{"record":{"id":"b98e9305fc1b495d","repo":"langflow-ai/langflow","slug":"invalid-transport-use-sse-or-streamablehttp","errorCode":null,"errorMessage":"Invalid transport. Use 'sse' or 'streamablehttp'.","messagePattern":"Invalid transport\\. Use 'sse' or 'streamablehttp'\\.","errorType":"http","errorClass":"HTTPException","httpStatus":400,"severity":"error","filePath":"src/backend/base/langflow/api/v1/mcp_projects.py","lineNumber":876,"sourceCode":"        # Get settings service to build the SSE URL\n        settings_service = get_settings_service()\n        if settings_service.auth_settings.AUTO_LOGIN and not settings_service.auth_settings.SUPERUSER:\n            # Without a superuser fallback, require API key auth for MCP installs.\n            should_generate_api_key = True\n        settings = settings_service.settings\n        host = settings.host or None\n        port = settings.port or None\n        if not host or not port:\n            raise HTTPException(status_code=500, detail=\"Host and port are not set in settings\")\n\n        # Determine command and args based on operating system\n        os_type = platform.system()\n\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","sourceCodeStart":858,"sourceCodeEnd":894,"githubUrl":"https://github.com/langflow-ai/langflow/blob/976ec789d2886a86de109c044d089d68e96c9a35/src/backend/base/langflow/api/v1/mcp_projects.py#L858-L894","documentation":"Error \"Invalid transport. Use 'sse' or 'streamablehttp'.\" thrown in langflow-ai/langflow.","triggerScenarios":"Occurs when an MCP client configuration request specifies a transport other than 'sse' or 'streamablehttp'.","commonSituations":"See trigger scenarios.","solutions":["Use transport 'sse' or 'streamablehttp'."],"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":"2026-08-15T17:31:12.345Z"}