# ADR-0131.G.1 — Capability axis: state-introducing verb classes

**Status:** Accepted
**Date:** 2026-05-23
**Author:** CORE agents
**Parent:** [ADR-0131.G](./ADR-0131.G-gsm8k-coverage-probe.md)

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## Context

ADR-0131.G introduced the GSM8K coverage probe to measure the capability of the bounded grammar layers while maintaining the safety rail (`wrong == 0`). This decision record details the first capability-axis iteration on top of the coverage probe (G.1), which extends the grammar parser to support a closed set of acquisition / action verbs that introduce quantity.

## Decision

We recognize that sentences of the form `<Entity> <verb> <N> <unit>` can introduce a quantity without an explicit "has/have" possession verb. The verbs fall into two classes:

### Class A — Pure-possession anchors (initial-possession slot)
Kept in `_INITIAL_HAS_RE`. These verbs have no semantic overlap with operation verbs and produce no candidate ambiguity:
- `had` (past possession)
- `started` / `started with` (opening state)

### Class B — Acquisition/action verbs (operation slot, add-kind)
Handled exclusively as `add` operations in `ADD_VERBS` / `SUBTRACT_VERBS`. The solver defaults the actor's pre-operation state to **0** when no initial possession exists, so a single-statement sentence like `"Sam buys 5 apples."` resolves correctly as `0 + 5 = 5`.

These verbs were *not* added to `_INITIAL_HAS_RE` because they also appear in the operation verb registry (`math_roundtrip.KIND_TO_VERBS`). Adding them to both registries causes **branch-disagreement refusals**: when a canonical "has" initial for entity E is followed by an acquisition sentence for the same E, the candidate-graph emitter produces two branches—one treating the acquisition as a second initial (wrong answer) and one treating it as an add operation (correct answer)—and the decision rule refuses on disagreement.

| Verb | Operation kind | Already in verb registry |
|------|---------------|--------------------------|
| `buys` / `bought` | `add` | `ADD_VERBS` |
| `collected` | `add` | `ADD_VERBS` |
| `saved` / `saved up` | `add` | `ADD_VERBS` |
| `makes` / `made` | `add` | `ADD_VERBS` |
| `sells` / `sold` | `subtract` | `SUBTRACT_VERBS` |

### Code Changes

1. **`_INITIAL_HAS_RE` narrowed** to pure possession anchors only:
   `(?P<anchor>has|have|had|started)(?:\s+(?:up|with))?`

2. **`CandidateInitial.__post_init__`** validation updated to match the narrower set.

3. **Optional verb particle** added to `_op_pattern` between verb and value:
   `(?:\s+(?:up|down|out|back|off|in|away))?`
   This allows the operation regex to match `"saved up N"`, `"picked up N"`, etc. without listing particle-bearing forms as initial anchors.

4. **`ADD_VERBS` / `SUBTRACT_VERBS`** in `math_roundtrip.py` already include all Class B verbs—no changes required there.

## Out of Scope

The following capabilities are explicitly deferred to sibling axes:
- **Rate-introducing verbs:** Multipliers and rates (e.g. "makes $18 an hour") continue to refuse on this axis.
- **Comparatives:** Multiplicative/additive comparison structures (e.g., "twice as many", "3 more than").
- **Acquisition-with-cost:** Transactional semantics (buying items at a given price).
- **Multi-statement coreference.**

## Invariants

- **`wrong == 0`**: Every evaluation run over both the G1 curated axis and the GSM8K probe must yield zero wrong answers.
- **Closed Set**: No synonymous expansion or paraphrase tolerance beyond the enumerated verbs.
- **Determinism**: Evaluator outputs must be byte-equal across consecutive runs.
- **No initial/operation overlap**: Verbs that appear in `ADD_VERBS` or `SUBTRACT_VERBS` must not also appear in `_INITIAL_HAS_RE`.
