diff --git a/apps/api/src/api/v1/webhooks.py b/apps/api/src/api/v1/webhooks.py
index 3c76e501..fad40c41 100644
--- a/apps/api/src/api/v1/webhooks.py
+++ b/apps/api/src/api/v1/webhooks.py
@@ -1350,6 +1350,14 @@ async def alertmanager_webhook(
                 notification_type="TYPE-1",
                 alert_category=alert_category,
             )
+            # 2026-04-15 ogt: TYPE-1 純資訊告警建立後立即關閉
+            # 設計原則: backup/heartbeat/info 告警無需追蹤狀態，通知即完成
+            # 防止 incidents 表無限累積 INVESTIGATING 記錄（ADR-073 漏洞修補）
+            background_tasks.add_task(
+                get_incident_service().resolve_incident,
+                _info_incident_id,
+                "info_notification",
+            )
             background_tasks.add_task(
                 get_telegram_gateway().send_info_notification,
                 incident_id=_info_incident_id,
diff --git a/apps/api/src/repositories/incident_repository.py b/apps/api/src/repositories/incident_repository.py
index 3e3558cd..f84d4748 100644
--- a/apps/api/src/repositories/incident_repository.py
+++ b/apps/api/src/repositories/incident_repository.py
@@ -79,7 +79,14 @@ def _incident_to_record_data(incident: Incident) -> dict[str, Any]:
         "resolved_at": incident.resolved_at,
         "closed_at": incident.closed_at,
         "frequency_snapshot": frequency_snapshot,
-        "alertname": incident.signals[0].alert_name if incident.signals else None,  # ADR-073 Phase 2-1
+        # ADR-073 Phase 2-1: alertname 欄位 — 優先從 signals[0].alert_name，
+        # fallback 到 signals[0].labels["alertname"]（防止 signal 建立時 alert_name 為空）
+        # 2026-04-15 ogt: 補 labels fallback（4 筆歷史 NULL 根因修復）
+        "alertname": (
+            (incident.signals[0].alert_name or
+             (incident.signals[0].labels or {}).get("alertname"))
+            if incident.signals else None
+        ),
         "notification_type": incident.notification_type,  # ADR-073 Phase 2-2
         "alert_category": incident.alert_category,         # ADR-073 Phase 2-2
     }