Thread:Project:Support desk/Lessc issue with MW1.25alpha (40a8070) -- Vector Skin (fd9a9f0)/reply

That's why it's not a good idea to use git master in production :) With lessc isn't included in mediawiki core anymore. If you don't install MediaWiki via a tarball installer, you need to install the vendor dir with   or you clone the mediawiki/vendor repo: