Note grepping for toast.showOnPageReload you'll find it is present in http://en.wikipedia.beta.wmflabs.org/w/load.php?debug=false&lang=en&modules=mobile.editor.api%2Ccommon%2Coverlay&skin=minerva&version=da39a3ee5e6b&* but mobile-pending-toast isn't
The inverse is true for http://en.wikipedia.beta.wmflabs.org/w/load.php?debug=false&lang=en&modules=mediawiki.confirmCloseWindow%7Cmobile.abusefilter%2CmicroAutoSize%7Cmobile.editor.api%2Ccommon%2Coverlay%7Coojs-ui%7Coojs-ui.styles%7Coojs-ui.styles.icons%2Cindicators%2Ctextures&skin=minerva&version=da39a3ee5e6b&* despite version being the same.
Basically different code is being loaded for 2 urls for unknown reasons. This is breaking mobile browser tests by serving incompatible code.
Maybe caused by the fix for T94074 ? I don't understand enough of this stuff to debug any more but please let me know how I can resolve this.