{"record":{"id":"b4a1cad6e8d1021b","repo":"langflow-ai/langflow","slug":"e-message","errorCode":null,"errorMessage":"{e.message}","messagePattern":"\\{e\\.message\\}","errorType":"http","errorClass":"HTTPException","httpStatus":500,"severity":"error","filePath":"src/backend/base/langflow/api/v1/mcp_projects.py","lineNumber":889,"sourceCode":"\n        use_mcp_composer = should_use_mcp_composer(project)\n        connection_urls: list[str]\n        transport_mode = (body.transport or \"sse\").lower()\n        if transport_mode not in {\"sse\", \"streamablehttp\"}:\n            raise HTTPException(status_code=400, detail=\"Invalid transport. Use 'sse' or 'streamablehttp'.\")\n\n        if use_mcp_composer:\n            try:\n                auth_config = await _get_mcp_composer_auth_config(project)\n                await get_or_start_mcp_composer(auth_config, project.name, project_id)\n                composer_streamable_http_url = await get_composer_streamable_http_url(project)\n                sse_url = await get_composer_sse_url(project)\n                connection_urls = [composer_streamable_http_url, sse_url]\n            except MCPComposerError as e:\n                await logger.aerror(\n                    f\"Failed to start MCP Composer for project '{project.name}' ({project_id}): {e.message}\"\n                )\n                raise HTTPException(status_code=500, detail=e.message) from e\n            except Exception as e:\n                error_msg = f\"Failed to start MCP Composer for project '{project.name}' ({project_id}): {e!s}\"\n                await logger.aerror(error_msg)\n                error_detail = \"Failed to start MCP Composer. See logs for details.\"\n                raise HTTPException(status_code=500, detail=error_detail) from e\n\n            # For OAuth/MCP Composer, use the special format\n            settings = get_settings_service().settings\n            command = \"uvx\"\n            args = [\n                *mcp_sdk_constraint_args(),\n                f\"mcp-composer{settings.mcp_composer_version}\",\n                \"--mode\",\n                \"http\",\n                \"--endpoint\",\n                composer_streamable_http_url,\n                \"--sse-url\",\n                sse_url,","sourceCodeStart":871,"sourceCodeEnd":907,"githubUrl":"https://github.com/langflow-ai/langflow/blob/976ec789d2886a86de109c044d089d68e96c9a35/src/backend/base/langflow/api/v1/mcp_projects.py#L871-L907","documentation":"Error \"{e.message}\" thrown in langflow-ai/langflow.","triggerScenarios":"Occurs when starting the MCP Composer raises an error whose message is propagated.","commonSituations":"See trigger scenarios.","solutions":["Address the error reported in the message and retry starting MCP Composer."],"exampleFix":null,"handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"backgroundTag":null,"analyzedSha":"976ec789d2886a86de109c044d089d68e96c9a35","analyzedAt":"2026-08-14T18:23:12.227Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}