On a hard refresh the TOC sidebar occasionally (~1 in 10) scrolled to and
highlighted the current chapter, then rewound to the very top of the list.
It is a scroll-position race in TOCView, not a progress/sectionHref reset (the
reading position stays correct throughout). OverlayScrollbars resets the wrapped
Virtuoso viewport's scrollTop to 0 when it initializes (deferred). Its
`initialized` callback re-scrolled only to `initialScrollTarget.index`, captured
at mount — and on a fresh refresh `progress` is not available yet, so that index
is 0 and the reset is never corrected. Whether OverlayScrollbars initializes
before or after the auto-scroll to the reading position is the timing race that
made it intermittent.
Re-apply the scroll to the current active item (via refs mirroring the live
flatItems/activeHref) in the `initialized` callback, falling back to the
mount-time index. Refs are used because OverlayScrollbars binds the callback at
mount and fires it later, so it must read the latest active item.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Huang Xin
6405ba31c8