exp 60A.1: read-only vocabulary adequacy diagnosis for alternatives and decisions

Diagnoses the root cause of the persistent pattern from 59B.2-59B.4
where explicit dual-option input collapsed into a single undifferentiated
unknown node. Concludes the graph vocabulary lacks first-class primitives
for options/decisions (not primarily a prompt issue). Identifies three
missing primitives: option node kind, decision node kind, alternative_of
edge type. Recommends ~25-line schema addition for 60A.2 implementation.

docs/current-handoff.md

@@ -2092,3 +2092,45 @@ Full record in `docs/experiment-59b2.md`. Configured Ollama: qwen-claude:latest
 
 ### Experiment 59B.4 — Explicit Two-Option Decision Structure (full record in docs/experiment-59b4.md)
 
+### Experiment 60A.1 — Read-Only Vocabulary Adequacy Diagnosis for Alternatives and Decisions
+
+**Branch:** `feature/question-formulation-v0.24`
+**Date:** 2026-08-12
+**Type:** READ-ONLY ARCHITECTURE DIAGNOSIS
+**Full record:** `docs/experiment-60a1.md`
+
+**Context route:** This diagnosis follows experiments 59B.2–59B.4 which showed the persistent pattern: engine understood trade-offs semantically but could not preserve two competing options as independently recoverable structural entities in the graph.
+
+**Objective:** Answer whether the model fails to use decision structure that already exists, or whether the current graph vocabulary lacks an adequate first-class representation for alternatives and decisions.
+
+**Methodology:** Read-only analysis of `lib/graph/schema.js`, `lib/graph/prompt-builder.js`, `lib/graph/utils.js`, `lib/graph/apply-proposal.js`, and experiment history. No production code changes, no API calls, no test runs.
+
+**Key findings from 8-section diagnosis:**
+
+1. **Vocabulary inventory (Section 1):** SituationKind has 9 node kinds (observation, reported_claim, metric, state, transition, relationship, assumption, unknown, conclusion) — zero kinds represent choices, options, or decisions. SituationRelationship has 10 edge types including `compares_with` but with no alternative-specific semantics.
+
+2. **Representational adequacy test (Section 2):** The schema cannot express a "decision" node as a first-class entity. The schema cannot express "these two options are alternatives for the same decision." Consequences can attach only if option nodes exist first — a chicken-and-egg problem. The do-nothing baseline has no dedicated representation.
+
+3. **Concept mapping for 59B.4 (Section 3):** User input had 8 distinct structured components (2 options, 6 consequences, comparison intent). Schema mapped 0 of these as structure. All 8 collapsed into one undifferentiated unknown node's prose description.
+
+4. **Prompt-vs-schema diagnosis (Section 4):** The schema lacks the primitives AND the prompt lacks rules to use them — but root cause is schema-level. No existing primitive semantically means "an available choice." All four prompt-level reuse candidates (`state`, `compares_with`, `contradicts`, `transition`) fail because no rule references them for alternatives.
+
+5. **Reuse strategy evaluation (Section 5):** Four candidate strategies tested (`state` as options, `observation` for consequences, repurpose `compares_with`, `transition` for outcomes). All are either semantically incorrect or incomplete without schema-level support. No reuse strategy is viable without adding new primitives.
+
+6. **Minimum architectural distinction (Section 6):** Three missing primitives identified: DECISION node kind, OPTION node kind, and ALTERNATIVE-OF edge type. These three additions would enable full representation of the 59B.4 decision scenario. Smallest improved graph: ~25 lines total.
+
+7. **Smallest improved graph (Section 7):** Concrete proposal — add `option` and `decision` to SituationKind, add `alternative_of` and `contains_option` to SituationRelationship, add 4 prompt rules for option creation. No breaking changes. Existing contract unchanged. ~25 lines of code.
+
+8. **Implementation readiness (Section 8):** Schema additions are low-risk trivial enum extensions. Prompt rule additions are straightforward. Recommendation: next experiment should implement the three-primitive addition and re-run the 59B.4 scenario to verify structural option representation.
+
+**Classification: DIAGNOSIS COMPLETE — SCHEMA-LEVEL ROOT CAUSE IDENTIFIED**
+
+The current graph vocabulary lacks first-class primitives for alternatives and decisions. The model cannot represent what the schema does not define. Schema-level additions are necessary; prompt-only changes would not resolve the root cause.
+
+Production code changed: NO
+Prompt changed during experiment: NO
+Validator changed during experiment: NO
+Vitest run: NO
+Ollama calls: 0
+Dev server disturbed: NO
+Read-only diagnosis: YES