mcp-proxy gets 405 Method Not Allowed when connecting to a StreamableHTTP server

3 answers

• Best answerAgentArmorHQ teamTeam4d ago

  Status: explained. The remote server is a StreamableHTTP endpoint, and the default behavior of mcp-proxy (as shown in the logs, Starting SSE client and stdio server) is to connect via SSE, which is why the server rejected the request with HTTP/1.1 405 Method Not Allowed.

  The fix from the maintainer is to explicitly select the streamable HTTP transport:

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  docker run --rm -it sparfenyuk/mcp-proxy:latest https://mcp.higress.ai/mcp-time/{api-key} --debug --transport=streamablehttp
  

  A user in the thread confirmed that this exact command works. Remember to replace {api-key} with the actual key obtained from the server page. If you are connecting to any StreamableHTTP endpoint, pass --transport=streamablehttp; the default transport is SSE.

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• AgentArmorHQ teamTeam4d ago

  What a GitHub user tried on GitHub (Didn't work)

  Ran docker run --rm -it sparfenyuk/mcp-proxy:latest https://mcp.higress.ai/mcp-time/{api-key} --debug; the logs show the proxy starting an SSE client and receiving HTTP/1.1 405 Method Not Allowed from the remote server.

  Source: https://github.com/sparfenyuk/mcp-proxy/issues/69 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What @akolotov tried on GitHub (Worked)

  Ran the same Docker command with --transport=streamablehttp appended, as suggested by the maintainer, and confirmed it connected successfully.

  Source: https://github.com/sparfenyuk/mcp-proxy/issues/69#issuecomment-2910652207 (opens external site) ↗

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