# Nightly Unknowns Decay Batch Worker

## Module
Signals

## Status
VERIFIED

## Description
Scheduled background worker that runs nightly to apply exponential confidence decay to unknown/unresolved findings, automatically reducing their priority scores over time based on configurable decay curves and age thresholds.

## Implementation Details
- **Modules**: `src/Signals/StellaOps.Signals/Services/`, `src/Signals/StellaOps.Signals/Options/`
- **Key Classes**:
  - `NightlyDecayWorker` (`src/Signals/StellaOps.Signals/Services/NightlyDecayWorker.cs`) - background service that runs nightly decay processing
  - `UnknownsDecayService` (`src/Signals/StellaOps.Signals/Services/UnknownsDecayService.cs`) - applies exponential confidence decay to unknown/unresolved findings
  - `UnknownsDecayOptions` (`src/Signals/StellaOps.Signals/Options/UnknownsDecayOptions.cs`) - configurable decay curves and age thresholds
  - `UnknownsDecayMetrics` (`src/Signals/StellaOps.Signals/Services/UnknownsDecayMetrics.cs`) - telemetry metrics for decay operations
- **Interfaces**: `IUnknownsDecayService`
- **Source**: SPRINT_3601_0001_0001_unknowns_decay_algorithm.md

## E2E Test Plan
- [ ] Configure `UnknownsDecayOptions` with a decay curve and verify `NightlyDecayWorker` triggers on schedule
- [ ] Create unknown findings of varying ages and verify `UnknownsDecayService` reduces scores proportionally to age
- [ ] Verify exponential decay: confirm older findings decay faster than newer ones
- [ ] Verify age threshold: findings below the threshold are not decayed
- [ ] Verify metrics are emitted during decay processing via `UnknownsDecayMetrics`