Created attachment 460957 [details] the html source code of the reduced test case When a <dialog> element has its height set to 'fit-content' and its child has its height set to '100%', the child is rendered with a height of 0px. Visit https://dialog-fit-content-style.glitch.me/ for a demo
Created attachment 460959 [details] testcase without dialog
<rdar://problem/97492632>
Still reproducible in WebKit ToT (268538@main). Since only reproducible in WebKit, marking this as 'BrowserCompat'. Firefox Nightly 120 and Chrome Canary 119 match each other.