fix: ble write handling

app/lib/services/devices/transports/ble_transport.dart

@@ -13,6 +13,7 @@ class BleTransport extends DeviceTransport {
   final StreamController<DeviceTransportState> _connectionStateController;
   final Map<String, StreamController<List<int>>> _streamControllers = {};
   final Map<String, StreamSubscription> _characteristicSubscriptions = {};
+  Future<void> _writeQueue = Future.value();
 
   List<BluetoothService> _services = [];
   DeviceTransportState _state = DeviceTransportState.disconnected;
@@ -187,12 +188,48 @@ class BleTransport extends DeviceTransport {
       throw Exception('Characteristic not found: $serviceUuid:$characteristicUuid');
     }
 
-    try {
-      await characteristic.write(data);
-    } catch (e) {
-      debugPrint('BLE Transport: Failed to write characteristic: $e');
-      rethrow;
-    }
+    final task = _writeQueue.then((_) async {
+      int retries = 0;
+      while (true) {
+        if (_state != DeviceTransportState.connected || !_bleDevice.isConnected) {
+          debugPrint('Skipping write: Device is disconnected');
+          return;
+        }
+
+        try {
+          await characteristic
+              .write(
+                data,
+                withoutResponse: characteristic.properties.writeWithoutResponse,
+                allowLongWrite: true,
+              )
+              .timeout(const Duration(seconds: 2));
+          return;
+        } catch (e) {
+          if (_isDisconnectionError(e)) {
+            debugPrint('Device Disconnected');
+            return;
+          }
+
+          if (!_bleDevice.isConnected) {
+            return;
+          }
+
+          final retryable = _isRetryable(e);
+          if (!retryable || retries >= 3) {
+            debugPrint('BLE write failed (stop retry) $serviceUuid:$characteristicUuid → $e');
+            rethrow;
+          }
+
+          final delay = 80 * (1 << retries);
+          await Future.delayed(Duration(milliseconds: delay));
+          retries++;
+        }
+      }
+    });
+
+    _writeQueue = task.catchError((_) {});
+    await task;
   }
 
   Future<BluetoothCharacteristic?> _getCharacteristic(String serviceUuid, String characteristicUuid) async {
@@ -209,6 +246,28 @@ class BleTransport extends DeviceTransport {
     );
   }
 
+  bool _isDisconnectionError(Object e) {
+    final msg = e.toString().toLowerCase();
+    final is133 = RegExp(r'\b133\b').hasMatch(msg);
+
+    return is133 ||
+        msg.contains("gatt_error") ||
+        msg.contains("unknown_ble_error") ||
+        msg.contains("device is disconnected") ||
+        msg.contains("the device is disconnected");
+  }
+
+  bool _isRetryable(Object e) {
+    if (e is FlutterBluePlusException) {
+      final desc = (e.description ?? "").toLowerCase();
+      if (e.code == 201 || desc.contains("busy")) return true;
+      return false;
+    }
+
+    final msg = e.toString().toLowerCase();
+    return msg.contains("busy") || RegExp(r'\b201\b').hasMatch(msg);
+  }
+
   @override
   Future<void> dispose() async {
     await _bleConnectionSubscription?.cancel();