When an AI application (e.g. Claude or ChatGPT) has been connected to your account, you can check this access, and revoke it if you no longer want the app to have access.
From your Personal Configuration area, click on ‘Account login & security’, and then scroll down to ‘Connected applications’

Pressing the ‘Revoke access’ button will prevent that particular connected application from connecting in future sessions.
In order to use the connected application again in the future, you will likely need to follow the connection steps again, or select a “reauthenticate" or similar option in the application.