# Runtime Node-Hash Evidence in Signals

## Module
Signals

## Status
VERIFIED

## Description
Runtime signal schemas extended with node-hash inputs, call-stack digests, and path hashes for deterministic joins with static reachability evidence.

## Implementation Details
- **Modules**: `src/Signals/StellaOps.Signals/Lattice/`, `src/Signals/StellaOps.Signals/Services/`, `src/Signals/StellaOps.Signals/Models/`
- **Key Classes**:
  - `ReachabilityLattice` (`src/Signals/StellaOps.Signals/Lattice/ReachabilityLattice.cs`) - lattice-based reachability state combining static and runtime evidence
  - `ReachabilityLatticeState` (`src/Signals/StellaOps.Signals/Lattice/ReachabilityLatticeState.cs`) - state model with node-hash and path-hash inputs
  - `UncertaintyTier` (`src/Signals/StellaOps.Signals/Lattice/UncertaintyTier.cs`) - uncertainty tier classification for reachability evidence
  - `ReachabilityFactDigestCalculator` (`src/Signals/StellaOps.Signals/Services/ReachabilityFactDigestCalculator.cs`) - calculates deterministic digests for reachability facts
  - `ReachabilityFactDocument` (`src/Signals/StellaOps.Signals/Models/ReachabilityFactDocument.cs`) - document model with node-hash and call-stack digest fields
- **Source**: SPRINT_20260112_005_SIGNALS_runtime_nodehash.md

## E2E Test Plan
- [ ] Ingest a runtime signal with node-hash evidence and verify `ReachabilityFactDigestCalculator` produces a deterministic digest
- [ ] Join runtime evidence with static reachability facts using node-hash and verify the join is correct
- [ ] Verify call-stack digest: capture a runtime call stack and confirm the digest matches the expected value
- [ ] Verify path hash: compute path hashes for runtime traces and confirm they match static analysis paths
- [ ] Verify `ReachabilityLattice` correctly merges runtime and static evidence into a combined reachability state