@evanphx Oh duh. I stopped searching after the first instance of nio4r found (top level) and didn't make it to celluloid requiring it.

How can I tell which gem in my Gemfile is requiring a specific gem (eg, nio4r)?

It’s an I-Spy kind of day.

https://youtu.be/dWGISTUyV7k

Whiskey Tango Foxtrot is amazing.
Full stop, go see it.

Today I found one of those “how did this to ever work?” bugs in production.