reportBackStack

Reports a back stack the app owns itself, rather than one androidx holds.

Navigation 3 has no NavController to hook: the back stack is a snapshot list belonging to the app, so there is nothing for the tool to discover and it has to be handed over. live.gravitylabs.porthole.compose.PortholeBackStack is the ergonomic way in; this is what it calls.

Safe to call on every change. A repeat of the current destination is dropped, so recomposition does not fill the lane with duplicates.