A benchmark score is trustworthy only if the model hasn't seen the answers and no one has optimized directly for the test. Both assumptions fail constantly. Training data contamination inflates scores by rewarding memorization; optimizing for a benchmark turns it from a measure into a target and destroys its meaning. This post is about the ways evaluation gets corrupted — and how to defend against them.
A benchmark score is trustworthy only if the model hasn't seen the answers and no one optimized directly for the test — and both assumptions fail constantly. Training-data contamination inflates scores by rewarding memorization; optimizing for a benchmark turns it from a measure into a target. Here's how evaluation gets corrupted, and how to defend it.
The scores that dominate model announcements — MMLU, GSM8K, HumanEval, and the rest — are benchmarks: standardized public tests that let the whole field compare models on common ground. They've driven enormous progress, but a benchmark is only as good as its design, and a number without understanding of what it measures is easy to misread. Knowing how benchmarks are built, and what makes a good one, is how you read a leaderboard critically instead of credulously.
The scores in model announcements — MMLU, GSM8K, HumanEval — are benchmarks: standardized public tests for comparing models on common ground. They've driven huge progress, but a benchmark is only as good as its design, and a number without understanding is easy to misread. Here's how they're built and what makes a good one.
How a single sprint of specialty-rule work — guided by a benchmark that wasn't afraid to print embarrassing numbers — turned a 'demo respiratory differential' into a five-condition rule-based diagnostic engine.