{"record":{"id":"b19759a319a05cd2","repo":"n8n-io/n8n","slug":"session-not-found","errorCode":null,"errorMessage":"Session not found","messagePattern":"Session not found","errorType":"http","errorClass":null,"httpStatus":404,"severity":"error","filePath":"packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts","lineNumber":178,"sourceCode":"\t\tif (toolCallInfo) {\n\t\t\tconst tool = tools.find((t) => t.name === toolCallInfo!.toolName);\n\t\t\tif (tool?.metadata?.sourceNodeName && typeof tool.metadata.sourceNodeName === 'string') {\n\t\t\t\ttoolCallInfo = { ...toolCallInfo, sourceNodeName: tool.metadata.sourceNodeName };\n\t\t\t}\n\t\t}\n\n\t\tif (sessionId && !transport && req.headers['mcp-session-id'] && serverName) {\n\t\t\tthis.logger.debug(\n\t\t\t\t`Recreating StreamableHTTP transport for session ${sessionId} on this main instance`,\n\t\t\t);\n\t\t\tconst recreated = await this.recreateStreamableHttpTransport(\n\t\t\t\tsessionId,\n\t\t\t\tserverName,\n\t\t\t\ttools,\n\t\t\t\tresp,\n\t\t\t);\n\t\t\tif (!recreated) {\n\t\t\t\tresp.status(404).send('Session not found');\n\t\t\t\treturn { wasToolCall: false };\n\t\t\t}\n\t\t\ttransport = this.sessionManager.getTransport(sessionId);\n\t\t}\n\n\t\tconst isToolCall = MessageParser.isToolCall(rawBody);\n\t\tconst isListToolsRequest = MessageParser.isListToolsRequest(rawBody);\n\n\t\tif (\n\t\t\tsessionId &&\n\t\t\t!transport &&\n\t\t\treq.query.sessionId &&\n\t\t\tthis.executionCoordinator.isQueueMode() &&\n\t\t\t(isToolCall || isListToolsRequest)\n\t\t) {\n\t\t\tthis.logger.debug(\n\t\t\t\t`SSE queue mode: forwarding ${isToolCall ? 'tool call' : 'list tools'} for session ${sessionId} via pub/sub`,\n\t\t\t);","sourceCodeStart":160,"sourceCodeEnd":196,"githubUrl":"https://github.com/n8n-io/n8n/blob/5ac6606e81f67bb9534255570cd4e86fd8101eee/packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts#L160-L196","documentation":"Error \"Session not found\" thrown in n8n-io/n8n.","triggerScenarios":"Thrown at packages/@n8n/nodes-langchain/nodes/mcp/McpTrigger/McpServer.ts:178 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":"2026-08-12T13:17:24.610Z"}