@yohangel / auth-express

1.0.0 ▾

1.0.0

MIT

GitHub

Better Auth for Express 5: mount the auth routes and protect APIs with requireAuth

Code3 filesContext~405 tokensscan passed

~405 tokens→ src/lib/auth-express/AGENTS.md→ .cursor/rules/genpm-yohangel-auth-express.mdc

This is exactly what your AI reads when it works in src/lib/auth-express. Nothing else is added to its context.

@yohangel/auth-express — rules for AI agents

Purpose

Connects @yohangel/auth to Express 5: mounts Better Auth on /api/auth/* and provides requireAuth / optionalAuth middleware that put the session in res.locals.

Module map

index.ts — mountAuth(app, opts), requireAuth, optionalAuth, AuthLocals type, createAuth re-export.

Integration (do this after installing)

Order matters — mount auth BEFORE body parsers:

import express from 'express';
import { mountAuth, requireAuth } from './lib/auth-express/index.js';
const app = express();
mountAuth(app, { sendEmail });          // /api/auth/*
app.use(express.json());
app.get('/api/me', requireAuth, (req, res) => res.json({ id: res.locals.user.id }));

Frontend on another origin: app.use(cors({ origin: ['https://app.example.com'], credentials: true })) before mountAuth, and list that origin in AUTH_TRUSTED_ORIGINS.
Behind a proxy/CDN set app.set('trust proxy', 1) and AUTH_IP_HEADER so rate limits use the real client IP.
Express 4 is not supported (route syntax *splat is Express 5). Project must be ESM ("type": "module").

Conventions

Protect routes with requireAuth; read res.locals.user / res.locals.session (typed by AuthLocals).
Authorization (who can do what) goes in your handlers after requireAuth, never on the client.

Don't

Don't put express.json() before mountAuth (Better Auth must read the raw body).
Don't use cors({ origin: '*', credentials: true }).
Don't return res.locals.session (contains the token) to the client.

# @yohangel/auth-express — rules for AI agents

## Purpose
Connects `@yohangel/auth` to Express 5: mounts Better Auth on `/api/auth/*` and provides `requireAuth` / `optionalAuth` middleware that put the session in `res.locals`.

## Module map
- `index.ts` — `mountAuth(app, opts)`, `requireAuth`, `optionalAuth`, `AuthLocals` type, `createAuth` re-export.

## Integration (do this after installing)
1. Order matters — mount auth BEFORE body parsers:
   ```ts
   import express from 'express';
   import { mountAuth, requireAuth } from './lib/auth-express/index.js';
   const app = express();
   mountAuth(app, { sendEmail });          // /api/auth/*
   app.use(express.json());
   app.get('/api/me', requireAuth, (req, res) => res.json({ id: res.locals.user.id }));
   ```
2. Frontend on another origin: `app.use(cors({ origin: ['https://app.example.com'], credentials: true }))` before `mountAuth`, and list that origin in `AUTH_TRUSTED_ORIGINS`.
3. Behind a proxy/CDN set `app.set('trust proxy', 1)` and `AUTH_IP_HEADER` so rate limits use the real client IP.
4. Express 4 is not supported (route syntax `*splat` is Express 5). Project must be ESM (`"type": "module"`).

## Conventions
- Protect routes with `requireAuth`; read `res.locals.user` / `res.locals.session` (typed by `AuthLocals`).
- Authorization (who can do what) goes in your handlers after `requireAuth`, never on the client.

## Don't
- Don't put `express.json()` before `mountAuth` (Better Auth must read the raw body).
- Don't use `cors({ origin: '*', credentials: true })`.
- Don't return `res.locals.session` (contains the token) to the client.

The exact tree that will be injected, after .genpmignore. Pinned to

src/lib/auth-express/index.tsread-only · 7145b9d

// @yohangel/auth-express — Better Auth en Express 5. Monta las rutas ANTES de express.json() y protege rutas con
// `requireAuth`. La sesión queda en `res.locals.session` / `res.locals.user`.
import { fromNodeHeaders, toNodeHandler } from 'better-auth/node';
import type { Express, NextFunction, Request, RequestHandler, Response } from 'express';
import { type AuthSession, type CreateAuthOptions, createAuth, getAuth } from '../auth/index.js';

export { createAuth };

/** Crea la instancia (si no existe) y monta /api/auth/* (Express 5: `*splat`). Llamar antes de `express.json()`. */
export function mountAuth(app: Express, opts: CreateAuthOptions & { basePath?: string } = {}): void {
  const { basePath = '/api/auth', ...authOpts } = opts;
  const auth = createAuth(authOpts);
  app.all(`${basePath}/*splat`, toNodeHandler(auth));
}

export type AuthLocals = { session: AuthSession['session'] | null; user: AuthSession['user'] | null };

async function load(req: Request, res: Response): Promise<AuthSession | null> {
  const s = await getAuth().api.getSession({ headers: fromNodeHeaders(req.headers) });
  res.locals.session = s?.session ?? null;
  res.locals.user = s?.user ?? null;
  return s;
}

/** 401 JSON si no hay sesión válida. */
export const requireAuth: RequestHandler = async (req: Request, res: Response, next: NextFunction) => {
  try {
    if (!(await load(req, res))) {
      res.status(401).json({ error: 'unauthorized' });
      return;
    }
    next();
  } catch (e) {
    next(e);
  }
};

/** Carga la sesión si existe, sin bloquear. */
export const optionalAuth: RequestHandler = async (req, res, next) => {
  try {
    await load(req, res);
    next();
  } catch (e) {
    next(e);
  }
};