fix: send catch_up on app resume to fetch messages missed during background

Matthias Nott

2026-03-24 62fc4821c4a66313c300328aa1cf19808a41e0de

fix: send catch_up on app resume to fetch messages missed during background

 lib/screens/chat_screen.dart
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@@ -164,6 +164,12 @@
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       _sendCommand('sync', activeId != null ? {'activeSessionId': activeId} : null);
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       // catch_up is sent after sessions arrive (in _handleSessions)
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     };
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+    _ws!.onResume = () {
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+      // App came back from background with connection still alive.
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+      // Send catch_up to fetch any messages missed during suspend.
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+      _chatLog('onResume: sending catch_up with lastSeq=$_lastSeq');
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+      _sendCommand('catch_up', {'lastSeq': _lastSeq});
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+    };
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     _ws!.onError = (error) {
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       debugPrint('MQTT error: $error');
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     };
 lib/services/mqtt_service.dart
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@@ -56,6 +56,7 @@
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   void Function()? onOpen;
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   void Function()? onClose;
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   void Function()? onReconnecting;
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+  void Function()? onResume;
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   void Function(String error)? onError;
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   ConnectionStatus get status => _status;
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@@ -524,10 +525,10 @@
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           _setStatus(ConnectionStatus.reconnecting);
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           connect();
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         } else {
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-          // Appears connected — just let it be. The MQTT keepalive will
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-          // detect dead connections and auto-reconnect will handle it.
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-          // Don't call onOpen (it resets sessionReady and causes flicker).
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-          _mqttLog('MQTT: appears connected on resume, keeping current state');
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+          // Appears connected — notify listener to fetch missed messages
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+          // via catch_up. Don't call onOpen (it resets sessionReady and causes flicker).
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+          _mqttLog('MQTT: appears connected on resume, triggering catch_up');
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+          onResume?.call();
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         }
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       case AppLifecycleState.paused:
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         break;