The base rule declared --scroll-shadow-size as var(--scroll-shadow-size,
48px) — a self-referential cycle, which computes to invalid and silently
resolves every mask below to none. The old ScrollShadow component masked
the bug by setting the variable inline; the hook-based path (the chat
scroller) sets only the data attributes, so the chat lost its top and
bottom scroll fades. A concrete 48px default restores them; inline
overrides from the component still win.
Bohdan Triapitsyn
043e71d725