Stripe Patterns Skill

Purpose

Guide safe and consistent Stripe integration. Routes to existing payment patterns and provides evidence templates for testing.

When This Skill Applies

• Creating or modifying checkout flows
• Implementing Stripe webhooks
• Working with subscriptions or invoices
• Testing payment functionality
• Handling refunds or disputes

Canonical Code References

Configuration

• Stripe Client Factory: lib/stripe-config.ts
• Use createStripeClient() for consistent API version
• Never hardcode API keys

API Routes

• Checkout Session: app/api/payments/create-checkout-session/route.ts
• Webhook Handler: app/api/payments/webhook/route.ts

Helpers

• Payment Helpers: utils/data/payments/ (use RLS context)
• Subscription Helpers: utils/data/subscriptions/
• Invoice Helpers: utils/data/invoices/

Critical Rules

Test Mode Safety Checklist

Before ANY payment work:

• ] Verify STRIPE_SECRET_KEY starts with sk_test_
• ] Confirm test webhook secret (whsec_... from Stripe CLI)
• ] Use test card numbers only (4242...)
• ] Never use production keys in development

Idempotency Checklist

For webhook handlers:

• ] Store event ID before processing
• ] Check for duplicate events
• ] Use database transactions
• ] Return 200 OK even on idempotency skip

typescript
// Idempotent webhook pattern
await withSystemContext(prisma, "webhook", async (client) => {
  // Check if already processed
  const existing = await client.webhook_events.findUnique({
    where: { stripe_event_id: event.id },
  });
  if (existing) {
    console.log(`Skipping duplicate event: ${event.id}`);
    return;
  }

  // Process and record
  await client.webhook_events.create({
    data: {
      stripe_event_id: event.id,
      event_type: event.type,
      processed_at: new Date(),
    },
  });
});

Webhook Signature Verification

ALWAYS verify webhook signatures:

typescript
import { stripe } from "@/lib/stripe-config";

const signature = request.headers.get("stripe-signature");
const event = stripe.webhooks.constructEvent(
  body,
  signature,
  process.env.STRIPE_WEBHOOK_SECRET,
);

Common Patterns

Create Checkout Session

typescript
import { createStripeClient } from "@/lib/stripe-config";
import { withUserContext } from "@/lib/rls-context";

export async function createCheckout(userId: string, priceId: string) {
  const stripe = createStripeClient();

  // Store user context for success handling
  const session = await stripe.checkout.sessions.create({
    mode: "subscription",
    line_items: [{ price: priceId, quantity: 1 }],
    success_url: `${process.env.NEXT_PUBLIC_APP_URL}/success?session_id={{CHECKOUT_SESSION_ID}}`,
    cancel_url: `${process.env.NEXT_PUBLIC_APP_URL}/pricing`,
    metadata: { userId },
  });

  return session;
}

Handle Subscription Events

typescript
// Webhook event types to handle
const SUBSCRIPTION_EVENTS = [
  "customer.subscription.created",
  "customer.subscription.updated",
  "customer.subscription.deleted",
  "invoice.payment_succeeded",
  "invoice.payment_failed",
];

Evidence Template for Linear

When completing payment work, attach this evidence block:

markdown
**Payment Testing Evidence**

- [ ] Test mode verified (`sk_test_` key)
- [ ] Webhook signature verification tested
- [ ] Idempotency tested (duplicate event handling)
- [ ] Success flow tested (card 4242...)
- [ ] Failure flow tested (card 4000000000000002)
- [ ] Subscription lifecycle tested (create/update/cancel)

**Test Results:**

- Checkout session: [session_id]
- Webhook events processed: [count]
- Subscription status: [active/cancelled]

Reference

• Stripe Config: lib/stripe-config.ts
• Webhook Route: app/api/payments/webhook/route.ts
• Payment Tests: __tests__/payments/
• Stripe Docs: https://stripe.com/docs