Accept additional response_types values from OAuth servers #1323
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OAuth servers may return additional response_types beyond what the client requested (e.g., ["code", "none"] instead of just ["code"]). Per RFC 7591 Section 3.2.1, servers can modify registration metadata and return all registered values including server-provisioned fields. For example, Keycloak returns ["code", "none"] even when just ["code"] was requested. - Changed response_types field from list[Literal["code"]] to list[str] - Added validation in registration handler to ensure "code" is present - Added tests for response_types flexibility This fixes compatibility issues with OAuth servers that return additional response_types while maintaining MCP's requirement for the "code" flow.
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felixweinberger
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pcarleton
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Sep 26, 2025
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OAuth servers may return additional response_types beyond what the client requested (e.g., ["code", "none"] instead of just ["code"]). Per RFC 7591 Section 3.2.1, servers can modify registration metadata and return all registered values including server-provisioned fields. For example, Keycloak returns ["code", "none"] even when just ["code"] was requested.
This fixes compatibility issues with OAuth servers that return additional response_types while maintaining MCP's requirement for the "code" flow.