# Adaptive Noise Gating for Vulnerability Graphs

## Module
Attestor

## Status
VERIFIED

## Description
Four-part noise reduction system is implemented: semantic edge deduplication with merged provenance sets, proof-strength hierarchy for confidence scoring, hysteresis damping for small flip-flop deltas, and explicit delta category classification.

## Implementation Details
- **ProofChain Graph**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Graph/` -- `InMemoryProofGraphService` deduplicates by semantic edge key and merges provenance values deterministically; `ProofGraphEdge` now carries provenance sets.
- **Proof Strength Hierarchy**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Generators/BackportProofGenerator.Confidence.cs` maps evidence into `Authoritative > BinaryProof > StaticAnalysis > Heuristic` strengths and applies bounded corroboration bonuses.
- **Stability Damping Gate**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/ChangeTrace/IChangeTraceAttestationService.cs` + `ChangeTraceAttestationService.Mapping.cs` + `ChangeTraceAttestationService.Helpers.cs` add configurable hysteresis threshold suppression for low-amplitude modified/rebuilt deltas.
- **Delta Classification**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Predicates/DeltaVerdictPredicate.Categorization.cs` adds explicit `New/Resolved/ConfidenceUp/ConfidenceDown/PolicyImpact` normalization and inference.
- **Tests**: `src/Attestor/__Tests/StellaOps.Attestor.ProofChain.Tests/Graph/InMemoryProofGraphServiceBehaviorTests.cs`, `src/Attestor/__Tests/StellaOps.Attestor.ProofChain.Tests/BackportProofGeneratorTests.cs`, `src/Attestor/__Tests/StellaOps.Attestor.ProofChain.Tests/ChangeTrace/ChangeTraceAttestationServiceTests.cs`, `src/Attestor/__Tests/StellaOps.Attestor.ProofChain.Tests/Statements/DeltaVerdictPredicateCategorizationTests.cs`.

## E2E Test Plan
- [x] Create a proof graph with redundant edges (same source/target, different provenance) and verify `InMemoryProofGraphService` deduplicates to one edge with merged provenance.
- [x] Submit evidence at different proof-strength tiers and verify confidence ordering.
- [x] Generate consecutive snapshots with minor score fluctuations below hysteresis threshold and verify flip-flop suppression.
- [x] Generate delta verdict changes and verify category mapping (`New/Resolved/ConfidenceUp/ConfidenceDown/PolicyImpact`).
- [x] Query a subgraph and verify only reachable nodes from root are included.

## Verification
- Verified on 2026-02-11 using `run-002`.
- Evidence:
  - `docs/qa/feature-checks/runs/attestor/adaptive-noise-gating-for-vulnerability-graphs/run-002/tier0-source-check.json`
  - `docs/qa/feature-checks/runs/attestor/adaptive-noise-gating-for-vulnerability-graphs/run-002/tier1-build-check.json`
  - `docs/qa/feature-checks/runs/attestor/adaptive-noise-gating-for-vulnerability-graphs/run-002/tier2-e2e-check.json`