core/docs/adr/ADR-0260-verb-predicate-band.md

ADR-0260 — Band v5-VP: verb-predicate arguments, decided

• Status: Accepted — ratified by Joshua Shay via the PR #111 merge (2a82c8a3, 2026-07-24)
• Date: 2026-07-24
• Arc: deduction-serve (ADR-0256 → 0257 → 0258 → 0259 → this)
• Governs: generate/proof_chain/verb.py, the en_verb_* shape-bands, their arena templates, the v2_verb lane split, and the _verb_band_surface serving tier.

1. Context

ADR-0258 §6.3 scoped verb predicates out of the member band: v3-MEM reads only copula sentences, so "All philosophers teach. Socrates is a philosopher. Therefore Socrates teaches." refused — despite being the plain English shape in which most non-logic subject matter states its rules (physics, biology, and every other domain speak in verb sentences, not is-a chains). The generalization arc (docs/plans/generalization-arc-2026-07-24.md Phase 1.1) makes this the single highest-leverage reading unlock: Phase 2's curriculum-entailment serving is gated on it.

The earlier bands each guard this territory out rather than misreading it: v2-EN refuses quantifier-led sentences (categorical_shape_out_of_band), is-a clauses (membership_shape_out_of_band), and unnormalized negation (internal_negation_unread); v3-MEM/v4-CM refuse copula-free sentences (sentence_shape_out_of_band). Pure verb-fact restatements with none of those triggers are ALREADY decided soundly by v2-EN as opaque clause-atoms — so this band's genuine territory is exactly the fall-through: arguments mixing verb sentences with quantified rules, membership facts, or does not negation.

2. Decision

Add generate.proof_chain.verb.read_verb_argument as the next fallback tier (after v1 / v1b / v2-EN / v3-MEM / v4-CM), extending v3-MEM's per-individual propositional lowering with a SECOND atom family in one shared space:

• Membership atoms (individual, class-group) — minted by v3-MEM's own _parse_singular / _parse_universal, reused verbatim (copula sentences keep their exact v3-MEM reading, refusals included).
• Verb atoms (individual, verb-lemma-group, object-term) — minted from verb facts (<name> <verb3sg> [<object>], does not negation, the sentential-not prefix) and verb universals (all|every|each|no [the] <class> <verb> [<object>]).

A verb universal instantiates at every named individual as mem(i, C) -> [~]verb(i) — so a membership fact minted by a copula sentence discharges a verb rule. The same verified ROBDD engine decides.

Bands (priority order): en_verb_negative (any negative universal, either kind) > en_verb_chain (≥2 universals) > en_verb_universal (exactly 1) > en_verb_fact (facts only). Rendered by render_entailment_verb — the member surface with the UNKNOWN scoping extended to the verb reading. Rides deduction_serving_enabled (default off); no new flag.

3. Why this is sound

1. Instantiation — identical to ADR-0258 §3: universal instantiation at named individuals is truth-preserving in every first-order model, and each (verb-group, object-term) pair is one opaque unary predicate over the same named-individual domain. ENTAILED / REFUTED / inconsistent verdicts over the lowered premises hold in every model of the original argument; completeness within the fragment lifts the same way (a propositional countermodel's domain is exactly the named individuals).
2. Agreement is the ONE new identification — a universal's base form ("teach") and a singular fact's 3sg form ("teaches") are identified iff related by a CLOSED relation: a verb-specific irregular table (has/have, goes/go, does/do; consulted first, sole authority for its tokens) else the three regular suffix rules (+s, +es after sibilants, y↔ies). The noun table is deliberately NOT reused — it would misroute verb forms like "lives" (noun: life; verb: live). Under-linking costs coverage, never soundness. Object terms link by exact token identity only.
3. Scope-tight segmentation — without a lexicon, an arbitrary copula-free token run cannot be soundly split into subject/verb/object; the band reads single-token name/class/verb/object shapes ONLY, and refuses everything longer, typed. A three-token sentence read as (subject, verb, object) is a disclosed reading, restated verbatim in the surface's "Given:" line.
4. Cascade honesty — every text this band decides was verified to be REFUSED by all four earlier bands (the arena templates and lane cases are constructed on the fall-through path serving actually uses), so this tier is pure widening: every previously-served argument is served byte-identically.

4. License and render

The four en_verb_* bands earned SERVE through the ADR-0199 arena (720/band committed, wrong=0, θ_SERVE=0.99; ledger resealed at 21 bands). The arena's by-construction gold is cross-checked template-by-template against the independent truth-table oracle over each template's INTENDED per-individual lowering, with no reader in the loop (INV-25). Unearned or ledger-stripped deployments serve the same sound answer hedged (_UNVERIFIED_SHAPE_DISCLOSURE), exactly as every earlier band.

5. Scope-outs (typed refusals today, future bands' territory)

1. Connective × verb composition — "If Socrates teaches then …" refuses mixed_structure_out_of_band; fusing v4-CM's connective grammar over verb leaves is the natural next composition.
2. Multi-token subjects/objects, PPs, adverbs, ditransitives — sentence_shape_out_of_band. Note one disclosed misreading inside the 3-token shape: an adverb in object position ("Lena runs quickly") is read as an object TERM — never unsound (worst case an over-scoped UNKNOWN), documented here rather than guessed at.
3. Tense — did not refuses tense_out_of_band; bare past forms ("taught") are indistinguishable from lemmas without a lexicon and read as distinct opaque lemmas (under-linking, sound).
4. Arity/subsumption — "teaches" does not entail "teaches logic" (nor vice versa) under the face-value reading; both directions stay UNKNOWN, scoped. Same posture v2-EN already takes for opaque clauses.
5. Plural/bare subjects in verb facts ("dogs bark") — read as an individual named "dogs" (disclosed in the UNKNOWN scoping); the copula analogue is refused by v3-MEM's bare-plural guard, but no copula means no plural signal in the closed grammar.
6. Existential (some) witnesses, identity/co-reference — unchanged scope-outs inherited from ADR-0258 §6 (existentials are the generalization arc's Phase 1.2, assigned to the Opus tier).

6. Verification

• tests/test_verb_argument_reader.py — 34 tests: gap-is-real cross-check, flagship lowering, every agreement rule, object-in-atom-key, chain discharge, cross-individual non-leakage, family separation (teacher/teaches), 14 typed refusals incl. delegated v3-MEM reasons, honesty caps, determinism.
• Surface/e2e/lane: tests/test_deduction_surface.py (+5), tests/test_deduction_serve_e2e.py (+1), tests/test_deduction_serve_lane.py (+1 over the 28-case v2_verb split) — full lane 134/134, wrong=0, all five splits.
• Arena: 4 × 720 committed, wrong=0, first seal run; corpus soundness asserted against the independent oracle before sealing (15,120 cases).