Resolve at event handling time: a native callback may have queued a shell before the module’s replacement event updated the pending destination.

Capture the old page, then commit the destination route through ordinary events. Initial hydration, query changes, and unsupported browsers need no snapshot.

Position an already committed destination and release its incoming capture. Called by the page’s layout effect, including when it contains only a shell. Never schedule an animation frame inside a native transition’s update phase.

Keep a pending native callback current when its module finishes first.

Follow a committed component while ancestor rows, code or fonts settle.

Restore against committed layout, releasing only after mounted code/data, layout-affecting images/fonts and two measured frames agree on the target. User input/navigation cancels immediately; the timeout only bounds failure.

Supersede pending page work while retaining the already mounted host.

Complete navigation after React commits the subscribed route and its shell. Releasing a height reservation must not replay scrolling or route completion.