Cursor's docs cover the self-hosted side. On your own Mac or Linux worker, computer use is off until you start the worker with agent worker --computer-use start. On a Mac, the CLI installs a helper app called Cursor Computer Use, and you have to grant that app Accessibility and Screen Recording yourself in System Settings. Granting them to Terminal or the Cursor app does nothing.
Linux workers use an X11 display and need packages like xdotool and ffmpeg installed. Linux also gets optional desktop sharing, so a teammate can watch or take control of the agent's screen from Cursor.
The docs also say agent worker debug confirms the helper is installed but doesn't check permissions, so the real test is a task that takes a screenshot and clicks something.