Created attachment 244760 [details] Example to reproduce the issue First bug #140541 should be fixed, but this issue was present before and it's still present in Blink (https://code.google.com/p/chromium/issues/detail?id=449481). Example (attached) to reproduce the issue ("Green" should be green and "Black" should be black): <style> .first-line-green::first-line { color: lime; } .flex { display: flex; } </style> <div class="first-line-green"> <div class="flex"> Black </div> Green </div> The flex is ignored as expected, however it doesn't go to the next element (like in the case of floated/positioned elements). BTW, the same happens for grids. From the spec (http://www.w3.org/TR/css-flexbox-1/#flex-containers): "the ::first-line and ::first-letter pseudo-elements do not apply to flex containers, and flex containers do not contribute a first formatted line or first letter to their ancestors." Also a mail from CSS WG mailing list confirming the expected behavior: http://lists.w3.org/Archives/Public/www-style/2014Dec/0305.html
As of right now, all browsers (Safari 16.1, Chrome Canary 109 and Firefox Nightly 108) and does not have any lime color for first line and they are matching each other. But I think if it is an issue, we should keep it open and also put it on Radar. I will leave for others to comment. Thanks!