# Vendor comparison / scanner parity tracking

## Module
Bench

## Status
VERIFIED

## Description
Scanner analyzer benchmark parity tracking capabilities are present through benchmark reports and metric exports. Fresh behavioral verification confirmed parity-report fields are emitted in benchmark JSON output and CLI error semantics are enforced for invalid configuration.

## What's Implemented
- **Scanner Analyzers Benchmark**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/` -- benchmark harness evaluating analyzer scenarios and recording metrics.
- **Baseline Loader**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Baseline/BaselineLoader.cs` -- loads baseline data for benchmark comparisons.
- **Baseline Entry**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Baseline/BaselineEntry.cs` -- baseline model.
- **Benchmark Scenario Report**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Reporting/BenchmarkScenarioReport.cs` -- per-scenario report model including regression and parity fields.
- **Benchmark JSON Writer**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Reporting/BenchmarkJsonWriter.cs` -- JSON report writer.
- **Prometheus Writer**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Reporting/PrometheusWriter.cs` -- Prometheus metrics exporter.
- **Vendor Parity Analyzer**: `src/Bench/StellaOps.Bench/Scanner.Analyzers/StellaOps.Bench.ScannerAnalyzers/Reporting/VendorParityAnalyzer.cs` -- computes vendor parity projections where vendor fixtures are available.

## E2E Test Plan
- [x] Run scanner-analyzers benchmark harness and verify JSON/Prometheus/CSV outputs are generated.
- [x] Validate benchmark JSON output contains `vendorParity` fields in scenario reports.
- [x] Verify baseline/regression metadata is emitted in benchmark JSON.
- [x] Verify negative-path behavior with missing config returns non-zero exit code.

## Verification
- Verified on 2026-02-11 via FLOW Tier 0/1/2 replay in `run-001`.
- Tier 0: `docs/qa/feature-checks/runs/bench/vendor-comparison-scanner-parity-tracking/run-001/tier0-source-check.json`
- Tier 1: `docs/qa/feature-checks/runs/bench/vendor-comparison-scanner-parity-tracking/run-001/tier1-build-check.json`
- Tier 2: `docs/qa/feature-checks/runs/bench/vendor-comparison-scanner-parity-tracking/run-001/tier2-integration-check.json`