title

This has container-type: inline-size set. In older browsers, the bubble's z-index should not work, because a stacking context is created, so it should be covered; in newer browsers it should be on top.

This has contain: layout set. The bubble's z-index should not work, because a stacking context is created, so it should be covered.

This has nothing set. The bubble's z-index should work and it should be on top.