From a922d6609f345be9c0c4d4ca1a75e56a825384e3 Mon Sep 17 00:00:00 2001
From: Theo Arends <11044339+arendst@users.noreply.github.com>
Date: Mon, 15 Dec 2025 12:37:12 +0100
Subject: [PATCH] Fix ESP32-P4 unique MQTT Client based on hosted MCU MAC
 address

---
 CHANGELOG.md                                   | 1 +
 RELEASENOTES.md                                | 1 +
 tasmota/tasmota.ino                            | 1 -
 tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino | 3 +++
 4 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 12c820c43..0f0f6bed0 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,7 @@ All notable changes to this project will be documented in this file.
 - DALI watchdog exception
 - TuyaMCU v1 exception 28 regression from v15.1.0.1 reverted PR24063 (#24220)
 - ESP8266 TasmotaSerial flush receive buffer on executing `TasmotaSerial.flush();`
+- ESP32-P4 unique MQTT Client based on hosted MCU MAC address
 
 ### Removed
 
diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 5371121d7..4276aacf5 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -120,5 +120,6 @@ The latter links can be used for OTA upgrades too like ``OtaUrl https://ota.tasm
 
 ### Fixed
 - ESP8266 TasmotaSerial flush receive buffer on executing `TasmotaSerial.flush();`
+- ESP32-P4 unique MQTT Client based on hosted MCU MAC address
 - DALI watchdog exception
 - TuyaMCU v1 exception 28 regression from v15.1.0.1 reverted PR24063 [#24220](https://github.com/arendst/Tasmota/issues/24220)
diff --git a/tasmota/tasmota.ino b/tasmota/tasmota.ino
index c1f911f3b..e32e490bb 100644
--- a/tasmota/tasmota.ino
+++ b/tasmota/tasmota.ino
@@ -671,7 +671,6 @@ void setup(void) {
   // Github inserts "release" or "commit number" before compiling using sed -i -e 's/TASMOTA_SHA_SHORT/TASMOTA_SHA_SHORT 85cff52-/g' tasmota_version.h
   snprintf_P(TasmotaGlobal.image_name, sizeof(TasmotaGlobal.image_name), PSTR("(" STR(TASMOTA_SHA_SHORT) "%s)"), PSTR(CODE_IMAGE_STR));  // Results in (85cff52-tasmota) or (release-tasmota)
 
-  Format(TasmotaGlobal.mqtt_client, SettingsText(SET_MQTT_CLIENT), sizeof(TasmotaGlobal.mqtt_client));
   Format(TasmotaGlobal.mqtt_topic, SettingsText(SET_MQTT_TOPIC), sizeof(TasmotaGlobal.mqtt_topic));
   if (strchr(SettingsText(SET_HOSTNAME), '%') != nullptr) {
     SettingsUpdateText(SET_HOSTNAME, WIFI_HOSTNAME);
diff --git a/tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino b/tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino
index 3f291159c..df18d9472 100644
--- a/tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino
+++ b/tasmota/tasmota_xdrv_driver/xdrv_02_9_mqtt.ino
@@ -1112,6 +1112,9 @@ void MqttConnected(void) {
 }
 
 void MqttReconnect(void) {
+  if (!strlen(TasmotaGlobal.mqtt_client)) {  // Do it here as it needs the MAC address from a possible hosted MCU available after WiFi connection
+    Format(TasmotaGlobal.mqtt_client, SettingsText(SET_MQTT_CLIENT), sizeof(TasmotaGlobal.mqtt_client));
+  }
   Mqtt.allowed = Settings->flag.mqtt_enabled && (TasmotaGlobal.restart_flag == 0);  // SetOption3 - Enable MQTT, and don't connect if restart in process
   if (Mqtt.allowed) {
 #if defined(USE_MQTT_AZURE_DPS_SCOPEID) && defined(USE_MQTT_AZURE_DPS_PRESHAREDKEY)