Oh most definitely. I don’t want my players to fail (if I can help it) and generally try to reward creative thinking, but also want their victories to be earned and not just fudged rolls or suddenly dumb NPCs.

I think where the line gets crossed is when they’re doing actions their character would never do, or they’re trying to poke holes in the set without a clear goal. I usually ask additional questions to see what they expect to happen (in case they are playing 4D chess), but sometimes they’re just trying to cause chaos, in which case I got to pull them aside and give them the talk.