diff --git a/sdk/build.gradle.kts b/sdk/build.gradle.kts
index 0d7beb7..2ef9688 100644
--- a/sdk/build.gradle.kts
+++ b/sdk/build.gradle.kts
@@ -3,6 +3,9 @@ plugins {
     id("org.jetbrains.kotlin.android")
 }
 
+group = "com.duooomi"
+version = "0.0.0-local"
+
 android {
     namespace = "com.duooomi.ble"
     compileSdk = 34
diff --git a/sdk/src/main/kotlin/com/duooomi/ble/core/BleClient.kt b/sdk/src/main/kotlin/com/duooomi/ble/core/BleClient.kt
index ae637a2..30e9e52 100644
--- a/sdk/src/main/kotlin/com/duooomi/ble/core/BleClient.kt
+++ b/sdk/src/main/kotlin/com/duooomi/ble/core/BleClient.kt
@@ -134,6 +134,16 @@ internal class BleClient(context: Context) {
             throw DuooomiBleError.BluetoothNotPoweredOn("Bluetooth is off")
         }
 
+        connectedGatt?.let { old ->
+            BleLog.i("Stale gatt present; cleaning up before reconnect", "BLE")
+            runCatching { old.disconnect() }
+            runCatching { old.close() }
+            connectedGatt = null
+            connectedDeviceId = null
+            writeCharacteristic = null
+            readCharacteristic = null
+        }
+
         val device = bluetoothAdapter?.getRemoteDevice(deviceId)
             ?: throw DuooomiBleError.ConnectionFailed("Device not found: $deviceId")
 
@@ -185,12 +195,17 @@ internal class BleClient(context: Context) {
         writeMutex.withLock {
             characteristic.writeType = BluetoothGattCharacteristic.WRITE_TYPE_NO_RESPONSE
             characteristic.value = data
-            val success = gatt.writeCharacteristic(characteristic)
+            var success = gatt.writeCharacteristic(characteristic)
             if (!success) {
-                BleLog.w("Write failed, len=${data.size}", "BLE")
-            } else {
-                BleLog.d("Write w/o response, len=${data.size}", "BLE")
+                BleLog.w("Write failed; retry once after 30ms, len=${data.size}", "BLE")
+                delay(30)
+                success = gatt.writeCharacteristic(characteristic)
             }
+            if (!success) {
+                BleLog.e("Write failed after retry, len=${data.size}", "BLE")
+                throw DuooomiBleError.WriteFailed("Gatt busy; write rejected")
+            }
+            BleLog.d("Write w/o response, len=${data.size}", "BLE")
         }
     }
 
@@ -294,6 +309,9 @@ internal class BleClient(context: Context) {
                 return
             }
 
+            connectedGatt = gatt
+            connectedDeviceId = gatt.device.address
+
             // Enable notifications on read characteristic
             val readChar = readCharacteristic!!
             gatt.setCharacteristicNotification(readChar, true)
@@ -302,16 +320,32 @@ internal class BleClient(context: Context) {
             )
             if (descriptor != null) {
                 descriptor.value = BluetoothGattDescriptor.ENABLE_NOTIFICATION_VALUE
-                gatt.writeDescriptor(descriptor)
+                val ok = gatt.writeDescriptor(descriptor)
+                if (ok) {
+                    // Resume in onDescriptorWrite, after the CCCD write is flushed.
+                    return
+                }
+                BleLog.w("writeDescriptor returned false; resuming anyway", "BLE")
             }
+            resumeConnect(gatt)
+        }
 
-            // Connection fully ready
-            connectedGatt = gatt
-            connectedDeviceId = gatt.device.address
-            val cont = connectContinuation
+        override fun onDescriptorWrite(
+            gatt: BluetoothGatt,
+            descriptor: BluetoothGattDescriptor,
+            status: Int
+        ) {
+            BleLog.d("Descriptor written: uuid=${descriptor.uuid}, status=$status", "BLE")
+            if (descriptor.uuid == java.util.UUID.fromString("00002902-0000-1000-8000-00805f9b34fb")) {
+                resumeConnect(gatt)
+            }
+        }
+
+        private fun resumeConnect(gatt: BluetoothGatt) {
+            val cont = connectContinuation ?: return
             connectContinuation = null
             BleLog.i("Characteristics ready; connection established", "BLE")
-            cont?.resume(gatt)
+            cont.resume(gatt)
         }
 
         @Suppress("DEPRECATION")
diff --git a/sdk/src/main/kotlin/com/duooomi/ble/core/BleTypes.kt b/sdk/src/main/kotlin/com/duooomi/ble/core/BleTypes.kt
index a757498..76a2415 100644
--- a/sdk/src/main/kotlin/com/duooomi/ble/core/BleTypes.kt
+++ b/sdk/src/main/kotlin/com/duooomi/ble/core/BleTypes.kt
@@ -24,6 +24,7 @@ sealed class DuooomiBleError(message: String) : Exception(message) {
     class DeleteFileFailed(val status: Int) : DuooomiBleError("Delete failed: status=$status")
     class PrepareTransferFailed(val status: String) : DuooomiBleError("Prepare failed: $status")
     class TransferFailed(reason: String) : DuooomiBleError("Transfer failed: $reason")
+    class WriteFailed(reason: String) : DuooomiBleError("Write failed: $reason")
     class UnsupportedFormat(val format: String) : DuooomiBleError("Unsupported file format: $format. Supported: jpeg, png, gif, mp4, webm, webp")
     object InvalidFrame : DuooomiBleError("Invalid protocol frame")
     object PermissionDenied : DuooomiBleError("Bluetooth permission denied")