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+# Phase 3B Execution Checklist
+
+**Phase**: Site I/O & Observability
+**Started**: 2026-03-16
+**Completed**: 2026-03-16
+
+---
+
+## Work Package Status
+
+All 35/35 WPs complete. See commit `389f5a0` for full implementation.
+
+## Verification Gate
+
+| # | Gate Criterion | Pass |
+|---|---------------|------|
+| 1 | OPC UA integration (adapter, subscribe, values flow) | [x] |
+| 2 | Script execution (3 trigger types, min-time, read/write, CallScript, CallShared) | [x] |
+| 3 | Alarm evaluation (3 condition types, state transitions, on-trigger scripts, no script on clear) | [x] |
+| 4 | Script trust model (forbidden APIs rejected, execution timeout) | [x] |
+| 5 | Recursion limit (depth enforced, error logged) | [x] |
+| 6 | Health monitoring (periodic reports, sequence numbers, offline/online detection) | [x] |
+| 7 | Event logging (all categories, retention, cap, remote query, pagination, keyword search) | [x] |
+| 8 | Debug view (subscribe, snapshot, stream, unsubscribe) | [x] |
+| 9 | Communication (all 8 patterns, timeouts, correlation IDs) | [x] |
+| 10 | Failover (DCL reconnect, health continuity, stream recovery, alarm re-eval) | [x] |
+| 11 | Negative tests (cross-instance blocked, alarm call direction, forbidden APIs, etc.) | [x] |
+
+## Summary
+
+- **Total WPs**: 35/35 complete
+- **New tests**: 197 (53 Communication+DCL + 89 SiteRuntime + 55 Health+EventLog)
+- **Cumulative tests**: 541 passing, 0 failed
+- **Build**: 0 errors, 0 warnings
+- **Verification gate**: 11/11 pass