# Adaptive Noise Gating for Vulnerability Graphs

## Module
Attestor

## Status
IMPLEMENTED

## Description
Four-part noise reduction system: (1) Semantic edge deduplication collapsing redundant edges with provenance sets, (2) Proof Strength hierarchy (Authoritative=100 > BinaryProof=80 > StaticAnalysis=60 > Heuristic=40), (3) Stability damping gate preventing flip-flopping verdicts with hysteresis thresholds, (4) Delta sections categorizing changes as New/Resolved/ConfidenceUp/ConfidenceDown/PolicyImpact.

## Implementation Details
- **ProofChain Graph**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Graph/` -- `InMemoryProofGraphService` (with `.Mutation`, `.Queries`, `.Subgraph` partials) provides the in-memory graph with node/edge deduplication. `ProofGraphEdge` and `ProofGraphEdgeType` define edge semantics including provenance sets. `ProofGraphNode` and `ProofGraphNodeType` classify node types with strength levels.
- **Delta Verdict System**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Predicates/DeltaVerdictPredicate.cs` and `DeltaVerdictPredicate.Budget.cs` implement delta categorization (New/Resolved/ConfidenceUp/ConfidenceDown). `DeltaVerdictChange.cs` and `VerdictDeltaSummary.cs` track per-finding changes.
- **Evidence Confidence**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Generators/BackportProofGenerator.Confidence.cs` computes confidence scores using proof-strength hierarchy. `EvidenceSummary.cs` aggregates evidence with strength weighting.
- **Change Trace**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/ChangeTrace/ChangeTraceAttestationService.cs` (with `.Helpers` and `.Mapping` partials) tracks changes over time for stability damping.
- **Verdict Delta Predicates**: `VerdictFindingChange.cs`, `VerdictRuleChange.cs` categorize changes by policy impact.
- **Tests**: `__Tests/StellaOps.Attestor.ProofChain.Tests/Statements/DeltaVerdictStatementTests.cs`, `ChangeTrace/ChangeTracePredicateTests.cs`

## E2E Test Plan
- [ ] Create a proof graph with redundant edges (same source/target, different provenance) and verify that `InMemoryProofGraphService` deduplicates them into a single edge with merged provenance sets
- [ ] Submit evidence at different proof-strength tiers (Authoritative, BinaryProof, StaticAnalysis, Heuristic) and verify the `BackportProofGenerator.Confidence` produces correct weighted confidence scores
- [ ] Generate two consecutive verdict snapshots with minor score fluctuations below the hysteresis threshold and verify that `ChangeTraceAttestationService` suppresses the flip-flop delta
- [ ] Generate a delta verdict where findings are added, resolved, and confidence-changed, then verify `DeltaVerdictPredicate` categorizes each change correctly (New/Resolved/ConfidenceUp/ConfidenceDown/PolicyImpact)
- [ ] Query a subgraph via `InMemoryProofGraphService.Subgraph` and verify only reachable nodes from the root are included, with correct edge types