I should note that even stranger behavior arises when adding a third tab. Here's a new version of the file: struct ContentView: View { var body: some View { TabView { Tab("Tab 1", systemImage: "document") { NavigationStack { VStack { Text("Tab 1") NavigationLink("Load Detail") { VStack { Text("Detail View") }.toolbarVisibility(.hidden, for: .bottomBar, .tabBar) } } } } Tab("Tab 2", systemImage: "map") { NavigationStack { VStack { Text("Tab 2") } } } Tab("Tab 3", systemImage: "heart") { VStack { Text("Toolbar entirely hidden") }.toolbarVisibility(.hidden, for: .bottomBar, .tabBar) } }.tabViewBottomAccessory { Button("Action") {} } } } This third tab contains a no-navigation stack view that simply hides the tab bar ( admittedly, this is somewhat nonsensical, but just showing the issue ). Upon clicking on this third tab, the tab bar disappears momentarily, then returns. When you navigate to another tab, then the tab bar disappears permanently. If you follow this sequence of steps: Open app Navigate to third tab Observe tab bar disappear Observe tab bar reappear Navigate to first tab Observe tab bar disappear Click on detail link Observe tab bar remains hidden Click on "back" Observe tab bar reappear This seems to indicate there might be two bugs at play: Tab bar / bottom bar visibility should affect the tab view bottom accessory, and does not When changing tab bar visibility from a contained view, the setting is not correctly respected across tabs

Thanks very much for the advice!

I've temporarily worked around this issue by adding an ObjC extension to NSProxy: @interface NSProxy (Plane) -(id) plane; @end @implementation NSProxy (Plane) -(id) plane { return nil; } @end which allows the app to continue initializing as normal. While breakpointing in that shim code, I also found the suspect caller in the breakpoint: I'm not quite sure what MRUIPlacementTargetFromAnchoringTarget is, and also, I do not currently have any anchors in my RealityView scene, so I suspect there might be some expectation that my older code is not meeting? Hopefully if this is a new expectation, that future exceptions might be a bit more self explanatory about what is required on behalf of the application.

Thanks for confirmation.