Is regex multiline supported?

I’m apparently not able to get the multiline functionality of a regex to work when the regex is applied by CodeMirror (this is using CodeMirror via LightTable’s search-and-replace functionality). On this LightTable issue, it is commented that “Internally, Light Table uses CodeMirror for searching and its code isn’t specifying the multiline flag for regexes”.

Is regex multiline supported in CodeMirror? If not, is that a missing feature, a bug, or something not desired?

Nope, CodeMirror stores its lines as separate strings, so running a multi-line regex on it is not supported (it’d have to either implement its own regex engine, or concatenate all the lines together every time it wanted to run a match, neither of which seem acceptable).