Scroll Area

Brutalist Scroll Area preserves the Base host-owned scrolling surface, normalized viewport facts, orientation, and resolved projection. It prefers composed chrome and adds rounded paper surfaces plus high-contrast Lavender/ink controls. A family-level host session continuously derives Thumb size and position from actual scroll facts and maps pointer dragging on the Thumb back to normalized scroll requests. Grabbing the Thumb does not create a second scroll state or make it an independent focus/ARIA control. Track-page presses and full Drag and Drop remain outside the current passing guarantee.

Use it for ChatUI conversation history, conversation lists, command results, logs, and dense SaaS panels. Surrounding layout must give Root an explicit size. The reference demo keeps the 12rem height and caps its responsive width at 20rem, preserving the desktop composition while keeping the complete Root and visual scrollbar inside phone preview frames.

In the Web composed projection, the two tracks reserve a lower-right intersection that contains neither track nor Thumb. A missing or display-hidden opposite track releases that space; a track without overflow retains its authored surface while its Thumb hides. This is host-local presentation, not a separate Corner control. The horizontal Scrollbar paints this reserved area with a private pointer-inert lavender surface and structural borders. A zero reservation clips that paint completely; the public family stays Root, Viewport, Scrollbar and Thumb.