ToolbarItem flickers when switching between tabs in iOS 26

How can I avoid the flickering ToolbarItem when switching between tabs, while still keeping a dedicated NavigationStack for each Tab?

I have unsuccessfully tried:

• Nesting the TabView inside another NavigationStack, but that seems to be a bad idea and also breaks switching to a different tab while having a detail view open
• ToolbarItem(id: "SomeId") for both buttons changes nothing
• Adding a .background(.red, in: .capsule) works for the inside of the button, but there's still a border around it that I can't get rid of
• .buttonStyle(.plain) does nothing

struct MyTabView: View {
    var body: some View {
        TabView {
            Tab {
                MyNavStack()
            } label: {
                Image(systemName: "house")
            }
            
            Tab {
                MyNavStack()
            } label: {
                Image(systemName: "star")
            }
        }
    }
}

struct MyNavStack: View {
    var body: some View {
        NavigationStack {
            List {
                NavigationLink("Mint", value: Color.mint)
                NavigationLink("Pink", value: Color.pink)
            }
            .navigationDestination(for: Color.self) { color in
                Text("You selected \(color.description)")
            }
            .toolbar {
                ToolbarItem(placement: .topBarLeading) {
                    Button("Flickers") { }
                }
            }
        }
    }
}

It seems that the flickering is coming from the "shared background" around the toolbar button.

The flickering can be prevented by hiding the shared background:

ToolbarItem(placement: .topBarLeading) {
    Button("Flickers") { }
}
.sharedBackgroundVisibility(.hidden) // 👈 here

However, when this is done, the button no longer looks like a glass button.

You can get it back to a similar appearance by applying a glass button style. It is also necessary to apply .fixedSize, otherwise the button is round and the label is truncated:

ToolbarItem(placement: .topBarLeading) {
    Button("Flickers") { }
        .fixedSize() // 👈 here
        .buttonStyle(.glass) // 👈 and here
}
.sharedBackgroundVisibility(.hidden)

This is close to the appearance that it had without the modifiers, but the button is just a bit smaller.

For better control of the appearance, you can use a custom ButtonStyle:

struct GlassCapsuleButton: ButtonStyle {
    func makeBody(configuration: Configuration) -> some View {
        configuration.label
            .fixedSize()
            .padding(11)
            .contentShape(.capsule)
            .glassEffect(.clear.interactive(), in: .capsule)
    }
}

As a convenience, a ButtonStyle extension can also be defined:

extension ButtonStyle where Self == GlassCapsuleButton {
    static var glassCapsule: Self { Self() }
}

Applying the custom button style:

ToolbarItem(placement: .topBarLeading) {
    Button("Flickers") { }
        .buttonStyle(.glassCapsule) // 👈 here
}
.sharedBackgroundVisibility(.hidden)