Squashed 'vendor/ruvector/' content from commit b64c2172

git-subtree-dir: vendor/ruvector
git-subtree-split: b64c21726f2bb37286d9ee36a7869fef60cc6900

docs/adr/coherence-engine/ADR-CE-004-signed-event-log.md

@@ -0,0 +1,42 @@
+# ADR-CE-004: Signed Event Log with Deterministic Replay
+
+**Status**: Accepted
+**Date**: 2026-01-22
+**Parent**: ADR-014 Coherence Engine Architecture
+
+## Context
+
+For audit, debugging, and compliance, the system must support:
+- Complete reconstruction of any past state
+- Verification that events were not tampered with
+- Replay for testing and analysis
+
+## Decision
+
+**Signed event log with deterministic replay.**
+
+Every event is:
+1. Assigned a monotonic sequence ID
+2. Serialized with timestamp and payload
+3. Signed with Blake3 hash including previous event's signature (chain)
+4. Stored append-only in PostgreSQL
+
+Replay:
+- Start from genesis or checkpoint
+- Apply events in sequence order
+- Deterministic: same events → same state
+
+## Consequences
+
+### Benefits
+- Tamper-evident: any modification breaks the hash chain
+- Complete auditability: reconstruct any historical state
+- Debugging: replay and inspect at any point
+
+### Risks
+- Storage grows indefinitely (mitigated by checkpoints)
+- Replay time scales with history length
+
+## References
+
+- ADR-014: Coherence Engine Architecture, Section 13