I've encountered an issue with the .fullScreenCover(isPresented:) modifier in SwiftUI while testing on iOS 18 beta. Previously, when presenting a full-screen cover, the background was opaque with a default white color. However, in this beta version, the background now appears to be transparent by default. This unexpected transparency is causing underlying views to be visible through the full-screen cover, which disrupts the intended user experience. To achieve the previous behavior, developers now need to manually set a background color, which was not necessary before.