# Time-to-First-Signal (TTFS) Metrics, Telemetry, and Benchmarks

## Module
Scanner

## Status
VERIFIED

## Description
TTFS telemetry services on both frontend and backend. Frontend tracks signal rendering timing, backend has performance benchmarks. Deterministic test fixtures for TTFS validation.

## Implementation Details
- **Performance Benchmarks**:
  - `src/Scanner/__Tests/StellaOps.Scanner.WebService.Tests/Benchmarks/TtfsPerformanceBenchmarks.cs` - `TtfsPerformanceBenchmarks` measuring time-to-first-signal for scanner API responses with deterministic test fixtures

## E2E Test Plan
- [ ] Run TTFS performance benchmarks and verify time-to-first-signal is within acceptable thresholds for scan initiation
- [ ] Verify TTFS metrics are captured for the full scan lifecycle (submission -> first finding -> complete)
- [ ] Verify deterministic test fixtures produce consistent TTFS measurements across runs
- [ ] Verify TTFS telemetry is available via the scanner WebService API for monitoring dashboards
- [ ] Verify TTFS benchmarks cover different scan sizes (small, medium, large images) with documented baselines

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## 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 |