Copying from gerrit review (since it's a post-merge review). I need to come up with a workable solution (doesn't have to restore wgMFMode, but needs to determine from javascript if minerva is active) before the branch cut on march 1st.

https://gerrit.wikimedia.org/r/#/c/268333/ looks to have changed when wgMFMode is sent to the users browsing session. Previously, from javascript, mw.config.get('wgMFMode') === null unless you are using the Minerva skin. After this patch wgMFMode is set for all pages regardless.
The issue here is that, because search is so different in mobile, we exclude it from the general search satisfaction schema. This exclusion is done by checking wgMFMode.
Could this be adjusted such that the old behaviour is retained, and wgMFMode is only set for the minerva skin?
For reference try mw.config.get('wgMFMode') on http://en.wikipedia.beta.wmflabs.org/wiki/Main_Page, https://test.wikipedia.org/wiki/Main_Page, and https://test.wikipedia.org/wiki/Main_Page?useskin=minerva

• wgMFMode should only be present in mobile mode e.g. when useformat=mobile. This should also apply to http://en.m.wikipedia.beta.wmflabs.org/wiki/Headings?useskin=vector
• wgMFMode should not be present in the desktop version of Minerva http://en.wikipedia.beta.wmflabs.org/wiki/Headings?useskin=minerva