An update.

So, I tried adding another IdP. This time with MS/Azure AD (using the tutorial https://fusionauth.io/docs/v1/tech/identity-providers/openid-connect/azure-ad). While going through the process, it seems that the port number was also added this redirect_uri here. So my guess is, it's hardcoded somewhere for the IdP stuff, and get inserted as part of the redirect without checking the domain/port FA is currenlty being run on.

Hi. I have a reverse proxy setup to forward https://auth.domain.com to http://localhost:9011 and it's working fine for normal login, and administration. However, using the included Google IdP, the login button would add the extra port number to my redirect_uri and thus makes it return the

Error 400: redirect_uri_mismatch

The error details:

Error 400: redirect_uri_mismatch

You can't sign in to this app because it doesn't comply with Google's OAuth 2.0 policy.

If you're the app developer, register the redirect URI in the Google Cloud Console.
Request details: redirect_uri=https://auth.domain.com:9011/oauth2/callback

As you can see, it includes the extra port 9011. I'm not sure if this is a bug or some setting that I not aware of. Any help would be appreciated. Thank you.