What Is Recorded About Your House

Sensors do not float in a vacuum. They rely on what sits beneath them: Home Assistant, MQTT brokers, Zigbee coordinators, and your Wi-Fi network. When a sensor goes quiet, it might be the sensor's fault, or it might be that the floor just fell out from under it.

Most of this wiki describes what Device Sentinel knows about your individual devices. This page covers what it knows about the house itself.

To understand why this matters, look at a real-world example: on one test house, the MQTT broker stopped working for sixteen minutes. That single failure took 75 devices offline. Without house-level recording, the daily brief would look like a disaster movie, warning you that more than half your home spontaneously died at the exact same second without explaining why.

Because Device Sentinel monitors the system itself, that disaster is collapsed into a single, obvious fix: The MQTT broker went down.

The Layers Device Sentinel Watches

Each time one of these fails, Device Sentinel records it. This gives you the context in your daily brief, and it prevents those massive, forced silences from ruining the learned rhythms of your devices.

• Home Assistant Restarts and Crashes: If Home Assistant restarts or loses power, it stops listening. These blackouts (and unclean shutdowns) are recorded so the resulting gaps in your sensors' timelines are blamed on the blackout, not the sensors.
• The MQTT Broker: Home Assistant doesn't have a native "MQTT Broker" sensor, making broker crashes practically invisible. Device Sentinel watches the broker directly. When the broker stops, the integration knows every device behind it is an innocent victim.
• The Coordinators (Zigbee2MQTT, ZHA): Device Sentinel watches the bridges: when they drop offline, and their pairing windows and configuration events, so your manual re-pairing efforts aren't mistakenly learned as a natural device freeze. (See The Bridge and Broker Sensors).
• The Wi-Fi Network: If you configure Wi-Fi watching, the drop and the return are recorded. A network drop takes out a dozen smart plugs at once; Device Sentinel counts the devices behind it so you know to fix the router, not the plugs. (See WiFi).
• Integration Outages and Reloads: If a specific integration crashes and stays down, the outage is recorded, including one that failed to start when Home Assistant restarts. And if an integration reloads, causing every device it owns to reload at once, Device Sentinel recognizes that burst as a reload rather than an organic network event.
• Your Own Hands: When you open a Maintenance Mode window, change a setting, change a device from its page on the dashboard, or wipe a device's history using the data trim tool, it's written down. A week from now, when you wonder why a device's history started over on a Tuesday, your daily brief will remind you exactly when you pressed the button.

Every one of these events is visible in the Last 24 Hours table of your daily brief, and the silences they explain are marked in the silence episodes report.

What You Tell It About Your Devices

The battery or power source and the type you set with the pencils on a device's page are kept in their own file, device_sentinel.answers, in Home Assistant's .storage folder beside Device Sentinel's other files. It is written only when you use a pencil, and a last-good copy is taken before each save; if the file can't be read at startup, it is restored from that copy and the daily brief says so. Back it up with the others: it holds answers you typed in, and Device Sentinel can't learn them again on its own. The diagnostics download lists each entry, and a device you remove from Home Assistant takes its entry with it.