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If you see “Failed to Fetch” or “Unable to connect to BrowserOS agent”, your agent has been killed.
Failed to fetch error

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Windows: Did you allow the BrowserOS Agent?

When BrowserOS starts for the first time on Windows, a popup will ask if you want to allow BrowserOS Agent to access the network. Click Allow — the agent runs as a separate process alongside the browser and needs this permission to work. If you clicked Cancel or missed this prompt, the agent won’t be able to connect.
Allow BrowserOS Agent network access prompt
To fix this, go to Windows Security → Allow an app through your network settings, and make sure BrowserOS Agent is enabled.

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Fix It

1

Go to Settings → MCP Server and click Restart

Open Settings from the sidebar, scroll to the MCP Server section, and click Restart. Wait a couple of minutes.
Click Restart in MCP Server Settings
2

If restart doesn't work, restart the BrowserOS Agent manually

  1. Open Task Manager — press Ctrl + Shift + Esc or right-click the taskbar and select Task Manager.
  2. In the search bar at the top, type browseros agent.
  3. Right-click BrowserOS Agent and select End task.
  4. Reopen BrowserOS — the agent will restart automatically.
Search for BrowserOS Agent in Task Manager and restart it
If the agent still doesn’t reconnect, end both BrowserOS and BrowserOS Agent in Task Manager, then reopen the app.

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Still Not Working?

The agent runs on port 9100 by default. If another application is using this port, BrowserOS cannot start the agent.
Find the process:
lsof -i :9100
Kill it (replace PID with the process ID from above):
kill -9 PID
Then restart BrowserOS.
Some firewalls may block local connections. Make sure your firewall allows connections to 127.0.0.1:9100.Windows users: Antivirus software sometimes triggers a false positive. Try temporarily disabling your antivirus and restarting BrowserOS.

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