Hermes

"Hermes Agent was updated while Hermes WebUI was running"

Last checked

The error

Server returned HTTP 409: Hermes Agent was updated while Hermes WebUI was running. Restart Hermes WebUI before retrying this action.

Wording quoted in issue #95882 of the Hermes Agent repo (August 2026). Current Hermes WebUI builds add: "WebUI cannot verify that the Agent update completed safely. Check the Agent update outcome and environment first. Restart Hermes WebUI manually before retrying this action."

Hermes WebUI, a separate community web interface, loads Hermes Agent's Python code into its own long-running process. After hermes update or a git pull changed the Agent, WebUI refuses new turns with a 409 rather than mix old and new code. Confirm the update finished with hermes doctor, then restart the WebUI backend. Refreshing the browser does not help.

Why it happens

WebUI tracks the Agent's git revision. When the revision changes or becomes unreadable while WebUI is running, Agent-backed actions return a retryable 409 agent_runtime_stale until the backend restarts.

  1. hermes update ran while WebUI was up. In August 2026 the updater restarted gateways and the dashboard but not hermes-webui services (issue #95882).
  2. A manual git pull or checkout in the Agent source folder.
  3. An update that failed or is still running, which WebUI reports through its agent_update_state field.

The fix

  1. 1 Check that the Agent update finished: hermes --version, then hermes doctor.
  2. 2 Restart WebUI the way you started it: ./ctl.sh restart, or systemctl --user restart hermes-webui.service for a user service.
  3. 3 For a foreground python3 bootstrap.py, stop it with Ctrl-C and start it again.
  4. 4 Retry the action in the browser.
systemctl --user restart hermes-webui.service

Still failing?

  • If the message appears although the Agent did not change, report it to the Hermes WebUI project with your launch method and both revisions.
  • If WebUI still fails after a clean restart, the Agent update itself may be incomplete: run hermes update again.

Related errors

Full guideHermes Agent Not Working? 14 Errors and Their Exact Fixes

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Frequently asked questions

Do I need to restart the whole computer or WSL?

No. Restarting the WebUI backend is enough once the Agent update has finished.

Is Hermes WebUI the same as the Hermes dashboard?

No. The dashboard (hermes dashboard, port 9119) ships with Hermes Agent. Hermes WebUI is a separate community project that runs alongside it.

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