If I run bin/puma, I'd like it to auto-detect and use config/puma.rb to configure and boot Rails. I'm trying to reduce development friction as much as possible, making the command as easy as possible to start. Running bin/rails makes WEBrick easy but we want to test locally with puma where possible. This will make puma one character simpler than WEBrick, thus winning the battle of the development servers. QED