<div style="display:inline-block;-webkit-writing-mode: horizontal-tb;background-color:orange"> <div style="height: auto; -webkit-writing-mode: vertical-rl; background-color: red">asdf</div> <div style="height: 100%; -webkit-writing-mode: vertical-rl; background-color: green">asdf</div> </div> http://plexode.com/eval3/#ht=%3Cdiv%20style%3D%22display%3Ainline-block%3B-webkit-writing-mode%3A%20horizontal-tb%3Bbackground-color%3Aorange%22%3E%0A%20%20%20%20%3Cdiv%20style%3D%22height%3A%20auto%3B%20-webkit-writing-mode%3A%20vertical-rl%3B%20background-color%3A%20red%22%3Easdf%3C%2Fdiv%3E%0A%20%20%20%20%3Cdiv%20style%3D%22height%3A%20100%25%3B%20-webkit-writing-mode%3A%20vertical-rl%3B%20background-color%3A%20green%22%3Easdf%3C%2Fdiv%3E%0A%3C%2Fdiv%3E%0A When you resize the window, the outer div should change size. If you make it display:block, it resizes correctly when you resize the window.
It seems to look fine in Safari Technology Preview 172 and looks similar to Chrome Canary 116. @Alan - do we need to track it?