Better-auth

Keep billing tied to your auth identity by syncing Better Auth users into PayKit customers.

The Better Auth integration story is simple: authenticate with Better Auth, then use the auth user or account ID as PayKit's referenceId.

Example pattern

import { auth } from "@/lib/auth";
import { paykit } from "@/lib/paykit";

export async function createBillingCheckout() {
  const session = await auth.api.getSession();

  if (!session?.user) {
    throw new Error("Unauthorized");
  }

  const customer = await paykit.customer.sync({
    referenceId: session.user.id,
    email: session.user.email ?? undefined,
    name: session.user.name ?? undefined,
  });

  return paykit.checkout.create({
    providerId: "stripe",
    customerId: customer.id,
    amount: 2900,
    description: "Starter plan",
    successURL: "https://app.example.com/billing/success",
  });
}

The important rule is that auth stays your identity layer. PayKit uses that identity to manage billing state and provider mappings.

Example pattern

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