Counting the letter 'a' with an LLM: probabilities, not answers, reveal where LLMs fall short

eptwts · x · 2026-09-20

A developer built a tiny app that uses an LLM ("Jev") to count the letter 'a' in a word, neatly illustrating a core LLM limitation: the model returns probabilities rather than a definitive answer, and while it's usually right, it can never be 100% sure about even an obvious question.

The takeaway: LLMs are useful, but you shouldn't use them in systems with zero margin for error — and there are plenty of simple tasks you'd never route through an LLM call in the first place.

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