"I want the text to will the whole available width"
->
"I want the text to fill the whole available width"

Safari/WebKit report:
https://bugs.webkit.org/show_bug.cgi?id=183209

Edge report:
https://developer.microsoft.com/en-us/microsoft-edge/platform/issues/16146968/

Thanks for the bug report, please next time try to create a reduced test case
(https://css-tricks.com/reduced-test-cases/).

I've been investigating it and I'm attached a much smaller example reproducing the issue.
The difference with Firefox is because the size of item in Firefox is 150px,
so the word is not wrapped.
While in Chrome it's 100px and the word is wrapped.

In the original example the problem was that in Firefox the item was bigger than 1200px
while in Chrome it was not.

I believe this is a duplicate of #786899, which we haven't fixed yet
as we're discussing it at CSSWG: https://github.com/w3c/csswg-drafts/issues/2177

Deleted: bug-817329.html 275 bytes

bug-817329.html 275 bytes View Download

> please next time try to create a reduced test case

As long as I have to use unpaid time, reporting the respective issue (including steps for reproducing, screenshots, the code restructured to work standalone/locally eg as zip, any additional requested info etc) and tracking progress for all the (currently 12) reported bugs is all I can do. I hope it's sufficient, and I hope it's appreciated - even without reduced test-cases.

Perhaps I should switch to reporting just security issues where there are bug bounty programs 😀 Seriously though, I hope that browsers will become less and less buggy (through reports and through shared web-platform tests etc), and I thoroughly appreciate all your work towards fully implemented and correctly working Grid in several(!) browsers.  (also, the work of Igalia etc)

Regarding this here issue:

Thanks for investigating! I hope that my background cell / background text can fill the whole available width soon.

I can't reproduce this anymore (in Chrome 65) - somehow this has been fixed it seems?

Nevermind - when I follow my steps using the stable code (the zip attached to this bug ticket) the issue is still there: the text breaks.