A sticky action bar needs viewport-level verification in the real application shell

A sticky action bar needs viewport-level verification in the real application shell: passing an isolated component test does not prove it stays reachable. Ancestor overflow containment can change the sticky scrolling boundary. When a page only needs horizontal clipping, a narrowly scoped overflow-x:clip can preserve the viewport sticky boundary while the wide table retains its own horizontal scroller. Verify page overflow, actions before and after scrolling, and keyboard access; do not globally change shared wrappers without checking other routes. Full-page screenshots alone can also misrepresent fixed elements after scrolling, so capture viewport screenshots.