Bun.serve

This guide shows how to use gau with a backend-only Bun server using Bun.serve.

Bun’s docs: Bun.serve.

1. Follow the basic setup

   Complete the Getting Started guide for installation, environment variables, and adding at least one OAuth provider.

2. Create your auth configuration

   Define your createAuth configuration.

   src/auth.ts

   import process from 'node:process'
   import { MemoryAdapter } from '@rttnd/gau/adapters/memory'
   import { createAuth } from '@rttnd/gau/core'
   import { GitHub } from '@rttnd/gau/oauth'
   
   export const auth = createAuth({
     adapter: MemoryAdapter(),
     providers: [
       GitHub({
         clientId: process.env.AUTH_GITHUB_ID!,
         clientSecret: process.env.AUTH_GITHUB_SECRET!,
       }),
     ],
     jwt: {
       secret: process.env.AUTH_SECRET!,
     },
     // When frontend runs on a different origin, set the trusted hosts, example:
     // trustHosts: ['http://localhost:5173'],
   })
   
   export type Auth = typeof auth

   Note

   gau handles CORS and CSRF. For cross-origin setups, configure trustHosts in createAuth.

3. Start a Bun.serve HTTP server

   createHandler(auth) returns a standard Fetch handler. You can use it directly inside Bun.serve.

   server.ts

   import { auth } from './src/auth'
   import { createHandler } from '@rttnd/gau/core'
   
   const handler = createHandler(auth)
   
   const server = Bun.serve({
     routes: {
       '/api/auth/*': req => handler(req),
       '/': new Response('OK'),
     },
   })
   
   console.log(`Server listening on ${server.url.hostname}:${server.url.port}`)

4. Try it

   Look at the Bun Example.

5. File Structure (example)

   • Directorysrc

     • auth.ts
     • index.ts
   • package.json

Notes

• By default, sessions use cookies when possible. If redirectTo points to a different origin (or a custom scheme for native apps), gau automatically returns the session token in the URL hash.
• You can force strategies via session.strategy: 'cookie' | 'token' in createAuth.