fix(aiops): suppress repeated llm alert loops

apps/api/src/api/v1/webhooks.py

@@ -53,6 +53,10 @@ from src.models.approval import (
 # [首席架構師] 移除 generate_alert_fingerprint 直接 import，改用 AlertAnalyzer.generate_fingerprint v1.2 2026-04-01 Asia/Taipei
 from src.models.webhook import AlertPayload, AlertResponse
 from src.services.alert_analyzer_service import AlertAnalyzer
+from src.services.alertmanager_llm_guard import (
+    ALERTMANAGER_LLM_INFLIGHT_LOCK_TTL_SECONDS,
+    try_acquire_alertmanager_llm_lock,
+)
 from src.services.approval_db import get_approval_service
 
 # Phase 17 P0: Service 層 (消除 Router 直接存取 Redis)
@@ -2150,12 +2154,22 @@ async def alertmanager_webhook(
     # 2026-04-14 Claude Haiku 4.5 Asia/Taipei
     # 位置：指紋生成後、LLM 分析前（短路子告警）
     # ==========================================================================
-    grouping_result = await get_alert_grouping_service().evaluate(
-        alertname=alertname,
-        namespace=namespace,
-        fingerprint=fingerprint,
-    )
-    if grouping_result.is_grouped:
+    try:
+        grouping_result = await get_alert_grouping_service().evaluate(
+            alertname=alertname,
+            namespace=namespace,
+            fingerprint=fingerprint,
+        )
+    except Exception as e:
+        grouping_result = None
+        logger.warning(
+            "alertmanager_grouping_failed_fail_open",
+            alert_id=alert_id,
+            fingerprint=fingerprint,
+            error=str(e),
+        )
+
+    if grouping_result and grouping_result.is_grouped:
         logger.info(
             "alertmanager_grouped_skip",
             alert_id=alert_id,
@@ -2258,6 +2272,21 @@ async def alertmanager_webhook(
                 approval_created=False,
             )
 
+        if not await try_acquire_alertmanager_llm_lock(fingerprint, alert_id):
+            logger.info(
+                "alertmanager_llm_inflight_suppressed",
+                alert_id=alert_id,
+                fingerprint=fingerprint,
+                ttl_seconds=ALERTMANAGER_LLM_INFLIGHT_LOCK_TTL_SECONDS,
+            )
+            return AlertResponse(
+                success=True,
+                message="🛡️ 告警已由同指紋背景 AI 分析處理中，跳過重複 LLM 呼叫",
+                alert_id=alert_id,
+                approval_created=False,
+                converged=True,
+            )
+
         # ==========================================================================
         # ADR-089 (2026-04-17 ogt + Claude Sonnet 4.6): 新告警 — 背景 LLM 分析
         # 立即回傳 202，AI 辯證在背景非同步執行
@@ -2271,6 +2300,7 @@ async def alertmanager_webhook(
             "source": "alertmanager",
             "target_resource": target_resource,
             "namespace": namespace,
+            "fingerprint": fingerprint,
             "message": message,
             "annotations": dict(alert.annotations) if alert.annotations else {},
             "metrics": {},
@@ -2303,11 +2333,18 @@ async def alertmanager_webhook(
         )
 
     except Exception as e:
-        logger.error("alertmanager_error", error=str(e))
-        raise HTTPException(
-            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
-            detail=f"Failed to process alert: {str(e)}",
-        ) from e
+        logger.error(
+            "alertmanager_degraded_accepted_no_retry",
+            alert_id=alert_id,
+            fingerprint=fingerprint,
+            error=str(e),
+        )
+        return AlertResponse(
+            success=False,
+            message="⚠️ 告警已接收但處理降級，避免 Alertmanager retry storm；已交由背景治理/人工介入追蹤",
+            alert_id=alert_id,
+            approval_created=False,
+        )
 
 
 @router.get(