Horizon is just a Django app, you could use this:

https://stackoverflow.com/questions/8408823/django-how-to-prevent-multiple-users-login-using-the-same-credentials

Nothing stops someone from installing their own Horizon if they have direct access to the API though…

On Wed, Aug 25, 2021 at 8:17 AM Soares Sarto, Ricardo <Ricardo.SoaresSarto@windriver.com> wrote:
Hi Everyone,

Is there any feature to prevent multiple login sessions for the
same user in Horizon?

That feature could be used to block a second login attempt for the
same user when another session already exists or invalidate the
the first session right after a second session is opened by the user.

Any reference documentation would be very helpful.

Kind regards,
rsoaress
--
Mohammed Naser
VEXXHOST, Inc.