From 0ef5f1fd653dc5797d256af9cba3e18292e379ea Mon Sep 17 00:00:00 2001 From: Adam Liddell Date: Thu, 10 Jul 2025 09:34:43 +0100 Subject: [PATCH] Handle ESP32 chunked MQTT messages missing topic on non-first chunks, causing panic (#5786) Co-authored-by: Samuel Sieb --- esphome/components/mqtt/mqtt_backend_esp32.cpp | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/esphome/components/mqtt/mqtt_backend_esp32.cpp b/esphome/components/mqtt/mqtt_backend_esp32.cpp index a096408aa5..623206a0cd 100644 --- a/esphome/components/mqtt/mqtt_backend_esp32.cpp +++ b/esphome/components/mqtt/mqtt_backend_esp32.cpp @@ -153,11 +153,15 @@ void MQTTBackendESP32::mqtt_event_handler_(const Event &event) { case MQTT_EVENT_DATA: { static std::string topic; if (!event.topic.empty()) { + // When a single message arrives as multiple chunks, the topic will be empty + // on any but the first message, leading to event.topic being an empty string. + // To ensure handlers get the correct topic, cache the last seen topic to + // simulate always receiving the topic from underlying library topic = event.topic; } ESP_LOGV(TAG, "MQTT_EVENT_DATA %s", topic.c_str()); - this->on_message_.call(!event.topic.empty() ? topic.c_str() : nullptr, event.data.data(), event.data.size(), - event.current_data_offset, event.total_data_len); + this->on_message_.call(topic.c_str(), event.data.data(), event.data.size(), event.current_data_offset, + event.total_data_len); } break; case MQTT_EVENT_ERROR: ESP_LOGE(TAG, "MQTT_EVENT_ERROR");