langflow-ai/langflow · error · HTTPException

{e.message}

Error message

{e.message}

What it means

Error "{e.message}" thrown in langflow-ai/langflow.

Source

Thrown at src/backend/base/langflow/api/v1/mcp_projects.py:889

        use_mcp_composer = should_use_mcp_composer(project)
        connection_urls: list[str]
        transport_mode = (body.transport or "sse").lower()
        if transport_mode not in {"sse", "streamablehttp"}:
            raise HTTPException(status_code=400, detail="Invalid transport. Use 'sse' or 'streamablehttp'.")

        if use_mcp_composer:
            try:
                auth_config = await _get_mcp_composer_auth_config(project)
                await get_or_start_mcp_composer(auth_config, project.name, project_id)
                composer_streamable_http_url = await get_composer_streamable_http_url(project)
                sse_url = await get_composer_sse_url(project)
                connection_urls = [composer_streamable_http_url, sse_url]
            except MCPComposerError as e:
                await logger.aerror(
                    f"Failed to start MCP Composer for project '{project.name}' ({project_id}): {e.message}"
                )
                raise HTTPException(status_code=500, detail=e.message) from e
            except Exception as e:
                error_msg = f"Failed to start MCP Composer for project '{project.name}' ({project_id}): {e!s}"
                await logger.aerror(error_msg)
                error_detail = "Failed to start MCP Composer. See logs for details."
                raise HTTPException(status_code=500, detail=error_detail) from e

            # For OAuth/MCP Composer, use the special format
            settings = get_settings_service().settings
            command = "uvx"
            args = [
                *mcp_sdk_constraint_args(),
                f"mcp-composer{settings.mcp_composer_version}",
                "--mode",
                "http",
                "--endpoint",
                composer_streamable_http_url,
                "--sse-url",
                sse_url,

View on GitHub (pinned to 976ec789d2)

Solutions

1. Address the error reported in the message and retry starting MCP Composer.

When it happens

Trigger: Occurs when starting the MCP Composer raises an error whose message is propagated.

Common situations: See trigger scenarios.

AI-assisted analysis of langflow-ai/langflow@976ec789d2 (2026-08-14). Data as JSON: /api/errors/b4a1cad6e8d1021b. Report an issue: GitHub.