diff --git a/README.md b/README.md
index 0e0a310..3cbce15 100644
--- a/README.md
+++ b/README.md
@@ -203,6 +203,6 @@ bash scripts/smoke-image.sh "$RUNTIME_IMAGE_ID"  # 已由管理员构建的本
 
 构建历史接口现默认分页（20条，最大100条），列表不再携带日志正文；日志通过 `/api/builds/{id}` 按需读取。升级面板后请刷新已打开的旧页面；外部脚本需按 API.md 更新，不能再依赖 `/api/builds` 返回全部历史或日志。
 
-合理替代方案为：stdlib HTTP Docker client而非官方SDK；每实例独立bridge而非共享bridge；服务端保管DSH cookie而非下发浏览器。前端已改用 Tailwind CSS + Radix 原语的 shadcn 风格组件（保留本地Monaco），桌面与移动端共用一套响应式界面。这些是选型差异，不降低功能、安全或验收标准，详见验收表。
+合理替代方案为：stdlib HTTP Docker client而非官方SDK；每实例独立bridge而非共享bridge；服务端保管DSH cookie而非下发浏览器。前端已改用 Tailwind CSS + Radix 原语的 shadcn 风格组件（保留本地Monaco），桌面与移动端共用一套响应式界面。界面跟随系统深浅色设置自动切换夜间模式（含 Monaco 编辑器），与内嵌 DSH 行为一致，无独立开关。这些是选型差异，不降低功能、安全或验收标准，详见验收表。
 
 同源路径代理仅适用于可信用户/插件，尚无独立origin及宿主/局域网出站防护。默认软配额不能阻止agent直接写满磁盘；硬quota是依赖宿主的可选增强，不是默认路线必做项。升级/恢复快照需额外容量，home快照上限1 GiB，模板7的 `/workspace` 就是实例home，会随home快照回滚；旧共享目录不随回滚恢复；中断及回滚失败仍可能需要管理员恢复。
diff --git a/web/index.html b/web/index.html
index 0477518..7e46cf3 100644
--- a/web/index.html
+++ b/web/index.html
@@ -1,2 +1,2 @@
 <!doctype html>
-<html lang="zh-CN"><head><meta charset="UTF-8"/><meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover"/><meta name="theme-color" content="#152b36"/><link rel="icon" type="image/svg+xml" href="/favicon.svg"/><title>DSH · 工作台</title></head><body><div id="root"></div><script type="module" src="/src/main.tsx"></script></body></html>
+<html lang="zh-CN"><head><meta charset="UTF-8"/><meta name="viewport" content="width=device-width, initial-scale=1.0, viewport-fit=cover"/><meta name="theme-color" media="(prefers-color-scheme: light)" content="#152b36"/><meta name="theme-color" media="(prefers-color-scheme: dark)" content="#101c22"/><link rel="icon" type="image/svg+xml" href="/favicon.svg"/><title>DSH · 工作台</title></head><body><div id="root"></div><script type="module" src="/src/main.tsx"></script></body></html>
diff --git a/web/src/MonacoProfileEditor.tsx b/web/src/MonacoProfileEditor.tsx
index 8c2a752..f798a87 100644
--- a/web/src/MonacoProfileEditor.tsx
+++ b/web/src/MonacoProfileEditor.tsx
@@ -3,6 +3,7 @@ import { useEffect, useRef } from 'react';
 import * as monaco from 'monaco-editor/esm/vs/editor/editor.api';
 import 'monaco-editor/esm/vs/basic-languages/yaml/yaml.contribution';
 import EditorWorker from 'monaco-editor/esm/vs/editor/editor.worker?worker';
+import { useNightMode } from './nightMode';
 
 // Vite emits this worker locally; no AMD loader or CDN is involved.
 self.MonacoEnvironment = { getWorker: () => new EditorWorker() };
@@ -21,6 +22,7 @@ export default function MonacoProfileEditor({ value, onChange, readOnly = false,
   change.current = onChange;
   const initialValue = useRef(value);
   const updating = useRef(false);
+  const dark = useNightMode();
   useEffect(() => {
     if (!host.current) return;
     const model = monaco.editor.createModel(initialValue.current, 'yaml');
@@ -28,6 +30,7 @@ export default function MonacoProfileEditor({ value, onChange, readOnly = false,
       model, automaticLayout: true, minimap: { enabled: false },
       scrollBeyondLastLine: false, tabSize: 2, insertSpaces: true,
       wordWrap: 'on', ariaLabel: label, readOnly,
+      theme: dark ? 'vs-dark' : 'vs',
     });
     editor.current = instance;
     const listener = instance.onDidChangeModelContent(() => {
@@ -44,5 +47,6 @@ export default function MonacoProfileEditor({ value, onChange, readOnly = false,
     }
   }, [value]);
   useEffect(() => { editor.current?.updateOptions({ readOnly, ariaLabel: label }); }, [readOnly, label]);
+  useEffect(() => { monaco.editor.setTheme(dark ? 'vs-dark' : 'vs'); }, [dark]);
   return <div role="group" aria-label={label} ref={host} style={{ height: 420, minWidth: 0, border: '1px solid var(--color-border, #d5dbe5)', borderRadius: 8, overflow: 'hidden' }} />;
 }
diff --git a/web/src/RuntimeWorkspace.tsx b/web/src/RuntimeWorkspace.tsx
index 61ac0cf..1c2431f 100644
--- a/web/src/RuntimeWorkspace.tsx
+++ b/web/src/RuntimeWorkspace.tsx
@@ -116,7 +116,7 @@ export function RuntimeWorkspace({ runtime, visible, manage, settings }: {
     </div>}
     {selected?.status === 'running' && <div className="flex min-h-0 flex-1 flex-col">
       {frameError && <div className="shrink-0 px-3 pt-2"><Alert>DSH 页面加载失败或登录已失效，请重新加载或在新窗口打开。</Alert></div>}
-      <iframe className="block min-h-0 w-full flex-1 border-0 bg-white" key={selected.id + ':' + revision} src={url} title={'DSH · ' + selected.name} referrerPolicy="same-origin" onError={() => setFrameError(true)} onLoad={event => {
+      <iframe className="block min-h-0 w-full flex-1 border-0 bg-card" key={selected.id + ':' + revision} src={url} title={'DSH · ' + selected.name} referrerPolicy="same-origin" onError={() => setFrameError(true)} onLoad={event => {
         try {
           const doc = event.currentTarget.contentDocument;
           const path = event.currentTarget.contentWindow?.location.pathname;
diff --git a/web/src/Workspace.tsx b/web/src/Workspace.tsx
index 7ef111e..83d6570 100644
--- a/web/src/Workspace.tsx
+++ b/web/src/Workspace.tsx
@@ -84,7 +84,7 @@ function WorkspaceFiles({instanceId, instanceName, controls, path, setPath}: Fil
         <details className="mt-2 text-[13px] text-muted-foreground">
           <summary className="cursor-pointer select-none font-medium text-primary">操作须知与敏感文件提醒</summary>
           <div className="mt-2 grid max-w-2xl gap-1.5">
-            <p className="m-0">实例数据目录为 /workspace（模板 7）；历史镜像的路径可能不同。这里管理文件，不会切换 DSH 会话的工作目录。</p>
+            <p className="m-0">实例数据目录为 /workspace；历史镜像的路径可能不同。这里管理文件，不会切换 DSH 会话的工作目录。</p>
             <p className="m-0">包含配置和密钥，请谨慎操作。{homeAccessNotice}</p>
             <p className="m-0">下载确认及文件名识别仅为操作提醒，不是权限边界；右键打开下载链接等方式可能绕过提示。</p>
           </div>
diff --git a/web/src/nightMode.test.ts b/web/src/nightMode.test.ts
new file mode 100644
index 0000000..c1b6728
--- /dev/null
+++ b/web/src/nightMode.test.ts
@@ -0,0 +1,32 @@
+import { afterEach, beforeEach, expect, it, vi } from 'vitest';
+const hooks = vi.hoisted(() => ({slots: [] as any[], cursor: 0, effects: [] as (() => void)[]}));
+vi.mock('react', async importOriginal => ({
+  ...await importOriginal<typeof import('react')>(),
+  useRef(value: unknown) { const i = hooks.cursor++; return hooks.slots[i] ??= {current:value}; },
+  useState(value: unknown) { const i = hooks.cursor++; if (!(i in hooks.slots)) hooks.slots[i] = value; return [hooks.slots[i], (v: unknown) => { hooks.slots[i] = v; }]; },
+  useEffect(fn: () => (() => void) | undefined, deps: unknown[]) {
+    const i = hooks.cursor++, previous = hooks.slots[i];
+    if (!previous || deps.some((v, n) => v !== previous.deps[n])) hooks.effects.push(() => { previous?.cleanup?.(); hooks.slots[i] = {deps, cleanup:fn()}; });
+  },
+}));
+import { useNightMode } from './nightMode';
+
+const media = {matches: false, addEventListener: vi.fn(), removeEventListener: vi.fn()};
+const render = () => { hooks.cursor = 0; const result = useNightMode(); hooks.effects.splice(0).forEach(effect => effect()); return result; };
+beforeEach(() => { hooks.slots = []; hooks.cursor = 0; hooks.effects = []; media.matches = false; vi.clearAllMocks(); vi.stubGlobal('window', {matchMedia: vi.fn(() => media)}); });
+afterEach(() => { hooks.slots.forEach(s => s?.cleanup?.()); vi.unstubAllGlobals(); });
+
+it('reflects the current system color scheme', () => {
+  media.matches = true;
+  expect(render()).toBe(true);
+  expect(media.addEventListener).toHaveBeenCalledWith('change', expect.any(Function));
+});
+
+it('updates when the system scheme changes and unsubscribes on cleanup', () => {
+  expect(render()).toBe(false);
+  const listener = media.addEventListener.mock.calls[0][1] as (event: MediaQueryListEvent) => void;
+  listener({matches: true} as MediaQueryListEvent);
+  expect(render()).toBe(true);
+  hooks.slots.forEach(s => s?.cleanup?.());
+  expect(media.removeEventListener).toHaveBeenCalledWith('change', listener);
+});
diff --git a/web/src/nightMode.ts b/web/src/nightMode.ts
new file mode 100644
index 0000000..476f884
--- /dev/null
+++ b/web/src/nightMode.ts
@@ -0,0 +1,16 @@
+import { useEffect, useState } from 'react';
+
+const query = () => window.matchMedia('(prefers-color-scheme: dark)');
+
+/** Tracks the OS dark-scheme preference, matching the automatic night mode of embedded DSH. */
+export function useNightMode() {
+  const [dark, setDark] = useState(query().matches);
+  useEffect(() => {
+    const media = query();
+    const update = (event: MediaQueryListEvent) => setDark(event.matches);
+    setDark(media.matches);
+    media.addEventListener('change', update);
+    return () => media.removeEventListener('change', update);
+  }, []);
+  return dark;
+}
diff --git a/web/src/style.css b/web/src/style.css
index f6980a0..14c2c31 100644
--- a/web/src/style.css
+++ b/web/src/style.css
@@ -51,6 +51,48 @@
   --touch-min: 2.75rem;
 }
 
+/* Automatic night mode: follow the OS color scheme, same as embedded DSH.
+   Dark values override the @theme variables above; utilities keep working
+   because they reference the variables at computed-value time. */
+@layer base {
+  :root {
+    color-scheme: light;
+  }
+  @media (prefers-color-scheme: dark) {
+    :root {
+      color-scheme: dark;
+      --color-background: #101c22;
+      --color-foreground: #d9e5e9;
+      --color-card: #17282f;
+      --color-card-foreground: #d9e5e9;
+      --color-muted: #1f333c;
+      --color-muted-foreground: #92acb6;
+      --color-border: #2c434d;
+      --color-input: #3a545f;
+      --color-ring: #4ec9ae;
+
+      --color-primary-hover: #15a192;
+
+      --color-secondary: #1e343c;
+      --color-secondary-foreground: #7fd8c5;
+
+      --color-destructive: #d45d53;
+      --color-destructive-muted: #3b2421;
+
+      --color-success: #4cba8f;
+      --color-success-muted: #173a2e;
+      --color-warning: #d9a94f;
+      --color-warning-muted: #3b3018;
+      --color-danger-muted: #3b2421;
+
+      /* Navigation chrome (--color-nav-*) is already dark in both schemes. */
+
+      --shadow-card: 0 1px 2px rgb(0 0 0 / 0.35), 0 1px 6px rgb(0 0 0 / 0.3);
+      --shadow-dialog: 0 24px 80px rgb(0 0 0 / 0.55);
+    }
+  }
+}
+
 @layer base {
   * {
     box-sizing: border-box;