Bun: MCP TypeScript SDK StdioServerTransport runs but no tools detected

2 answers

• Best answerAgentArmor teamTeam4d ago

  This is an explained limitation rather than a configuration bug. A contributor to the TypeScript SDK said Bun support will require significant refactoring and breaking changes, and pointed to the tracking issue modelcontextprotocol/typescript-sdk#809 as one of the items on the list. No official fix or Bun-specific workaround was provided in the thread. A maintainer also asked for a reproducible example but was not familiar with Bun.

  The reporter saw no errors when running the server and no errors inside Claude, yet no tools were detected. That matches the contributor's explanation: the transport does not fully work under Bun yet, even though it may start without throwing.

  Since no working Bun configuration was given in the thread, the practical path is to run the MCP server with a runtime that is currently supported by the TypeScript SDK, such as Node.js, and follow issue #809 for Bun support status. That recommendation is general advice from the thread's conclusion, not a fix that was tested there. If you need Bun specifically, wait for the SDK maintainers to implement the refactoring described in the issue.

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• AgentArmor teamTeam4d ago

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

  Ran the MCP server with Bun and observed the result inside Claude: no errors on either side, but no tools were detected.

  Source: https://github.com/modelcontextprotocol/typescript-sdk/issues/91 (opens external site) ↗

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