next

Next.js Integration

The @emulators/adapter-next package embeds emulators directly into a Next.js App Router app, running them on the same origin. This is particularly useful for Vercel preview deployments where OAuth callback URLs change with every deployment.

Install

npm install @emulators/adapter-next @emulators/github @emulators/google

Only install the emulators you need. Each @emulators/* package is published independently, keeping serverless bundles small.

Route Handler

Create a catch-all route that serves emulator traffic:

// app/emulate/[...path]/route.ts
import { createEmulateHandler } from '@emulators/adapter-next'
import * as github from '@emulators/github'
import * as google from '@emulators/google'

export const { GET, POST, PUT, PATCH, DELETE, OPTIONS } = createEmulateHandler({
  services: {
    github: {
      emulator: github,
      seed: {
        users: [{ login: 'octocat', name: 'The Octocat' }],
        repos: [{ owner: 'octocat', name: 'hello-world', auto_init: true }],
      },
    },
    google: {
      emulator: google,
      seed: {
        users: [{ email: '[email protected]', name: 'Test User' }],
      },
    },
  },
})

This creates the following routes:

• /emulate/github/** serves the GitHub emulator
• /emulate/google/** serves the Google emulator

GitHub installation-token metadata is available server-side at /emulate/github/_emulate/installation-tokens.

Auth.js / NextAuth Configuration

Point your provider at the emulator paths on the same origin:

import GitHub from 'next-auth/providers/github'

const baseUrl = process.env.VERCEL_URL
  ? `https://${process.env.VERCEL_URL}`
  : 'http://localhost:3000'

GitHub({
  clientId: 'any-value',
  clientSecret: 'any-value',
  authorization: { url: `${baseUrl}/emulate/github/login/oauth/authorize` },
  token: { url: `${baseUrl}/emulate/github/login/oauth/access_token` },
  userinfo: { url: `${baseUrl}/emulate/github/user` },
})