Upgrade to 2026.9.4 from 2026.9.3 fails and is rolled back automatically

The problem

Upgrade to 2026.9.4 fails and is rolled back automatically. What happens is:

• Initiate the upgrade
• HA restarts but then shows it is still on 2026.9.3
• Inspecting the Supervisor log file shows 2026.9.4 failed to start and that it automatically rolled back to 2026.9.3

I tried submitting my log files to Google AI and it always point to the fact that it crashes 10 seconds after it tries to start 2026.9.4, after which it then automatically rolls back to 2026.9.3.

I've done the following since then:

• Cleaned up legacy format in configuration.yaml
• Cleaned up duplicate Dashboard resources

I've also gone through multiple attempts of retrying the upgrade while doing the following (Google AI flags these as potential reasons for the failed upgrade):

• Restarting HA in safe mode
• Deleted the log file because it was flagging SQLite database not shutdown properly
• Switched to mariadb
• Disabled apps and integrations, e.g. Battery Sentinel+, Keymaster, Alarmo, Spook, Broadlink, etc.
• Renamed the custom_components folder to custom_components_old
• Upgrading using the CLI

None of these worked and I still got the same issue.

FYI, I tried these yesterday while I was on Supervisor 2026.9.2. I saw and upgraded to Supervisor 2026.9.3 today but I still ran into the same issues when I retried upgrading to Core 2026.9.4.

What version of Home Assistant Core has the issue?

2026.9.4

What was the last working version of Home Assistant Core?

2026.9.3

What type of installation are you running?

Home Assistant OS

Integration causing the issue

No response

Link to integration documentation on our website

No response

Diagnostics information

No response

Example YAML snippet

Anything in the logs that might be useful for us?

Following shows up in Supervisor log files:

2026-09-29 07:29:15.073 INFO (MainThread) [supervisor.docker.homeassistant] Starting Home Assistant ghcr.io/home-assistant/qemux86-64-homeassistant with version 2026.9.4
2026-09-29 07:29:15.073 INFO (MainThread) [supervisor.homeassistant.core] Wait until Home Assistant is ready
2026-09-29 07:29:25.081 ERROR (MainThread) [supervisor.homeassistant.core] Home Assistant has crashed!
2026-09-29 07:29:25.082 CRITICAL (MainThread) [supervisor.homeassistant.core] HomeAssistant update failed -> rollback!

Additional information

home-assistant_2026-09-28T23-31-04.771Z.log

supervisor_2026-09-28T23-31-14.541Z.log