v0 has diff view for each generation. Look for the Toggle Diff View button in the editor toolbar to enable/disable it. If it’s not showing up for you, try a hard refresh (Shift+F5 or Cmd+Shift+R) to clear out any caching issues in the UI.
The response you provided is based on the old editor. Could you clarify why the upgrade to the new editor is being enforced?
After upgrading, the diff comparison button is missing. This issue only occurs in projects upgraded from the old editor; newly created projects are not affected.
You can try duplicating the project and making some changes to verify whether the diff comparison button appears.