diff --git a/apps/api/src/api/v1/ai_governance.py b/apps/api/src/api/v1/ai_governance.py
index 158e734c8..de5628192 100644
--- a/apps/api/src/api/v1/ai_governance.py
+++ b/apps/api/src/api/v1/ai_governance.py
@@ -284,7 +284,25 @@ async def get_km_stale_candidates(
         project_id=project_id,
         limit=limit,
     )
-    return await query_km_stale_candidates(project_id=project_id, limit=limit)
+    try:
+        return await query_km_stale_candidates(project_id=project_id, limit=limit)
+    except Exception as exc:
+        logger.warning(
+            "km_stale_candidates_readback_degraded",
+            project_id=project_id,
+            limit=limit,
+            error_type=type(exc).__name__,
+        )
+        return KnowledgeStaleCandidatesResponse(
+            project_id=project_id,
+            total_stale=0,
+            returned=0,
+            threshold_days=0,
+            writes_on_read=False,
+            manual_review_required=True,
+            items=[],
+            generated_at=now_taipei(),
+        )
 
 
 # =============================================================================
@@ -405,6 +423,38 @@ async def get_km_stale_owner_review_completion_queue(
         )
     except KmStaleOwnerReviewError as exc:
         raise HTTPException(status_code=exc.status_code, detail=exc.detail) from exc
+    except Exception as exc:
+        logger.warning(
+            "km_stale_owner_review_completion_queue_readback_degraded",
+            project_id=project_id,
+            status_bucket=status_bucket,
+            priority_tiers=priority_tier,
+            recommended_completion_outcome=recommended_completion_outcome,
+            batch_governance_event_id=batch_governance_event_id,
+            can_preview=can_preview,
+            limit=limit,
+            error_type=type(exc).__name__,
+        )
+        return KnowledgeStaleOwnerReviewCompletionQueueResponse(
+            project_id=project_id,
+            status_bucket=status_bucket,
+            priority_tiers=priority_tier or [],
+            recommended_completion_outcome=recommended_completion_outcome,
+            batch_governance_event_id=batch_governance_event_id,
+            can_preview=can_preview,
+            total=0,
+            returned=0,
+            pending_count=0,
+            ready_count=0,
+            blocked_count=0,
+            completed_count=0,
+            failed_count=0,
+            writes_on_read=False,
+            manual_review_required=True,
+            batch_writes_allowed=False,
+            items=[],
+            generated_at=now_taipei(),
+        )
 
 
 # =============================================================================
diff --git a/apps/api/tests/test_ai_governance_endpoints.py b/apps/api/tests/test_ai_governance_endpoints.py
index 2094b8ece..76e868dc0 100644
--- a/apps/api/tests/test_ai_governance_endpoints.py
+++ b/apps/api/tests/test_ai_governance_endpoints.py
@@ -742,6 +742,28 @@ class TestKmReviewDraftDedupe:
             "signoz",
         ]
 
+    def test_km_stale_candidates_endpoint_readback_exception_returns_empty_queue(self, client):
+        """stale candidates 背景讀取失敗時應 fail-soft，不讓 Work Items 收到 500."""
+        with patch(
+            "src.api.v1.ai_governance.query_km_stale_candidates",
+            new=AsyncMock(side_effect=RuntimeError("temporary stale candidates failure")),
+        ):
+            r = client.get(
+                "/api/v1/ai/governance/km-stale-candidates"
+                "?project_id=awoooi&limit=20"
+            )
+
+        assert r.status_code == 200
+        data = r.json()
+        assert data["schema_version"] == "km_stale_candidates_v1"
+        assert data["project_id"] == "awoooi"
+        assert data["total_stale"] == 0
+        assert data["returned"] == 0
+        assert data["writes_on_read"] is False
+        assert data["manual_review_required"] is True
+        assert data["items"] == []
+        assert data["generated_at"]
+
     def test_build_km_stale_candidate_prioritizes_linked_evidence(self):
         """有 Incident / PlayBook / Sentry / SigNoz 脈絡的 stale KM 應排前面。"""
         record = KnowledgeEntryRecord(
@@ -1302,6 +1324,43 @@ class TestKmReviewDraftDedupe:
         assert data["items"][0]["can_preview"] is True
         assert data["items"][1]["writes_km_on_confirm"] is False
 
+    def test_owner_review_completion_queue_readback_exception_returns_empty_queue(
+        self,
+        client,
+    ):
+        """completion queue 背景讀取失敗時應 fail-soft，不讓 Work Items 收到 500."""
+        with patch(
+            "src.api.v1.ai_governance.query_km_stale_owner_review_completion_queue",
+            new=AsyncMock(side_effect=RuntimeError("temporary completion queue failure")),
+        ):
+            r = client.get(
+                "/api/v1/ai/governance/km-stale-owner-review-completion-queue"
+                "?project_id=awoooi&status_bucket=all&priority_tier=P0"
+                "&recommended_completion_outcome=refresh_with_evidence"
+                "&can_preview=true&limit=30"
+            )
+
+        assert r.status_code == 200
+        data = r.json()
+        assert data["schema_version"] == "km_stale_owner_review_completion_queue_v1"
+        assert data["project_id"] == "awoooi"
+        assert data["status_bucket"] == "all"
+        assert data["priority_tiers"] == ["P0"]
+        assert data["recommended_completion_outcome"] == "refresh_with_evidence"
+        assert data["can_preview"] is True
+        assert data["total"] == 0
+        assert data["returned"] == 0
+        assert data["pending_count"] == 0
+        assert data["ready_count"] == 0
+        assert data["blocked_count"] == 0
+        assert data["completed_count"] == 0
+        assert data["failed_count"] == 0
+        assert data["writes_on_read"] is False
+        assert data["manual_review_required"] is True
+        assert data["batch_writes_allowed"] is False
+        assert data["items"] == []
+        assert data["generated_at"]
+
     def test_completion_queue_batch_preview_endpoint_is_dry_run_only(self, client):
         fake = KnowledgeStaleOwnerReviewCompletionBatchPreviewResponse(
             project_id="awoooi",