@client-compose/fastify

Fastify adapter for the Client Compose composer: a plugin serving POST …/screens/:screen and POST …/actions/:action.

Tier: core · Protocol: v0 · Fastify 5 · Node 20+

npm install @client-compose/composer @client-compose/fastify

import Fastify, { type FastifyRequest } from "fastify";
import { createComposer } from "@client-compose/composer";
import { composerPlugin } from "@client-compose/fastify";

const composer = createComposer<Ctx, FastifyRequest>({
  screens,
  actions,
  context: (request) => ({ viewer: request.user }), // whatever your hooks decorated it with
});

const app = Fastify();
await app.register(composerPlugin(composer), { prefix: "/compose" });

• context receives the Fastify request.
• Inside the plugin, bodies reach the composer as they were sent, so malformed JSON gets the protocol's own 400 bad_request. Your other routes keep Fastify's usual parsing.