The Two Sources of Noise Every LLM Evaluation System Must Handle

Home Articles The Two Sources of Noise Every LLM Evaluation System Must Handle The Two Sources of Noise Every LLM Evaluation System Must Handle July 22, 2026 · 4 min read · Tags: #llm #testing #evaluation #reliability #architecture Traditional tests are binary. LLM evaluations are a forecast. We spent three weeks chasing ghosts in our prompt templates. We’d run our benchmark, get an 84%, tweak a word, and see it drop to 81%. We’d revert the change, run it again, and watch it swing to 87%. Nothing in the code had changed. LLMs aren’t unit tests. They’re probabilistic, but we treated them like compiled binaries. When your test suite is a forecast, a single scoreboard is a lie. Why scoreboards lie A score looks like a measurement. It isn’t. It’s an estimate.

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