How do you detect and prevent benchmark contamination, and why are public LLM leaderboards often inflated?

If a benchmark leaked into pretraining, the score measures memorization, not ability. The signal is the detection methods (n-gram overlap, canaries, perturbation tests) and why fresh held-out evals matter.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.