docs: record proposition question formulation fix

docs/current-handoff.md

@@ -164,6 +164,16 @@ Experiment 54N tested whether an interpretation disagreement can be judged for m
   - `npx vitest run tests/graph/question-formulator.test.js tests/graph/question-formulation-v0.24.test.js` → PASS (45/45)
 - **Still unproven live:** the exact 60B.21 product-launch regression in the full end-to-end path.
 
+### 60B.26 proposition question formulation fix
+
+- 60B.25 diagnosed two deterministic causes of awkward proposition questions: whole-description extraction (including rationale) and treating `whether...` propositions as finished direct questions.
+- `extractMeaning()` now performs bounded proposition extraction for nominal/status-like unknowns whose descriptions begin with `whether...`, stopping at clear rationale boundaries such as `;`, `, so that`, `, because`, and `matters because`.
+- `whether...` is no longer treated as a direct interrogative for question framing; it now uses the existing deterministic evidence phrasing (`What evidence would clarify whether X?`).
+- Direct interrogatives and wh-questions remain preserved unchanged.
+- Focused verification passed:
+  - `npx vitest run tests/graph/question-formulator.test.js` → PASS (29/29)
+- **Still unproven live:** the exact 60B.24 regression through the full end-to-end runtime path.
+
 ### When This Knowledge-Management Phase Is Complete
 
 Provisional criteria for review (all confirmed met by Experiment 38 cold-start test):

docs/experiment-60b26.md

@@ -0,0 +1,123 @@
+# Experiment 60B.26 — Proposition Question Formulation Fix
+
+**Branch:** `feature/proposition-question-shape-v0.30`  
+**Date:** 2026-08-13  
+**Status:** COMPLETE
+
+## Objective
+
+Implement the smallest deterministic fix so `whether...` propositions are turned into concise evidence questions without carrying explanatory rationale, while preserving direct interrogatives and wh-questions.
+
+## 60B.25 Diagnosis Applied
+
+60B.25 isolated two deterministic causes:
+
+1. `extractMeaning(...)` returned the full description, including explanatory rationale.
+2. `isInterrogativeMeaning(...)` treated `whether...` propositions as if they were already finished direct questions.
+
+The intended correction was:
+
+> clean unresolved proposition + existing evidence framing
+
+not grammatical rewriting into `Will/Does/Is...`.
+
+## Exact Proposition-Extraction Rule
+
+The bounded extraction change stays inside `lib/graph/question-formulator.js`.
+
+For the existing narrow path where:
+
+- the label is nominal / status-like (`status|likelihood|probability|chance|risk|uncertainty`)
+- and the description begins with `whether...`
+
+the formulator now extracts only the proposition portion.
+
+Implemented rule:
+
+- match `whether ...`
+- stop at the first clear rationale boundary:
+  - `;`
+  - `, so that ...`
+  - `, because ...`
+  - `matters because ...`
+
+This is bounded to explicit `whether...` proposition extraction only. It is **not** a global semicolon truncation rule.
+
+## Exact Whether / Evidence-Framing Rule
+
+The formulator now distinguishes:
+
+- **direct interrogatives**
+  - `Will our largest client leave if we relocate?`
+  - `What would change the preferred option?`
+- **indirect unresolved propositions**
+  - `whether the supplier will renew the contract`
+
+`whether...` is no longer treated as a direct interrogative.
+
+Instead, it is routed through the existing deterministic evidence phrasing:
+
+```text
+What evidence would clarify whether X?
+```
+
+No subject/auxiliary inversion was added.
+
+## Preserved Direct Interrogatives
+
+Direct question labels remain preserved as question-ready:
+
+- yes/no direct interrogatives still pass through unchanged
+- wh-questions still pass through unchanged
+
+This also preserves 60B.20-style behaviour.
+
+## Focused Test Result
+
+Command run:
+
+```bash
+npx vitest run tests/graph/question-formulator.test.js
+```
+
+Result:
+
+```text
+PASS (29/29)
+```
+
+Covered regressions:
+
+1. Exact 60B.24 rationale stripping regression
+2. Clean `whether...` proposition without rationale
+3. Direct interrogative preserved
+4. Wh-question preserved
+5. Source node description unchanged
+6. Non-`whether` semicolon content not globally truncated
+
+## What Remains Unproven Until Live 60B.24 Rerun
+
+This experiment proves the deterministic question-formulation layer behaves correctly for the fixed regression shape and focused test coverage.
+
+Still unproven live:
+
+- the exact end-to-end 60B.24 continuation through the full runtime path
+- whether any upstream live-model variation changes the selected unknown or surrounding graph state before formulation
+
+## Production Boundary Confirmed
+
+Changed:
+
+- `lib/graph/question-formulator.js`
+- `tests/graph/question-formulator.test.js`
+
+Not changed:
+
+- prompt builder
+- schema
+- apply-proposal
+- question-target selection
+- materiality
+- reasoning-context compatibility
+- provider integration
+- harness