core/docs/briefs/parallel-2026-05-23/L13-ADR-0131-G31-numerics-extensions.md

L13 brief — ADR-0131.G.3.1 — Numerics extensions (fractions + multi-currency + multi-token cardinals + word-num-adjective)

Worktree setup (do this first, non-negotiable):

git worktree add ../core-adr-0131-g31-numerics-ext -b feat/adr-0131-g31-numerics-ext origin/main
cd ../core-adr-0131-g31-numerics-ext

Scope. Follow-up to ADR-0131.G.3 (PR #183) extending literal recognition to the four shapes explicitly deferred in that ADR's "Out of scope, explicitly deferred to G.3.1+" section. The parent ADR's canonical-unit architectural decisions (cent for money via en_units_v1, pack-driven not regex-spam, refusal-first) stay absolute — this iteration extends scope inside those constraints, not around them.

Closed-set scope (this iteration only):

1. Fractions end-to-end. _resolve_value in generate/math_candidate_parser.py already handles N/M token-level (returns float via Fraction(N,M)). Land axis cases that exercise fractions through the full pipeline — likely requires widening _INITIAL_HAS_RE's (?:of|in|for|with) <NP> substance-qualifier handling so Bob has 3/4 of a cup. parses cleanly (the fraction is the value; of a cup carries the unit). Closed-set: digit/digit literal with M > 0.
2. Multi-currency. Extend _money_unit_normalization (math_candidate_parser.py) and _unit_grounds (math_roundtrip.py, the "$" in source_span check) to recognize ¢ € £ ¥ ₱. Each gets its own canonical unit per en_units_v1. Verify en_units_v1.lexicon.jsonl actually contains euro / pound / yen / peso before wiring; if any is missing, defer that currency to G.3.2 rather than hardcoding a unit name the pack doesn't recognize.
3. Space-separated multi-word cardinals. one hundred, two thousand five hundred. parse_compound_cardinal in language_packs/numerics_loader.py already supports these; the parser's _VALUE regex doesn't yet match space-separated sequences because they'd span the unit slot boundary. Either (a) add a separate extractor that pre-passes value-slot whitespace runs through parse_compound_cardinal, or (b) widen _VALUE to greedily match cardinal-word sequences. Pick one approach, document the choice in the ADR.
4. Word-number-adjective compositions. five full boxes per ADR-0127 substance-qualifier precedent. Adjective inserted between cardinal and unit head noun; treat as part of the unit phrase, not a separate value-slot widening.

Reference docs (read these, only these):

1. docs/decisions/ADR-0131.G.3-numerics.md — the parent; what's already done, what's deferred, the canonical-unit decision you must respect.
2. docs/decisions/ADR-0127-units-pack-and-units-aware-parser.md — substance-qualifier precedent for axis 4.

What to ship:

• Parser extensions in generate/math_candidate_parser.py (+ generate/math_roundtrip.py for new grounding cases).
• New axis lane at evals/math_capability_axes/G3_numerics/v1.1/ — additive sibling to v1. Do not modify v1 (evals/math_capability_axes/G3_numerics/v1/); it's frozen as the audit-trail artifact for #183. v1.1 carries fresh cases.jsonl, runner.py, report.json.
• Curated cases: ≥4 per axis + ≥4 refusal probes pinning what's still out of scope (percentages 50%, scientific notation 1e3, locale separators 1,000, three-decimal money $1.234).
• Tests: tests/test_adr_0131_G31_numerics_extensions.py — per-axis at-least-one passing, refusal probes refuse typed, wrong == 0, replay byte-equality, parent v1 lane still passes (no regression).
• ADR: docs/decisions/ADR-0131.G.3.1-numerics-extensions.md — cite #183 parent + ADR-0127 substance-qualifier precedent. Document the axis-3 approach choice (extractor vs _VALUE widening).
• Refresh evals/gsm8k_math/train_sample/v1/train_sample_coverage_report.json — fractions or compound cardinals may now unlock some GSM8K cases.

Hard constraints:

• wrong == 0 on the v1.1 axis lane AND the GSM8K probe.
• Pack-driven, not regex-spam. Every recognized literal traces to en_numerics_v1 or en_units_v1. No inline alternations for things the pack should own.
• en_units_v1.canonical_unit precedence stays absolute (cent for money, etc.) — same architectural decision G.3 set. New currencies normalize to their pack-pinned canonical unit; do not invent surface units.
• Closed set per axis. Refusal probes prove the boundary. If a paraphrase isn't in the closed set, it must refuse, not coerce.
• Determinism: v1.1/report.json byte-equal across runs.
• No solver / binding-graph changes. If a fraction parses but doesn't solve through, file a follow-up ADR; don't stub the solver.
• Don't modify v1. It's the audit-trail artifact for #183 and stays frozen.
• Field invariant untouched. No changes to algebra/, chat/, core/.

Out of scope (do not touch):

• Percentages, scientific notation, locale separators, three-decimal money (these become refusal-probe cases — closed-set boundary).
• ADR-0131.4 promotion-gate wiring (main agent's parallel work).
• Anything in algebra/, chat/, core/.

Target branch. PR against main. Title: feat(ADR-0131.G.3.1): numerics extensions (fractions + multi-currency + multi-token cardinals + word-num-adjective) — axis lane N/N. Body: per-axis case counts, currencies actually wired (vs. deferred to G.3.2 because missing from pack), axis-3 approach choice + rationale, link to ADR, GSM8K probe delta if any (admission may or may not move depending on which cases the extensions unlock).

Exit criterion. CI green; v1.1 axis runner exits 0 with wrong == 0; v1 lane unchanged; GSM8K probe admitted_wrong == 0 preserved.

Only run tests that exercise files you change plus the axis lane + GSM8K probe + the parent v1 lane. Do not run the full suite — that's the lead's job at integration.

Do not stack on another agent's branch. Target main directly.