The rails console command only accepts two flags --environment and --[no-]sandbox. However, the rails console is built on top of IRB and Ruby, so it can accept flags that those commands understand.

You can't pass an IRB flag directly to rails console though because it doesn't consider those part of its repertoire.

$ rails console --sandbox -r './vendor/setup_records.rb'

It will put the session in sandbox mode, but it doesn't know what to do with -r. We have to explicitly separate its flags from flags that should be passed through. This is done with the -- CLI convention.

$ rails console --sandbox -- -r './vendor/setup_records.rb'

Everything after the -- gets passed along to IRB.