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Sprint 26 Engineering Log
Program Context
- Phase: Phase 6
- Sprint: Sprint 26
- Status: Completed
- Primary Architecture Layers: Audit & State Plane, Cryptographic Integrity
Architectural Intent
Implement the append-only Merkle ledger runtime based on Sprint 25 model definitions.
Implementation Detail
Implemented:
- Append-only Merkle tree runtime with deterministic left-right growth and duplicate-last odd node strategy.
- Immutable execution leaf persistence with hash-chained JSONL records.
- Periodic root generation based on fixed leaf cadence.
- Root signing using control-plane signing authority contract.
- Root verification routine that validates both deterministic root recomputation and signature integrity.
- Tamper simulation coverage that detects immutable record mutation.
Security and Control Posture
- Immutable leaf chain prevents silent mutation of persisted evidence.
- Root signing establishes control-plane authority over ledger checkpoints.
- Verification path fails closed on root mismatch or signature mismatch.
QA and Validation Evidence
- Unit tests validate deterministic root behavior, persistence, periodic root cadence, signature verification, and tamper detection.
- Sprint QA test confirms roadmap closure lines and core module contract presence.
Risk Register
- Risk: production authority integration currently relies on abstract signer contract.
- Mitigation: wire Vault transit-backed signer adapter in Sprint 27/28 verifier runtime.
Forward Linkage
Sprint 27 adds inclusion proof API, deterministic rebuild/export, and read-only verifier node workflows.
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