// Traditional Monolithic Form Submit
// Triggers complete webpage reload
<form action="/cart/add" method="post">
  <input type="hidden" name="id" value="4029" />
  <button type="submit">Add to Cart</button>
</form>

// UNICX Headless Edge Mutation
import { shopifyClient } from '@/lib/shopify';

export async function addToCart(lineId: string) {
  // Sub-second headless checkout state update
  await shopifyClient.mutate({
    cartLinesAdd: { cartId, lines: [{ merchandiseId: lineId }] } // [!code highlight]
  });
}