Installation and Setup
A door sensor stops reporting but still reads "closed". A temperature sensor freezes on a plausible number. A coin cell slides under 10 percent while every dashboard shows it green. Home Assistant cannot tell you, because a device that stopped talking looks exactly like a device with nothing new to say.
Device Sentinel watches for that. It learns how often each of your devices normally reports, then notices when one stops. No timeouts to guess at, no list to maintain.
It takes about five minutes to install and asks you nothing.
Device Sentinel is in pre-release. It is developed quickly and updates occasionally change behaviour, so read the release notes before you update.
You need Home Assistant 2026.5.0 or newer, and HACS. Nothing goes in configuration.yaml, now or ever.
Device Sentinel is not in the default HACS store yet, so it is added as a custom repository.
One click, if you already have HACS:
That opens HACS on your own instance with the repository already filled in. Download it, restart Home Assistant, then go to Settings, Devices and Services, Add Integration and search for Device Sentinel.
By hand, if you would rather:
- Open HACS, click the three-dot menu, and choose Custom repositories.
- Paste
https://github.com/TheThinkingHome/device_sentinel, choose the Integration category, and click Add. - Find Device Sentinel in HACS and download it.
- Restart Home Assistant.
- Go to Settings, Devices and Services, Add Integration, and search for Device Sentinel.
Setup asks nothing at all. There is one instance, no options dialog, and every setting has a working default behind the Configure button for later. It starts watching your hardware the moment you add it.
Do this first, because it decides how much Device Sentinel can see.
Many integrations ship their battery, link-quality and last-contact sensors turned off, so the readings exist on your devices but nothing in Home Assistant is recording them. Device Sentinel can only learn from what is switched on.
Open Settings, Devices and Services, Device Sentinel, and click through to its own device page. Three buttons sit there: Enable Battery, Enable Signals, and Enable Last Seen. Each turns on entities of that one kind, on watched devices only, and leaves anything you switched off yourself alone.
Press all three unless you have a reason not to. The Device Page explains what each one reaches.
This one is worth doing now too, and it is a Home Assistant setting rather than a Device Sentinel one.
Go to Settings, System, Network, and look under Home Assistant URL. There are two fields: Internet, the address that reaches your house from outside, and Local network, the address you use on your own wifi.
Device Sentinel builds the link to your signal chart from these. With an external address set, that link works from your phone when you are out. With only an internal one, it works at home. With neither, the link has no address to point at and will not open from an email at all.
Set at least one. Set the external one if you have it.
Straight away. Every device in your registry is being watched. Discovery is automatic and there is nothing to add. Low battery detection is live from the first reading, at 20 percent, on every device whose battery sensor is switched on.
Within minutes. Two files appear:
-
/local/device_sentinel/daily_brief.htmlis the report written for a person: what is wrong now, and what happened over the last day, in plain language. It arrives by email too, once you tell it where to send it. -
/local/device_sentinel/signal_dwell.htmlis a colour chart of every device's radio link, worst first.
Both are good dashboard cards. Point a Webpage card at those addresses; they never change.
Over the first week. Freeze detection turns itself on device by device, as each one learns its own rhythm. A device added years from now does the same thing on its own. There is no learning mode to switch off and no global timer.
So an empty-looking report on the first day is the integration working, not failing. It has nothing to report yet because it has not yet seen your house misbehave.
Two folders, created for you.
config/www/device_sentinel/ holds the two pages above, plus a dated copy of each going back fourteen days.
config/device_sentinel/ holds three Markdown files for when you want to look deeper: what has been learned per device, which devices are watched and why, and a record of every unusual silence. The Reports explains them.
All of it is Device Sentinel's to clean up. If you ever delete the integration, it removes everything it wrote: both folders, its storage, and every backup copy it took. An uninstall leaves nothing behind.
On a system that has never had a config/www folder, Home Assistant will not serve the /local address until it has been restarted once with that folder present. From 0.10.24 Device Sentinel handles this itself and the links work on the first boot. On an earlier version, restart Home Assistant once more and it is fixed permanently.
Most releases are published as pre-releases while they are proven, and HACS hides those by default. You do not need them; this section is for anyone who wants to help test.
Under Settings, Devices and Services, Entities, filter to show disabled entities and find the Device Sentinel repository switch. Enable it, then turn it on. In HACS, choose Redownload, then Need a different version?.
With that switch off you are only ever offered fully released versions, and the main branch is never offered at all.
- Notifications and Daily Brief is the one configuration screen worth visiting now, to tell it where to send things.
- How Device Sentinel Learns explains what it is doing while it watches.
- FAQ and Troubleshooting for anything that looks wrong.