fix(governance): fail soft owner review readbacks

apps/api/src/api/v1/ai_governance.py

@@ -341,6 +341,24 @@ async def get_km_stale_owner_reviews(
         )
     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_reviews_readback_degraded",
+            project_id=project_id,
+            dispatch_status=dispatch_status,
+            limit=limit,
+            error_type=type(exc).__name__,
+        )
+        return KnowledgeStaleOwnerReviewInboxResponse(
+            project_id=project_id,
+            dispatch_status=dispatch_status,
+            total=0,
+            returned=0,
+            writes_on_read=False,
+            manual_review_required=True,
+            items=[],
+            generated_at=now_taipei(),
+        )
 
 
 # =============================================================================
@@ -366,10 +384,35 @@ async def get_km_stale_owner_review_burndown(
         project_id=project_id,
         limit=limit,
     )
-    return await query_km_stale_owner_review_burndown(
-        project_id=project_id,
-        limit=limit,
-    )
+    try:
+        return await query_km_stale_owner_review_burndown(
+            project_id=project_id,
+            limit=limit,
+        )
+    except Exception as exc:
+        logger.warning(
+            "km_stale_owner_review_burndown_readback_degraded",
+            project_id=project_id,
+            limit=limit,
+            error_type=type(exc).__name__,
+        )
+        return KnowledgeStaleOwnerReviewBurnDownResponse(
+            project_id=project_id,
+            burn_down_status="no_data",
+            current_snapshot=None,
+            entries_to_threshold=0,
+            pending_owner_reviews=0,
+            completed_owner_reviews=0,
+            completion_audit_total=0,
+            stale_ratio_recheck_total=0,
+            latest_stale_count_delta=None,
+            latest_stale_ratio_delta=None,
+            writes_on_read=False,
+            manual_review_required=True,
+            returned=0,
+            items=[],
+            generated_at=now_taipei(),
+        )
 
 
 # =============================================================================

apps/api/tests/test_ai_governance_endpoints.py

@@ -1028,6 +1028,29 @@ class TestKmReviewDraftDedupe:
         assert data["items"][0]["workflow_stage"] == "waiting_owner_review"
         assert data["items"][0]["batch_dispatch_id"] == "dispatch-batch-001"
 
+    def test_owner_review_inbox_readback_exception_returns_empty_inbox(self, client):
+        """owner review inbox 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_inbox",
+            new=AsyncMock(side_effect=RuntimeError("temporary inbox failure")),
+        ):
+            r = client.get(
+                "/api/v1/ai/governance/km-stale-owner-reviews"
+                "?project_id=awoooi&dispatch_status=pending&limit=30"
+            )
+
+        assert r.status_code == 200
+        data = r.json()
+        assert data["schema_version"] == "km_stale_owner_review_inbox_v1"
+        assert data["project_id"] == "awoooi"
+        assert data["dispatch_status"] == "pending"
+        assert data["total"] == 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_owner_review_inbox_context_keeps_batch_and_priority_visible(self):
         record = KnowledgeEntryRecord(
             id="km-001",
@@ -1156,6 +1179,33 @@ class TestKmReviewDraftDedupe:
         assert data["latest_stale_count_delta"] == -1
         assert data["items"][0]["recheck_dispatch_id"] == "dispatch-recheck-001"
 
+    def test_owner_review_burndown_readback_exception_returns_no_data(self, client):
+        """burndown 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_burndown",
+            new=AsyncMock(side_effect=RuntimeError("temporary burndown failure")),
+        ):
+            r = client.get(
+                "/api/v1/ai/governance/km-stale-owner-review-burndown"
+                "?project_id=awoooi&limit=20"
+            )
+
+        assert r.status_code == 200
+        data = r.json()
+        assert data["schema_version"] == "km_stale_owner_review_burndown_v1"
+        assert data["project_id"] == "awoooi"
+        assert data["burn_down_status"] == "no_data"
+        assert data["entries_to_threshold"] == 0
+        assert data["pending_owner_reviews"] == 0
+        assert data["completed_owner_reviews"] == 0
+        assert data["completion_audit_total"] == 0
+        assert data["stale_ratio_recheck_total"] == 0
+        assert data["writes_on_read"] is False
+        assert data["manual_review_required"] is True
+        assert data["returned"] == 0
+        assert data["items"] == []
+        assert data["generated_at"]
+
     def test_owner_review_burndown_items_compute_chronological_delta(self):
         older_snapshot = {
             "stale_count": 119,