Web Sign-in / OOBE - No reaction when using passkeys when Entra federated with Google IdP

Hello everyone,

Our Entra ID tenant is federated with Google Workspace, acting as an idP. The goal is to use the Web Sign-in feature so our users can authenticate via Google directly from the Windows login screen.

The federation is working. Standard authentication (password + SMS code, Authenticator code, or notification) works without any problems. However, I have users with complex passwords who would like to use a passkey. This is where the problem lies:

• The user selects the "Use a security key" option in the webview window displaying Google.
• The QR code is displayed correctly.
• The user scans it with their phone and successfully completes the biometric verification.
• The prompt closes on the phone.

The prompt closes on Windows, but there is no further interaction. The page remains the same; Google seems to be waiting for the authentication process to complete. It doesn't seem to be receiving a success signal or the passkey to send to WebView and Google to complete authentication.

Do you have any ideas on how to resolve this? At this point, I suspect Windows is missing something...

Thanks in advance for your feedback!