CIMD is unavailable because the server did not advertise CIMD support

ChatGPT Apps SDK
,
1

Hello,

The ChatGPT documentation is somewhat ambiguous but a reasonable reading of it would suggest that CIMD is not currently supported by ChatGPT. However, the UI has a selection for CIMD and produces this error:

CIMD is unavailable because the server did not advertise CIMD support.

The authorization server we are connecting to does support CIMD though - it works in all Claude products and several other agents that use CIMD besides. The authorization server intentionally does not support DCR; CIMD only.

Specifically we can see in this dialog (and our back-end logs) that ChatGPT was able to connect to both the mcp server’s /.well-known/oauth-protected-resource/mcp and the authorization server’s /.well-known/oauth-authorization-server:

image
image939Ă—1228 151 KB

The OAuth server’s metadata includes “client_id_metadata_document_supported”: true, which is the only change to metadata that is required according to CIMD spec.

So what gives? Does ChatGPT currently support CIMD, and if so why does it not detect the advertised support in our authorization server.

âžś  curl -s https://login.test.affinity.vc/.well-known/oauth-authorization-server | jq
{
  "issuer": "https://login.test.affinity.vc",
  "authorization_endpoint": "https://login.test.affinity.vc/auth/oauth2/authorize",
  "token_endpoint": "https://login.test.affinity.vc/auth/oauth2/token",
  "jwks_uri": "https://login.test.affinity.vc/.well-known/jwks.json",
  "scopes_supported": [
    "api",
    "api.read",
    "mcp",
    "offline_access"
  ],
  "response_types_supported": [
    "code"
  ],
  "response_modes_supported": [
    "query"
  ],
  "grant_types_supported": [
    "authorization_code",
    "refresh_token"
  ],
  "token_endpoint_auth_methods_supported": [
    "none",
    "client_secret_basic"
  ],
  "ui_locales_supported": [
    "en-US"
  ],
  "code_challenge_methods_supported": [
    "S256"
  ],
  "client_id_metadata_document_supported": true
}
2

Hi @collinsauve

Thanks for sharing the detailed breakdown, this is helpful.

From what you’ve described, it looks like ChatGPT isn’t currently detecting or falling back to CIMD correctly, even when the authorization server advertises support (client_id_metadata_document_supported: true). In these cases, the flow may still expect Dynamic Client Registration, which would explain the error you’re seeing.

As a temporary workaround, you could try bypassing automatic client registration entirely by using a manually configured OAuth client (i.e., user-defined client setup). This approach has worked in similar setups where DCR isn’t supported or CIMD isn’t picked up as expected.

That said, this does seem like a gap in how CIMD support is detected/handled. It would be worth opening a support ticket (if you haven’t already) and sharing:

  • Your MCP server URL
  • The .well-known/oauth-authorization-server response
  • Any relevant logs/screenshots

That should help the team take a closer look at whether CIMD support is behaving as intended here.

~SD