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promptbrittle

confirmedPython · CPUModel behavior & reasoningJuly 5, 2026

the question

How much does prompt format alone -- not content -- move accuracy?

what came out

On GSM8K, semantically-equivalent formats swing accuracy 25 points (0.42 to 0.68) on the same questions (McNemar p 0.006), with reasoning elicitation the biggest lever. The wording is a hyperparameter.

method & receipts

  • Result: confirmed
  • Reproducible one script re-runs the whole thing from scratch.
  • Machine-readable claims every reported number, in a checkable file.
  • Tested — a correctness/benchmark suite ships alongside the code.

→ read the code and re-run it

github.com/v-code01/promptbrittle