Not sure if everyone will share my definition, but I wouldn’t call this monkey-patching. Yes, it is dynamic addition of methods at runtime, but almost everything in Ruby is runtime, including method definition in the common case. So I reserve the term for when one library intrusively (and often globally) modifies the behaviour of another, i.e. some clear sense of a control boundary being crossed, which is only slightly less technical because we can still denote clear boundaries. And in this case it looks like intentional (albeit naive) behaviour within the library in question.