docs/BEAT_LEVERS.md

Beat-the-competition levers — measured

Built: 2026-07-22T13:18:23.675085+00:00 Law: S=K(T1+T2+T3) pin D1D38A (unchanged)

L1 — Product dual-student ensemble (no ref peek)

System	sacreBLEU
opus-mt-de-en b5	33.88
NLLB-600M b5	33.37
Product ensemble (NLL pick)	34.54
Oracle uF1 ensemble (upper)	37.13
Picks	{'opus': 1751, 'nllb': 1252}

L3 — WMT finetune student (opus-mt-de-en)

Metric	Value
steps	2500
train pairs	60000
avg loss last 100	2.1199
WMT test sacreBLEU	32.2
chrF	58.85
path	D:\training data\pflt_linguistics\13_huggingface\models\Helsinki-NLP__opus-mt-de-en-wmt-ft

L2 — Neural-first hybrid chat

Metric	Value
sacreBLEU	48.74
BLEU-4	51.38
routes	{'neural': 2800, 'densify': 400}
gap to chat 45	-3.74

Gaps to beat commercial mid-bar

Bar	Gap
Best single → 40	6.12
Product ensemble → 40	5.46
Finetuned → 40	7.8
Best single → 48	14.12

Mid-40 cleared? False

Next if still short of 40

1. Longer finetune / full WMT train epoch
2. Ensemble finetuned-opus + NLLB
3. Larger student (NLLB-1.3B) when disk allows

L3b — Safer finetune (freeze encoder, lr=2e-5, 1500 steps)

Metric	Value
WMT test sacreBLEU	33.86
vs base opus 33.88	-0.02 (flat / no win)
Aggressive FT v1 (full model 2500 steps)	32.2 (regressed)

Finding: Short domain FT of opus-mt-de-en does not cross 40. Need longer careful training, better data filter, or larger student.

L2 win

Neural-first hybrid chat 48.74 sacre (routes neural=2800 densify=400) — past chat mid bar 45.