Review finding MQ-36-01: a hidden first button was chosen as the initial focus target and as a Tab trap stop, so focus never entered the dialog. Filter out controls with a negative tabIndex, a hidden/aria-hidden/inert ancestor, display: none or visibility: hidden; on open, skip any control whose focus() does not take, falling back to the dialog panel. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>