The framework for apps that outgrow serverless.

Serverless API route (default)

// src/api/orders.ts
export async function POST(req, reply) {
  const order = await createOrder(req.parsedBody);
  return reply.json(order);
}

Same project. Now it's a websocket server.

// src/api/live/room.ts
export const kind = 'hot';   // ← the line

const clients = new Set();
export function websocket(peer, req) {
  clients.add(peer);
  peer.on('message', (m) => {
    for (const c of clients) c.send(m);
  });
  peer.on('close', () => clients.delete(peer));
}