https://jsfiddle.net/xup8c9wg/1/ Working version on other browsers shows a full height teal rectangle. Adding `height: 100%` to `.parent` fixes the issue.
<rdar://problem/29464663>
I am not able to reproduce this bug in Safari 16.1 and it matches with other browsers (Chrome Canary 109 and Firefox Nightly 108) showing full teal rectangle on left side. Marking this as "RESOLVED CONFIGURATION CHANGED", please reopen if it is reproducible for anyone.