ADR-0175 Phase 2 — a NEW lane (evals/gsm8k_math/practice/v1/), separate from the
wrong=0-pinned serving runner which is NOT modified. Runs the 50 cases in
practice mode: scores correct/wrong/refused as practice metrics, feeds per-class
counts into the Phase 1 ledger, diagnoses every refusal (§8), emits an
elimination record per wrong.
- classify_operation: gold-derived primary op class {multiplicative,divisive,
additive} from <<a*b=c>> calc annotations (Tier-1 checkable in practice).
- diagnose_refusal (§8): skill_gap / knowledge_gap / genuine_ambiguity router.
- EliminationRecord (§9): wrong attempt gold caught -> pruning signal.
- PracticeReport: counts + per-class ledger + diagnoses + eliminations; as_dict.
- run_practice(cases, scorer=...): injectable scorer for tests; defaults to the
candidate-graph scorer (read-only — never alters serving).
Live result mirrors serving (3 correct / 0 wrong / 47 refused of 50) because the
engine still refuses rather than guesses — attempts/eliminations go live in
Phase 3. But the diagnosis is already actionable: 35 skill_gap / 12 knowledge_gap
/ 0 genuine_ambiguity — 74% of refusals are skill gaps (Phase 3's search target),
quantifying the skill-vs-knowledge split.
Invariants: #1 seal (serving still 3/47/0; no generate/chat import of the lane),
#3 determinism (report byte-identical across runs). Elimination + wrong-tolerance
paths unit-tested via injected scorer (no live wrongs yet).
Verified: Phase 1+2 53/53, serving train_sample tests 4/4 (seal), smoke 67/67,
ruff clean.
d90887b80f