Encountering 400 - Invalid Request error during the Microsoft Entra External ID user flow because of Entra incorrectly passing an unsupported username parameter to Google's OAuth 2.0 endpoint

Question

Encountering 400 - Invalid Request error during the Microsoft Entra External ID user flow because of Entra incorrectly passing an unsupported username parameter to Google's OAuth 2.0 endpoint

Uday Devarakonda 30

I am currently facing an authentication issue while integrating Google login via Microsoft Entra External ID (SignInSignUp user flow) for my application, and I would appreciate your guidance in resolving it.

Issue Summary:

When users select “Sign in with Google” directly from my application, the authentication flow works as expected and login is successful.

However, when users attempt to log in via the Microsoft Entra SignInSignUp user flow, the authentication fails with a 400 – Invalid Request error.

Observed Error:

The Google authentication screen displays the following error:

Access blocked: Authorization Error

Error 400: invalid_request

Parameter not allowed for this message type: username

Request details: flowName=GeneralOAuthFlow

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Expected Behavior:

Users should be able to authenticate successfully using Google accounts through the Entra SignInSignUp user flow, similar to the direct “Sign in with Google” experience in the application.

Additional Context

Google identity provider is configured under External Identities → Identity Providers in Entra.
Client ID and Client Secret are configured.
The issue seems to arise specifically during the Entra-orchestrated Google authentication flow, not during direct Google OAuth login.

Your guidance would be greatly appreciated, as resolving this is critical for us to enable smooth onboarding of Gmail-based external users.

Thanks in advance for your support.

Jussi Palo 21 Reputation points

2026-02-12T14:34:27.3166667+00:00

Same problem, no workaround or fix available.
Nikolaos Fragos 0 Reputation points

2026-02-14T17:23:57.1866667+00:00
I am also encountering a persistent Error 400: invalid_request with flowName=GeneralOAuthFlow when trying to use Google as an External Identity Provider via Microsoft Entra External ID (CIAM). My application is built with ASP.NET Core 9 and uses Microsoft.Identity.Web to connect to my CIAM tenant (pafame.ciamlogin.com). I have already verified that the Authorized Redirect URIs in the Google Cloud Console exactly match the Azure CIAM endpoint (https://pafame.ciamlogin.com/common/oauth2/nativeclient), and the Client ID/Secret are correctly configured in the Azure Portal. The error occurs during the redirect from Azure to Google's OAuth 2.0 endpoint. Since flowName=GeneralOAuthFlow is part of Google's newer identity flow, is there a known issue with how CIAM constructs the initial authorization request (e.g., missing mandatory parameters like nonce or state, or an unsupported prompt value) that would cause Google to reject it as an invalid request?"

// This line initializes the standard OIDC flow to Azure Entra

builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)

.AddMicrosoftIdentityWebApp(builder.Configuration) .EnableTokenAcquisitionToCallDownstreamApi(allScopes) .AddDistributedTokenCaches(); ```// This section ensures the app handles callbacks correctly builder.Services.Configure<OpenIdConnectOptions>(OpenIdConnectDefaults.AuthenticationScheme, options => { ```typescript options.TokenValidationParameters.RoleClaimType = "roles"; // Standard error handling for OIDC options.Events ??= new OpenIdConnectEvents(); options.Events.OnRemoteFailure = context => { /* ... handling logic ... */ }; ```});
Shubham Sharma 11,185 Reputation points Microsoft External Staff Moderator

2026-02-19T14:06:43.44+00:00

Uday Devarakonda

Following up to check if the resolution provided was helpful. Please let us know if you need any further assistance.
Marko Vodopija 0 Reputation points

2026-02-21T17:37:32.7233333+00:00

What resolution? There is no resolution for this. I've raised the support ticket but there is no answer for last 3 weeks.
Thanmayi Godithi 7,110 Reputation points Microsoft External Staff Moderator

2026-02-26T11:40:24.02+00:00

Hi @Uday Devarakonda,

Just checking in to see if you had a chance to see the previous response posted by @Nikolaos Fragos. Please "Accept the answer" if the information helped you. This will help us and others in the community as well. If you have any further questions do let us know.
Matthew Young 0 Reputation points

2026-03-02T21:14:23.4066667+00:00

This issue is still happening today and there is no fix or workaround!!
Tristan Le Forestier 0 Reputation points

2026-03-07T08:47:53.29+00:00

Same issue as well