Nest in Home Assistant: Migrate Your Pub/Sub Topic Before November 30, 2026

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Rocks on Galaxy
Maison connectee
25 Oct, 2026
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On November 30, 2026, Google will stop publishing Nest events to the Pub/Sub topics it hosts on behalf of developers. That sounds like an obscure cloud detail, but if you connected a Nest thermostat, camera or doorbell to Home Assistant before 2025, it is very likely the pipe that carries every temperature change, motion alert and doorbell press to your dashboard. Miss the deadline and the integration will not throw a big red error: your entities will simply stop updating, and automations that wait for a Nest event will quietly never fire.

The fix takes about fifteen minutes and costs nothing for a typical home. This guide shows how to check whether you are affected, compares the three migration paths, walks through the manual steps that work today, and explains what the upcoming Home Assistant 2026.11 release adds to make the switch easier.

Key takeaways

Google-hosted topics in the format projects/sdm-prod/topics/enterprise-… stop receiving events after November 30, 2026 (Google release notes, September 29, 2026).

Topics you created in your own Google Cloud project, for example projects/<your-project>/topics/home-assistant-nest, are not affected.

Migrating does not invalidate your OAuth tokens or Partner Connections permissions, so you do not have to re-link your Google account.

Home Assistant has merged a Reconfigure flow and two Repairs for this migration; they are expected in 2026.11. Until then, the manual console method works on any version.

Step 0: are you actually affected?

Everything depends on one string: the Pub/Sub topic shown for your project in the Device Access Console (console.nest.google.com/device-access). Open the console, click the project you created for Home Assistant and look at the Pub/Sub topic line.

What you see	Who created it	Status after Nov 30	What to do
`projects/sdm-prod/topics/enterprise-<project-id>`	Google, automatically (projects set up before January 23, 2025)	No more events	Migrate now
`projects/<your-cloud-project>/topics/home-assistant-…`	Home Assistant or you, in your own Cloud project	Unchanged	Nothing
`projects/<your-cloud-project>/topics/<any-name>`	You, manually	Unchanged	Nothing (check the subscription still exists)
Topic disabled or empty	-	No events today either	Follow the setup steps below

The Home Assistant Nest documentation uses exactly this test in its troubleshooting section: a topic starting with projects/sdm-prod/topics is a legacy Google-hosted topic. Google has not offered hosted topics to new projects since January 23, 2025, so if you set up Nest in Home Assistant recently, you are almost certainly fine.

What breaks, and what keeps working

Home Assistant's Nest integration reads the initial state of your devices from the Smart Device Management (SDM) API at startup, then relies on a Pub/Sub subscription for every update after that. Once events stop, here is the practical impact:

Thermostats: current temperature, humidity, HVAC action and set points freeze at their last value until Home Assistant restarts.
Cameras and doorbells: the event entities for motion, person, sound and doorbell chime stop firing, as do the automations and notifications built on them.
Still working: commands you send from Home Assistant (changing a set point, opening a live stream) go through the SDM API, not Pub/Sub, and the Google Home app itself is unaffected.

That silent failure mode is the real danger. A doorbell automation that used to flash your lights or announce a visitor on a speaker will not complain; it will just never trigger again.

Three ways to migrate

Path	Available	Effort	Keeps entities and automations	Best for
Manual: new topic in Cloud Console + Device Access Console	Today, any HA version	About 15 min, two web consoles	Yes, if you also point HA at the new subscription	Anyone who wants to be done before the deadline
Reconfigure flow in Home Assistant	Expected in 2026.11 (merged into the dev branch)	Pick or create a topic and subscription in a dialog	Yes, the integration is not removed	Users who update promptly in early November
Delete and re-add the integration	Today	Full re-authorization	Entity IDs usually return, but check dashboards and automations	Broken setups you want to rebuild anyway

The manual method, step by step

These steps follow Google's Subscribe to Events guide and the Home Assistant documentation. You can use the Cloud Console web interface or Cloud Shell; the commands are shown for Cloud Shell.

Open the right Cloud project. Use the same Google Cloud project that holds your OAuth client for Home Assistant, and make sure the Cloud Pub/Sub API is enabled.

Create the topic. Google recommends no message retention:

gcloud pubsub topics create home-assistant-nest --message-retention-duration=0s

Let Google publish to it. Grant the publisher role to Google's SDM group on the topic itself, not on the project's IAM page:

gcloud pubsub topics add-iam-policy-binding projects/YOUR_PROJECT/topics/home-assistant-nest \
  --member="group:sdm-publisher@googlegroups.com" \
  --role="roles/pubsub.publisher"

Disable the old topic. In the Device Access Console, open your project and disable the existing sdm-prod Pub/Sub topic.
Enable events with the new topic. Click the three-dot menu next to Pub/Sub topic, choose Enable events with PubSub topic, paste the full name projects/YOUR_PROJECT/topics/home-assistant-nest and select Add & Validate. An error here almost always means the permission in step 3 is missing.
Connect Home Assistant. On 2026.11 or later, open Settings > Devices & services > Nest and use Reconfigure to select the new topic and let it create a subscription. On older versions, remove and re-add the integration so it picks up the new topic.
Test. Change the set point in the Google Home app or walk past a camera, then confirm the entity updates in Home Assistant. In the Cloud Console, the topic's Metrics tab should show published messages.

Cost is not a concern for a home: Pub/Sub has a free tier of 10 GiB of throughput per month (Pub/Sub pricing), and Nest event messages are small JSON payloads.

What Home Assistant 2026.11 changes

Three pull requests merged in October target this migration. They sit in the development branch and should ship with 2026.11; Home Assistant publishes a new monthly release on the first Wednesday of the month, after a one-week beta (release FAQ).

The setup flow stops offering Google-hosted topics

PR #187052 removes sdm-prod topics from the list shown during configuration, so nobody new can pick a topic that is about to die.

A Reconfigure flow for topic and subscription

PR #187156 adds a Reconfigure option that lets you select or create a topic and subscription without removing the integration. It reuses a valid OAuth token, defaults to your current choices, and tries to delete the old subscription that Home Assistant had created.

Repairs that tell you what is wrong

PR #188119 raises a warning in Settings > Repairs when the configured topic is missing or still starts with projects/sdm-, and a separate error when the Pub/Sub subscription cannot be found. The OHF Daily summary describes it as an in-app route behind the migration advice.

Troubleshooting

Symptom	Likely cause	Fix
"Add & Validate" fails in the Device Access Console	Publisher role missing or granted at project level	Add `sdm-publisher@googlegroups.com` as Pub/Sub Publisher on the topic's Permissions tab
Home Assistant: "Failed to create subscriber… was not found"	Subscription deleted (by default after 31 days of inactivity)	Recreate it via Reconfigure or re-adding the integration; set the subscription to never expire
Thermostat updates but camera events never arrive	Google Home notification settings or Partner Connections permissions	Re-check camera access in Partner Connections Manager and the Home app event settings
Asked to sign in again every 7 days	OAuth consent screen left in Testing mode	Publish the consent screen to Production, then reauthorize once

Home Assistant analysis: who should bother, and is it time to leave the cloud?

For most Nest owners in Home Assistant the answer is simple: do the migration this weekend. It is free, reversible and does not touch your devices. The people who should act first are those whose Nest setup dates back to 2021–2024, the period when the Device Access Console created hosted topics automatically.

The deadline is also a reminder of how fragile the SDM path is. It already requires a one-time US$5 Device Access fee, does not work with Google Workspace or Advanced Protection accounts, and depends on two Google consoles that change over time. If your goal is a durable, local smart home, look at the alternatives:

Thermostats: Google says the Nest Learning Thermostat (4th gen) is Matter-certified, which opens a path to control through Home Assistant's Matter integration. Our Matter thermostat and radiator valve guide covers the options.
Cameras and doorbells: Nest cameras are not Matter devices. If local events matter more than the Google ecosystem, see our Matter cameras buyer's guide.
The bigger picture: our Home Assistant 2026 guide and our Matter hubs guide explain how to keep cloud integrations to a minimum.

Our view at Rocks on Galaxy: keep Nest if it works for you, but migrate the topic now, and plan any new purchase around Matter or local APIs so the next cloud deadline does not reach your automations.

FAQ

Will I lose my Nest devices in Home Assistant on December 1?

No. The devices and entities stay, but if you still use a Google-hosted topic they stop receiving real-time updates and events. Commands sent from Home Assistant keep working through the SDM API.

Do I need to pay the US$5 Device Access fee again?

No. The fee is a one-time registration for your Device Access account. Migrating the topic happens inside your existing project.

Does the migration log me out or reset my automations?

Google states that changing the Pub/Sub topic does not invalidate existing access tokens or OAuth permissions. With the Reconfigure flow in 2026.11 the integration is not removed, so entity IDs and automations stay in place.

Can I just wait for Home Assistant 2026.11?

Yes, if you update in early November and act on the Repair warning before November 30. The manual method is the safer option if you tend to skip releases, and it gives you a few weeks to test.