# Reachability Graph Service (Slice and Replay)

## Module
Attestor

## Status
VERIFIED

## Description
Full reachability graph service with slice extraction, deterministic replay, storage, and REST API.

## Implementation Details
- **Reachability Subgraph Predicate**: `src/Attestor/__Libraries/StellaOps.Attestor.ProofChain/Predicates/ReachabilitySubgraphPredicate.cs` -- predicate for attested reachability subgraphs (slices).
- **Reachability Subgraph Statement**: `Statements/ReachabilitySubgraphStatement.cs` -- in-toto statement wrapping the subgraph slice.
- **Proof Graph Service**: `Graph/InMemoryProofGraphService.cs` (with `.Queries`, `.Subgraph`) -- graph service supporting subgraph extraction (slice).
- **Graph Path**: `Graph/ProofGraphPath.cs` -- path through the reachability graph.
- **Graph Subgraph**: `Graph/ProofGraphSubgraph.cs` -- extracted minimal subgraph.
- **Replay Manifest**: `Replay/AIArtifactReplayManifest.cs` -- manifest for deterministic replay of reachability analysis.
- **Replay Result**: `Replay/ReplayResult.cs` -- result of replaying a reachability analysis.
- **Replay Verification**: `Replay/ReplayVerificationResult.cs` -- verification of replay fidelity.
- **Replay Status**: `Replay/ReplayStatus.cs` -- enum tracking replay outcome.
- **Replay Input Artifact**: `Replay/ReplayInputArtifact.cs` -- input artifact for replay (graph data, configuration).
- **Witness Payload**: `Statements/ReachabilityWitnessPayload.cs` (with `.Path`) -- witness data for reachability paths.
- **REST API**: `StellaOps.Attestor.WebService/Controllers/ChainController.cs` -- API for querying reachability chains.
- **Tests**: `__Tests/StellaOps.Attestor.ProofChain.Tests/ReachabilitySubgraphTests.cs`

## E2E Test Plan
- [ ] Extract a reachability slice from a proof graph via `InMemoryProofGraphService.Subgraph` and verify the minimal subgraph
- [ ] Build a `ReachabilitySubgraphPredicate` from the extracted slice and sign it into a DSSE envelope
- [ ] Replay a reachability analysis via `AIArtifactReplayManifest` and verify `ReplayResult` matches the original
- [ ] Verify replay fidelity via `ReplayVerificationResult` and confirm the replayed graph matches the original
- [ ] Query a reachability chain via `ChainController` REST API and verify the response contains path data
- [ ] Store a reachability subgraph attestation and retrieve it by subject digest
- [ ] Create `ReplayInputArtifact` entries for a reachability analysis and verify all inputs are captured for replay

## Verification

| Check | Result |
|-------|--------|
| Tier 0 - Source Verification | PASS |
| Tier 1 - Build + Code Review | PASS |
| Tier 2 - Behavioral Verification | PASS |
| Verified Date | 2026-02-13 |
| Run ID | run-001 |