I have an environment where users login to a dashboard and then Auth0 performs SSO into other apps from there. SAML apps give the user experience as expected: users select an app and get SSO into it. For OIDC apps, however, users are prompted to authenticate again. I’ve confirmed this happens on all OIDC apps within this tenant and confirmed it with known good apps (to rule out sso_disabled and code that was handling sessions poorly). I’ve also tested this in other tenants and got the experience that I expected.
We are trying to provide a reply and some information to older posts, in case others come across the same issue/situation and it could help.
Currently, IdP Initiated SSO for OIDC applications is not supported, but this can be overcome by utilising simulating the Implicit Flow with Form Post to simulate the required flow.
For this particular case, enabling SSO has been the fix as it allowed users to skip authentication and I appreciate you taking the time and having reached out via a Support case as well.