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docs/features/checked/scanner/oci-layer-manifest-infrastructure-for-delta-scanning.md

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+# OCI Layer Manifest Infrastructure for Delta Scanning
+
+## Module
+Scanner
+
+## Status
+VERIFIED
+
+## Description
+Infrastructure for OCI manifest snapshotting with layer digest resolution and diffID-based layer tracking. Provides layer reuse detection across image versions and a registry client abstraction to support delta scanning workflows. Distinct from generic "OCI Ancestry Extraction" in known features.
+
+## Implementation Details
+- **Manifest Snapshot Service**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/IOciManifestSnapshotService.cs` - `IOciManifestSnapshotService` interface for manifest snapshot operations
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/OciManifestSnapshotService.cs` - `OciManifestSnapshotService` captures and compares OCI manifest snapshots for delta scanning
+- **Manifest Models**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Models/OciManifestSnapshot.cs` - `OciManifestSnapshot` representing a point-in-time manifest state with layer digests
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Models/ManifestComparisonResult.cs` - `ManifestComparisonResult` identifies added, removed, and unchanged layers between snapshots
+- **Layer Digest Resolution**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Resolution/ILayerDigestResolver.cs` - Interface for resolving layer digests to diffIDs
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Resolution/LayerDigestResolver.cs` - `LayerDigestResolver` resolves compressed layer digests to uncompressed diffIDs for consistent tracking
+- **Layer Reuse Detection**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Reuse/LayerReuseDetector.cs` - `LayerReuseDetector` identifies unchanged layers across image versions to skip re-analysis
+- **Persistence**:
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Persistence/IManifestSnapshotRepository.cs` - Repository interface for snapshot storage
+  - `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/Persistence/ManifestSnapshotRepository.cs` - PostgreSQL-backed snapshot persistence
+- **DI Registration**: `src/Scanner/__Libraries/StellaOps.Scanner.Manifest/ManifestServiceCollectionExtensions.cs`
+
+## E2E Test Plan
+- [ ] Scan an image and verify a manifest snapshot is captured with all layer digests and diffIDs
+- [ ] Rescan a newer version of the same image and verify manifest comparison correctly identifies added, removed, and unchanged layers
+- [ ] Verify layer reuse detection skips unchanged layers in subsequent scans, reducing scan time
+- [ ] Verify diffID-based tracking correctly matches layers across manifest versions despite compressed digest differences
+- [ ] Verify manifest snapshots are persisted and retrievable for historical comparison
+
+---
+
+## 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 |