Use this when the question is whether the site actually WORKS for a keyboard-only or switch-device user — tab order, focus traps, whether the focus ring is visible at all — which no stored scan and no static markup check can answer. Run it before claiming keyboard accessibility for a page, and again after deploying any tab-order, focus or skip-link fix. It tabs through the page the way a keyboard-only user does and reports what breaks: focus traps, elements with no visible focus indicator, focus hidden behind sticky headers, controls that cannot be reached at all, controls that ignore Enter and Space, and tab order that contradicts the visual or document order. Focus indicators are measured by comparing rendered pixels rather than CSS, because indicators come from outline, box-shadow, border and background alike. Findings carry a confidence: the order rules in particular are nudges for a human to confirm, not assertions. A focus-obscured finding names the element doing the covering, once per occluder, and counts distinct covered elements — with stops carrying the tab-stop total when the ring revisits them. A focus-trap finding that may be an open modal behaving correctly says so and says what to check by hand. The response states the viewport the walk was performed in, because the obscured and offscreen results are geometry, and endedBy says which of three things stopped the walk: the ring closing ("ring-closed"), the step ceiling ("max-steps") or the run's time budget ("time-budget"). Only the first means the ring was fully walked. Each finding's selectors array holds up to 5 examples, with count the true total and selectorsTruncated set when more were cut; full: true returns them all from the stored run. A run that lands on a bot-protection interstitial rather than the page is reported as void, never as clean, and a void run carries no stops or findings at all. Where the interstitial title is contradicted by the walk itself, the run stands and carries challengeSuspected instead: trust the walk, not the title. Read-only.