neat idea. do you hook into the filesystem directly or is this more of a wrapper around specific apps

It hooks into the filesystem directly. Undo runs as a background watcher on a folder/project, sees file changes regardless of which app made them, and snapshots local history into ~/.undo/.

So it’s not wrapping specific apps like Cursor, VS Code, etc. Any editor or tool that writes files is covered.

It's also OSS, you can check it out.

Is there a way to actually delete a file? e.g. you accidentally created a very large file or something?

What do you mean by? rm huge-file.zip should delete the file for you.

If it's not that, I'm happy to understand or open an issue if you try it out. It's OSS