Mar 23, 2026
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5
minute read
I A/B Test My Prompts Like a Scientist
Most teams evolve prompts by feel. Change something, eyeball the output, ship it if nobody screams. This is alchemy, not engineering. When your system is non-deterministic, a single successful run proves nothing. I built an eval harness that runs prompt versions head-to-head — 10 runs each, scored on behavior, measured on cost and latency. No vibes. No guessing. Just data that tells you exactly what improved, what regressed, and what it costs.
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