Stripe PaymentsSAFE

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The instruction file, verbatim from the audited commit — this is the text the model reads, and the surface the audit's instruction layer examines. Quoted here so you can judge it without cloning anything.

---
name: stripe-payments
description: "Add Stripe payments to a web app — Checkout Sessions, Payment Intents, subscriptions, webhooks, customer portal, and pricing pages. Covers the decision of which Stripe API to use, produces working integration code, and handles webhook verification. No MCP server needed — uses Stripe npm package directly. Triggers: 'add payments', 'stripe', 'checkout', 'subscription', 'payment form', 'pricing page', 'billing', 'accept payments', 'stripe webhook', 'customer portal'."
compatibility: claude-code-only
allowed-tools:
  - Read
  - Write
  - Edit
  - Bash
  - Glob
  - Grep
---

# Stripe Payments

Add Stripe payments to a web app. Covers the common patterns — one-time payments, subscriptions, webhooks, customer portal — with working code. No MCP server needed.

## Which Stripe API Do I Need?

| You want to... | Use | Complexity |
|----------------|-----|-----------|
| Accept a one-time payment | Checkout Sessions | Low — Stripe hosts the payment page |
| Embed a payment form in your UI | Payment Element + Payment Intents | Medium — you build the form, Stripe handles the card |
| Recurring billing / subscriptions | Checkout Sessions (subscription mode) | Low-Medium |
| Save a card for later | Setup Intents | Low |
| Marketplace / platform payments | Stripe Connect | High |
| Let customers manage billing | Customer Portal | Low — Stripe hosts it |

**Default recommendation**: Start with Checkout Sessions. It's the fastest path to accepting money. You can always add embedded forms later.

## Setup

### Install

```bash
npm install stripe @stripe/stripe-js
```

### API Keys

```bash
# Get keys from: https://dashboard.stripe.com/apikeys
# Test keys start with sk_test_ and pk_test_
# Live keys start with sk_live_ and pk_live_

# For Cloudflare Workers — store as secrets:
npx wrangler secret put STRIPE_SECRET_KEY
npx wrangler secret put STRIPE_WEBHOOK_SECRET

# For local dev — .dev.vars:
STRIPE_SECRET_KEY=sk_test_...
STRIPE_WEBHOOK_SECRET=whsec_...
STRIPE_PUBLISHABLE_KEY=pk_test_...
```

### Server-Side Client

```typescript
import Stripe from 'stripe';

// Cloudflare Workers
const stripe = new Stripe(c.env.STRIPE_SECRET_KEY);

// Node.js
const stripe = new Stripe(process.env.STRIPE_SECRET_KEY!);
```

## One-Time Payment (Checkout Sessions)

The fastest way to accept payment. Stripe hosts the entire checkout page.

### Create a Checkout Session (Server)

```typescript
app.post('/api/checkout', async (c) => {
  const { priceId, successUrl, cancelUrl } = await c.req.json();

  const session = await stripe.checkout.sessions.create({
    mode: 'payment',
    line_items: [{ price: priceId, quantity: 1 }],
    success_url: successUrl || `${new URL(c.req.url).origin}/success?session_id={CHECKOUT_SESSION_ID}`,
    cancel_url: cancelUrl || `${new URL(c.req.url).origin}/pricing`,
  });

  return c.json({ url: session.url });
});
```

### Redirect to Checkout (Client)

```typescript
async function handleCheckout(priceId: string) {
  const res = await fetch('/api/checkout', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({ priceId }),
  });
  const { url } = await res.json();
  window.location.href = url;
}
```

### Create Products and Prices

```bash
# Via Stripe CLI (recommended for setup)
stripe products create --name="Pro Plan" --description="Full access"
stripe prices create --product=prod_XXX --unit-amount=2900 --currency=aud --recurring[interval]=month

# Or via Dashboard: https://dashboard.stripe.com/products
```

**Hardcode price IDs** in your code (they don't change):
```typescript
const PRICES = {
  pro_monthly: 'price_1234567890',
  pro_yearly: 'price_0987654321',
} as const;
```

## Subscriptions

Same as one-time but with `mode: 'subscription'`:

```typescript
const session = await stripe.checkout.sessions.create({
  mode: 'subscription',
  line_items: [{ price: PRICES.pro_monthly, quantity: 1 }],
  success_url: `${origin}/dashboard?session_id={CHECKOUT_SESSION_ID}`,
  cancel_url: `${origin}/pricing`,
  // Link to existing customer if known:
  customer: customerId, // or customer_email: '[email protected]'
});
```

### Check Subscription Status

```typescript
async function hasActiveSubscription(customerId: string): Promise<boolean> {
  const subs = await stripe.subscriptions.list({
    customer: customerId,
    status: 'active',
    limit: 1,
  });
  return subs.data.length > 0;
}
```

## Webhooks

Stripe sends events to your server when things happen (payment succeeded, subscription cancelled, etc.). **You must verify the webhook signature.**

### Webhook Handler (Cloudflare Workers / Hono)

```typescript
app.post('/api/webhooks/stripe', async (c) => {
  const body = await c.req.text();
  const sig = c.req.header('stripe-signature')!;

  let event: Stripe.Event;
  try {
    // Use constructEventAsync for Workers (no Node crypto)
    event = await stripe.webhooks.constructEventAsync(
      body,
      sig,
      c.env.STRIPE_WEBHOOK_SECRET
    );
  } catch (err) {
    console.error('Webhook signature verification failed:', err);
    return c.json({ error: 'Invalid signature' }, 400);
  }

  switch (event.type) {
    case 'checkout.session.completed': {
      const session = event.data.object as Stripe.Checkout.Session;
      // Fulfill the order — update database, send email, grant access
      await handleCheckoutComplete(session);
      break;
    }
    case 'customer.subscription.updated': {
      const sub = event.data.object as Stripe.Subscription;
      await handleSubscriptionChange(sub);
      break;
    }
    case 'customer.subscription.deleted': {
      const sub = event.data.object as Stripe.Subscription;
      await handleSubscriptionCancelled(sub);
      break;
    }
    case 'invoice.payment_failed': {
      const invoice = event.data.object as Stripe.Invoice;
      await handlePaymentFailed(invoice);
      break;
    }
  }

  return c.json({ received: true });
});
```

### Register Webhook

```ba

SAFEgrade B · trust 89/100 Nothing in the source contradicts what it says it does. Grade A is reserved for packages that have also passed the behavioural sandbox.

What the source does

Filesystem

none-observed

Network

none-observed

Shell

none-observed

Dependencies

pinned

Secrets in source

none-found

Findings (1)

stripe products create --name="Pro Plan" --description="Full access"

Gates applied: no_behavioural_pass.