(I couldn't find a list for "Frontend standards group" and I'm not sure if all its engineers are on the design list.)
I congratulated James_F on IRC for VisualEditor/ OOjs UI adopting the mediawiki.ui style, but then it went topsy-turvy:
*spagewmf* I missed that VisualEditor is now using the mediawiki.ui style formerly known as "Agora" *James_F* No, we are not. Agora and MediaWiki.ui are both previous designs. This one is different, apparently. Don't ask me how. :-) It's mostly similar, at least. It's the MediaWiki Theme for OOjs UI.
*spagewmf* How is WMF keeping the "simple" mw-ui-button mw-ui-constructive and OOjs UI's more elaborate oo-ui-widget > oo-ui-buttonElement oo-ui-flaggedElement-constructive CSS in sync? Are we able to share LESS rules? *James_F* MW UI isn't being kept in sync with the new design, I believe. I don't think it's credible to try to marry the technologies together with shared files – it'd be a huge amount of work for a short-term hack.
*spagewmf* The mw-ui- classes are a lot easier for humans to grok/reuse, e.g. https://en.wikipedia.org/wiki/Template:Clickable_button It could be very cool for pages to have OOjs UI gadgets someday. *James_F* Well, tough. :-) MW-UI won't be around for much longer.
How soon is "short-term" and "not much longer"? It's less than a year since mediawiki.ui.button made it into the default set of page modules and the Living Style Guide http://tools.wmflabs.org/styleguide/desktop/section-2.html appeared. Are devs going to continue working on $wgUseMediaWikiUIEverywhere to deliver UX consistency?
I understand the approach espoused by the Frontend standards group https://www.mediawiki.org/wiki/Frontend_standards_group is "use OOjs UI https://www.mediawiki.org/wiki/OOjs_UI components" and I'm excited to see Bartosz prototyping the UserLogin form in oojs-ui/php. But it'll be a long time before the 15 extensions using mediawiki.ui have all transitioned to OOjs UI.
I look forward to the "Frontend standards" session at the developer summit. “The future has arrived — it’s just not evenly distributed yet.”
Cheers, -- =S Page WMF Tech writer