core/docs/decisions/ADR-0136.S.2-conditional-op-question.md

ADR-0136.S.2 — Conditional-Op Question (Statement-Layer Corridor)

Status: Active Date: 2026-05-23 Parent: ADR-0136

---

Context

After S.0 (context-sentence classifier) and S.1 (rate/event statement parsing) landed, the GSM8K train-sample probe sat at 2/50 admitted (gsm8k-0014, gsm8k-0018), wrong == 0.

A taxonomy pass over the remaining 48 refused cases identified gsm8k-0042 as the next single-barrier unlock:

Ella has 4 bags with 20 apples in each bag and six bags with 25 apples in
each bag.  If Ella sells 200 apples, how many apples does Ella has left?

The initial-state sentence already parses via _CONJ_EMBEDDED_RE (ADR-0131.G.4 embedded quantifier) to InitialPossession(entity="Ella", value=230, unit="apples"). The only barrier is the question form, which neither _Q_ENTITY_RE nor _Q_TOTAL_RE cover: the If <Entity> <verb> <N> <unit>, how many <unit2> does <Entity2> <aux> [left|...]? shape combines a conditional-action operand with the entity-recall question.

---

Decision

Add a conditional-op question extractor and a corresponding short-circuit in parse_and_solve that:

1. Matches the closed shape If <Entity> <verb> <N> <unit>, how many <unit2> does <Entity2> <aux> [<qualifier>]?
2. Classifies <verb> against two closed sets:
   • _COND_SUBTRACT_VERBS (sell/sells/sold, give/gives/gave, eat/eats/ate, use, lose, spend, donate, remove, take, send, pay, drop, throw)
   • _COND_ADD_VERBS (buy/buys/bought, get/gets/got, receive, find, add, collect, pick, earn, gain)
3. Refuses on any of: unknown verb, unit mismatch (<unit> vs <unit2> after canonicalization), entity mismatch (<Entity> vs <Entity2> case-insensitively), N <= 0.
4. In parse_and_solve: if the question yields exactly one CandidateConditionalOpQuestion, collect all extract_initial_candidates from every statement sentence and look for exactly one matching IC by (entity, unit). If found, compute initial_value ± operand by verb polarity; emit only when answer >= 0. Refuses otherwise.

The short-circuit is structurally identical to the S.1 capacity/earnings paths: it bypasses graph construction, returns selected_graph=None, and preserves wrong == 0 by refusing rather than guessing on any ambiguity.

---

Invariants

• admitted_wrong == 0 preserved by:
  • Single-match (entity, unit) requirement before emission
  • Non-negative answer gate
  • Closed verb sets — no wildcards
• Context-filler safety rail unchanged (S.0)
• No solver/graph/verifier changes — extractor lives in math_candidate_parser.py; short-circuit lives in math_candidate_graph.py

---

Honest GSM8K delta

Stage	Admitted	Wrong
Pre-S.0	0/50	0
Post-S.1	1/50 (0014)	0
Post-S.0 classifier	2/50 (+0018)	0
Post-S.2	3/50 (+0042)	0

gsm8k-0042 admits with answer == 30.0 (expected: 30).

---

Consequences

• The S.x corridor now spans parser (S.1 capacity/earnings, S.2 question shape) and pre-pass classifier (S.0). Future phases (S.3 compound statements, S.4 coreference) extend this pattern.
• The canonical GSM8K runner (evals/gsm8k_math/runner.py) still asserts selected_graph is not None on admission and therefore cannot score the short-circuit admissions. The report.json artifact remains stale (0/50/0); the honest count is asserted via direct parse_and_solve test (test_gsm8k_post_s2_admission_honest). Aligning the canonical runner with the short-circuit paths is deferred (out of S.2 scope).

---

Deferred

• Conditional-op question forms with more than one operand (e.g. "If she gives away 3 and buys 5, …") — needs two-op composition.
• Question forms without does <Entity> aux (e.g. "how many apples remain?") — needs a sibling regex.
• Conditional questions where the conditional and the question reference different units that are unit-related (e.g. dollars↔cents) — needs unit-relation taxonomy.