The Probability Pixie
It worked yesterday, I swear.
The Probability Pixie is the monster of non-deterministic output. The same prompt produces different results each time, and the developer who got a great answer on Tuesday can't reproduce it on Wednesday. Consistency becomes a matter of luck.
- Symptom
- Brittle prompts checked into the repo, demos that work once and never again, and bug reports that read 'the AI used to do this.'
- Why it matters
- Treating a probabilistic component as a deterministic one is how reliable systems quietly become superstitious ones. The failure mode is subtle — usually similar enough to slip past review.
- What the chapter gives you
- Where in your stack the Pixie is most dangerous, how to constrain non-determinism without losing the value, and the contracts to put around AI-touching code.
From Volume 1 of The AI Developer's Field Guide
Read the full chapter in The AI Developer's Field Guide.
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