# SPRINT_7100 Summary — VEX Trust Lattice

**Epic**: VEX Trust Lattice for Explainable, Replayable Decisioning
**Total Duration**: 12 weeks (6 sprints)
**Status**: TODO
**Source Advisory**: `docs/product-advisories/archived/22-Dec-2026 - Building a Trust Lattice for VEX Sources.md`

---

## Executive Summary

Implement a sophisticated 3-component trust vector model (Provenance, Coverage, Replayability) for VEX sources, enabling explainable and deterministically replayable vulnerability decisioning. This replaces the current single-weight trust model with a mathematically rigorous lattice-based approach that produces signed, auditable verdict manifests.

### Key Features

1. **Trust Vector (P/C/R)**: 3-component scoring per VEX source
2. **Claim Scoring**: `ClaimScore = BaseTrust(S) * M * F` with strength and freshness multipliers
3. **Policy Gates**: Minimum confidence, unknowns budget, source quotas, reachability requirements
4. **Verdict Manifest**: DSSE-signed, indexed, replayable verdicts
5. **Trust Algebra UI**: Visual explanation panel for trust decisions
6. **Calibration**: Rolling trust weight adjustment based on post-mortem truth

---

## Sprint Overview

| Sprint ID | Topic | Duration | Status | Key Deliverables |
|-----------|-------|----------|--------|------------------|
| **7100.0001.0001** | Trust Vector Foundation | 2 weeks | TODO | TrustVector, ClaimStrength, FreshnessCalculator, ClaimScoreCalculator |
| **7100.0001.0002** | Verdict Manifest & Replay | 2 weeks | TODO | VerdictManifest, DSSE signing, PostgreSQL store, replay verification |
| **7100.0002.0001** | Policy Gates & Lattice Merge | 2 weeks | TODO | ClaimScoreMerger, MinimumConfidenceGate, SourceQuotaGate, UnknownsBudgetGate |
| **7100.0002.0002** | Source Defaults & Calibration | 2 weeks | TODO | DefaultTrustVectors, CalibrationManifest, TrustCalibrationService |
| **7100.0003.0001** | UI Trust Algebra Panel | 2 weeks | TODO | TrustAlgebraComponent, confidence meter, P/C/R bars, claim table |
| **7100.0003.0002** | Integration & Documentation | 2 weeks | TODO | Architecture docs, trust-lattice.md, verdict-manifest.md, API reference |

---

## Gap Analysis (Advisory vs. Current Implementation)

| Advisory Feature | Current State | Gap Severity | Sprint |
|-----------------|---------------|--------------|--------|
| 3-Component Trust Vector (P/C/R) | Single weight per provider | MAJOR | 7100.0001.0001 |
| Claim Strength Multiplier (M) | Status-based adjustments only | MEDIUM | 7100.0001.0001 |
| Freshness Decay (F) | Fixed staleness penalties (-5%/-10%) | MEDIUM | 7100.0001.0001 |
| ClaimScore = BaseTrust*M*F | Not implemented | MAJOR | 7100.0001.0001 |
| Conflict Mode + Replay Proof | K4 conflict detection, no down-weight | MINOR | 7100.0002.0001 |
| Verdict Manifest (DSSE-signed) | Not implemented | MAJOR | 7100.0001.0002 |
| Policy Gates (min confidence, quotas) | Partial (jurisdiction rules) | MEDIUM | 7100.0002.0001 |
| Deterministic Replay Pinning | Determinism prioritized, no manifest | MEDIUM | 7100.0001.0002 |
| UI Trust Algebra Panel | Not implemented | MEDIUM | 7100.0003.0001 |
| Calibration Manifest | Not implemented | MINOR | 7100.0002.0002 |

---

## Batch A: Core Models (Sprints 7100.0001.0001–0002)

### Sprint 7100.0001.0001: Trust Vector Foundation
**Owner**: Excititor Team + Policy Team
**Working Directory**: `src/Excititor/__Libraries/StellaOps.Excititor.Core/`
**Deliverables**:
- [ ] `TrustVector` record with P/C/R components and configurable weights
- [ ] `ClaimStrength` enum with evidence-based multipliers (0.40–1.00)
- [ ] `FreshnessCalculator` with configurable half-life decay (default 90 days)
- [ ] `ClaimScoreCalculator` implementing `BaseTrust(S) * M * F`
- [ ] Extended `VexProvider` with TrustVector configuration
- [ ] Unit tests for scoring calculations (determinism validation)

**Tests**: ≥90% coverage, determinism assertions

---

### Sprint 7100.0001.0002: Verdict Manifest & Replay
**Owner**: Authority Team + Excititor Team
**Working Directory**: `src/Authority/__Libraries/StellaOps.Authority.Core/`
**Deliverables**:
- [ ] `VerdictManifest` model with inputs pinning
- [ ] `VerdictManifestBuilder` for deterministic assembly
- [ ] DSSE signing for verdict manifests via Signer module
- [ ] `IVerdictManifestStore` interface and PostgreSQL implementation
- [ ] Indexing by (asset_digest, CVE, policy_hash, lattice_version)
- [ ] Replay verification endpoint
- [ ] Integration tests with determinism assertions

**Tests**: DSSE signing tests, replay verification tests

---

## Batch B: Policy Integration (Sprints 7100.0002.0001–0002)

### Sprint 7100.0002.0001: Policy Gates & Lattice Merge
**Owner**: Policy Team
**Working Directory**: `src/Policy/__Libraries/StellaOps.Policy/`
**Deliverables**:
- [ ] Extend `TrustLatticeEngine` with ClaimScore-based merge
- [ ] Implement conflict penalty (delta=0.25) on contradictory claims
- [ ] `MinimumConfidenceGate` policy hook (prod requires ≥0.75)
- [ ] `UnknownsBudgetGate` policy hook (fail if unknowns > N)
- [ ] `SourceQuotaGate` (cap influence at 60% unless corroborated)
- [ ] `ReachabilityRequirementGate` for criticals
- [ ] Policy configuration schema (YAML/JSON)
- [ ] Unit tests for all gates with edge cases

**Tests**: Gate edge cases, conflict scenarios

---

### Sprint 7100.0002.0002: Source Defaults & Calibration
**Owner**: Excititor Team
**Working Directory**: `src/Excititor/__Libraries/StellaOps.Excititor.Core/`
**Deliverables**:
- [ ] Default trust vectors for Vendor/Distro/Internal source classes
- [ ] `SourceClassification` service for auto-classification
- [ ] `CalibrationManifest` model for tuning history
- [ ] Calibration comparison (claim vs. post-mortem truth)
- [ ] Learning rate adjustment (±0.02/epoch)
- [ ] Configuration for calibration policy

**Tests**: Default vector tests, calibration accuracy tests

---

## Batch C: UI & Integration (Sprints 7100.0003.0001–0002)

### Sprint 7100.0003.0001: UI Trust Algebra Panel
**Owner**: UI Team
**Working Directory**: `src/Web/StellaOps.Web/`
**Deliverables**:
- [ ] `TrustAlgebraComponent` Angular component
- [ ] Confidence meter visualization (0–1 scale)
- [ ] P/C/R stacked bar chart for winning claim
- [ ] Claim comparison table with conflict toggle
- [ ] Policy chips display with YAML viewer (read-only in replay)
- [ ] "Reproduce verdict" replay button
- [ ] E2E tests for trust algebra panel

**Tests**: Component tests, accessibility tests

---

### Sprint 7100.0003.0002: Integration & Documentation
**Owner**: Docs Guild + All Teams
**Working Directory**: `docs/` and cross-module integration
**Deliverables**:
- [ ] Update `docs/modules/excititor/architecture.md` with trust lattice
- [ ] Create `docs/modules/excititor/trust-lattice.md` specification
- [ ] Update `docs/modules/policy/architecture.md` with gates
- [ ] Create `docs/modules/authority/verdict-manifest.md` specification
- [ ] Add JSON Schema for VerdictManifest to `docs/attestor/`
- [ ] Update API reference with verdict manifest endpoints
- [ ] Integration tests: end-to-end trust lattice flow
- [ ] Update `etc/*.yaml.sample` configuration files

**Tests**: Documentation review, E2E integration tests

---

## Dependencies

```mermaid
graph TD
    A[7100.0001.0001 Trust Vector] --> B[7100.0001.0002 Verdict Manifest]
    A --> C[7100.0002.0001 Policy Gates]
    B --> D[7100.0002.0002 Calibration]
    C --> D
    B --> E[7100.0003.0001 UI Panel]
    C --> E
    D --> F[7100.0003.0002 Integration]
    E --> F
```

---

## Technical Design

### Trust Vector Formula

```
BaseTrust(S) = wP*P + wC*C + wR*R

Where:
- P = Provenance score [0..1]
- C = Coverage score [0..1]
- R = Replayability score [0..1]
- wP = 0.45 (default)
- wC = 0.35 (default)
- wR = 0.20 (default)
```

### Claim Score Formula

```
ClaimScore = BaseTrust(S) * M * F

Where:
- M = Claim strength multiplier [0.40..1.00]
- F = Freshness decay = max(exp(-ln(2) * age_days / half_life), floor)
- half_life = 90 days (default)
- floor = 0.35 (minimum freshness)
```

### Default Trust Vectors by Source Class

| Source Class | P | C | R |
|-------------|---|---|---|
| Vendor | 0.90 | 0.70 | 0.60 |
| Distro | 0.80 | 0.85 | 0.60 |
| Internal | 0.85 | 0.95 | 0.90 |

### Claim Strength Values

| Evidence Type | Strength (M) |
|--------------|--------------|
| Exploitability analysis + reachability proof | 1.00 |
| Config/feature-flag reason with evidence | 0.80 |
| Vendor blanket statement | 0.60 |
| Under investigation | 0.40 |

---

## Success Metrics

### Technical Metrics
- **Determinism**: 100% bit-identical verdict manifests for same inputs
- **Performance**: Verdict computation <100ms for 1k claims (p95)
- **Accuracy**: Calibration drift <5% per epoch
- **Scalability**: 100k verdicts/day without degradation

### Business Metrics
- **Explainability**: 100% of verdicts include full audit trail
- **Compliance**: DSSE-signed verdicts meet audit requirements
- **Customer adoption**: ≥30% enable trust algebra UI (12 months)

---

## Architectural Decisions

| Decision | Rationale |
|----------|-----------|
| Extend, don't replace | Build trust vectors alongside existing append-only linksets |
| Backward compatibility | Existing `VexProvider.Trust.Weight` maps to legacy mode |
| Scoring at evaluation time | No ingestion-time decisioning per AOC-19 |
| Air-gap support | Trust vectors work offline with local signature verification |
| Calibration as separate manifest | Allows auditable tuning history |

---

## Quick Links

**Sprint Files**:
- [SPRINT_7100_0001_0001 - Trust Vector Foundation](SPRINT_7100_0001_0001_trust_vector_foundation.md)
- [SPRINT_7100_0001_0002 - Verdict Manifest & Replay](SPRINT_7100_0001_0002_verdict_manifest_replay.md)
- [SPRINT_7100_0002_0001 - Policy Gates & Merge](SPRINT_7100_0002_0001_policy_gates_merge.md)
- [SPRINT_7100_0002_0002 - Source Defaults & Calibration](SPRINT_7100_0002_0002_source_defaults_calibration.md)
- [SPRINT_7100_0003_0001 - UI Trust Algebra Panel](SPRINT_7100_0003_0001_ui_trust_algebra.md)
- [SPRINT_7100_0003_0002 - Integration & Documentation](SPRINT_7100_0003_0002_integration_documentation.md)

**Documentation**:
- [Trust Lattice Specification](../modules/excititor/trust-lattice.md)
- [Verdict Manifest Specification](../modules/authority/verdict-manifest.md)
- [Excititor Architecture](../modules/excititor/architecture.md)

**Source Advisory**:
- [22-Dec-2026 - Building a Trust Lattice for VEX Sources](../product-advisories/archived/22-Dec-2026%20-%20Building%20a%20Trust%20Lattice%20for%20VEX%20Sources.md)

---

**Last Updated**: 2025-12-22
**Next Review**: Weekly during sprint execution