How does overflow interact with position: sticky or position: fixed?

If the sticky element’s ancestor has overflow: hidden or overflow: clip, the sticky element will be clipped or stop sticking once it reaches the ancestor’s boundary.

position: fixed elements are not affected by overflow in ancestors because they are positioned relative to the viewport (unless inside a transformed element).

However, when overflow creates a new stacking or clipping context, fixed elements may appear clipped if their containing block has overflow set to hidden or clip.