Currently, Auth0 does not support forwarding upstream parameters, such as login_hint, to SAML identity providers during the authentication redirect.
We request the ability to pass standard and custom query parameters to SAML IdPs seamlessly. This feature would close an existing gap in functionality and align SAML connection capabilities with those of other protocols (such as OIDC), which already support upstream parameter passing.
Use case: We are implementing frictionless SSO experiences for enterprise users, federating via SAML. By enabling the relay of parameters login_hint to the upstream SAML IdP, we can pre-populate user credentials on the provider’s login page. This removes the redundant step of users having to re-enter their email addresses, thereby reducing login friction, saving time, and significantly improving the overall end-user authentication flow.