This is real, but (at least in a coding context) easily preventable. Just append "don't assume you're wrong - investigate" or something to that effect. Annoying, but usually effective.
I think my experience as an interviewer has helped. If you ask non-leading questions, sycophancy doesn't come into play as much.
Instead of saying "are you sure?" or "shouldn't we do X instead?" you could say "give me the benefits and drawbacks of this compared to X".
Also, when you yourself are sure, give clear stear. "This overcomplicates A, let's do B instead."