A container query on a component nobody had placed narrowly

A container query written in 2023 for a case that had never occurred, exercised for the first time in December.

.card-slot { container-type: inline-size; }

@container (min-width: 30rem) {
  .card { grid-template-columns: 8rem 1fr; }
}

/* two years, and every instance was in a wide column.
   the narrow branch had never rendered.
   in December somebody put one in a sidebar and it
   was correct on the first attempt. */

A branch that has never executed is a branch that has never been verified, and this one happened to be right — which is luck rather than evidence. The general lesson is to render both branches in the component gallery deliberately, because a container query has two behaviours and only one of them is exercised by the pages that exist.