mcp-stateless-starter
Starter kit for building stateless MCP servers using the 2026 spec, enabling horizontal scaling without session affinity.
README
Stateless MCP Server Starter (2026 Spec)
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-Methodheader 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/mcpPOST routesrc/tools.ts— tool definitions (echo,now)src/client.ts— example client that connects + calls a toolvercel.json— zero-config Vercel deployDockerfile— for Fly/Cloud Run
Resources
License
MIT — fork freely.
Built by Varritech. We turn AI prototypes into shipped products.
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