core/docs/analysis/gsm8k-workstream-a-gate-a2a-unit-partition-lookback-2026-06-17.md

GSM8K Workstream A Gate A2a — unit partition implementation lookback

Date: 2026-06-17 Gate: A2a — unit_partition recognizer-injector + typed solver primitive Status: Implementation complete (PR-ready; not merged) Ratification: docs/analysis/gsm8k-workstream-a-gate-a2a-unit-partition-ratification-2026-06-17.md

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1. What shipped

Surface	Change
PartitionChunk + unit_partition kind	generate/math_problem_graph.py
_apply_unit_partition + pack bind (divide lemma)	generate/math_solver.py
_verify_unit_partition_step	generate/math_verifier.py
Roundtrip + DIVIDE_VERBS widen (cut, separate)	generate/math_roundtrip.py
_match_unit_partition, DCS yield guard	generate/recognizer_match.py
inject_unit_partition	generate/recognizer_anchor_inject.py
Exemplars + synthesis + accepted proposal	teaching/admissibility_exemplars/unit_partition_v1.jsonl, teaching/recognizer_synthesis.py, teaching/proposals/proposals.jsonl
Tests	tests/test_recognizer_unit_partition_inject.py, tests/test_math_candidate_graph_unit_partition_injection.py, frontier/microscope extensions

Lead exemplar: case 0002 partition stmt She splits it up into 25-foot sections. now matches ShapeCategory.UNIT_PARTITION and injects CandidateOperation(kind="unit_partition") with result_unit=sections.

DCS yield: _match_discrete_count_statement returns None when _is_unit_partition_v1_surface holds — prevents Initial(25, foot) misread.

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2. Solid

• New unit_partition kind writes quotient under result_unit, not dividend unit — bare divide reuse avoided.
• Closed v1 template: partition verb + into + single \d+-(measure) + optional counted noun.
• Pronoun subject (She) emits with requires_pronoun_resolution; existing lookback path applies.
• wrong=0 preserved on live train_sample ephemeral runner; unit_partition recognized_no_injection = 0.
• Pinned report.json unchanged (6/44/0 historical artifact).

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3. Gaps (no live risk)

• graph_intent: "partition" is new; no separate graph_planner hook (out of v1 scope).
• Pack lemma maps unit_partition → existing divide entry (semantically division; kind discriminates result_unit contract).
• No dedicated binding_graph admissibility hook; partition ops reach solver only via injector + roundtrip.

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4. Drift from ratification

Ratification claim	Implementation
separate verb	Included in matcher regex + DIVIDE_VERBS
Actor binding “no cross-sentence pronoun beyond session rules”	Uses existing ADR-0174 lookback; no new binding logic
report.json rebaseline	Intentionally skipped

No amendment required.

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5. Hazards reviewed

Hazard	Verdict
Over-recognition on \d+-(hour|foot) alone	Mitigated: requires verb + into; 2-hour drive does not match unit_partition
DCS wins race on 0002	Mitigated: DCS yield returns None
Quotient stored under feet	Mitigated: PartitionChunk.result_unit
Pseudo-accumulation 996 (confuser-v1-0007)	Full 0002 still refuses; no correct lift claimed
Non-exact quotient	Solver + verifier refuse (SolveError / VerificationError)

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6. Metric movement (ephemeral live runner)

Metric	Before	After (expected)
wrong	0	0
correct	6	≥ 6 (no lift guaranteed)
refused	44	≤ 44
unit_partition no-injection	1 (0002 via DCS misroute)	0
discrete_count_statement no-injection	19	likely 18 (−1 reclassification)

Case 0002 partition stmt reclassifies; full solve to 15 remains refused until composition ratification.

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7. Validation run

git diff --check origin/main...HEAD
pytest tests/test_recognizer_unit_partition_inject.py -q
pytest tests/test_math_candidate_graph_unit_partition_injection.py -q
pytest tests/test_gsm8k_frontier_report.py -q
pytest tests/test_gsm8k_post_gate_a1_frontier_microscope.py -q
pytest tests/test_candidate_graph_recognizer_wiring.py -q

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8. Explicit non-goals (held)

• No full 0002 composition, no report.json rebaseline, no sealed-lane pin movement
• No Gate A1b, Inc4, broad DCS, determine() / FrameVerdict / CLOSE
• No graph_planner.py changes