diff --git a/.agents/skills/ui-minimal-luxury/SKILL.md b/.agents/skills/ui-minimal-luxury/SKILL.md
index af6c976..cab0720 100644
--- a/.agents/skills/ui-minimal-luxury/SKILL.md
+++ b/.agents/skills/ui-minimal-luxury/SKILL.md
@@ -386,6 +386,12 @@ description: 定義 Star Cloud 管理後台的「極簡奢華風」設計規範
     :selected="request('company_id')"
     :placeholder="__('All Companies')"
 />
+
+{{-- 下拉選單遮擋處理範例 --}}
+<div class="relative focus-within:z-20">
+    <label>...</label>
+    <x-searchable-select ... />
+</div>
 ```
 
 ---
@@ -435,4 +441,35 @@ async fetchPage(url) {
 | 基本資訊 | 翠綠 Emerald | `bg-emerald-500/10 text-emerald-500` |
 | 硬體／插槽 | 琥珀 Amber | `bg-amber-500/10 text-amber-500` |
 | 系統／進階 | 靛藍 Indigo | `bg-indigo-500/10 text-indigo-500` |
-| 危險／刪除 | 玫瑰 Rose | `bg-rose-500/10 text-rose-500` |
\ No newline at end of file
+| 危險／刪除 | 玫瑰 Rose | `bg-rose-500/10 text-rose-500` |
+---
+
+## 10. Z-Index 堆疊與遮擋處理 (Z-Index Stacking)
+
+> [!IMPORTANT]
+> 當頁面或 Modal 中存在多個垂直排列的 x-searchable-select 時，為防止選單開展時被下一個欄位遮擋，嚴禁使用固定的 z-index。
+
+### 10.1 動態層級提升模式
+必須在欄位容器上使用 focus-within:z-[index]，確保正在操作的欄位永遠處於堆疊最前方。
+
+| 使用場景 | 推薦 Class |
+|---------|------------|
+| 一般表單頁面 | relative focus-within:z-[20] |
+| 模態框 (Modal) 內 | relative focus-within:z-[60] |
+
+### 10.2 代碼範例
+```html
+<div class="space-y-4">
+    <!-- 型號選單 -->
+    <div class="relative focus-within:z-[60]">
+        <label>型號</label>
+        <x-searchable-select ... />
+    </div>
+
+    <!-- 公司選單 -->
+    <div class="relative focus-within:z-[60]">
+        <label>公司</label>
+        <x-searchable-select ... />
+    </div>
+</div>
+```
diff --git a/resources/views/admin/basic-settings/machines/edit.blade.php b/resources/views/admin/basic-settings/machines/edit.blade.php
index b995832..70cedb1 100644
--- a/resources/views/admin/basic-settings/machines/edit.blade.php
+++ b/resources/views/admin/basic-settings/machines/edit.blade.php
@@ -131,7 +131,7 @@
                             <input type="text" name="location" value="{{ old('location', $machine->location) }}" class="luxury-input w-full" placeholder="{{ __('e.g., Taipei Station') }}">
                         </div>
 
-                        <div>
+                        <div class="relative focus-within:z-[30]">
                             <label class="block text-xs font-bold text-slate-400 uppercase tracking-[0.15em] mb-2">{{ __('Machine Model') }} <span class="text-rose-500">*</span></label>
                             <x-searchable-select 
                                 name="machine_model_id" 
@@ -143,7 +143,7 @@
                             </x-searchable-select>
                         </div>
                         @if(auth()->user()->isSystemAdmin())
-                        <div>
+                        <div class="relative focus-within:z-[30]">
                             <label class="block text-xs font-bold text-slate-400 uppercase tracking-[0.15em] mb-2">{{ __('Company') }}</label>
                             <x-searchable-select 
                                 name="company_id" 
diff --git a/resources/views/admin/basic-settings/machines/index.blade.php b/resources/views/admin/basic-settings/machines/index.blade.php
index a2eac7c..bd4b925 100644
--- a/resources/views/admin/basic-settings/machines/index.blade.php
+++ b/resources/views/admin/basic-settings/machines/index.blade.php
@@ -770,7 +770,7 @@
                                     placeholder="{{ __('Enter machine location') }}">
                             </div>
 
-                            <div class="relative z-40">
+                            <div class="relative focus-within:z-[60]">
                                 <label
                                     class="block text-[11px] font-black text-slate-400 uppercase tracking-[0.2em] mb-2">
                                     {{ __('Model') }} <span class="text-rose-500">*</span>
@@ -782,7 +782,7 @@
                                 </x-searchable-select>
                             </div>
 
-                            <div class="relative z-50">
+                            <div class="relative focus-within:z-[60]">
                                 <label
                                     class="block text-[11px] font-black text-slate-400 uppercase tracking-[0.2em] mb-2">
                                     {{ __('Owner') }}