Law 26 · Evaluation & Measurement
Vibes Don't Scale
Eyeballing outputs feels like progress until you can't tell if a change helped.
The principle
The common root cause of failed LLM products is the absence of solid evals. Teams ship on vibe checks, iterate blind, and can't tell whether a prompt change improved anything. Manual spot-checking doesn't survive scale or a second engineer. Evals are to AI products what unit tests are to software: the up-front cost that makes every later change cheap and safe.
The mechanism, the warning signs, a worked example, and the apply-it recipe for this law are in the complete edition.
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