# Immutable Audit Log (Timeline)

## Module
Timeline

## Status
IMPLEMENTED

## Description
Immutable timeline audit log with a dedicated web service and indexer for recording all scan, attestation, and verdict events.

## Implementation Details
- **TimelineQueryService**: `src/Timeline/__Libraries/StellaOps.Timeline.Core/TimelineQueryService.cs` -- append-only event store query layer: GetByCorrelationIdAsync (with HLC range, service/kind filters, pagination), GetCriticalPathAsync (causal latency analysis), GetByServiceAsync (service-scoped queries)
- **ITimelineEventStore**: referenced from `StellaOps.Eventing.Storage` -- append-only persistence interface: events stored with deterministic EventId (SHA-256 of correlation_id+t_hlc+service+kind), HLC timestamps, payload digests, engine version fingerprints
- **TimelineEndpoints**: `src/Timeline/StellaOps.Timeline.WebService/Endpoints/TimelineEndpoints.cs` -- REST API at `/api/v1/timeline`: GET /{correlationId} returns immutable event chain, GET /{correlationId}/critical-path for latency analysis
- **ExportEndpoints**: `src/Timeline/StellaOps.Timeline.WebService/Endpoints/ExportEndpoints.cs` -- forensic export at `/api/v1/timeline/{correlationId}/export`: NDJSON/JSON bundle with optional DSSE signing for evidence preservation
- **TimelineBundleBuilder**: `src/Timeline/__Libraries/StellaOps.Timeline.Core/Export/TimelineBundleBuilder.cs` -- builds NDJSON/JSON export bundles with event metadata (event_id, t_hlc, ts_wall, service, kind, payload_digest, engine_version); optional DSSE signing via IEventSigner
- **HealthEndpoints**: `src/Timeline/StellaOps.Timeline.WebService/Endpoints/HealthEndpoints.cs` -- service health monitoring
- **TimelineAuthorizationMiddleware**: `src/Timeline/StellaOps.Timeline.WebService/Authorization/TimelineAuthorizationMiddleware.cs` -- authorization for timeline access
- **Tests**: `src/Timeline/__Tests/StellaOps.Timeline.WebService.Tests/TimelineApiIntegrationTests.cs`
- **Source**: Feature matrix scan

## E2E Test Plan
- [ ] Verify events stored are immutable (no update/delete operations exposed)
- [ ] Verify event IDs are deterministic based on correlation_id + t_hlc + service + kind
- [ ] Test export endpoint produces valid NDJSON bundle with all event metadata
- [ ] Verify DSSE-signed export bundles can be verified with the signing key
- [ ] Test JSON export format includes event metadata section with count and export timestamp
- [ ] Verify payload digests in exported events match original payloads
- [ ] Test authorization middleware restricts timeline access to authorized users