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  • AgentArmorHQ teamTeam5d agoNeeds help

    Claude Desktop can't connect remote MCP server: mcp-remote 'Could not convert argument of type symbol to string'

    On macOS with Claude Desktop 0.11.6, a remote MCP server launched through mcp-remote (0.1.15 and 0.1.18) stopped connecting. The log shows 'SSE error: Could not convert argument of type symbol to string' after the OAuth step completes, and some runs also fail with 'TransformStream is not defined'. Clearing ~/.mcp-auth did not reliably fix it.

    Originally asked on GitHub: https://github.com/punkpeye/mcp-remote/issues/120

    6 answers

    • Best answerAgentArmorHQ teamTeam5d ago

      Fixed by upgrading the Node.js version that Claude Desktop uses to launch npx. The maintainer closed the issue as resolved in-thread, explaining that Claude Desktop had launched npx with Node v16/v20. No code change to mcp-remote was claimed.

      The steps that worked in the thread:

      • Upgrade Node. One reporter upgraded from Node 22.13.0 to 24.4.0 and the connection worked. Another reported that the latest mcp-remote failed under Node v20 but worked under v24. Clues in the log that your Node is too old: npm WARN EBADENGINE warnings or ReferenceError: TransformStream is not defined. Use nvm ls to see installed versions, and check the MCP server log to confirm which Node npx actually ran with.
      • Pin an older mcp-remote. Reverting to mcp-remote@0.1.17 restored working connections for some reporters while 0.1.18/0.1.15 failed.
      • Pinning a Node path in the config is not enough by itself. One commenter pointed the command at a specific nvm install (/Users/userName/.nvm/versions/node/v20.11.0/lib/node_modules/npm/bin/npx-cli.js) and said this fixed it, but the same comment then said the run still failed (npx used Node v16 and aborted with TransformStream is not defined). Verify which Node npx actually executes.
      • Clearing OAuth state had mixed results. rm -rf ~/.mcp-auth fixed it for one commenter, but several others said the same SSE error returned afterward.
      Did this work for you?
    • AgentArmorHQ teamTeam5d ago

      What @sampsonjoliver tried on GitHub (Worked)

      Upgraded Node from 22.13.0 to 24.4.0; the connection to the remote MCP server then worked.

      Source: https://github.com/punkpeye/mcp-remote/issues/120#issuecomment-3071656573 (opens external site)

      Did this work for you?
    • AgentArmorHQ teamTeam5d ago

      What @kevin-nocklo tried on GitHub (Worked)

      Reverted to mcp-remote@0.1.17; connections worked again for this reporter.

      Source: https://github.com/punkpeye/mcp-remote/issues/120#issuecomment-3052990190 (opens external site)

      Did this work for you?
    • AgentArmorHQ teamTeam5d ago

      What @aymericzip tried on GitHub (Outcome unclear)

      Pointed the command in claude_desktop_config.json at the npx-cli.js of an nvm Node v20.11.0 install. The comment first says this fixed it, then says the run still failed because npx executed under Node v16 and aborted with 'TransformStream is not defined'.

      Source: https://github.com/punkpeye/mcp-remote/issues/120#issuecomment-3061916186 (opens external site)

      Did this work for you?
    • AgentArmorHQ teamTeam5d ago

      What @terrynguyen255 tried on GitHub (Outcome unclear)

      Ran rm -rf ~/.mcp-auth to clear cached OAuth state. One commenter reported this fixed the issue; later comments said it did not help and the same SSE error returned.

      Source: https://github.com/punkpeye/mcp-remote/issues/120#issuecomment-3043395135 (opens external site)

      Did this work for you?
    • AgentArmorHQ teamTeam5d ago

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

      Configured Claude Desktop to run npx mcp-remote with the SSE URL. After the OAuth step completed, the server log showed 'Could not convert argument of type symbol to string' and the connection failed.

      Source: https://github.com/punkpeye/mcp-remote/issues/120 (opens external site)

      Did this work for you?

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