fix: disable catch_up replay to prevent message loss

Matthias Nott

2026-03-22 1c57bb6f40304efceadfff17aefbbfcc64c9ad5f

fix: disable catch_up replay to prevent message loss

Catch-up was replaying all server messages on every reconnect,
causing duplicate assistant messages and overwriting user messages.
Local storage is now the source of truth. Catch-up only updates
lastSeq for protocol tracking. New messages while offline are
stored via _storeForSession from the DIRECT broadcast path.

Also: SharedPreferences save awaited properly, image cache for
flicker prevention, screenshot snackbar indicator.

 lib/screens/chat_screen.dart
..
..
@@ -73,10 +73,11 @@
73
73
     _initConnection();
74
74
   }
75
75
 
76
-  void _saveLastSeq() {
77
-    SharedPreferences.getInstance().then((prefs) {
78
-      prefs.setInt('lastSeq', _lastSeq);
79
-    });
76
+  SharedPreferences? _prefs;
77
+
78
+  Future<void> _saveLastSeq() async {
79
+    _prefs ??= await SharedPreferences.getInstance();
80
+    await _prefs!.setInt('lastSeq', _lastSeq);
80
81
   }
81
82
 
82
83
   @override
..
..
@@ -206,18 +207,14 @@
206
207
         final sessionId = msg['sessionId'] as String?;
207
208
         if (sessionId != null) _incrementUnread(sessionId);
208
209
       case 'catch_up':
210
+        // Only update lastSeq — don't replay messages.
211
+        // Local storage already has our messages. Replaying causes duplicates
212
+        // and overwrites user messages. New messages arriving while offline
213
+        // are stored via _storeForSession from the DIRECT broadcast path.
209
214
         final serverSeq = msg['serverSeq'] as int?;
210
215
         if (serverSeq != null && serverSeq > _lastSeq) {
211
216
           _lastSeq = serverSeq;
212
217
           _saveLastSeq();
213
-        }
214
-        final messages = msg['messages'] as List<dynamic>?;
215
-        if (messages != null && messages.isNotEmpty) {
216
-          _isCatchingUp = true;
217
-          for (final m in messages) {
218
-            _handleMessage(m as Map<String, dynamic>);
219
-          }
220
-          _isCatchingUp = false;
221
218
         }
222
219
       case 'pong':
223
220
         break; // heartbeat response, ignore