Agentic checkout
An agentic checkout is a checkout an AI agent can finish without a human hand on the mouse: every required choice can be made from readable data, and every required control can be operated without hovering, dragging or waiting for an animation to settle.
Most checkouts were never tested this way. They were tested by people, who forgive a great deal: a button that only appears on hover, a required field with no label, a confirmation step that depends on a script finishing. A person works around all of it without noticing. An agent stops.
The useful test is not whether the checkout is modern. It is whether each step can be completed by something reading the page as text and submitting forms.
Why it matters to a store
A checkout failure is the most expensive kind, because everything before it already worked. The agent found the store, judged the product suitable, chose you over an alternative, and then could not pay. That is a purchase you had won.