diff --git a/apps/api/src/services/decision_manager.py b/apps/api/src/services/decision_manager.py
index 291d47ec..c5187065 100644
--- a/apps/api/src/services/decision_manager.py
+++ b/apps/api/src/services/decision_manager.py
@@ -678,6 +678,25 @@ class DecisionManager:
         action = _re.sub(r"<deployment_name>", _target, action)
         action = _re.sub(r"<[^>]+>", _target, action)
 
+        # 安全守衛: 替換後仍含 "unknown" 或未替換的 <...>/{...} → 拒絕執行
+        # 主機層告警（HostHighCpuLoad 等）沒有 deployment 名稱，不應盲目執行
+        if "unknown" in action or _re.search(r"[<{][^>}]+[>}]", action):
+            logger.warning(
+                "auto_execute_blocked_unresolved_placeholder",
+                incident_id=incident.incident_id,
+                action=action,
+                target=_target,
+                reason="action 含未解析的 placeholder 或 unknown，拒絕執行",
+            )
+            token.state = DecisionState.ERROR
+            token.error = f"Auto-execute blocked: unresolved placeholder in action: {action[:80]}"
+            await self._save_token(token)
+            asyncio.create_task(
+                _push_auto_repair_result(incident, action, success=False,
+                                         error="無法確認 deployment 名稱，請人工確認後手動執行")
+            )
+            return
+
         try:
             # 延遲導入避免循環依賴
             from src.models.approval import ApprovalRequest, ApprovalStatus