Yeah, this is a known issue on iOS — even if you wrap a BackdropFilter with ClipOval or ClipRRect, you'll still sometimes see a square blur behind your widget. That’s because Flutter applies the blur using a saveLayer, and on iOS, it doesn't fully follow the clipping shape when compositing that layer. So even though your widget looks round, the blur gets painted as a full rectangle behind it. It’s a rendering quirk on iOS (see issue #115920), and for now, the safest workaround is to skip BackdropFilter on iOS and fake the glass effect using semi-transparent colors, light borders, and a bit of shadow.