How to Add Stripe Payments to Your AI-Built App

AI coding tools can scaffold a Stripe checkout flow quickly, but they consistently miss critical pieces: webhook handlers for payment confirmation, error handling for failed charges, subscription lifecycle management, and proper security for payment-related API routes. A payment integration that 'works in testing' can lose real money in production if these gaps aren't addressed.

Payments should always be verified server-side. Never trust the client to confirm a payment was successful. The flow: your frontend creates a Checkout Session via your backend, Stripe handles the payment page, then Stripe sends a webhook to your server confirming the payment. Your server processes the webhook and updates your database. This is the only reliable pattern.

Install the Stripe SDK. Create an API route that generates a Checkout Session with the correct line items, success URL, and cancel URL. On the frontend, redirect to Stripe's hosted checkout page. Never build your own credit card form unless you have a specific reason — Stripe Checkout handles PCI compliance for you.

Webhooks are how Stripe tells your app that a payment succeeded, failed, or was refunded. Create an API endpoint that receives Stripe webhook events. Verify the webhook signature to prevent spoofed events. Handle at minimum: checkout.session.completed, invoice.paid, invoice.payment_failed, and customer.subscription.deleted. Make webhook handlers idempotent — Stripe may send the same event multiple times.

For recurring payments, use Stripe's Billing portal. Create Products and Prices in the Stripe dashboard. Use checkout.session.completed to provision access. Use customer.subscription.deleted to revoke access. Stripe's Customer Portal lets users manage their own subscriptions without you building UI for plan changes, cancellations, and payment method updates.

Storing the Stripe secret key in client-side code (anyone can see it). Not verifying webhook signatures (attackers can fake payment confirmations). Granting access immediately after checkout redirect instead of waiting for webhook confirmation. Not handling failed payments or expired cards on subscriptions. Missing test mode vs live mode environment variable switching.