ArrangementView
Props
Give the arrangement a bounded size, usually flex: 1. The platform determines whether a split is appropriate; an axis restriction does not force two panes to stay visible.
The component adds no safe-area padding. Place it within the safe area supplied by your screen/navigation container, or handle insets in your content.
ArrangementView.Primary / ArrangementView.Secondary
ArrangementView.Primary and ArrangementView.Secondary are slot markers: they render no view of their own and do not affect layout. Put your own pane component inside each one. Both must be direct children of ArrangementView, in either order. Any other direct child is ignored, and a missing, duplicated, or unrecognized child logs a warning in development builds.
Give each pane's root flex: 1 to fill its assigned space.
In overlay mode the primary is in front of the secondary. Use a transparent primary background and pointerEvents="box-none" on its full-size React wrapper for floating controls; its visible controls can still receive touches. Hiding a pane does not unmount its React tree.