| Where the swing comes from | What it really is | What we did |
|---|---|---|
| Question sample | which questions you draw | frozen seed ✓ |
| Provider routing | one "model" silently served from different backends & quant levels — a mixture, not a model | pin the provider ✓ |
| Answer parsing | scoring a truncated-but-correct reply as wrong | strict + re-ask ✓ |
| Real LLM noise | temp 0 still isn't bit-exact | irreducible — but only ±1–2, and we measure it |