I tested with “Don’t keep activities” on the emulator, and it definitely works to some degree on my real device because before I added support it wouldn’t take long in the background for the app to lose its current state.

Also, if I put the app in the background while navigated to a subscreen the same thing can happen (restarts at home screen eventually). So this seems to be independent of my own handling of saved instance state.

Android 12 BTW

This is the little test app I am now running on my 4a; I have it navigated to the subscreen and in the background. I will let you know what happens to it (I am expecting that after a while it will reopen on the home screen).

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            val navController = rememberNavController()
            NavHost(navController = navController, startDestination = "Home") {
                composable(
                    route = "Home",
                ) {
                    Column {
                        Text("Home Screen")
                        Button(onClick = { navController.navigate("Subscreen") }
                        ) {
                            Text(text = "Click to go to Subscreen")
                        }

                    }
                }
                composable(
                    route = "Subscreen",
                ) {
                    Text("Subscreen")
                }
            }
        }
    }
}

Overnight the app disappeared from Recents, and when I reopened it from its icon it started in its ”cold start” state. This does not seem to be a Compose issue though, since other apps on my phone do the same. I haven’t really found the pattern except it seems to only happen after long periods of not using the phone (which usually means only overnight).  Some apps survive, not necessarily the same ones from night to night, and I don't have to have a lot of apps open. I'll try to write something up and submit it. Thanks.

Issue I submitted: "Recent apps disappear and are not restored from saved instance state" https://issuetracker.google.com/u/1/issues/211580605