Add Streamable HTTP transport for remote deployments

[ThomsenDrake]

Summary

Adds Streamable HTTP transport so the server can be deployed remotely (Railway, Fly.io, etc.) and accessed over the network by any MCP client. All changes serve this goal:

• Streamable HTTP transport: New startHttpServer() using Express + StreamableHTTPServerTransport with stateful session management. The server exposes a single /mcp endpoint handling POST (JSON-RPC), GET (SSE streaming), and DELETE (session cleanup).
• Transport auto-detection: When PORT is set or MCP_TRANSPORT=http, the server starts in HTTP mode. Otherwise it uses stdio as before — no breaking changes for existing local users.
• Optional bearer token auth: When MCP_AUTH_TOKEN is set, all requests require a valid token. On HTTP this uses the standard Authorization header. On stdio it validates an auth field in the JSON-RPC message via a Transform stream that strips the field before it hits the SDK's strict Zod parser. When unset, auth is disabled (the default for local usage).
• Fix dotenv stdout corruption: dotenv.config({ quiet: true }) — dotenv v17+ logs to stdout by default, which corrupts the MCP stdio protocol. This is a bug that affects the existing server regardless of transport.

Why

The server currently only supports stdio transport, which requires the MCP client to spawn it as a local process. This makes it impossible to deploy remotely or share a single server instance across multiple agents. Streamable HTTP transport is the standard MCP solution for remote servers, and bearer token auth is necessary to secure a network-exposed endpoint.

Client configuration

With a remote deployment, any stdio-based MCP client can connect via mcp-remote:

{
  "mcpServers": {
    "privy": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://your-deployment.example.com/mcp",
        "--header",
        "Authorization:${AUTH_HEADER}"
      ],
      "env": {
        "AUTH_HEADER": "Bearer your_secret_token"
      }
    }
  }
}

Testing

All scenarios verified locally and on a live Railway deployment:

Scenario	Transport	Result
PORT set, valid bearer token	HTTP	✅ Initialize + tools/list
PORT set, invalid token	HTTP	✅ 401 Unauthorized
PORT set, no token	HTTP	✅ 401 Unauthorized
PORT set, no MCP_AUTH_TOKEN	HTTP	✅ No auth enforced
PORT unset, valid auth field	stdio	✅ Normal response
PORT unset, invalid auth field	stdio	✅ -32600 error
PORT unset, no MCP_AUTH_TOKEN	stdio	✅ No auth enforced

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	@​types/​express@​5.0.6

View full report