If sign-out was initiated by a client application, then the client first redirected the user to the end session endpoint. This can be determined if a logoutId is passed to the login page and the returned LogoutRequest’s PostLogoutRedirectUri is set.
If there is a PostLogoutRedirectUri value, then it’s important how this URL is used to redirect the user. The logout page typically should not directly redirect the user to this URL. Doing so would skip the necessary front-channel notifications to clients.