Hi,
Jmix application like any regular vaadin application stores authentication in a regular servlet session. JWT token is not sent on each navigation to application page, so there is no way to validate access tokens because there are no access tokens there.
Speaking about the the logging out from the application when a user has logged out from another one - the back-channel logout is not supported in OIDC add-on. I’ve created an issue for this.
If you want to implent this in your own project, you can always disable the standard Jmix OIDC auto-configuration and provide your own one. An example of how to do this can be found in this topic