html – CSS container inline-size and glued youngster

It is a tough mockup from my undertaking. The mother or father has a container question, whereas the kid is supported to be mounted (ocasionally). If mother or father has container question inline-size, youngster is now not mounted to web page.

Can this behavour be prevented? I notice if I apply inline-size to youngster as an alternative of mother or father, it appears to work, however I’m looking for an answer to have inline-size on mother or father if potential.

.mother or father {
  place: relative;
  top: 150px;
  background: #eee;
  max-width: 300px;
  container: dialog_data / inline-size;
}

.youngster {
  background: purple;
  top: 100px;
  high: auto!necessary;
  place: mounted!necessary;
  z-index: 2147483648;
  backside: 20px!necessary;
  left: 20px!necessary;
  margin: 0!necessary;
  width: 100%;
  box-shadow: 0 0 10px rgb(0 0 0 / 50%);
}