Stateless Starter

Production-ready Model Context Protocol server that scales horizontally on plain HTTP — no sticky sessions, no shared Redis, no deep packet inspection at the gateway. Aligned with the 2026-07-28 MCP Specification Release Candidate.

Why stateless

The 2025 MCP transport required sticky sessions and a shared session store to survive horizontal scale-out. The 2026 spec drops both. Any MCP request can land on any instance behind a round-robin load balancer.

This repo is the minimum example: an MCP server exposing two tools (echo, now) using the stateless HTTP transport, deployable to Vercel/Fly/Cloudflare Workers without changes.

Stack

• Node 22 + TypeScript
• @modelcontextprotocol/sdk (HTTP transport)
• Zero state — every request is self-contained
• Routes on Mcp-Method header so reverse proxies can shard without parsing JSON-RPC

Quick start

npm install
npm run dev          # http://localhost:3000/mcp
npm run test:client  # runs against local server

Deploy

# Vercel
vercel deploy

# Fly.io
fly launch

# Cloudflare Workers
wrangler deploy

All three work because the server holds zero session state between requests.

What changed vs 2025 transport

2025 (SSE + sessionId)	2026 (stateless HTTP)
Mcp-Session-Id header required	No session header
Server holds session map	Server holds nothing
Sticky LB required	Round-robin LB works
tools/list re-requested per session	Cached client-side per ttlMs
SSE stream for server→client	Server-Sent Events optional, only for tasks primitive

File map

• src/server.ts — Express server, single /mcp POST route
• src/tools.ts — tool definitions (echo, now)
• src/client.ts — example client that connects + calls a tool
• vercel.json — zero-config Vercel deploy
• Dockerfile — for Fly/Cloud Run

Resources

• 2026-07-28 MCP Spec RC
• 2026 MCP Roadmap
• MCP Server Cards spec

License

MIT — fork freely.

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