Build a full-stack ecommerce checkout web app with cart items, quantities, promo codes, subtotal, shipping, tax, and order confirmation.
Agnes AI builds exactly what you write, the sandbox serves it, and Playwright runs hidden tests against the real app.

The visible checkout is the easy part. Hidden tests reveal whether your spec encodes cents math, stock rules, async safety, and mobile checkout behavior.
Good specs name these explicitly. Vague ones don't.