@moneydevkit/better-auth

Better Auth plugin for MoneyDevKit. Automatically links authenticated users to MDK customers.

Installation

npm install @moneydevkit/better-auth better-auth

You'll also need a MoneyDevKit UI package for your framework:

• Next.js
• Replit

Setup

1. Environment variables

MDK_ACCESS_TOKEN=your_api_key
MDK_MNEMONIC=your_wallet_mnemonic

2. Server plugin

// lib/auth.ts
import { betterAuth } from "better-auth"
import { moneydevkit } from "@moneydevkit/better-auth"

export const auth = betterAuth({
  // ... your config
  plugins: [moneydevkit()]
})

3. Client plugin

import { createAuthClient } from "better-auth/react"
import { moneydevkitClient } from "@moneydevkit/better-auth/client"

const authClient = createAuthClient({
  plugins: [moneydevkitClient()]
})

// Same API as useCheckout().createCheckout from @moneydevkit/nextjs
const result = await authClient.createCheckout({
  type: 'AMOUNT',
  amount: 500,
  currency: 'USD',
  successUrl: '/checkout/success',
})

if (result.data) {
  window.location.href = result.data.checkoutUrl
}

4. Framework setup

Follow the setup guide for your framework's MoneyDevKit package (route handler, checkout page, config):

• Next.js setup
• Replit setup

How it works

The plugin adds a /moneydevkit/checkout endpoint that:

• If user is authenticated: maps user.id → customer.externalId, auto-fills email/name
• If no session: creates checkout without customer info (guest checkout)

This links all checkouts to the same MDK customer record for returning users.