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docs/features/checked/scanner/false-negative-drift-tracking-and-metrics.md

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+# False-negative drift (FN-Drift) tracking and metrics
+
+## Module
+Scanner
+
+## Status
+VERIFIED
+
+## Description
+FN-Drift calculation, metrics export, and classification change history tracking with dedicated Postgres migration.
+
+## Implementation Details
+- **FN-Drift Calculation**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Services/FnDriftCalculator.cs` - Calculates false-negative drift metrics
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Services/FnDriftMetricsExporter.cs` - Exports FN-Drift metrics for telemetry
+- **Classification Change Tracking**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Services/ClassificationChangeTracker.cs` - Tracks classification changes over time
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Models/ClassificationChangeModels.cs` - Change models
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Repositories/IClassificationHistoryRepository.cs` - Repository interface
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Storage/Repositories/ClassificationHistoryRepository.cs` - PostgreSQL repository
+
+## E2E Test Plan
+- [ ] Run multiple scans over time and verify `FnDriftCalculator` computes drift metrics based on classification changes
+- [ ] Verify classification change history is persisted and queryable
+- [ ] Verify FN-Drift metrics are exported to the telemetry system
+- [ ] Verify classification changes (e.g., vulnerable -> not_affected -> vulnerable) are tracked with timestamps
+- [ ] Verify drift metrics accurately reflect the rate of false-negative changes over time
+
+---
+
+## Verification
+
+| Check | Result |
+|-------|--------|
+| Tier 0 - Source files exist | PASS |
+| Tier 1 - Build + code review | PASS |
+| Tier 2 - Integration tests | PASS |
+| Verified | 2026-02-13T18:10:00Z |