diff --git a/src/components/Sidebar.tsx b/src/components/Sidebar.tsx
index 889e3ec..8ef34f4 100644
--- a/src/components/Sidebar.tsx
+++ b/src/components/Sidebar.tsx
@@ -1,5 +1,6 @@
 import { memo, useCallback, useEffect, useRef, useState } from 'react'
 import { useDismiss } from '../hooks/useDismiss'
+import Tooltip from './Tooltip'
 import { listDir, workspaceSearch, type DirEntry, type WorkspaceSearchFile } from '../services/platform'
 import { isPathInside, parentDirOf, pathsEqual } from '../utils/text'
 import type { OutlineItem } from '../utils/text'
@@ -306,28 +307,30 @@ function WorkspaceSearch({ root, tauriMode, onOpen }: {
           onChange={(e) => setQuery(e.target.value)}
           onKeyDown={(e) => { if (e.key === 'Enter') void run() }}
         />
-        <button
-          className="ws-search-go"
-          disabled={searching || !query.trim()}
-          onClick={() => void run()}
-          title="搜索（Enter）"
-          aria-label="搜索"
-        >
-          {searching ? (
-            <span className="ws-spin" aria-hidden="true" />
-          ) : (
-            <svg width="15" height="15" viewBox="0 0 24 24" aria-hidden="true"><circle cx="11" cy="11" r="7" fill="none" stroke="currentColor" strokeWidth="1.8" /><path d="M20.5 20.5 16.7 16.7" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" /></svg>
-          )}
-        </button>
-      </div>
-      <div className="ws-search-opts">
-        <button
-          className={`chip-toggle${caseSensitive ? ' on' : ''}`}
-          aria-pressed={caseSensitive}
-          onClick={() => setCaseSensitive((v) => !v)}
-        >
-          区分大小写
-        </button>
+        <Tooltip label="区分大小写">
+          <button
+            className={`ws-search-aa${caseSensitive ? ' on' : ''}`}
+            aria-pressed={caseSensitive}
+            aria-label="区分大小写"
+            onClick={() => setCaseSensitive((v) => !v)}
+          >
+            Aa
+          </button>
+        </Tooltip>
+        <Tooltip label="搜索（Enter）">
+          <button
+            className="ws-search-go"
+            disabled={searching || !query.trim()}
+            onClick={() => void run()}
+            aria-label="搜索"
+          >
+            {searching ? (
+              <span className="ws-spin" aria-hidden="true" />
+            ) : (
+              <svg width="15" height="15" viewBox="0 0 24 24" aria-hidden="true"><circle cx="11" cy="11" r="7" fill="none" stroke="currentColor" strokeWidth="1.8" /><path d="M20.5 20.5 16.7 16.7" stroke="currentColor" strokeWidth="1.8" strokeLinecap="round" /></svg>
+            )}
+          </button>
+        </Tooltip>
       </div>
       {error && <div className="sidebar-empty">{error}</div>}
       {results && (
diff --git a/src/components/Tooltip.tsx b/src/components/Tooltip.tsx
new file mode 100644
index 0000000..f5d5a4f
--- /dev/null
+++ b/src/components/Tooltip.tsx
@@ -0,0 +1,15 @@
+import type { ReactNode } from 'react'
+
+/**
+ * 自绘悬浮提示：跟随当前主题（界面变量），不用浏览器原生 title 气泡。
+ * 纯 CSS 悬停/聚焦显示，带一点延迟避免划过时闪烁；气泡本身不拦截鼠标。
+ * 子元素应自带 aria-label，气泡只作视觉呈现（aria-hidden）。
+ */
+export default function Tooltip({ label, children }: { label: string; children: ReactNode }) {
+  return (
+    <span className="tooltip-wrap">
+      {children}
+      <span className="tooltip-bubble" aria-hidden="true">{label}</span>
+    </span>
+  )
+}
diff --git a/src/styles.css b/src/styles.css
index d1be11c..656f2a5 100644
--- a/src/styles.css
+++ b/src/styles.css
@@ -337,15 +337,18 @@ kbd { background: var(--code-bg); border: 1px solid var(--border); border-radius
 .filetree-head.drop-target { background: var(--accent-weak); box-shadow: inset 0 0 0 1px var(--accent); border-radius: 6px; }
 .ws-search { display: flex; flex-direction: column; gap: 8px; padding: 10px; min-height: 0; }
 .ws-search-box { display: flex; gap: 6px; align-items: stretch; }
-.ws-search-go { flex: none; width: 32px; display: inline-flex; align-items: center; justify-content: center; border: 1px solid var(--border); background: var(--bg); color: var(--text-dim); border-radius: 6px; cursor: pointer; padding: 0; }
+.ws-search-go { flex: none; width: 32px; height: 100%; display: inline-flex; align-items: center; justify-content: center; border: 1px solid var(--border); background: var(--bg); color: var(--text-dim); border-radius: 6px; cursor: pointer; padding: 0; }
 .ws-search-go:hover:not(:disabled) { color: var(--text); border-color: var(--accent); background: var(--hover); }
 .ws-search-go:disabled { opacity: 0.45; cursor: default; }
 .ws-spin { width: 13px; height: 13px; border: 2px solid var(--border); border-top-color: var(--accent); border-radius: 50%; animation: ws-spin 0.7s linear infinite; }
 @keyframes ws-spin { to { transform: rotate(360deg); } }
-.ws-search-opts { display: flex; gap: 6px; }
-.chip-toggle { font-size: 12px; font-family: inherit; padding: 3px 10px; border-radius: 999px; border: 1px solid var(--border); background: transparent; color: var(--text-dim); cursor: pointer; }
-.chip-toggle:hover { color: var(--text); background: var(--hover); }
-.chip-toggle.on { background: var(--accent-weak); color: var(--text); border-color: transparent; }
+.ws-search-box .ws-search-aa { flex: none; display: inline-flex; align-items: center; justify-content: center; height: 100%; padding: 0 8px; border: 1px solid var(--border); background: var(--bg); color: var(--text-dim); border-radius: 6px; cursor: pointer; font-family: inherit; font-size: 12.5px; font-weight: 600; letter-spacing: 0.2px; }
+.ws-search-box .ws-search-aa:hover { color: var(--text); border-color: var(--accent); background: var(--hover); }
+.ws-search-box .ws-search-aa.on { background: var(--accent-weak); color: var(--text); border-color: transparent; }
+/* 自绘悬浮提示（Tooltip 组件）：跟随主题变量，悬停/聚焦延迟浮现 */
+.tooltip-wrap { position: relative; display: inline-flex; align-items: stretch; }
+.tooltip-wrap .tooltip-bubble { position: absolute; left: 50%; bottom: calc(100% + 6px); transform: translateX(-50%) translateY(2px); background: var(--bg-editor); color: var(--text); border: 1px solid var(--border); box-shadow: 0 6px 18px rgba(0, 0, 0, 0.18); font-size: 12px; font-weight: 400; line-height: 1.4; padding: 4px 8px; border-radius: 6px; white-space: nowrap; pointer-events: none; opacity: 0; transition: opacity 0.15s ease, transform 0.15s ease; z-index: 80; }
+.tooltip-wrap:hover .tooltip-bubble, .tooltip-wrap:focus-within .tooltip-bubble { opacity: 1; transform: translateX(-50%) translateY(0); transition-delay: 0.35s; }
 /* 自绘下拉（Dropdown 组件）：按钮对齐 .input，展开层沿用应用菜单语言 */
 .dropdown { position: relative; }
 .dropdown-button { width: 100%; display: flex; align-items: center; justify-content: space-between; gap: 8px; border: 1px solid var(--border); background: var(--bg); color: var(--text); border-radius: 6px; padding: 5px 9px; font-size: 13px; font-family: inherit; cursor: pointer; text-align: left; }