Why Did My Nest Thermostat Stop Working in Home Assistant After Firmware 6.4-5?
- Firmware 6.4-5 changed the SDM API response schema and the HA integration parser does not know how to read the new format
- OAuth token that HA uses to talk to the Nest SDM API got invalidated by a server-side change tied to the firmware rollout
- API rate limits tightened in 6.4-5 and HA default polling interval now exceeds the allowed request frequency
Problem Description
Your Nest thermostat still works from Google Home and from the physical dial, but Home Assistant shows the climate entity as unavailable. Temperature stopped updating on your dashboard. Automations that set the thermostat at night or when you leave the house silently stopped firing. This happened the day Google pushed firmware 6.4-5. The update changed something in the SDM API response that the Home Assistant Nest integration depends on for real-time state. Multiple users confirmed the breakage on GitHub issue 148294 in the home-assistant/core repository — the climate entity goes unavailable and stays that way until you re-authenticate the integration.
Why This Happens in Real Homes
This breaks every few months when Google pushes a firmware update that changes the SDM API response format. The HA integration was reading a specific field structure, Google changed it, and now the parser chokes and marks the entity unavailable. The thermostat itself is totally fine — it is just the API contract between Google and HA that got broken.
The fastest fix is usually just updating HA and re-adding the integration. If the HA team has not patched it yet, removing and re-adding forces a fresh OAuth handshake that sometimes works around the schema change. Do not touch your Google Cloud project unless you have verified the credentials are actually expired — deleting it by accident is a two-day recovery.
Symptoms
- Home Assistant climate entity for the Nest thermostat shows unavailable with a yellow warning triangle
- Temperature readings stopped updating on your HA dashboard — last reading frozen at whatever it was before the update
- Night mode and leave-home automations that set the thermostat via HA silently stopped running
- Google Home app still controls the thermostat perfectly so you know the hardware is fine
- HA logs show SDM API timeout or authentication errors for the Nest integration every few minutes
- Restarting Home Assistant does not fix it — the entity comes back unavailable every time
Recognize these? Here's what usually causes it.
Common Causes
- Firmware 6.4-5 changed the SDM API response schema and the HA integration parser does not know how to read the new format
- OAuth token that HA uses to talk to the Nest SDM API got invalidated by a server-side change tied to the firmware rollout
- API rate limits tightened in 6.4-5 and HA default polling interval now exceeds the allowed request frequency
- Device trait structure changed in the firmware update — the temperature and HVAC mode fields moved or renamed
- Google Cloud SDM project credentials expired at the same time as the firmware update making it look like the firmware caused it
- Local mDNS advertisement format changed so HA local discovery fails even though cloud API might still work
Most fixes happen in the first 3 steps.
Do not delete your Google Cloud SDM project trying to troubleshoot this. Deleting the project nukes all API access and you have to create a new one from scratch — new device access console registration, new OAuth consent screen, new credentials. That takes 24 to 48 hours to provision. Just remove and re-add the integration in HA instead.
Tools & Requirements
Step-by-Step Solution
Confirm 6.4-5 Is What Broke It
On the Nest thermostat, press the ring, go to Settings, then Technical Info. Check the Software version. If it says 6.4-5 or higher, that is your culprit. In HA, go to Settings then Devices and Services then Nest, click your thermostat device, and look at the climate entity. If it shows Unavailable and the last state change timestamp lines up with when the firmware pushed, you have confirmed the connection. The thermostat is fine — Google just changed the API contract that HA was relying on.
Update Home Assistant Before You Touch Anything Else
The HA development team usually patches Nest integration issues within days of a Google firmware push. Go to Settings then System then Updates. If there is an update available, install it and restart. Check the release notes for anything mentioning Nest SDM, firmware 6.4, or climate entity fixes. If the update fixes it, you are done. Do not remove the integration, do not mess with your Google Cloud project, just update and restart. If you are already on the latest version and it is still broken, move to the next step.
Remove and Re-Add the Nest Integration
Go to Settings then Devices and Services. Find Nest, click the three-dot menu, then Delete. Wait 30 seconds. Click Add Integration, search for Nest, and follow the SDM authentication flow. Google will ask you to sign in and authorize HA access to your Nest devices — accept all thermostat permissions. After re-adding, the climate entity should reappear within a minute. Test by changing the temperature from the HA dashboard and confirming the thermostat responds. The re-authentication forces a fresh OAuth token that matches the current API schema the firmware expects.
Verify Your Google Cloud SDM Project Is Still Alive
Sometimes what looks like a firmware problem is actually your Google Cloud credentials expiring at the same time. Go to console.cloud.google.com, sign in with the Google account linked to your Nest, and go to APIs and Services then Credentials. Your OAuth 2.0 Client ID should show as active. Then check APIs and Services then Enabled APIs and confirm Smart Device Management API is listed. If anything is disabled, expired, or shows an error, fix it here first. Re-enable the API, regenerate the client secret if needed, and update the credentials in your HA Nest integration configuration.
Watch GitHub for the Permanent Fix and Pin Your Expectations
Bookmark github.com/home-assistant/core/issues/148294. The community is active on this one and workarounds get posted within hours of a breaking change. Common interim fixes include adjusting the SDM polling interval in the integration config or adding a manual re-auth automation that triggers weekly. Long term, the HA team will ship a proper patch — these Google API breaks happen every few months and they always get fixed. If you want to stop being surprised, consider also running your thermostat through a local proxy like matter-bridge so you are not 100 percent dependent on Google Cloud.
Quick Solutions
Still having issues? This is usually the deeper cause below.
Schedules that skip randomly are usually a daylight-saving holdover — delete and recreate the schedule to clear the corrupted entry.
After any Nest firmware update, check your Home Assistant integration immediately. Do not wait for automations to fail silently at 2 AM when your house gets cold. Google ships firmware without warning and does not document API-breaking changes in their consumer release notes.
Firmware updates that wipe settings are more common than brands admit — many devices silently reset to factory defaults on an OTA push with no warning.
- Firmware 6.4-5 changed the SDM API response schema and
- OAuth token that HA uses to talk to the
- API rate limits tightened in 6.4-5 and HA default
- Device trait structure changed in the firmware update —
- Google Cloud SDM project credentials expired at the same
Before you go — try one of these (they fix most cases).
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Official Manufacturer Manual
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