{"record":{"id":"21d204c132bfe5eb","repo":"n8n-io/n8n","slug":"no-transport-found-for-sessionid","errorCode":null,"errorMessage":"No transport found for sessionId","messagePattern":"No transport found for sessionId","errorType":"http","errorClass":null,"httpStatus":401,"severity":"error","filePath":"packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts","lineNumber":239,"sourceCode":"\t\t\t\tawait new Promise<void>((resolve) => {\n\t\t\t\t\tthis.resolveFunctions[callId] = resolve;\n\t\t\t\t\tconst requestHandled = transport.handleRequest(req, resp, message as IncomingMessage);\n\t\t\t\t\tif (isToolCall && transport.transportType === 'sse') {\n\t\t\t\t\t\t// SSE answers the POST with 202 before the tool has run, so completing the\n\t\t\t\t\t\t// request must not resolve here — the CallTool handler does that once the\n\t\t\t\t\t\t// tool finished. A transport failure still resolves so we never hang.\n\t\t\t\t\t\tvoid requestHandled.catch(() => resolve());\n\t\t\t\t\t} else {\n\t\t\t\t\t\tvoid requestHandled.finally(resolve);\n\t\t\t\t\t}\n\t\t\t\t});\n\t\t\t} finally {\n\t\t\t\tdelete this.resolveFunctions[callId];\n\t\t\t\tdelete this.pendingGateResults[callId];\n\t\t\t}\n\t\t} else {\n\t\t\tthis.logger.warn(`No transport found for session ${sessionId}`);\n\t\t\tresp.status(401).send('No transport found for sessionId');\n\t\t}\n\n\t\tresp.flush?.();\n\n\t\t// A not-ready gate makes the CallTool handler short-circuit (returning the\n\t\t// actionable response over the transport instead of executing). Report it as\n\t\t// not a tool call so the node does not also trigger a workflow execution.\n\t\tconst wasGated = !!gateResult && !gateResult.readyToExecute;\n\n\t\treturn {\n\t\t\twasToolCall: MessageParser.isToolCall(rawBody) && !wasGated,\n\t\t\ttoolCallInfo,\n\t\t\tmessageId,\n\t\t};\n\t}\n\n\tasync handleDeleteRequest(req: express.Request, resp: CompressionResponse): Promise<void> {\n\t\tconst sessionId = this.getSessionId(req);","sourceCodeStart":221,"sourceCodeEnd":257,"githubUrl":"https://github.com/n8n-io/n8n/blob/5ac6606e81f67bb9534255570cd4e86fd8101eee/packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts#L221-L257","documentation":"Error \"No transport found for sessionId\" thrown in n8n-io/n8n.","triggerScenarios":"Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts:239 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":[],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"5ac6606e81f67bb9534255570cd4e86fd8101eee","analyzedAt":"2026-08-12T05:26:35.080Z","schemaVersion":2},"datasetVersion":"2026-08-12T18:17:37.767Z"}