@client-compose/express

Express adapter for the Client Compose composer. Serves POST …/screens/{screen} and POST …/actions/{action} wherever you mount it.

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

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

import express from "express";
import { createComposer } from "@client-compose/composer";
import { composerHandler } from "@client-compose/express";

const composer = createComposer<Ctx, express.Request>({
  screens,
  actions,
  context: (req) => ({ viewer: req.user }), // whatever your middleware put on the request
});

const app = express();
app.use(passport.session());
app.use("/compose", composerHandler(composer));

• context receives the Express request, so sessions, req.user and anything else your middleware sets reach every island and action.
• It works with or without express.json() in front of it. If that parser rejects a composer request's body, the app still gets the protocol's 400 bad_request, not Express's error page.
• Other paths under the mount go to the next handler; other methods get 405.