[mcv]

Adding a parameter that has a sensible default value? I don't think I'd want that to break anything.

[Klonoar]

The inverse here - specifying {} directly - does not at a glance imply a default value is being constructed.

(Or perhaps it does and this is just some Ruby-ism I'm not exposed to)

[andolanra]

That's kind of the point of default values, though. If you wanted to make a change to the method and you want it to break to alert you to all the calls, then you can add a keyword without adding a default value for it.

    def foo(kwargs = {}, frob:)
      kwargs
    end