diff --git a/apps/api/src/api/v1/webhooks.py b/apps/api/src/api/v1/webhooks.py
index 9e4e1535..0bf6154b 100644
--- a/apps/api/src/api/v1/webhooks.py
+++ b/apps/api/src/api/v1/webhooks.py
@@ -1334,6 +1334,62 @@ async def _process_new_alert_background(
             except Exception as _shadow_err_cs2:
                 logger.warning("shadow_auto_approve_failed", error=str(_shadow_err_cs2))
 
+            # 2026-04-27 ogt + Claude Sonnet 4.6: CS2 規則引擎自動執行
+            # 設計：is_rule_based=True 確定性高，滿足條件直接執行，不等人工審核
+            # 安全防線：CRITICAL / destructive patterns / NO_ACTION / 空 kubectl → 全部降級 PENDING
+            try:
+                from src.services.auto_approve import _DESTRUCTIVE_PATTERNS
+                from src.models.approval import ApprovalRequest, ApprovalStatus
+                from src.services.approval_execution import ApprovalExecutionService
+
+                _destructive_set = set(p.lower() for p in _DESTRUCTIVE_PATTERNS)
+                _can_auto = (
+                    bool(rule_kubectl)
+                    and rule_risk != RiskLevel.CRITICAL
+                    and not any(p in rule_kubectl.lower() for p in _destructive_set)
+                    and "NO_ACTION" not in rule_action
+                )
+                if _can_auto:
+                    _auto_approval = ApprovalRequest(
+                        incident_id=None,  # 尚未建立，稍後 update_incident_id 補上
+                        action=rule_action,
+                        description=approval_create.description,
+                        requested_by="auto_approve_rule_engine",
+                        required_signatures=0,
+                        status=ApprovalStatus.APPROVED,
+                        risk_level=rule_risk.value,
+                        matched_playbook_id=_approval_metadata_cs2.get("playbook_id"),
+                    )
+                    # 使用 DB 中剛建立的 approval.id 讓 executor 可回寫
+                    _auto_approval.id = approval.id
+
+                    _cs2_executor = ApprovalExecutionService()
+                    _cs2_exec_success = await _cs2_executor.execute_approved_action(_auto_approval)
+
+                    # 更新 DB approval 執行狀態
+                    try:
+                        await service.update_execution_status(approval.id, _cs2_exec_success)
+                    except Exception as _upd_err:
+                        logger.warning(
+                            "cs2_auto_execute_status_update_failed",
+                            approval_id=str(approval.id),
+                            error=str(_upd_err),
+                        )
+
+                    logger.info(
+                        "rule_engine_auto_executed",
+                        approval_id=str(approval.id),
+                        rule_id=rule_response.get("rule_id", "unknown"),
+                        kubectl=rule_kubectl,
+                        exec_success=_cs2_exec_success,
+                    )
+            except Exception as _auto_err:
+                logger.warning(
+                    "cs2_auto_execute_failed_degraded_to_pending",
+                    approval_id=str(approval.id),
+                    error=str(_auto_err),
+                )
+
             incident_id = await create_incident_for_approval(
                 approval_id=str(approval.id),
                 risk_level=rule_risk.value,
diff --git a/apps/api/tests/test_rule_engine_auto_execute.py b/apps/api/tests/test_rule_engine_auto_execute.py
new file mode 100644
index 00000000..44d989df
--- /dev/null
+++ b/apps/api/tests/test_rule_engine_auto_execute.py
@@ -0,0 +1,166 @@
+"""
+CS2 規則引擎自動執行條件邏輯測試
+==================================
+測試範圍：webhooks.py CS2 路徑的 _can_auto 條件判斷邏輯
+
+設計原則:
+- 不測試 DB/K8s 端點（屬 integration test 範疇）
+- 直接測試 _can_auto 的五個安全條件是否正確
+- 從 auto_approve 導入真實的 _DESTRUCTIVE_PATTERNS（不 mock）
+
+安全防線驗證：
+1. rule_kubectl 空字串 → False
+2. CRITICAL risk → False
+3. DESTRUCTIVE_PATTERNS 命中 → False
+4. NO_ACTION 在 rule_action → False
+5. 全條件滿足 → True
+
+建立：2026-04-27 ogt + Claude Sonnet 4.6 (台北時區)
+"""
+
+from src.models.approval import RiskLevel
+from src.services.auto_approve import _DESTRUCTIVE_PATTERNS
+
+
+def _evaluate_can_auto(
+    rule_kubectl: str,
+    rule_risk: RiskLevel,
+    rule_action: str,
+) -> bool:
+    """
+    複製 webhooks.py CS2 路徑的 _can_auto 邏輯，用於單元測試。
+    任何修改 webhooks.py 邏輯的人，必須同步更新此函數。
+    """
+    _destructive_set = set(p.lower() for p in _DESTRUCTIVE_PATTERNS)
+    return (
+        bool(rule_kubectl)
+        and rule_risk != RiskLevel.CRITICAL
+        and not any(p in rule_kubectl.lower() for p in _destructive_set)
+        and "NO_ACTION" not in rule_action
+    )
+
+
+class TestCS2CanAutoConditions:
+    """驗證 CS2 _can_auto 五個安全防線"""
+
+    # ── 正向：全條件滿足 ─────────────────────────────────────────────────
+
+    def test_all_conditions_met_returns_true(self):
+        """kubectl 非空 + medium risk + 無破壞性 + 非 NO_ACTION → True"""
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl rollout restart deployment/api -n prod",
+            rule_risk=RiskLevel.MEDIUM,
+            rule_action="重啟 API Deployment | kubectl rollout restart deployment/api -n prod",
+        ) is True
+
+    def test_low_risk_returns_true(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl rollout restart deployment/worker -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="重啟 Worker | kubectl rollout restart deployment/worker -n prod",
+        ) is True
+
+    # ── 防線 1：kubectl 空字串 ─────────────────────────────────────────────
+
+    def test_empty_kubectl_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="",
+            rule_risk=RiskLevel.LOW,
+            rule_action="NO_ACTION - 主機記憶體觀察",
+        ) is False
+
+    def test_whitespace_only_kubectl_returns_false(self):
+        # webhooks.py line 1265: rule_kubectl = str(...).strip()
+        # 因此 whitespace-only 在到達 _can_auto 前已被 strip 為空字串
+        # 此測試驗證調用方的前置處理行為
+        assert _evaluate_can_auto(
+            rule_kubectl="",  # strip() 後的結果
+            rule_risk=RiskLevel.LOW,
+            rule_action="重啟 | 某指令",
+        ) is False
+
+    # ── 防線 2：CRITICAL risk ─────────────────────────────────────────────
+
+    def test_critical_risk_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl rollout restart deployment/db -n prod",
+            rule_risk=RiskLevel.CRITICAL,
+            rule_action="重啟 DB | kubectl rollout restart deployment/db -n prod",
+        ) is False
+
+    # ── 防線 3：DESTRUCTIVE_PATTERNS ────────────────────────────────────
+
+    def test_delete_pod_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl delete pod api-xxx-yyy -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="刪除 Pod | kubectl delete pod api-xxx-yyy -n prod",
+        ) is False
+
+    def test_delete_pods_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl delete pods --all -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="刪除所有 Pod | kubectl delete pods --all -n prod",
+        ) is False
+
+    def test_scale_to_zero_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl scale deployment/api --replicas=0 -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="縮容 | kubectl scale deployment/api --replicas=0",
+        ) is False
+
+    def test_kubectl_drain_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl drain node-1 --ignore-daemonsets",
+            rule_risk=RiskLevel.MEDIUM,
+            rule_action="驅逐節點 | kubectl drain node-1",
+        ) is False
+
+    def test_rollout_undo_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl rollout undo deployment/api -n prod",
+            rule_risk=RiskLevel.MEDIUM,
+            rule_action="回滾 | kubectl rollout undo deployment/api",
+        ) is False
+
+    def test_destructive_pattern_case_insensitive(self):
+        """大寫 DELETE POD 也必須攔截"""
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl DELETE POD api-xxx -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="刪除 | kubectl DELETE POD",
+        ) is False
+
+    # ── 防線 4：NO_ACTION ────────────────────────────────────────────────
+
+    def test_no_action_in_action_string_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl get pods -n prod",
+            rule_risk=RiskLevel.LOW,
+            rule_action="NO_ACTION - 觀察主機狀態",
+        ) is False
+
+    def test_no_action_prefix_returns_false(self):
+        assert _evaluate_can_auto(
+            rule_kubectl="",
+            rule_risk=RiskLevel.LOW,
+            rule_action="NO_ACTION - 主機記憶體正常",
+        ) is False
+
+    # ── 邊界：_DESTRUCTIVE_PATTERNS 非空 ────────────────────────────────
+
+    def test_destructive_patterns_list_not_empty(self):
+        """確保 _DESTRUCTIVE_PATTERNS 未被意外清空"""
+        assert len(_DESTRUCTIVE_PATTERNS) > 0
+
+    # ── 組合：多個防線同時觸發 ───────────────────────────────────────────
+
+    def test_critical_and_destructive_both_block(self):
+        """CRITICAL + destructive，任一條件都應攔截"""
+        assert _evaluate_can_auto(
+            rule_kubectl="kubectl delete deployment/api -n prod",
+            rule_risk=RiskLevel.CRITICAL,
+            rule_action="刪除 Deployment | kubectl delete deployment/api",
+        ) is False