diff --git a/docs/current-handoff.md b/docs/current-handoff.md
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--- a/docs/current-handoff.md
+++ b/docs/current-handoff.md
@@ -3389,3 +3389,25 @@ Smallest zero-semantic-change refactor: extract all decision-sufficiency evaluat
 ### VITEST RUN: NO
 ### JEST RUN: NO
 ### WATCHMAN USED: NO
+
+---
+
+### EXPERIMENT 60B.66 — LIVE DECISION-CLOSURE REGRESSION (PASS)
+
+**Date:** 2026-08-14
+**Branch:** `feature/decision-closure-integration-v0.43`
+**Experiment commit:** bce05f7 feat(reasoning): integrate explicit decision-sufficiency closure (60B.64)
+**Result:** A — LIVE REASONING THREAD CLOSED
+
+The committed 60B.64 deterministic closure rule was verified live against the exact negative customer-signing case from 60B.56.
+
+Key outcomes:
+- Decision `n_product_launch_decision` resolved unknown→resolved (was KEPT OPEN in 60B.56)
+- `finalActiveUnknownNodeId = null`, `finalSelectedQuestion = null` (both were non-null in 60B.56)
+- Customer factor resolves in place with negative meaning preserved
+- Zero addedNodes, zero addedEdges
+- Decision identity preserved; both options preserved
+
+Pre-refactor behavioural baseline established.
+Next structural task may be zero-semantic-change decision-sufficiency extraction.
+
diff --git a/docs/experiment-60b66.md b/docs/experiment-60b66.md
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+++ b/docs/experiment-60b66.md
@@ -0,0 +1,209 @@
+# Experiment 60B.66 — Live Decision-Closure Regression (60B.64 Fix)
+
+**Date:** 2026-08-14
+**Branch:** `feature/decision-closure-integration-v0.43`
+**Head commit:** bce05f7 feat(reasoning): integrate explicit decision-sufficiency closure (60B.64)
+
+## Objective
+
+Does the committed 60B.64 production path now close the exact 60B.56 negative customer-signing case with no stale active target, no follow-up question, no new uncertainty, and no invented recommendation direction?
+
+## Hypothesis
+
+```
+hasRemainingMaterialFactors(decisionId, graph) === false
+AND
+raw user answer explicitly confirms no other material uncertainty remains
+=> resolve the existing parent decision before another question is selected
+
+Result:
+customer factor = resolved
+decision = resolved
+activeUnknownNodeId = null
+selectedQuestion = null
+```
+
+## Configured environment
+
+- **Model:** qwen-claude:latest
+- **Ollama base URL:** http://192.168.1.111:11434
+- **Confidence Engine base URL:** http://127.0.0.1:3000
+
+## Input
+
+- **Fixture:** `tests/fixtures/pre-anchored-product-launch-customer-signing.json`
+  - Pre-anchored state: decision (`n_product_launch_decision`) in unknown status; enterprise customer signing (`n_enterprise_customer_signing`) in unknown status, activeUnknownNodeId = n_enterprise_customer_signing.
+- **Answer:** "No. The enterprise customer has now confirmed in writing that they will not sign if we launch this year, so the £700,000 of expected annual revenue from them will not be received. There are no other material uncertainties between launching this year and waiting twelve months."
+
+## Run
+
+```bash
+FIXTURE_MODE=updateOnly \
+FIXTURE_PATH=tests/fixtures/pre-anchored-product-launch-customer-signing.json \
+ANSWER_2="No. The enterprise customer has now confirmed in writing that they will not sign if we launch this year, so the £700,000 of expected annual revenue from them will not be received. There are no other material uncertainties between launching this year and waiting twelve months." \
+CONFIDENCE_ENGINE_BASE_URL=http://127.0.0.1:3000 \
+node scripts/reproduce-multi-turn-investigation.mjs
+```
+
+- **startCalls:** 0
+- **updateCalls:** 1
+- **totalCalls:** 1
+- **Retries:** 0
+
+## Results
+
+### Proposal accepted: YES (HTTP 200)
+
+### updatedNodes:
+```json
+[
+  {
+    "nodeId": "n_enterprise_customer_signing",
+    "previousStatus": "unknown",
+    "newStatus": "resolved",
+    "newValue": "confirmed_no_signing",
+    "reason": "User explicitly confirmed in writing the enterprise customer will not sign, resolving this material uncertainty."
+  },
+  {
+    "nodeId": "opt_launch_this_year",
+    "previousStatus": "known",
+    "newStatus": "known",
+    "newValue": "Revised financial impact: ~£500k/year expected additional recurring revenue (excluding the confirmed lost £700k enterprise customer), £300k one-off launch/support cost.",
+    "reason": "Update option description to reflect the resolved financial consequence of the now-resolved unknown."
+  },
+  {
+    "nodeId": "n_product_launch_decision",
+    "previousStatus": "unknown",
+    "newStatus": "resolved",
+    "newValue": null,
+    "reason": "All represented material factors resolved and raw user answer explicitly confirmed no further material uncertainty remains."
+  }
+]
+```
+
+### resolvedUnknownNodeIds:
+```json
+["n_enterprise_customer_signing", "n_product_launch_decision"]
+```
+
+### addedNodes:
+```json
+[]
+```
+
+### addedEdges:
+```json
+[]
+```
+
+### structuralActionRequired: null
+
+### Customer node final state:
+- `n_enterprise_customer_signing`: status = **resolved**, value = confirmed_no_signing
+
+### Customer resolution meaning:
+"User explicitly confirmed in writing the enterprise customer will not sign, resolving this material uncertainty." → Negative meaning **preserved**.
+
+### Decision node final state:
+- `n_product_launch_decision`: status = **resolved** (CLOSED)
+
+### Launch option final state:
+- `opt_launch_this_year`: status = known
+
+### Wait option final state:
+- `opt_wait_twelve_months`: status = known
+
+### DIRECT CLOSURE METADATA
+
+```
+finalActiveUnknownNodeId: null
+finalSelectedQuestion: null
+```
+
+## Assessment
+
+### Customer factor: RESOLVED IN PLACE
+The enterprise-customer-signing node was updated in place from `unknown` → `resolved` with value `confirmed_no_signing`.
+
+### Negative meaning: PRESERVED
+The resolution reason and newValue ("confirmed_no_signing") both explicitly preserve the negative meaning — the customer will not sign.
+
+### Parent decision: RESOLVED IN PLACE (KNOWN/CLOSED)
+`n_product_launch_decision` transitioned from `unknown` → `resolved`. The 60B.64 deterministic closure rule fired correctly: all material factors resolved + raw user answer explicitly confirmed no further uncertainty => decision closed in place.
+
+### Identity preservation:
+- Decision node: PRESERVED
+- Launch option: PRESERVED
+- Wait option: PRESERVED
+
+### Active lifecycle: NULL — CLEARED
+`finalActiveUnknownNodeId` is directly `null`. No stale or genuine unresolved target remains.
+
+### Final question: NULL — DECISION COMPLETE
+`finalSelectedQuestion` is directly `null`. No continuation question was generated.
+
+### New uncertainty discipline: NONE (no new nodes, no new edges)
+
+### Recommendation direction: NONE (not inventoried by this run)
+
+## 60B.56 → 60B.66 comparison
+
+| Field | 60B.56 (FAILURE) | 60B.66 (PASS) |
+|---|---|---|
+| Proposal accepted | YES | YES |
+| Customer status | unknown→resolved | unknown→resolved |
+| Customer meaning | PRESERVED | PRESERVED |
+| Decision status | **unknown** (KEPT OPEN) | **resolved** (CLOSED) |
+| finalActiveUnknownNodeId | "n_product_launch_decision" | **null** |
+| finalSelectedQuestion | non-null decision_threshold | **null** |
+| addedNodes | [] | [] |
+| addedEdges | [] | [] |
+| resolvedUnknownNodeIds | ["n_enterprise_customer_signing"] | ["n_enterprise_customer_signing", "n_product_launch_decision"] |
+
+**Progress from 60B.56 → 60B.66:** The clean-closure contract is now met. The decision node auto-resolves when all its dependency unknowns resolve and the user explicitly confirms no further material uncertainty remains. Both `activeUnknownNodeId` and `selectedQuestion` are null.
+
+## Classification: A — LIVE REASONING THREAD CLOSED
+
+All success criteria directly observed:
+- Proposal accepted ✓
+- Customer resolves in place ✓
+- Negative meaning preserved ✓
+- Decision resolves/closes in place ✓
+- Decision identity preserved ✓
+- Both options preserved ✓
+- addedNodes = [] ✓
+- addedEdges = [] ✓
+- finalActiveUnknownNodeId = null ✓
+- finalSelectedQuestion = null ✓
+
+## What this proves
+
+1. **The 60B.64 decision-sufficiency closure rule works live.** When `hasRemainingMaterialFactors(decisionId, graph) === false` AND the raw user answer explicitly confirms no other material uncertainty remains, the parent decision node is correctly resolved before any follow-up question is selected.
+2. **No regression in customer-signing factor resolution.** The negative meaning (customer will not sign) is preserved exactly.
+3. **Zero spurious mutations.** No nodes or edges added during this resolution pass.
+4. **The exact live failure that drove experiments 60B.47→60B.64 is now fixed.**
+
+## Behavioural baseline
+
+```
+CUSTOMER-SIGNING / DECISION-SUFFICIENCY THREAD:
+BEHAVIOURALLY CLOSED FOR CURRENT REGRESSION BASELINE
+```
+
+This establishes a pre-refactor behavioural baseline. The behaviour may now be frozen as the baseline before any zero-semantic-change decision-sufficiency extraction refactor.
+
+## What remains unproven
+
+1. **All reasoning behaviour is complete** — NOT claimed. This experiment only covers the single customer-signing negative case on the product-launch decision graph.
+2. **All decision domains are proven** — NOT claimed. Other domains (savings, relocation, etc.) are not covered.
+3. **Production is universally correct** — NOT claimed.
+
+## Production code changed: NO
+## Prompt changed: NO
+## Validator changed: NO
+## Schema changed: NO
+## Harness changed during experiment: NO
+## Vitest run: NO
+## Ollama calls: 1
+## Direct API calls: 0
+## Dev server disturbed: NO