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Agent LighthouseAgent Lighthouse

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    operability-safety/drag-and-slider-dependency

    Gesture-only controls with no discrete alternative

    What it checks

    Flags controls whose only operation path is a continuous pointer gesture, with no click, keyboard or typed-value alternative beside them. Five cases are reported:

    • a range slider with no numeric input or select in the same field group;
    • a role="slider" with no aria-valuenow, aria-valuemin, aria-valuemax or accessible name;
    • a draggable list with no move buttons or position select, on a cart, checkout, builder, configure or order URL only;
    • a drop zone with no <input type="file"> inside or beside it;
    • a carousel with swipe handlers and no next or previous button.

    Only the reorder case is limited to transaction paths. The other four are checked on every scanned page. No slider, draggable list, drop zone or carousel on the scanned pages is not applicable. Any finding fails.

    Why it matters

    Falsifiable claim: continuous pointer gestures require an agent to synthesise a pointerdown, a sequence of intermediate pointermove events, and a pointerup at a computed pixel offset. There is no feedback loop between steps, and no way to verify the interim value. Every other agent action is discrete and verifiable. WebSuite measures slider interaction at 0% success for both agents tested — the single worst primitive in its taxonomy — and Anthropic separately documents scrollbars and dropdowns as tricky under mouse control, recommending keyboard shortcuts instead. Test: pair the slider with a numeric <input> bound to the same value; the agent’s success on ‘set max price to 300’ goes from 0 to near-certain because it becomes a fill action.

    Evidence

    • WebSuite: Systematically Evaluating Why Web Agents Fail — arXiv (study, URL verified 2026-10-17)
    • Slider interaction succeeded 0% for both agents tested, natbot and SeeAct, over 32 trials. No other interaction in the study’s table scores lower. Date and select inputs, which take a discrete value, scored far higher.
    • Computer use tool — Anthropic (vendor-doc, verified 2026-10-17)
    • “Some UI elements (such as dropdowns and scrollbars) might be tricky for Claude to manipulate using mouse movements. If you experience this, try prompting the model to use keyboard shortcuts.”
    • Understanding SC 2.5.7: Dragging Movements — W3C WAI (spec, verified 2026-10-17)
    • WCAG 2.2 at level AA: “All functionality that uses a dragging movement for operation can be achieved by a single pointer without dragging”, unless dragging is essential. The fixes it names are the ones this audit looks for: “an input beside a slider could allow any user to enter a precise value”, and forward and backward buttons on a carousel.
    • Playwright — locator.setInputFiles() — Microsoft (vendor-doc, verified 2026-10-17)
    • setInputFiles “expects Locator to point to an input element.” A drop zone with no file input gives an agent nothing to set files on.

    How it scores

    Tier per evidence policy: scored — grade B meets the A/B bar required for scored audits.

    Grade: B — strong empirical measurement. WebSuite measures slider interaction at 0% for both agents tested. Anthropic documents the same weakness for mouse-driven controls. WCAG 2.5.7 names the discrete alternatives, but it is an accessibility requirement with no documented agent consumer, so it does not lift the grade to A.

    Example finding

    A hotel search gates results behind a dual-thumb price range slider (two divs with no role and no aria-value*) and a drag-only date range. Asked to find rooms under 200 EUR, the agent has no readable current value, no keyboard path and no numeric input. It drags approximately, and cannot read where it landed. It returns results for the wrong range, while asserting the filter was applied.

    Sources