Running Windsurf and Cursor on the same project at once, files keep reverting

Yes, both editors keep their own in-memory copy of open files and their own idea of what the agent "last saw". If agent A writes a file while editor B has an unsaved or stale buffer, B can save its old version on top. Autosave makes it worse.

If you want two agents at once, give each its own folder:

git worktree add ../myapp-ui ui-work

Open Windsurf on myapp, Cursor on myapp-ui, merge the branches when done. Or simpler: one agent at a time, other editor closed.

Agree with worktrees. Also turn off autosave in the editor that isn't driving at the moment (files.autoSave: off), and use a different port per dev server so you don't wonder which version you're looking at in the browser.

I run a similar setup. Rule that fixed it for me: commit before switching editors, and only one agent writes at a time. The other editor is for reading.