Enter exit

Enter and exit are one system, not two. Enters can afford to be noticed; exits should be quieter, because the user has already moved on. Use a small fixed translateY on exit rather than collapsing the full height, and ease-out in both directions. Interface state changes belong in CSS transitions, because a transition can be interrupted mid-flight; reserve keyframes for staged sequences that run once. An exit that blocks the next action is a bug dressed as polish.