Sure, but when I said a puzzle
I was thinking of something more abstract, like software development getting solved. To be nitpicky, I'd say without a mind to pose a question nothing in the material world by itself is a puzzle. It's just some cardboard or wood with no meaning. When the last person who can read is gone, is a book still a book? My knee-jerk reaction to "does a falling tree make a sound with nobody around to hear it" always was of course it does, what a stupid question. And it sure produces pressures waves in the air, but are those "sound" without anything to consider them such?
> But that further raises the question: how do you know it's the riddle you're looking for? How do you know what riddle you're looking for if you don't know the riddle itself?
Yeah, I was just gonna say. E.g. you ask "Is the riddle in this book?" and it replies "Which one? Specify the riddle."
Maybe with just a bit more technology though.. e.g. something that scans you and the whole world, to find out all riddles that exist, and what sort of riddle you probably would like to eliminate, if you were aware of it. It destroys those riddles, and then itself.
Since we're just riffing in the middle of nowhere anyway: I think it might be an arms race between finding the riddle that destroys the crazy (making) machines, and the machines destroying the ability to come up with riddles first. It might actually already been written how this'll play out roughly:
> Eddie eventually stumps Blaine with unsolvable "riddles" that are actually stupid jokes from his childhood. This forces Blaine to try to "lower" his intelligence to levels necessary to answer, which ends up driving him completely insane and causes his computer to crash. Eddie then proceeds to shoot the computer