Add failure backoff for sync auto triggers

docs/progress.md

@@ -2,6 +2,23 @@
 
 Updated: 2026-02-15
 
+## Latest Milestone (2026-02-15): Sync Auto-Trigger Backoff
+
+Improved sync trigger resilience for repeated failures:
+
+- Updated `lib/features/sync/sync_auto_trigger_controller.dart`:
+  - tracks consecutive sync failures
+  - applies exponential cooldown backoff before auto-trigger retries
+  - resets backoff after a successful sync run
+- Added coverage:
+  - `test/features/sync/sync_auto_trigger_controller_test.dart`
+  - validates cooldown behavior after failures
+
+Validation for this milestone:
+
+- `flutter analyze` -> pass
+- `flutter test` -> pass
+
 ## Latest Milestone (2026-02-15): Reminder Delivery Interface Wiring
 
 Implemented the notification scheduling boundary and connected it to local data
@@ -68,7 +85,7 @@ Validation for this milestone:
    - current UX shows and dismisses rejections; still missing guided
      resolve/retry/inspect flows per entity.
 3. Sync trigger maturity:
-   - add connectivity-aware triggers and backoff policy for repeated failures.
+   - connectivity-aware triggers are still missing.
 4. Test depth:
    - add integration tests for auth + sync + CRUD end-to-end app flows.
 

lib/features/sync/sync_auto_trigger_controller.dart

@@ -1,3 +1,5 @@
+import 'dart:math' as math;
+
 import 'package:flutter/foundation.dart';
 import 'package:relationship_saver/features/sync/sync_coordinator.dart';
 
@@ -18,6 +20,7 @@ class SyncAutoTriggerController {
 
   bool _running = false;
   DateTime? _lastTriggeredAt;
+  int _consecutiveFailures = 0;
 
   @visibleForTesting
   bool get isRunning => _running;
@@ -25,6 +28,9 @@ class SyncAutoTriggerController {
   @visibleForTesting
   DateTime? get lastTriggeredAt => _lastTriggeredAt;
 
+  @visibleForTesting
+  int get consecutiveFailures => _consecutiveFailures;
+
   /// Triggers `syncNow` when not already running and outside cooldown window.
   Future<bool> trigger({bool ignoreCooldown = false}) async {
     if (_running) {
@@ -35,19 +41,34 @@ class SyncAutoTriggerController {
     final DateTime? last = _lastTriggeredAt;
     if (!ignoreCooldown &&
         last != null &&
-        now.difference(last) < minimumInterval) {
+        now.difference(last) < _cooldownForCurrentState()) {
       return false;
     }
 
     _running = true;
     _lastTriggeredAt = now;
     try {
-      await _syncNow();
+      final SyncRunResult result = await _syncNow();
+      if (result.success) {
+        _consecutiveFailures = 0;
+      } else {
+        _consecutiveFailures += 1;
+      }
       return true;
     } catch (_) {
+      _consecutiveFailures += 1;
       return true;
     } finally {
       _running = false;
     }
   }
+
+  Duration _cooldownForCurrentState() {
+    if (_consecutiveFailures <= 0) {
+      return minimumInterval;
+    }
+    final int cappedFailures = math.min(_consecutiveFailures, 4);
+    final int multiplier = 1 << cappedFailures;
+    return minimumInterval * multiplier;
+  }
 }

test/features/sync/sync_auto_trigger_controller_test.dart

@@ -30,6 +30,29 @@ void main() {
     expect(controller.lastTriggeredAt, now);
   });
 
+  test('applies backoff after failed sync attempts', () async {
+    DateTime now = DateTime(2026, 2, 15, 14);
+    bool shouldFail = true;
+
+    final SyncAutoTriggerController controller = SyncAutoTriggerController(
+      syncNow: () async => _result(success: !shouldFail),
+      now: () => now,
+      minimumInterval: const Duration(seconds: 60),
+    );
+
+    final bool first = await controller.trigger();
+    now = now.add(const Duration(seconds: 61));
+    final bool second = await controller.trigger();
+    now = now.add(const Duration(seconds: 60));
+    shouldFail = false;
+    final bool third = await controller.trigger();
+
+    expect(first, isTrue);
+    expect(second, isFalse);
+    expect(third, isTrue);
+    expect(controller.consecutiveFailures, 0);
+  });
+
   test('does not run a second sync while a run is still in progress', () async {
     int callCount = 0;
     final Completer<void> completer = Completer<void>();