SwiftUI sheet: background appears above the sheet when using .presentationDetents (iOS 26 regression)

I’ve encountered what appears to be a SwiftUI rendering bug on iOS 26+ when using .presentationDetents.

When I present a sheet normally, any SwiftUI background (even a simple Color.clear or .background(Color.red.opacity(0.5))) correctly appears behind the sheet.

But the moment I add:

.presentationDetents([.medium])

…the exact same background starts rendering above the sheet, even though:

This feels like a regression in SwiftUI’s detent-sheet.

Minimal reproducible example

struct LoginScreen: View {
    @State var show = false
    
    var body: some View {
        ZStack {
            Color.red.opacity(0.3)      // should stay under sheet
            Button("Show") { show = true }
        }
        .sheet(isPresented: $show) {
            Text("Sheet")
                .presentationDetents([.medium])   // ← adding this causes incorrect stacking
        }
    }
}

Expected Behavior**

• The red background should remain behind the sheet.

• This is the case in iOS 18.5 / 18.6 and earlier versions.

• This is also the case as long as .presentationDetents is not used.

Actual Behavior

• On iOS 26.0 / 26.1, when .presentationDetents is applied, the root background (and overlays) draw above the sheet.

• This happens even in the simplest ZStack setup.

• .zIndex does not fix the issue.

• .overlay exhibit the same incorrect ordering.

Environment

Is this a known regression with .presentationDetents behavior on iOS 26?
Is there a workaround that keeps the sheet above the app’s root backgrounds?

Any insight appreciated.