A thread on the Home Assistant community forum describes something many owners may not realise: the Supervisor updates itself. The poster found out from the logs. The Supervisor restarted mid-afternoon without any prompt, and while it did, the Mosquitto add-on stopped responding on its port. The MQTT broker missed values during that window.
The poster had expected an update notice and a chance to choose the timing, as with Home Assistant OS or Core. According to a reply in the thread, the Supervisor is the one part of Home Assistant that updates automatically. This is one owner’s report and the replies of other forum members, not an announcement from the Home Assistant team, so treat the details as community knowledge. The thread is worth reading in full.
Why this matters if you run MQTT
MQTT is a publish/subscribe layer, and it needs a broker running somewhere. Home Assistant’s own documentation recommends the official Mosquitto Broker app for this. Zigbee2MQTT, Tasmota, ESPHome and OpenMQTTGateway can all use it. If the broker lives inside Home Assistant, a Supervisor restart takes the broker down with everything else, and anything published in that gap may never be recorded.
For most homes a short gap is harmless. It matters more if you log energy use, track a freezer temperature, or trigger automations off a sensor that only reports occasionally. Nothing in the thread says how long the outage lasted or which readings were lost beyond the poster’s own broker.
Two fixes the thread offers
- Move the broker out of Home Assistant. One reply suggests running it standalone on a different machine or in a virtual environment, so Home Assistant restarts no longer touch it. The trade-off is one more service for you to run, update and secure.
- Turn off Supervisor auto-updating and update on your own schedule. Another reply says this is possible and points to a longer feature-request thread on blocking Supervisor auto-updates. The thread does not give the exact steps, and we are not going to guess at menu paths. Read that discussion before changing anything.
What to check before you rely on it
- Look at your logs for Supervisor restarts and compare the times against gaps in your sensor history.
- List what depends on your broker. If Zigbee2MQTT is how your Zigbee devices reach Home Assistant, a broker outage affects them too. Zigbee2MQTT needs a broker by design.
- Decide whether a few missed minutes matter for your setup. If they do, a separate always-on broker is the cleaner answer.
- Keep your own update routine. Backing up before you update and choosing a quiet hour is good practice, but the Supervisor is the one piece that may not wait for you.
Where this leaves Zigbee owners
Our stance has not changed. As of today Zigbee is the more mature option in Home Assistant: a big proven catalogue, fully local, very low power. This episode is not a reason to rip anything out. Working Zigbee gear does not need replacing; keep it until it dies. The takeaway is narrower: if your Zigbee runs through Zigbee2MQTT, your broker is part of the chain, so protect it. Owners using ZHA, the built-in integration, do not need an MQTT broker for Zigbee. We have no information on how a Supervisor restart affects ZHA, and the thread does not cover it.
Matter, the industry’s direction, does not use MQTT either. It runs through the Matter integration and its own server. But it is younger, and it has its own network requirements. None of that is a reason to move just because of this story.