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.