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+---
+id: fccd4277-a253-4f7f-8065-7a9cffd64354
+type: fix
+title: "Fix: Prevent duplicate POSTs when audit update fails after successful delivery in outbound-event-handler"
+tags: [esb-monorepo, tac, outbound-event-handler, error-handling, fix, cloud-functions, idempotency, duplicate-prevention]
+importance: 0.7
+confidence: 0.8
+created: "2026-02-25T17:47:36.634745+00:00"
+updated: "2026-02-25T17:47:36.634745+00:00"
+---
+
+# Fix: Duplicate POST Prevention on Audit Failure
+
+## Project
+esb-monorepo — TAC `outbound-event-handler` (GCF)
+
+## Problem
+Bitbucket Rovo Dev flagged a code design issue: if `update_processed_events()` fails at Step 5 (after all POSTs to `outbound-object-router` succeeded), the function returned HTTP 500. Cloud Scheduler treats any 5xx as a failure and retries, causing duplicate POSTs to the downstream router for events that were already delivered.
+
+## Root Cause
+The final audit DB update call (`update_processed_events`) was not wrapped in error handling. A transient DB failure at that step caused the function to surface a 500, even though all delivery work was complete.
+
+## Fix
+Wrapped the final `update_processed_events` call in a `try/except` block:
+- Logs the audit error at ERROR level
+- Still returns **200** because all deliveries succeeded — the audit failure is non-fatal
+- Cloud Scheduler will NOT retry, preventing duplicate POSTs
+
+## Important Distinction
+The partial-progress flush in the POST failure path (~line 165) is intentionally **NOT** wrapped. In that case we DO want 500 returned so Cloud Scheduler retries the failed POST delivery.
+
+```python
+# Step 5 — audit update: non-fatal, deliveries already complete
+try:
+    update_processed_events(processed_ids)
+except Exception as e:
+    logger.error("Audit update failed after successful delivery: %s", e)
+
+return make_response("OK", 200)
+```
+
+## Test Added
+`test_audit_update_failure_after_all_posts_succeed_returns_200`
+
+## Commit
+`320b871` on `dev-object-handler` branch