Hey, thanks for the report. This is a known issue. The extension host is not starting properly on some Windows machines after recent updates, which breaks notebooks, terminal, and AI at the same time.
A few things to try:
- Clear extension cache. Close Cursor, delete these folders, then restart:
%APPDATA%\Cursor\CachedExtensions
%APPDATA%\Cursor\CachedExtensionVSIXs
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Full profile reset. Close Cursor, rename
%APPDATA%\CursortoCursor_backup, then launch Cursor. This creates a fresh profile. If it works, reimport your extensions from VS Code. -
Disable Python Environment extension. Some users found it conflicts with the Jupyter kernel and causes the hang. Worth trying if you use it.
-
If nothing helps, you can roll back to an earlier version to unblock your work for now.
Also, if you can grab the red errors from Help > Toggle Developer Tools > Console right after startup, that would help us narrow down why the extension host fails on your setup.
There is an active thread with the same issue here: [Bug] Jupyter Notebooks & AI Panel broken after upgrading to Cursor 3
The team is aware of this. Your report helps with prioritization. Let me know how it goes.