This is a known issue our team is actively investigating. ERROR_EXTENSION_HOST_TIMEOUT happens entirely on the client side: when a chat starts, Cursor’s extension host has about 30 seconds to register the agent execution provider, and when it doesn’t register in time you get this error. Because the request never actually reaches us, it tends to repeat on every new chat once the extension host is in a bad state.
A few things to try, roughly in order:
-
Fully quit and relaunch Cursor - quit the app completely, not just “Reload Window.” Once the extension host gets stuck it usually won’t recover on its own, but a clean restart often clears it.
-
Add Cursor to your antivirus / Windows Defender exclusions. On Windows, the most common cause we’ve seen is security software scanning Cursor’s files during startup and pushing extension host initialization past the timeout. The exact processes and paths to exclude are here: Endpoint Security. Restart and test afterward.
-
Check the Extension Host log -
Ctrl+Shift+P→ Output → choose Extension Host from the dropdown. If it’s empty or stops partway, the host isn’t finishing startup (which points to #2). If it shows normal output, that’s useful to know too. -
Make sure your workspace folder is trusted - an untrusted workspace can silently block the agent from activating.
One thing that would help me narrow this down: you mentioned trying --disable-extensions over SSH - does the timeout also happen when you open a local Windows folder, or only over Remote-SSH? Over SSH the extension host runs on the remote machine, so the fix would be different.
There’s an active thread tracking this same 3.6.31 Windows error if you’d like to follow along: Agent execution provider did not respond in time.