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docs/features/checked/policy/release-gate-levels.md

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+# Release Gate Levels (G0-G4)
+
+## Module
+Policy
+
+## Status
+IMPLEMENTED
+
+## Description
+Five gate levels (G0 through G4) with escalating requirements. GateSelector computes RRS, maps to gate level, and applies budget modifiers (Yellow/Red/Exhausted escalations). Each gate level has defined requirements matching the advisory specification.
+
+## Implementation Details
+- **PolicyGateEvaluator**: `src/Policy/StellaOps.Policy.Engine/Gates/PolicyGateEvaluator.cs`
+  - Multi-gate evaluation with escalating strictness per gate level
+  - Gate levels mapped from Risk Readiness Score (RRS) and budget status
+  - 5 sequential gates with configurable thresholds per level
+  - Lattice states drive gate decisions: U, SR, SU, RO, RU, CR, CU, X
+  - Uncertainty tiers: T1 (High) -> strictest, T4 (Negligible) -> most permissive
+- **PolicyGateOptions**: `src/Policy/StellaOps.Policy.Engine/Gates/PolicyGateOptions.cs` -- per-level gate configuration
+- **PolicyGateDecision**: `src/Policy/StellaOps.Policy.Engine/Gates/PolicyGateDecision.cs` -- decision model with per-gate results
+- **RiskSimulationService**: `src/Policy/StellaOps.Policy.Engine/Simulation/RiskSimulationService.cs`
+  - Signal-based RRS computation with severity mapping
+  - Severity: Critical>=90, High>=70, Medium>=40, Low>=10
+  - Distribution and percentile calculation for gate level determination
+- **Budget integration**: Budget status (Yellow/Red/Exhausted) escalates gate level
+  - `BudgetEndpoints.cs`: `src/Policy/StellaOps.Policy.Engine/Endpoints/BudgetEndpoints.cs`
+  - `RiskBudgetEndpoints.cs`: `src/Policy/StellaOps.Policy.Engine/Endpoints/RiskBudgetEndpoints.cs`
+- **Ledger**: `src/Policy/StellaOps.Policy.Engine/Ledger/` -- tracks gate decisions for compliance
+
+## E2E Test Plan
+- [ ] Evaluate artifact with low RRS (minimal risk); verify gate level maps to G0 (minimal requirements)
+- [ ] Evaluate artifact with high RRS (many critical findings); verify gate level escalates to G3 or G4
+- [ ] Evaluate with budget status Yellow; verify gate level escalates by one level
+- [ ] Evaluate with budget status Exhausted; verify gate level escalates to maximum (G4)
+- [ ] Evaluate at G0: verify only basic evidence completeness is checked
+- [ ] Evaluate at G4: verify all gates apply strictest thresholds (lattice state, VEX trust, uncertainty, confidence)
+- [ ] Verify each gate level (G0-G4) has progressively stricter thresholds
+- [ ] Verify gate decision includes per-gate Pass/Warn/Block results for audit trail
+- [ ] Verify ledger records gate level and decision for compliance