popolon reports on irc that links like [[zh:wikisource:Foo]] do not work (Those types of links resolve to pages like http://zh.wikipedia.org/wiki/wikisource:foo, which should in turn http redirect to wikisource)
Expected behaviour: [[zh:wikisource:foo]] goes to https://zh.wikisource.org/foo
Actual behaviour: [[zh:wikisource:foo]] goes to https://en.wikisource.org/foo
Links of the form [[zh:s:Foo]] still work as expected.
popolon is quite sure that the [[zh:wikisource:Foo]] links worked as of Feb 8 as he made the edit at https://fr.wikipedia.org/w/index.php?title=Ge_Hong&diff=prev&oldid=101057358 , and wasn't sure how interwiki links worked so tested his edit carefully.
Based on http://pastebin.com/raw.php?i=suk6eGzF, there are 288 links on fr.wikipedia.org that are based on this assumption about how interlanguage interwikis work. There's also a further 1671 pages using [[wikisource:]] style links, which now link to the wrong project.
I don't see anything relavent in any apache config changes, mediawiki config change, or WikimediaMaintenance extension. [[meta:interwiki map]] links wikisource: to en.wikisource.org, but its done that for a while, last interwiki cache update was appearently jan 15. I think it is quite possible that interwiki map was being overriden somewhere in our complex system of interwiki links.
Version: unspecified
Severity: enhancement