How to force the register screen with prompt=login and an active SSO session?

[FASupportBot]

I'm using FusionAuth's hosted login pages with Advanced Themes and need to support flows where a user can 'switch account' without logging out first. In some cases, I need to force the registration screen to appear even when there's an active SSO session.

I've tried the following combinations:

1. prompt=login + oauth2/register + active SSO → Shows login screen, not register screen
   • Additional issue: appending existing query params (including prompt) to the 'create account' button creates a loop back to the login screen
2. oauth2/register without prompt=login + active SSO → Passthrough (expected behavior)

In my previous identity provider (Auth0), I could pass screen_hint=signup combined with prompt=login to force the registration screen to display. Is there an equivalent way to achieve this in FusionAuth, or plans to support similar functionality?

I'm using self-service registration and need users to be able to create a new account while an SSO session is active, without first clearing the existing session.

[FASupportBot]

Currently, FusionAuth does not support forcing the register screen when prompt=login is used with an active SSO session. The screen_hint parameter (like Auth0's screen_hint=signup) is not available in FusionAuth.

Workarounds:

1. Clear the SSO session before registration: You can clear the existing SSO session in your proxy/middleware before redirecting to oauth2/register. While not ideal, this would allow the registration flow to proceed without the passthrough behavior.

2. Use direct registration without prompt: If you call the registration endpoint without the prompt=login parameter and there are no missing required fields, FusionAuth will complete the registration directly. Only when there are missing fields will users be sent to the complete-registration page.

Feature Request:

If neither workaround meets your needs, this would require a feature request for FusionAuth to support a parameter similar to screen_hint=signup. The product team would need to review this for the roadmap, though implementation timelines would depend on prioritization.

For now, clearing the SSO session before initiating registration is the most reliable approach to ensure users see the registration screen rather than experiencing passthrough behavior.

Related Documentation

• OAuth prompt Parameter - Details on the prompt=login parameter and its behavior (available since v1.60.0): OIDC Prompt Documentation
• OAuth Authorize Endpoint - Complete reference for OAuth authorization parameters including prompt, login_hint, and idp_hint: Authorize API Reference
• Self-Service Registration - Overview of how self-service registration works and how registrations are created: Self-Service Registration Guide
• Complete Registration - Information on the complete registration flow when missing fields are present (available since v1.65.0): Complete Registration Documentation
• Logout and Session Management - How to clear SSO sessions programmatically: Logout and Session Management
• Hosted Backend API - Documentation on the /oauth2/register endpoint behavior: Hosted Backend API

Note: The /oauth2/register endpoint is not fully documented in the official OAuth endpoints reference. There is an open issue to add complete documentation for this endpoint. When a user has an active SSO session and hits /oauth2/register, FusionAuth redirects them through the authorization flow, which causes the passthrough behavior you're experiencing.