modelcontextprotocol / modelcontextprotocol/csharp-sdk

OAuth token refresh fails with AADSTS9010010

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area-auth bug P2
Dominant language
C#
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Merged PRs (30d)
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Description

Describe the bug
We are using C# SDK to build our MCP and host in AKS which is oAuth protected. When we add the server in github cli at the beginning, the auth works fine. But while calling refresh_token after ~1 hour (when the access token expires) and the SDK attempts a silent refresh, the call fails with this with AADSTS9010010 (The resource parameter provided in the request doesn't match with the requested scopes).

To Reproduce
Steps to reproduce the behavior:

  1. Add a http mcp server protected by oAuth (I used internal Microsoft tenant to register an app to protect the MCP endpoint). The metadata looks like below
builder.Services.AddAuthentication(options =>
{
    options.DefaultChallengeScheme = McpAuthenticationDefaults.AuthenticationScheme;
    options.DefaultAuthenticateScheme = JwtBearerDefaults.AuthenticationScheme;
})
.AddJwtBearer(options =>
{
    options.MapInboundClaims = false;
    options.Authority = $"{instance}/{tenantId}/v2.0";
    options.TokenValidationParameters = new TokenValidationParameters
    {
        ValidateIssuer = true,
        ValidateAudience = true,
        ValidateLifetime = true,
        ValidateIssuerSigningKey = true,
        ValidAudiences = new[] { EntraAppConstants.APIAppClientId, apiAppName },
        ValidIssuers = new[]
        {
            $"{instance}/{tenantId}/v2.0",
            $"https://sts.windows.net/{tenantId}/",
            $"{instance}/{ameTenantId}/v2.0",
            $"https://sts.windows.net/{ameTenantId}/",
        },
        NameClaimType = "name",
        RoleClaimType = "roles",
    };

    options.MetadataAddress = $"{instance}/{tenantId}/v2.0/.well-known/openid-configuration";

})
.AddMcp(options =>
{
    var metadata = new ModelContextProtocol.Authentication.ProtectedResourceMetadata
    {
        AuthorizationServers = { $"{instance}/{tenantId}/v2.0", $"{instance}/{ameTenantId}/v2.0" },
        ScopesSupported = [$"{apiAppName}/my_scope"],
    };

    options.ResourceMetadata = metadata;
});
{
"resource": "https://mcp.******.azure.com/",
"authorization_servers": [
"https://login.microsoftonline.com/72f988bf-86f1-41af-91ab-2d7cd011db47/v2.0",
"https://login.microsoftonline.com/**************/v2.0"
],
"bearer_methods_supported": [
"header"
],
"scopes_supported": [
"api://my_app_name/my_scope"
]
}

Connect the mcp from cli & get 1st time auth done, do some tool calling activity & leave the cli open for an hour. After an hour come back & try to do another tool call, and the call will fail with auth error.

Additional context
Seems same issue is present here too for python SDK: 2578

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by tracing the C# SDK's silent refresh flow around the refresh_token call and compare the protected resource metadata, authorization servers, resource, and scopes shown in the report. Reproduce with the provided AKS-hosted MCP setup, then verify that a tool call still succeeds after the access token expires without the AADSTS9010010 mismatch.

Written by the indexing model from the issue text.

Assessment

Tech stack
csharp
Domain
api, authentication
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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