If you've ever wanted to add an interface to a codebase and gotten pushback, you already know the argument: "That's twice the code for the same thing." And honestly? It was a fair point. You'd write the contract — the interface, the abstract class, the protocol — and then write the implementation. Two files where one would do. That's more surface area, more indirection, and more to maintain. The Ruby and Rails communities built an entire philosophy around this: convention over configuration, less ceremony, fewer keystrokes. If the framework could infer your intent, why spell it out? Then AI happened. I was recently chatting with a CEO about what current-generation software engineers get wrong, and he put it cleanly: "Abstract interfaces were challenging a few months ago just because it required twice as much code. But with AI, lines of code are free. The reason we still need such constructs is because at some point a human still needs to look at the code.…