# Graph Explorer API with Streaming Tiles

## Module
Graph

## Status
IMPLEMENTED

## Description
Graph query and visualization API providing streaming tile-based graph rendering, path queries, diff computation between graph revisions, RBAC-enforced exports (SVG/PNG/GraphML), and overlay support for policy/VEX/reachability annotations.

## Implementation Details
- **API program**: `src/Graph/StellaOps.Graph.Api/Program.cs` -- minimal API endpoints for graph queries, diffs, exports, search, paths, lineage, overlays
- **Query service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphQueryService.cs`, `InMemoryGraphQueryService.cs` -- graph node/edge query
- **Search service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphSearchService.cs`, `InMemoryGraphSearchService.cs` -- full-text graph search
- **Path service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphPathService.cs`, `InMemoryGraphPathService.cs` -- graph path traversal
- **Diff service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphDiffService.cs`, `InMemoryGraphDiffService.cs` -- diff computation between graph revisions
- **Export service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphExportService.cs`, `InMemoryGraphExportService.cs` -- RBAC-enforced export (SVG/PNG/GraphML)
- **Lineage service**: `src/Graph/StellaOps.Graph.Api/Services/IGraphLineageService.cs`, `InMemoryGraphLineageService.cs` -- lineage traversal
- **Overlay service**: `src/Graph/StellaOps.Graph.Api/Services/IOverlayService.cs`, `InMemoryOverlayService.cs` -- policy/VEX/reachability overlays
- **Reachability delta**: `src/Graph/StellaOps.Graph.Api/Services/IReachabilityDeltaService.cs`, `InMemoryReachabilityDeltaService.cs` -- reachability delta computation
- **Rate limiting**: `src/Graph/StellaOps.Graph.Api/Services/RateLimiterService.cs` -- API rate limiting
- **Metrics**: `src/Graph/StellaOps.Graph.Api/Services/GraphMetrics.cs` -- Prometheus-compatible API metrics
- **Audit**: `src/Graph/StellaOps.Graph.Api/Services/IAuditLogger.cs` -- audit logging for graph access
- **Contracts**: `src/Graph/StellaOps.Graph.Api/Contracts/SearchContracts.cs`, `LineageContracts.cs`, `ReachabilityContracts.cs`
- **Tests**: `src/Graph/__Tests/StellaOps.Graph.Api.Tests/` -- QueryServiceTests, SearchServiceTests, PathServiceTests, DiffServiceTests, ExportServiceTests, LineageServiceTests, LoadTests, MetricsTests, RateLimiterServiceTests, GraphApiContractTests
- **Source**: SPRINT_0207_0001_0001_graph.md

## E2E Test Plan
- [ ] Verify graph query API returns nodes and edges for given criteria
- [ ] Test streaming tile rendering for large graphs
- [ ] Verify diff computation between two graph revisions
- [ ] Test RBAC-enforced export in SVG/PNG/GraphML formats
- [ ] Verify overlay annotations for policy/VEX/reachability layers
- [ ] Test search API returns relevant results with ranking