A universal adapter for MCP's transport mess

What it does Supergateway is a transport translator for Model Context Protocol servers. If your MCP server only speaks stdio, it wraps it and exposes it as SSE, WebSockets, or the newer Streamable HTTP transport. It also works in reverse: point it at a remote SSE or Streamable HTTP server and it shows up locally as a plain stdio command — handy for clients like Claude Desktop or Cursor that expect local processes.

The interesting bit It’s honest glue code, and that’s the point. MCP’s transport landscape is fragmented (stdio, SSE, WS, Streamable HTTP), and rather than rewriting servers, Supergateway just pipes JSON-RPC between shapes — including stateful Streamable HTTP sessions with configurable timeouts.

Key highlights

• Bidirectional: stdio→SSE/WS/Streamable HTTP, and SSE or Streamable HTTP→stdio
• Auth headers and OAuth2 bearer tokens can be injected on the remote side
• CORS control (including regex-matched origins) and custom health endpoints
• Ships as Docker images, including variants bundled with uvx and Deno
• Tested with Node’s built-in test runner, fully offline via a mock MCP server

Caveats

• The README notes a Cursor bug with spaces in CLI args — you must use --oauth2Bearer instead of --header for Authorization
• Tests require Node 24+, which is stricter than most projects

Verdict Anyone bridging MCP servers between local and remote worlds — debugging with MCP Inspector, exposing a stdio server over the network, or wiring a hosted MCP into a stdio-only client — will find this saves an afternoon. If all your servers and clients already agree on a transport, skip it.