Maybe it was this ticket in September?

https://phabricator.wikimedia.org/T146686

I’ll try to get a full stack trace later today when I have access to the wiki again.

DanB

From: Wikitech-l [mailto:wikitech-l-bounces@lists.wikimedia.org] On Behalf Of Alex Monk Sent: Monday, December 19, 2016 9:38 AM To: Wikimedia developers wikitech-l@lists.wikimedia.org Subject: Re: [Wikitech-l] VisualEditor in 1.28 - fails after upgrade from 1.27

I feel like that sessions error was something we fixed months ago but can't find details right now. Certainly not the first time I've seen it...

...

BadMethodCallException from line 845 of <...>/w/includes/session/

SessionManager.php:

...

Sessions are disabled for this entry point