# EPSS Feed Connector (Concelier Three-Stage Pattern)

## Module
Concelier

## Status
VERIFIED

## Description
Concelier connector for EPSS (Exploit Prediction Scoring System) feed ingestion following three-stage Fetch/Parse/Map pattern. Reuses Scanner's EpssCsvStreamParser for CSV parsing, supports ETag conditional requests, air-gap bundle fallback, priority band classification (Critical/High/Medium/Low at 0.70/0.40/0.10 thresholds), and daily scheduled ingestion (10:00 UTC).

## Implementation Details
- **Modules**: `src/Concelier/__Libraries/StellaOps.Concelier.Connector.Epss/`
- **Key Classes**:
  - `EpssConnector` (`src/Concelier/__Libraries/StellaOps.Concelier.Connector.Epss/Internal/EpssConnector.cs`) - `IFeedConnector` implementation with three-stage Fetch/Parse/Map pattern
  - `EpssConnectorPlugin` (`src/Concelier/__Libraries/StellaOps.Concelier.Connector.Epss/EpssConnectorPlugin.cs`) - `IConnectorPlugin` registration for DI discovery
- **Interfaces**: `IFeedConnector`, `IConnectorPlugin`
- **Source**: SPRINT_4000_0002_0001_epss_feed_connector.md

## E2E Test Plan
- [x] Trigger EPSS connector ingestion and verify EPSS scores are fetched and stored for CVE IDs
- [x] Verify priority band classification: CVEs with EPSS > 0.70 are classified as Critical, 0.40-0.70 as High, 0.10-0.40 as Medium, < 0.10 as Low
- [x] Verify ETag conditional requests: second ingestion with unchanged data returns 304 and skips re-parsing
- [x] Verify air-gap bundle fallback: configure offline mode and verify ingestion falls back to local bundle
- [x] Verify daily scheduled ingestion runs at the configured time

## Verification
- **Run ID**: run-003
- **Date**: 2026-02-12
- **Tests**: 46 passed, 0 failed (StellaOps.Concelier.Connector.Epss.Tests)
- **Verdict**: PASS - All behavioral assertions verified including three-stage Fetch/Parse/Map pattern, ETag conditional request handling, band classification at all thresholds, deterministic CSV parsing, cursor round-trip fidelity, and options validation.