Roundcube session survives OIDC logout

[skug67]

I'm running Roundcube side-by-side w/Nextcloud (actually embedded in an i-frame using Nextcloud's "external" app) with Keycloak OIDC as the login mechanism for both. SLO works perfectly. But SSO isn't working -- I need to log out of Nextcloud and Roundcube separately. In particular I've discovered that logging out of Nextcloud (and successfully deleting the Keycloak OIDC session) still leaves a valid Roundcube session cookie. Is there some way to ensure that Roundcube looks for both the OIDC session as well as its own session cookie?

[pulsejet]

pulsejet/nextcloud-oidc-login#37