diff --git a/api/README.md b/api/README.md
new file mode 100644
index 0000000..8cc76f9
--- /dev/null
+++ b/api/README.md
@@ -0,0 +1,48 @@
+# Checkout API
+
+Serverless Stripe Checkout integration for the Agentic Engineering course.
+
+## Deploy
+
+### Cloudflare Worker (recommended)
+
+```bash
+npm install -g wrangler
+cd api
+wrangler deploy checkout.js --name checkout-api
+wrangler secret put STRIPE_SECRET_KEY
+```
+
+### Vercel
+
+```bash
+cd api
+vercel deploy --prod
+vercel secrets add STRIPE_SECRET_KEY sk_live_...
+```
+
+### Standalone
+
+```bash
+export STRIPE_SECRET_KEY="sk_live_..."
+node checkout.js
+# Listens on port 8787
+```
+
+## Price IDs
+
+Create these products in Stripe Dashboard, then update `site/checkout.md` with the real price IDs:
+
+| Product | Amount | Stripe Price ID |
+|---------|--------|----------------|
+| Self-Paced | $97 | `price_self_paced` → replace with real ID |
+| Enterprise | $199 | `price_enterprise` → replace with real ID |
+| Cohort | $247 | `price_cohort` → replace with real ID |
+
+## How It Works
+
+1. User clicks "Buy" → redirected to `/checkout?plan=self-paced`
+2. Frontend calls `/api/checkout` with the price ID
+3. API creates a Stripe Checkout Session
+4. User is redirected to Stripe's hosted checkout page
+5. After payment, user is redirected to `/checkout/success`
diff --git a/api/checkout.js b/api/checkout.js
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index 0000000..e607942
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+++ b/api/checkout.js
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+/**
+ * Stripe Checkout Session API
+ * Deploy as a Cloudflare Worker, Vercel function, or standalone server.
+ *
+ * Environment variables needed:
+ * - STRIPE_SECRET_KEY: sk_live_... or sk_test_...
+ * - FRONTEND_URL: https://git.fdsa.agency (or your domain)
+ *
+ * Usage:
+ * POST /api/checkout
+ * Body: { "price_id": "price_abc123", "mode": "payment", "customer_email": "..." }
+ */
+
+const stripeEndpoint = 'https://api.stripe.com/v1/checkout/sessions'
+
+async function handleRequest(request) {
+ // CORS for frontend
+ if (request.method === 'OPTIONS') {
+ return new Response(null, {
+ headers: {
+ 'Access-Control-Allow-Origin': '*',
+ 'Access-Control-Allow-Methods': 'POST, OPTIONS',
+ 'Access-Control-Allow-Headers': 'Content-Type',
+ },
+ })
+ }
+
+ if (request.method !== 'POST') {
+ return new Response(JSON.stringify({ error: 'Method not allowed' }), { status: 405 })
+ }
+
+ const stripeKey = globalThis.STRIPE_SECRET_KEY || process?.env?.STRIPE_SECRET_KEY
+ const frontendUrl = globalThis.FRONTEND_URL || process?.env?.FRONTEND_URL || 'https://git.fdsa.agency'
+
+ if (!stripeKey) {
+ return new Response(JSON.stringify({ error: 'Stripe not configured' }), {
+ status: 500,
+ headers: { 'Access-Control-Allow-Origin': '*' },
+ })
+ }
+
+ try {
+ const { price_id, mode, customer_email } = await request.json()
+
+ const body = new URLSearchParams({
+ 'mode': mode || 'payment',
+ 'success_url': `${frontendUrl}/checkout/success?session_id={CHECKOUT_SESSION_ID}`,
+ 'cancel_url': `${frontendUrl}/checkout/cancel`,
+ 'allow_promotion_codes': 'true',
+ 'line_items[0][price]': price_id,
+ 'line_items[0][quantity]': '1',
+ })
+
+ if (customer_email) {
+ body.set('customer_email', customer_email)
+ }
+
+ const stripeResp = await fetch(stripeEndpoint, {
+ method: 'POST',
+ headers: {
+ 'Authorization': `Bearer ${stripeKey}`,
+ 'Content-Type': 'application/x-www-form-urlencoded',
+ },
+ body: body.toString(),
+ })
+
+ const data = await stripeJson(stripeResp)
+
+ if (!stripeResp.ok) {
+ throw new Error(data.error?.message || 'Stripe error')
+ }
+
+ return new Response(JSON.stringify({ url: data.url, session_id: data.id }), {
+ status: 200,
+ headers: {
+ 'Content-Type': 'application/json',
+ 'Access-Control-Allow-Origin': '*',
+ },
+ })
+ } catch (e) {
+ return new Response(JSON.stringify({ error: e.message }), {
+ status: 500,
+ headers: {
+ 'Content-Type': 'application/json',
+ 'Access-Control-Allow-Origin': '*',
+ },
+ })
+ }
+}
+
+async function stripeJson(response) {
+ const text = await response.text()
+ try {
+ return JSON.parse(text)
+ } catch {
+ // Stripe sometimes returns unexpected formats — parse query string
+ const params = new URLSearchParams(text)
+ const obj = {}
+ for (const [k, v] of params) {
+ // Handle nested keys like 'error.message'
+ const parts = k.split('.')
+ if (parts.length > 1) {
+ let cursor = obj
+ for (let i = 0; i < parts.length - 1; i++) {
+ cursor[parts[i]] = cursor[parts[i]] || {}
+ cursor = cursor[parts[i]]
+ }
+ cursor[parts[parts.length - 1]] = v
+ } else {
+ obj[k] = v
+ }
+ }
+ return obj
+ }
+}
+
+// Cloudflare Worker entry
+export default { fetch: handleRequest }
+
+// Node.js entry
+if (typeof module !== 'undefined' && require?.main === module) {
+ const http = require('http')
+ const server = http.createServer((req, res) => {
+ // Minimal Node.js adapter — assumes body is JSON
+ let body = ''
+ req.on('data', chunk => body += chunk)
+ req.on('end', async () => {
+ globalThis.process = process
+ globalThis.request = new Request(`http://localhost${req.url}`, {
+ method: req.method,
+ headers: req.headers,
+ body: body || undefined,
+ })
+ const response = await handleRequest(globalThis.request)
+ res.writeHead(response.status, Object.fromEntries(response.headers))
+ res.end(await response.text())
+ })
+ })
+ const port = process.env.PORT || 8787
+ server.listen(port, () => console.log(`Checkout API on :${port}`))
+}
diff --git a/site/.vitepress/dist/404.html b/site/.vitepress/dist/404.html
index 927ed84..4157099 100644
--- a/site/.vitepress/dist/404.html
+++ b/site/.vitepress/dist/404.html
@@ -6,12 +6,12 @@
Page Not Found | Agentic Engineering the Hard Way
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+
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+
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+
@@ -29,7 +29,7 @@
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+