{"record":{"id":"bd9514b82462d37b","repo":"vercel/next.js","slug":"not-found-mcp-endpoint-is-at-mcp","errorCode":null,"errorMessage":"Not found. MCP endpoint is at /mcp\n","messagePattern":"Not found\\. MCP endpoint is at /mcp\n","errorType":"http","errorClass":null,"httpStatus":404,"severity":"error","filePath":"packages/next/src/cli/internal/turbo-trace-server.ts","lineNumber":238,"sourceCode":"        md += '_No spans found._\\n'\n      }\n\n      for (const span of spans) {\n        md += renderSpanMarkdown(span)\n      }\n\n      if (page < totalPages) {\n        md += `Use \\`page=${page + 1}\\` to see more results.\\n`\n      }\n\n      return { content: [{ type: 'text', text: md }] }\n    }\n  )\n\n  // Start the HTTP server for MCP (served at /mcp).\n  const server = http.createServer(async (req, res) => {\n    if (req.url !== '/mcp') {\n      res.writeHead(404, { 'Content-Type': 'text/plain' })\n      res.end('Not found. MCP endpoint is at /mcp\\n')\n      return\n    }\n    const transport = new StreamableHTTPServerTransport({\n      sessionIdGenerator: undefined,\n    })\n    try {\n      res.on('close', () => transport.close())\n      await mcpServer.connect(transport)\n      let body = ''\n      req.setEncoding('utf8')\n      await new Promise<void>((resolve, reject) => {\n        req.on('data', (chunk: string) => {\n          body += chunk\n        })\n        req.on('end', resolve)\n        req.on('error', reject)\n      })","sourceCodeStart":220,"sourceCodeEnd":256,"githubUrl":"https://github.com/vercel/next.js/blob/0eb377541648e63402a47b38fee00a8d0ce8f8f1/packages/next/src/cli/internal/turbo-trace-server.ts#L220-L256","documentation":"The turbo-trace-server's HTTP handler responds 404 with this text for any request whose URL is not /mcp; the internal trace server exposes only the MCP (Streamable HTTP) endpoint, so every other path is deliberately rejected.","triggerScenarios":"Thrown at packages/next/src/cli/internal/turbo-trace-server.ts:238 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Point your MCP client at the /mcp endpoint of the trace server instead of the requested path."],"exampleFix":null,"handlingStrategy":"validation","validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"0eb377541648e63402a47b38fee00a8d0ce8f8f1","analyzedAt":"2026-08-19T02:10:13.922Z","contentChangedAt":"2026-08-19T02:10:13.922Z","schemaVersion":2},"datasetVersion":"2026-09-14T05:17:10.506Z"}