# Excititor · Graph Overlay Prep (GRAPH-21-002)

- **Date:** 2025-11-20
- **Depends on:** GRAPH-21-001 linkout contract
- **Working directory:** `src/Excititor/StellaOps.Excititor.WebService`

## Overlay payload
- Aggregates output of GRAPH-21-001 into overlay items for inspectors:
  - `purl`
  - `summary`: `open`, `not_affected`, `under_investigation`, `no_statement` counts
  - `latestModifiedAt` (ISO-8601 UTC)
  - `justifications[]` (optional) — unique justification codes present for the PURL
  - `provenance` — `sources[]` (unique source IDs), `lastEvidenceHash`
- Endpoint: `GET /v1/graph/overlays?purl=<purl>[&purl=...]&includeJustifications=true|false`
- Sorting: results ordered by input PURL list; within overlays, `justifications` sorted ascending.

## Caching
- Cache key: tenant + sorted PURL list + `includeJustifications` flag; ttl 5 minutes default, configurable `excititor:graph:overlayTtlSeconds`.
- Cache metadata returned: `cached: true|false`, `cacheAgeMs`.

## Acceptance for prep completion
- Overlay shape and caching contract defined; implementation can proceed once GRAPH-21-001 is available.