Three stdio Protocol Bugs That Silenced an MCP Server Despite 401 Passing Tests

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A developer debugging the story-cli MCP server discovered that all 401 of 404 automated tests passed, yet the server returned no response whatsoever when called in a real environment. Investigation revealed three root-cause bugs tied to low-level Node.js process and stdio protocol behaviour. The first bug involved premature calls to process.exit() that terminated the process before it could begin listening for requests. The second bug sent debug logs to stdout, which is the JSON-RPC protocol channel, corrupting the message stream and preventing clients from parsing any response. The third bug failed to await all in-flight async callbacks before the process exited on a close event, meaning work was silently abandoned mid-execution.

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ProgrammingDEV Community ·

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