Why Static Accessibility Scanners Miss What AI Agents Hit

This button passes every automated accessibility scan we've thrown at it: <button class= "btn-primary" type= "button" > Check availability </button> And it breaks every AI agent that tries to book a room through it. The markup is clean: a real <button> , a proper accessible name from its text content, an explicit type . Nothing to flag. The failure isn't in the button, it's in what happens after the click. And no static scanner ever clicks. What a scanner actually sees Static accessibility scanners evaluate the DOM at a point in time. Usually the initial render: HTML parsed, framework hydrated, nothing interacted with. They check that state against WCAG rules, missing alt text, contrast ratios, label associations, heading order. That's genuinely useful. It's also a photograph of a lobby, when the task happens in the hallways. Here's what never appears in the initial DOM of a typical booking flow: The date picker that mounts when the check-in field receives focus The error message injected after a failed form submit The room-selection modal that opens on "Check availability" The loading state between "Book now" and the confirmation A scanner reports zero issues on all of these, for the simple reason that at scan time, none of them exist. What an agent actually traverses An AI agent completing a booking doesn't evaluate a snapshot. It walks the flow: reads the accessibility tree, decides on an action, performs it, waits for the interface to respond, reads the tree again. Every state transition is a place where the tree can lie to it. Let's look at three patterns we keep finding in real audits. All three pass static scans. All three stop an agent. 1. The modal that exists on screen but not in the tree { isOpen && ( < div className = "modal-overlay" > < div className = "modal" > < h2 > Select your room </ h2 > < RoomList rooms = { available } /> </ div > </ div > )} Visually: a modal. In the accessibility tree: a div soup appended somewhere in the body, with no role="di