGatewayProvider)
-          .pullChanges(cursor: _cursor);
-
       setState(() {
-        _cursor = result.cursor;
+        _status = 'Cleared pending sync queue.';
-        _status = 'Pulled ${result.changes.length} changes successfully.';
-      });
-    } catch (error) {
-      setState(() {
-        _status = 'Pull failed. Staying offline-safe. ($error)';
-      });
-    } finally {
-      setState(() {
-        _busy = false;
-      });
-    }
-  }
-
-  Future<void> _pushSample() async {
-    setState(() {
-      _busy = true;
-      _status = 'Pushing local sample changes...';
-    });
-
-    final List<ChangeEnvelope> changes = <ChangeEnvelope>[
-      ChangeEnvelope(
-        schemaVersion: 1,
-        entityType: 'capture',
-        entityId: 'capture-${_uuid.v4()}',
-        op: ChangeOperation.upsert,
-        modifiedAt: DateTime.now().toUtc(),
-        clientMutationId: _uuid.v4(),
-        payload: const <String, dynamic>{
-          'summary': 'Shared a thoughtful check-in after work.',
-          'sentiment': 'positive',
-        },
-      ),
-    ];
-
-    try {
-      final SyncPushResult result = await ref
-          .read(backendGatewayProvider)
-          .pushChanges(changes: changes, cursor: _cursor);
-
-      setState(() {
-        _cursor = result.cursor;
-        _status =
-            'Push complete. accepted=${result.accepted.length}, rejected=${result.rejected.length}';
-      });
-    } catch (error) {
-      setState(() {
-        _status = 'Push failed. Local data remains safe. ($error)';
       });
     } finally {
+      if (mounted) {
         setState(() {
           _busy = false;
         });
       }
     }
   }
+
+  Future<void> _run(
+    Future<SyncRunResult> Function(SyncCoordinator coordinator) action,
+  ) async {
+    setState(() {
+      _busy = true;
+      _status = 'Running sync operation...';
+    });
+
+    try {
+      final SyncRunResult result = await action(
+        ref.read(syncCoordinatorProvider),
+      );
+      setState(() {
+        _status = result.message;
+      });
+    } catch (error) {
+      setState(() {
+        _status = 'Sync operation failed unexpectedly. ($error)';
+      });
+    } finally {
+      if (mounted) {
+        setState(() {
+          _busy = false;
+        });
+      }
+    }
+  }
+}

test/features/sync/sync_coordinator_test.dart

@@ -0,0 +1,115 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:relationship_saver/features/local/local_repository.dart';
+import 'package:relationship_saver/features/sync/sync_coordinator.dart';
+import 'package:relationship_saver/features/sync/sync_queue_repository.dart';
+import 'package:relationship_saver/features/sync/sync_state.dart';
+import 'package:relationship_saver/integrations/backend/backend_gateway_fake.dart';
+import 'package:relationship_saver/integrations/backend/backend_gateway_provider.dart';
+import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  setUp(() {
+    SharedPreferences.setMockInitialValues(<String, Object>{});
+  });
+
+  test('pushPending flushes queued local mutations', () async {
+    final ProviderContainer container = ProviderContainer(
+      overrides: [backendGatewayProvider.overrideWithValue(_TestGateway())],
+    );
+    addTearDown(container.dispose);
+
+    await container.read(localRepositoryProvider.future);
+    await container
+        .read(localRepositoryProvider.notifier)
+        .addPerson(
+          name: 'Queued Person',
+          relationship: 'Friend',
+          notes: 'sync me',
+          tags: <String>['test'],
+        );
+
+    final SyncState before = await container.read(
+      syncQueueRepositoryProvider.future,
+    );
+    expect(before.pendingChanges.length, 1);
+
+    final SyncRunResult result = await container
+        .read(syncCoordinatorProvider)
+        .pushPending();
+
+    expect(result.success, isTrue);
+    expect(result.accepted, 1);
+
+    final SyncState after = await container.read(
+      syncQueueRepositoryProvider.future,
+    );
+    expect(after.pendingChanges, isEmpty);
+    expect(after.cursor, isNotNull);
+  });
+
+  test('pullRemote applies backend changes into local repository', () async {
+    final SyncPullResult pullResult = SyncPullResult(
+      cursor: 'cursor-remote-1',
+      changes: <ChangeEnvelope>[
+        ChangeEnvelope(
+          schemaVersion: 1,
+          entityType: 'person',
+          entityId: 'p-remote-1',
+          op: ChangeOperation.upsert,
+          modifiedAt: DateTime(2026, 2, 15, 8).toUtc(),
+          clientMutationId: 'remote-1',
+          payload: const <String, dynamic>{
+            'name': 'Remote Person',
+            'relationship': 'Sibling',
+            'affinityScore': 88,
+            'nextMoment': '2026-02-20T12:00:00Z',
+            'tags': <String>['remote'],
+            'notes': 'arrived from backend',
+          },
+        ),
+      ],
+    );
+
+    final ProviderContainer container = ProviderContainer(
+      overrides: [
+        backendGatewayProvider.overrideWithValue(
+          _TestGateway(pullResult: pullResult),
+        ),
+      ],
+    );
+    addTearDown(container.dispose);
+
+    await container.read(localRepositoryProvider.future);
+
+    final SyncRunResult result = await container
+        .read(syncCoordinatorProvider)
+        .pullRemote();
+
+    expect(result.success, isTrue);
+    expect(result.pulled, 1);
+
+    final localState = await container.read(localRepositoryProvider.future);
+    final bool hasRemote = localState.people.any(
+      (person) => person.id == 'p-remote-1' && person.name == 'Remote Person',
+    );
+    expect(hasRemote, isTrue);
+
+    final SyncState queueState = await container.read(
+      syncQueueRepositoryProvider.future,
+    );
+    expect(queueState.cursor, 'cursor-remote-1');
+  });
+}
+
+class _TestGateway extends BackendGatewayFake {
+  _TestGateway({this.pullResult});
+
+  final SyncPullResult? pullResult;
+
+  @override
+  Future<SyncPullResult> pullChanges({String? cursor, int limit = 200}) async {
+    return pullResult ?? super.pullChanges(cursor: cursor, limit: limit);
+  }
+}

test/features/sync/sync_queue_repository_test.dart

@@ -0,0 +1,103 @@
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:relationship_saver/features/sync/sync_queue_repository.dart';
+import 'package:relationship_saver/integrations/backend/models/backend_models.dart';
+import 'package:shared_preferences/shared_preferences.dart';
+
+void main() {
+  setUp(() {
+    SharedPreferences.setMockInitialValues(<String, Object>{});
+  });
+
+  test('enqueue persists and can be reloaded', () async {
+    final ProviderContainer container = ProviderContainer();
+
+    await container
+        .read(syncQueueRepositoryProvider.notifier)
+        .enqueue(_change(id: 'p-1', mutationId: 'cm-1'));
+    final SyncStateData firstState = await _readState(container);
+    expect(firstState.pending.length, 1);
+
+    container.dispose();
+
+    final ProviderContainer reloaded = ProviderContainer();
+    addTearDown(reloaded.dispose);
+    final SyncStateData reloadedState = await _readState(reloaded);
+    expect(reloadedState.pending.length, 1);
+    expect(reloadedState.pending.first.clientMutationId, 'cm-1');
+  });
+
+  test(
+    'applyPushResult removes completed mutation ids and tracks rejections',
+    () async {
+      final ProviderContainer container = ProviderContainer();
+      addTearDown(container.dispose);
+
+      final SyncQueueRepository notifier = container.read(
+        syncQueueRepositoryProvider.notifier,
+      );
+
+      await notifier.enqueueAll(<ChangeEnvelope>[
+        _change(id: 'p-1', mutationId: 'cm-a'),
+        _change(id: 'p-2', mutationId: 'cm-b'),
+      ]);
+
+      await notifier.applyPushResult(
+        SyncPushResult(
+          cursor: 'cursor-2',
+          accepted: const <MutationAck>[MutationAck(clientMutationId: 'cm-a')],
+          rejected: const <MutationRejection>[
+            MutationRejection(
+              clientMutationId: 'cm-b',
+              code: 'VALIDATION_FAILED',
+              message: 'invalid payload',
+            ),
+          ],
+        ),
+        at: DateTime(2026, 2, 15, 12),
+      );
+
+      final SyncStateData state = await _readState(container);
+      expect(state.pending, isEmpty);
+      expect(state.cursor, 'cursor-2');
+      expect(state.rejected.length, 1);
+      expect(state.lastError, contains('Push rejected'));
+    },
+  );
+}
+
+class SyncStateData {
+  const SyncStateData({
+    required this.cursor,
+    required this.pending,
+    required this.rejected,
+    required this.lastError,
+  });
+
+  final String? cursor;
+  final List<ChangeEnvelope> pending;
+  final List<MutationRejection> rejected;
+  final String? lastError;
+}
+
+Future<SyncStateData> _readState(ProviderContainer container) async {
+  final state = await container.read(syncQueueRepositoryProvider.future);
+  return SyncStateData(
+    cursor: state.cursor,
+    pending: state.pendingChanges,
+    rejected: state.lastRejected,
+    lastError: state.lastError,
+  );
+}
+
+ChangeEnvelope _change({required String id, required String mutationId}) {
+  return ChangeEnvelope(
+    schemaVersion: 1,
+    entityType: 'person',
+    entityId: id,
+    op: ChangeOperation.upsert,
+    modifiedAt: DateTime(2026, 2, 15, 12).toUtc(),
+    clientMutationId: mutationId,
+    payload: const <String, dynamic>{'name': 'Alex', 'relationship': 'Friend'},
+  );
+}