Troubleshooting Cognito OAuth for Claude-facing MCP

theDaveAt · reddit · 2026-08-21

The author is encountering issues integrating AWS Cognito OAuth for user authentication in an MCP service. While the flow works via manual testing with curl and a local callback URL, it fails in the Claude desktop app after the login screen, returning a generic "unable to authenticate" error. A shim for the missing codechallengemethodssupported has been implemented. The author is seeking confirmation on the required callback URL.

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