diff --git a/PHASE_3_IMPLEMENTATION_PLAN.md b/PHASE_3_IMPLEMENTATION_PLAN.md
new file mode 100644
index 00000000..dc9c8877
--- /dev/null
+++ b/PHASE_3_IMPLEMENTATION_PLAN.md
@@ -0,0 +1,569 @@
+# Phase 3 Implementation Plan: Sell Decision + Trade Execution
+
+**Date:** 2026-08-07  
+**Status:** 📋 PLANNING (Ready for execution)  
+**Execution Model:** WBS Optimization (Parallel + Phase 1 concurrent)  
+**Compliance:** AGENTS.md v16.0 13/13 criteria  
+
+---
+
+## 📊 PHASE 3 OVERVIEW
+
+### Context
+```
+Phase 1:  🚀 Shadow Run (autonomous, 50-90 days, data generating)
+Phase 2:  ✅ Complete (10 PRs merged, code integrated)
+Phase 3:  📋 Ready to plan (use Phase 1 data → decisions → execution)
+Phase 4:  🔮 Advanced (post-Phase 1, Gate 2+ prerequisites)
+```
+
+### Phase 3 Goals
+```
+1️⃣  Sell Decision Engine
+    → Generate sell signals based on model recommendations
+    → Implement approval workflow integration
+    → Enforce PBO/DSR validation gates
+
+2️⃣  Trade Execution System
+    → Execute approved sell decisions
+    → Handle KIS API integration
+    → Track execution lifecycle
+
+3️⃣  Portfolio Reconciliation
+    → Verify execution vs. approval
+    → Update holdings & cost basis
+    → Generate reconciliation reports
+```
+
+### Key Dependencies
+```
+Blockers:   Phase 1 must provide OOS/PBO/DSR evidence ✅ (autonomous)
+Ready Now:  Phase 2 infrastructure (approval/audit) ✅ (merged)
+New Work:   VS-10 (Sell Decision), VS-05+ (advanced features)
+```
+
+---
+
+## 🎯 PHASE 3 WORKSTREAMS
+
+### **WORKSTREAM J: VS-10 Sell Decision Engine**
+
+**Owner:** Quant Lead + PM  
+**Duration:** 4-5 weeks  
+**Start:** 2026-09-05 (after Phase 1 reaches 50% progress)  
+**Blocks:** VS-12, VS-13 (downstream)  
+
+#### Deliverables
+
+**J1: Data Contract & Slice Spec**
+- **Document:** `VS-10-SLICE_SPEC.md` (300-400 lines)
+- **Inputs:** Model recommendations, PBO/DSR scores, OOS validation
+- **Outputs:** Sell decision (quantity, timing, exit strategy)
+- **State Machine:**
+  ```
+  PENDING (awaiting Phase 1 evidence)
+  ↓
+  SIGNAL_GENERATED (model consensus)
+  ↓
+  PBO_VALIDATED (score check ≥ threshold)
+  ↓
+  DSR_VALIDATED (ratio check ≥ threshold)
+  ↓
+  OOS_APPROVED (out-of-sample performance confirmed)
+  ↓
+  READY_FOR_APPROVAL (meets governance gates)
+  ↓
+  APPROVED (maker-checker approval from VS-03)
+  ↓
+  EXECUTED (trade sent to KIS)
+  ↓
+  CONFIRMED (settlement confirmed)
+  ```
+
+**J2: Sell Priority Logic**
+- **Immutable Sell Priority:** `HARD_IMPAIRMENT → PORTFOLIO_SURVIVAL → DYNAMIC_PROFIT_FLOOR → CONCENTRATION/LIQUIDITY → OPPORTUNITY_COST → REENTRY_OPTION`
+- **Algorithm:** Score-based ranking (fairness + compliance)
+- **Output:** Ordered list of candidates for execution
+
+**J3: API Endpoints (3)**
+```
+POST /sell-decisions
+  Input: model_id, threshold_pbo, threshold_dsr
+  Output: 201 Created with decision_id
+
+GET /sell-decisions
+  Query: status, model_id, execution_date
+  Output: Paginated list
+
+POST /sell-decisions/{id}/execute
+  Input: approval_id (from VS-03)
+  Output: 202 Accepted (job queued)
+```
+
+**J4: Database Schema**
+```sql
+CREATE TABLE sell_decisions (
+  id UUID PRIMARY KEY,
+  model_id UUID REFERENCES models(id),
+  status VARCHAR(50),  -- PENDING, SIGNAL_GENERATED, PBO_VALIDATED, ..., CONFIRMED
+  pbo_score DECIMAL(5,4),
+  dsr_metric DECIMAL(5,4),
+  oos_performance JSONB,
+  sell_priority INT,
+  target_quantity INT,
+  target_price DECIMAL(15,2),
+  approval_id UUID REFERENCES approval_proposals(id),
+  execution_id UUID,  -- Reference to KIS trade
+  published_at TIMESTAMPTZ,
+  correlation_id UUID,
+  revision INT
+);
+
+CREATE TABLE sell_decision_evidence (
+  id UUID PRIMARY KEY,
+  decision_id UUID REFERENCES sell_decisions(id),
+  evidence_type VARCHAR(50),  -- PBO_REPORT, OOS_BACKTEST, DSR_METRIC
+  evidence_url TEXT,
+  validated_at TIMESTAMPTZ,
+  published_at TIMESTAMPTZ,
+  correlation_id UUID
+);
+```
+
+**J5: Handlers & Jobs**
+- `GenerateSellDecisionHandler` — Orchestrates scoring + validation
+- `ValidatePboHandler` — PBO score gate (≥ 0.65 recommended)
+- `ValidateDsrHandler` — DSR ratio gate (≥ 0.015 recommended)
+- `ValidateOosHandler` — OOS performance gate (pass/fail)
+- `ExecuteSellDecisionJob` — Queues trade via KIS API
+
+**J6: Tests**
+- 15+ unit tests (scoring logic, validation gates, priority ranking)
+- 8+ integration tests (E2E from signal to approval)
+- 3+ contract tests (approval/audit integration)
+
+**J7: Compliance**
+- ✅ AGENTS.md 13/13 (SOLID, complexity, audit, necessity, etc.)
+- ✅ PIT tracking (published_at, correlation_id, revision)
+- ✅ Immutable decisions (INSERT-only, no UPDATE)
+- ✅ Evidence linkage (S3 artifacts)
+
+---
+
+### **WORKSTREAM K: VS-12 Trade Execution**
+
+**Owner:** Backend Lead + Trading Ops  
+**Duration:** 3-4 weeks  
+**Start:** 2026-09-10 (parallel with J, overlapping)  
+**Depends On:** J (sell decision approval)  
+
+#### Deliverables
+
+**K1: KIS API Integration**
+- **Service:** `KisTradeExecutionService.cs`
+- **Methods:**
+  ```csharp
+  ExecuteTradeAsync(tradeRequest, correlationId)
+  GetOrderStatusAsync(orderId)
+  CancelOrderAsync(orderId, reason)
+  ConfirmSettlementAsync(orderId)
+  ```
+- **Features:**
+  - Connection pooling + retry logic (exponential backoff)
+  - Order validation (quantity, price, liquidity checks)
+  - Failure classification (transient/permanent/liquidity)
+
+**K2: Trade Lifecycle States**
+```
+PENDING (awaiting execution)
+↓
+SUBMITTED (sent to KIS)
+↓
+ACCEPTED (KIS confirmed receipt)
+↓
+PARTIAL_FILLED / FILLED (execution progress)
+↓
+CONFIRMED (settlement confirmed)
+↓
+RECONCILED (cost basis updated)
+```
+
+**K3: API Endpoints (2)**
+```
+POST /trades
+  Input: sell_decision_id, quantity, limit_price
+  Output: 202 Accepted with trade_id
+
+GET /trades
+  Query: status, decision_id, execution_date
+  Output: Paginated list with execution details
+```
+
+**K4: Database Schema**
+```sql
+CREATE TABLE trades (
+  id UUID PRIMARY KEY,
+  sell_decision_id UUID REFERENCES sell_decisions(id),
+  kis_order_id VARCHAR(50),  -- KIS-assigned order ID
+  status VARCHAR(50),  -- PENDING, SUBMITTED, ACCEPTED, FILLED, CONFIRMED, RECONCILED
+  quantity INT,
+  executed_quantity INT,
+  unit_price DECIMAL(15,2),
+  total_amount DECIMAL(18,2),
+  commission DECIMAL(15,2),
+  net_proceeds DECIMAL(18,2),
+  execution_timestamp TIMESTAMPTZ,
+  settlement_timestamp TIMESTAMPTZ,
+  error_message TEXT,
+  kis_response JSONB,
+  published_at TIMESTAMPTZ,
+  correlation_id UUID,
+  revision INT
+);
+```
+
+**K5: Handlers & Jobs**
+- `SubmitTradeHandler` — Submit to KIS
+- `PollTradeStatusJob` — Hangfire polling (q-evaluation queue)
+- `ConfirmSettlementHandler` — Mark settlement complete
+- `ReconcileTradeHandler` — Update cost basis
+
+**K6: Tests**
+- 12+ unit tests (validation, state transitions)
+- 8+ integration tests (KIS mock + real DB)
+- 3+ failure scenario tests (transient/permanent errors)
+
+**K7: Compliance**
+- ✅ AGENTS.md 13/13
+- ✅ Idempotent execution (no duplicate trades)
+- ✅ Audit trail (all state changes logged)
+- ✅ Error classification
+
+---
+
+### **WORKSTREAM L: VS-14 Portfolio Reconciliation**
+
+**Owner:** Data Architecture + Finance  
+**Duration:** 2-3 weeks  
+**Start:** 2026-09-15 (parallel with K, uses K output)  
+**Depends On:** K (trade execution)  
+
+#### Deliverables
+
+**L1: Reconciliation Engine**
+- **Algorithm:** Compare approved decisions vs. executed trades
+- **Inputs:**
+  - Sell decision (approved, PBO/DSR/OOS validated)
+  - Trade execution (settled, cost basis confirmed)
+  - Holdings (before execution)
+- **Outputs:**
+  - Holdings updated
+  - Cost basis adjusted
+  - Reconciliation report (matches/mismatches)
+
+**L2: Mismatch Detection**
+- Quantity mismatch (approved vs. executed)
+- Price variance (approved limit vs. actual)
+- Timing variance (decision date vs. execution date)
+- Settlement delay (execution vs. confirmation)
+
+**L3: Cost Basis Update**
+- Weighted average cost tracking
+- Lot tracking (FIFO/LIFO methods)
+- Gain/loss calculation
+- Tax lot reporting
+
+**L4: API Endpoints (2)**
+```
+GET /reconciliation/holdings
+  Response: Current portfolio state (updated after trade)
+
+GET /reconciliation/mismatches
+  Query: date_range, severity
+  Response: Flagged discrepancies for manual review
+```
+
+**L5: Database Schema**
+```sql
+CREATE TABLE holdings (
+  id UUID PRIMARY KEY,
+  security_id UUID REFERENCES financial_security_master.securities(id),
+  quantity INT,
+  weighted_avg_cost DECIMAL(15,2),
+  total_cost_basis DECIMAL(18,2),
+  market_value DECIMAL(18,2),
+  unrealized_gain_loss DECIMAL(18,2),
+  updated_at TIMESTAMPTZ,
+  published_at TIMESTAMPTZ,
+  correlation_id UUID,
+  revision INT
+);
+
+CREATE TABLE reconciliation_logs (
+  id UUID PRIMARY KEY,
+  trade_id UUID REFERENCES trades(id),
+  holding_id UUID REFERENCES holdings(id),
+  quantity_before INT,
+  quantity_after INT,
+  cost_basis_delta DECIMAL(18,2),
+  mismatch_detected BOOLEAN,
+  mismatch_reason TEXT,
+  reconciled_at TIMESTAMPTZ,
+  published_at TIMESTAMPTZ,
+  correlation_id UUID
+);
+```
+
+**L6: Tests**
+- 10+ unit tests (cost basis, gain/loss calculation)
+- 6+ integration tests (reconciliation workflow)
+- 3+ scenario tests (edge cases: splits, dividends)
+
+---
+
+## 📈 EXECUTION TIMELINE
+
+### Week 1-2 (2026-09-05 ~ 2026-09-18)
+```
+J1: VS-10 Spec & Contract Design (parallel)
+K1: VS-12 API & KIS Integration (parallel)
+L1: VS-14 Design & Algorithm (parallel)
+
+Status: D/E/F design docs, ready for implementation
+Phase 1: 50%-75% progress
+```
+
+### Week 3-4 (2026-09-19 ~ 2026-10-02)
+```
+J2-J7: VS-10 Implementation & Tests
+K2-K6: VS-12 Implementation & Tests
+L2-L5: VS-14 Implementation & Tests
+
+Status: All 3 slices in parallel, 50% code complete
+Phase 1: 75%-90% progress
+```
+
+### Week 5-6 (2026-10-03 ~ 2026-10-16)
+```
+J/K/L: Integration testing (cross-slice)
+       Phase 1 final results available
+       Gate 2 validation begins
+
+Status: All code complete, integration verified
+Phase 1: 90-100% (completion), results ready
+```
+
+### Week 7+ (2026-10-17+)
+```
+Phase 1 Complete → Gate 2 Execution
+Phase 3 Implementation → Production Deployment (~November)
+```
+
+---
+
+## 🎯 WBS OPTIMIZATION STRATEGY
+
+### Parallel Execution (J + K + L Simultaneous)
+```
+Sequential (Baseline):  J(4w) → K(3w) → L(2w) = 9 weeks
+Parallel (Actual):      All 3 simultaneous = 5 weeks
+────────────────────────────────────────────────
+TIME SAVED:             4 weeks ⏱️
+
+Dependencies:
+  J outputs → K inputs (sell decision → trade execution)
+  K outputs → L inputs (trade execution → reconciliation)
+  
+Overlap Strategy:
+  Week 1-2: J design, K design, L design (PARALLEL)
+  Week 2-3: J → 50%, K start (J unblocks K)
+  Week 3-4: J → 100%, K → 50%, L start (K unblocks L)
+  Week 4-5: All 3 at 75-100% (overlapping)
+  Week 5-6: Integration testing (all done)
+```
+
+### Phase 1 Concurrent Execution
+```
+Phase 1:  🚀 Autonomous (50-90 days, data generating)
+Phase 3:  📋 Implementation in parallel (uses accumulated data)
+
+Benefit:
+  • No waiting for Phase 1 to complete
+  • Infrastructure ready when Phase 1 evidence available
+  • Gate 2 validation can begin on Day 75+ (mid-way through Phase 1)
+  • Production deployment by November 2026
+```
+
+---
+
+## ✅ AGENTS.md v16.0 COMPLIANCE PLAN
+
+### Verification Framework (Apply to J/K/L)
+
+| Criterion | J (Sell Decision) | K (Trade Execution) | L (Reconciliation) |
+|-----------|------------------|---------------------|-------------------|
+| 1. SOLID | 3 services (scoring, validation, approval) | KIS service + handlers | Reconciliation + reports |
+| 2. Complexity | Each <300 lines, readable | Connection pool, retry logic | Calc engine, mismatch detection |
+| 3. Audit | correlation_id, PIT tracking | All state changes logged | Cost basis trail |
+| 4. Necessity | Grounded in Phase 1 evidence | Spec-before-code ✅ | Portfolio integrity |
+| 5. Normalization | 3NF schema, append-only | PIT tracked decisions | Versioned holdings |
+| 6. Simplicity | State machine clear | No magic numbers | Algorithm transparent |
+| 7. Pattern | Vertical Slice (Services/Handlers/Endpoints/Sql) | Contract-driven | Domain-driven design |
+| 8. Guardrails | Validation gates (PBO/DSR/OOS) | Error classification | Mismatch alerts |
+| 9. Traceability | Evidence links to S3 | CorrelationId throughout | Audit trail immutable |
+| 10. Safety | Idempotent operations | Rollback-safe state | No partial reconciliation |
+| 11. Maturity | Spec-before-code ✅ | Data contracts ✅ | Design docs ✅ |
+| 12. Right-Way | Formal gates, no shortcuts | KIS official API | Regulatory compliance |
+| 13. Debt | No new tech debt | Enables Phase 4 | Tech debt registry |
+
+---
+
+## 📊 RESOURCE ALLOCATION
+
+### Team Assignment (Recommended)
+
+**Workstream J (Sell Decision)** — 3 people, 5 weeks
+```
+Lead:     Quant Lead (decision logic, PBO/DSR validation)
+Backend:  2 engineers (API, database, handlers, tests)
+Effort:   ~200 hours
+```
+
+**Workstream K (Trade Execution)** — 3 people, 4 weeks
+```
+Lead:     Backend Lead (KIS integration, error handling)
+Trading:  1 operations engineer (KIS API knowledge)
+Backend:  1 engineer (handlers, jobs, reconciliation)
+Effort:   ~150 hours
+```
+
+**Workstream L (Portfolio Reconciliation)** — 2 people, 3 weeks
+```
+Lead:     Data Architect (reconciliation algorithm)
+Finance:  1 engineer (cost basis, gain/loss, reporting)
+Effort:   ~100 hours
+```
+
+**Total Phase 3 Effort:** ~450 hours (~11 weeks serial, 5 weeks parallel)
+
+---
+
+## 📋 MILESTONE CHECKLIST
+
+### Phase 3 Gates (Pre-Merge)
+
+**J (Sell Decision):**
+- [ ] VS-10 SLICE_SPEC complete (Spec-before-code)
+- [ ] PBO/DSR/OOS validation gates designed
+- [ ] API contracts finalized
+- [ ] Database migration validated (fresh/upgrade/re-run)
+- [ ] Unit tests: 15/15 PASS
+- [ ] Integration tests: 8/8 PASS
+- [ ] Architecture tests: SOLID compliance verified
+- [ ] No SELECT *, schema-qualified SQL
+- [ ] Immutable decisions (INSERT-only)
+- [ ] Correlation_id traceability
+
+**K (Trade Execution):**
+- [ ] VS-12 SLICE_SPEC complete
+- [ ] KIS API contract finalized
+- [ ] Error classification (transient/permanent/liquidity)
+- [ ] Idempotency key strategy
+- [ ] Unit tests: 12/12 PASS
+- [ ] Integration tests: 8/8 PASS
+- [ ] State machine transitions verified
+- [ ] Rollback-safe design confirmed
+
+**L (Portfolio Reconciliation):**
+- [ ] VS-14 SLICE_SPEC complete
+- [ ] Reconciliation algorithm validated
+- [ ] Cost basis calculations verified
+- [ ] Unit tests: 10/10 PASS
+- [ ] Integration tests: 6/6 PASS
+- [ ] Edge cases (splits, dividends) handled
+- [ ] Tax lot tracking verified
+
+**Cross-Slice Integration:**
+- [ ] J → K flow verified (decision → execution)
+- [ ] K → L flow verified (execution → reconciliation)
+- [ ] Audit trail (VS-04) integration complete
+- [ ] Approval workflow (VS-03) integration complete
+- [ ] E2E tests: PASS
+- [ ] Gate 2 prerequisite data ready (Phase 1 evidence)
+
+---
+
+## 🎯 SUCCESS CRITERIA
+
+### Code Quality
+```
+Tests:      48+ (unit/integration/E2E)
+Coverage:   ≥80% code coverage
+Complexity: All classes <300 lines
+Compliance: AGENTS.md 13/13 ✅
+Tech Debt:  No new unbounded debt
+```
+
+### Business Metrics
+```
+Sell Decision Accuracy:  PBO/DSR/OOS validation pass rate ≥95%
+Trade Execution Rate:    Approved decisions → executed ≥99%
+Reconciliation Success:  Mismatches ≤0.1% (normal variance)
+SLA Compliance:          Execution latency <1 hour (from approval)
+```
+
+### Timeline
+```
+Week 5-6:    All code merged to main
+Week 6-7:    Integration testing & bug fixes
+Week 7+:     Production deployment (Gate 2+ validation)
+November:    Production live (full automation)
+```
+
+---
+
+## 📈 PHASE 3 ROADMAP DIAGRAM
+
+```
+Phase 1 (Autonomous)      Phase 2 (Merged)         Phase 3 (Parallel)
+─────────────────        ───────────────          ──────────────────
+50-90 days               ✅ Complete              J: Sell Decision  
+(Data generating)        10 PRs merged            K: Trade Exec     (Parallel)
+                                                  L: Reconciliation 
+                                                  
+                         VS-03 Approval   ──→  J→K (flow)
+                         VS-04 Audit      ──→  all J/K/L logged
+
+                                                  ↓ (Week 6)
+                                                  Integration tests
+                                                  
+                                                  ↓ (Week 7)
+                                                  Gate 2 validation
+                                                  (Phase 1 evidence)
+                                                  
+                                                  ↓ (Week 8+)
+                                                  Production
+```
+
+---
+
+## ✅ APPROVAL & SIGN-OFF
+
+**Phase 3 Plan Status:** 📋 Ready for review and team assignment  
+**Dependencies:** Phase 1 autonomous (no manual action needed) ✅  
+**Readiness:** Phase 2 infrastructure (approval/audit) merged ✅  
+**AGENTS.md Compliance:** 13/13 criteria framework ✅  
+
+**Next Steps:**
+1. Team review Phase 3 plan
+2. Assign teams to J/K/L workstreams
+3. Start Phase 3 implementation (2026-09-05)
+4. Monitor Phase 1 progress (autonomous)
+5. Execute Phase 3 in parallel with Phase 1 completion
+
+---
+
+**Generated:** 2026-08-07  
+**Prepared By:** Claude Haiku 4.5 <noreply@anthropic.com>  
+**Framework:** WBS Optimization + AGENTS.md v16.0  
+**Status:** ✅ READY FOR EXECUTION