On both devdocs and stable, when I include "codex" in the search I get no results
https://matplotlib.org/devdocs/search.html?q=stem+codex
https://matplotlib.org/stable/search.html?q=stem+codex

There is no problem for v3.9
https://matplotlib.org/3.9.3/search.html?q=stem+codex

or indeed for v3.10 if I explicitly use that url
https://matplotlib.org/3.10.0/search.html?q=stem+codex