IssueTracker

I'd like to add that this automatic removal of the NavGraph at the top of the stack is also making it hard for me to implement proper lateral top-level navigation.
A practical case where this kind of navigation happens is with a Material Design bottom navigation bar, where I have a NavHost above the bottom bar.

Given this navigation scheme:
A - B   (top-level)
     B1 (first sub-level)

When starting the Activity, the back stack is
0. A
1. NavGraph

If I wanted to navigate to B laterally, I would do:
navController.popBackStack(R.id.navGraph, false)
navController.navigate(R.id.B)

But the resulting back stack is:
0. B

Now, navigating between top-level destinations actually works (though popBackStack returns false); the problem arises again if I navigate to B1:
0. B1
1. B

When navigating from B1 to a top-level destination like A, the stack becomes:
0. A
1. B1
2. B

That is, A is not a top-level destination in the back stack: if I press back from A, I intend to exit the app, but I'm taken back to B1.

It would be nice to have a fixed reference to the bottom of the stack. Right now I'm working around this with a horrible ` while (navController.popBackStack()) continue`.