Container tabs not confirming any more

I have been using container tabs to juggle my corporate and personal github accounts. Until very recently, clicking a link from another app (email, etc) would start to open a new tab and then pop up a dialog asking me to confirm which container to use (see first attachment). Unfortunately, now when I click on links it just loads straight to my "OSS github" container, which naturally produces a 404 error because my personal github account doesn't have access to the corporate repo (see second attachment). At first, I thought I had accidentally clicked the "remember my decision" box. But the confirmation dialog still works if I open a new tab and paste the link in the address bar. It just doesn't work when other apps try to open a link in Firefox. Is the new behavior intentional? Or did something accidentally break?