diff --git a/AGENTS.md b/AGENTS.md
index 0cce7035..a020ed87 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -78,6 +78,8 @@ Use focused tests while iterating. Before handing off a code change, run the ful
 
 `pnpm dev` starts Core and can attach to local QQ processes; use it only when runtime testing is intended. `pnpm dev:web` starts the frontend, which expects a WebUI backend. Follow the existing test fakes for isolated work rather than starting a live account unnecessarily.
 
+WebUI deployment targets use a reversible presentation overlay. Read [the host appearance contract](packages/webui/INTEGRATIONS.md) before changing it. Keep target validation in `@snowluma/common/webui-target`, implementations in the frontend target registry, and saved preferences separate from effective appearance. Default deployments must not load target assets or host listeners; do not put target-name branches in business pages.
+
 ## Implementation rules
 
 - **Fix the cause.** Reproduce failures at the owning layer and add a regression test for the observable behavior. Avoid account-, filename-, or example-specific patches.
diff --git a/packages/common/package.json b/packages/common/package.json
index 6f8d87d9..8f99da4a 100644
--- a/packages/common/package.json
+++ b/packages/common/package.json
@@ -8,6 +8,10 @@
   "main": "./src/index.ts",
   "types": "./src/index.ts",
   "exports": {
+    "./webui-target": {
+      "types": "./src/webui-target.ts",
+      "default": "./src/webui-target.ts"
+    },
     "./update-source": {
       "types": "./src/update-source.ts",
       "default": "./src/update-source.ts"
diff --git a/packages/common/src/webui-target.ts b/packages/common/src/webui-target.ts
new file mode 100644
index 00000000..1c2ab81c
--- /dev/null
+++ b/packages/common/src/webui-target.ts
@@ -0,0 +1,100 @@
+/** Browser-safe contract shared by startup, the WebUI and embedding hosts.
+ * Targets are deployment choices; they never belong in the saved UI preferences. */
+export const WEBUI_TARGETS = {
+    maibot: {
+        label: '麦麦 / 一键包',
+        styles: ['millennium'],
+        defaultStyle: 'millennium',
+    },
+} as const;
+
+export type WebuiTarget = keyof typeof WEBUI_TARGETS;
+export type WebuiColorMode = 'light' | 'dark' | 'system';
+
+export type WebuiPresentation = {
+    [T in WebuiTarget]: {
+        version: 1;
+        target: T;
+        style: (typeof WEBUI_TARGETS)[T]['styles'][number];
+        mode: WebuiColorMode;
+    };
+}[WebuiTarget];
+
+/** null releases the override for this document, without changing deployment opt-in. */
+export type WebuiPresentationUpdate = WebuiPresentation | { version: 1; target: null };
+export const WEBUI_PRESENTATION_EVENT = 'snowluma:host-appearance';
+export const WEBUI_TARGET_BOOTSTRAP_ID = 'snowluma-webui-target';
+
+export function resolveWebuiTarget(raw: string | undefined): WebuiTarget | null {
+    if (raw === undefined || raw.trim() === '') {
+        return null;
+    }
+
+    const value = raw.trim();
+
+    if (!Object.hasOwn(WEBUI_TARGETS, value)) {
+        throw new Error(
+            `Invalid SNOWLUMA_WEBUI_TARGET: ${JSON.stringify(value)}. Expected ${Object.keys(WEBUI_TARGETS).join(', ')} or an empty value.`,
+        );
+    }
+
+    return value as WebuiTarget;
+}
+
+export function defaultWebuiPresentation(target: WebuiTarget): WebuiPresentation {
+    return { version: 1, target, style: WEBUI_TARGETS[target].defaultStyle, mode: 'system' };
+}
+
+export function parseWebuiPresentation(value: unknown): WebuiPresentationUpdate {
+    if (
+        !value ||
+        typeof value !== 'object' ||
+        !('version' in value) ||
+        value.version !== 1 ||
+        !('target' in value)
+    ) {
+        throw new TypeError('Invalid host appearance: expected a version 1 presentation');
+    }
+
+    if (value.target === null) {
+        return { version: 1, target: null };
+    }
+
+    if (typeof value.target !== 'string' || !Object.hasOwn(WEBUI_TARGETS, value.target)) {
+        throw new TypeError('Invalid host appearance target');
+    }
+
+    const target = value.target as WebuiTarget;
+    const styles: readonly string[] = WEBUI_TARGETS[target].styles;
+
+    if (!('style' in value) || typeof value.style !== 'string' || !styles.includes(value.style)) {
+        throw new TypeError(`Invalid host appearance style for ${target}`);
+    }
+
+    if (
+        !('mode' in value) ||
+        (value.mode !== 'light' && value.mode !== 'dark' && value.mode !== 'system')
+    ) {
+        throw new TypeError('Invalid host appearance color mode');
+    }
+
+    // Both discriminants have been checked against the same target registry.
+    return { version: 1, target, style: value.style, mode: value.mode } as WebuiPresentation;
+}
+
+/** Inject before the cached pre-paint theme script. Default HTML stays byte-for-byte intact. */
+export function injectWebuiTarget(html: string, target: WebuiTarget | null): string {
+    if (target === null) {
+        return html;
+    }
+
+    if (!html.includes('<head>')) {
+        throw new Error('WebUI HTML is missing <head>; cannot inject runtime target');
+    }
+
+    const json = JSON.stringify(defaultWebuiPresentation(target)).replaceAll('<', '\\u003c');
+    return html.replace(
+        '<head>',
+        `<head>\n    <script id="${WEBUI_TARGET_BOOTSTRAP_ID}" type="application/json">${json}</script>`,
+    );
+}
diff --git a/packages/common/tests/webui-target.test.ts b/packages/common/tests/webui-target.test.ts
new file mode 100644
index 00000000..67578702
--- /dev/null
+++ b/packages/common/tests/webui-target.test.ts
@@ -0,0 +1,51 @@
+import { describe, expect, it } from 'vitest';
+import {
+    defaultWebuiPresentation,
+    injectWebuiTarget,
+    parseWebuiPresentation,
+    resolveWebuiTarget,
+} from '../src/webui-target';
+
+describe('deployment presentation contract', () => {
+    it('requires explicit opt-in and rejects misspelled deployments', () => {
+        expect(resolveWebuiTarget(undefined)).toBeNull();
+        expect(resolveWebuiTarget('  ')).toBeNull();
+        expect(resolveWebuiTarget('maibot')).toBe('maibot');
+        expect(() => resolveWebuiTarget('mai-bot')).toThrow('SNOWLUMA_WEBUI_TARGET');
+        expect(() => resolveWebuiTarget('__proto__')).toThrow('SNOWLUMA_WEBUI_TARGET');
+    });
+
+    it('keeps the unconfigured document intact and injects before cached appearance', () => {
+        const html = '<html><head><script>readSavedAppearance()</script></head></html>';
+        expect(injectWebuiTarget(html, null)).toBe(html);
+        const injected = injectWebuiTarget(html, 'maibot');
+        expect(injected.indexOf('snowluma-webui-target')).toBeLessThan(
+            injected.indexOf('readSavedAppearance'),
+        );
+        expect(injected).toContain(JSON.stringify(defaultWebuiPresentation('maibot')));
+        expect(() => injectWebuiTarget('broken html', 'maibot')).toThrow('missing <head>');
+    });
+
+    it('validates the version, target, style and color mode without accepting arbitrary CSS', () => {
+        const valid = defaultWebuiPresentation('maibot');
+        expect(parseWebuiPresentation(valid)).toEqual(valid);
+        expect(
+            parseWebuiPresentation({ ...valid, mode: 'dark', css: 'body{display:none}' }),
+        ).toEqual({ ...valid, mode: 'dark' });
+        expect(parseWebuiPresentation({ version: 1, target: null })).toEqual({
+            version: 1,
+            target: null,
+        });
+
+        for (const input of [
+            null,
+            {},
+            { ...valid, version: 2 },
+            { ...valid, target: 'other' },
+            { ...valid, style: 'modern' },
+            { ...valid, mode: 'blue' },
+        ]) {
+            expect(() => parseWebuiPresentation(input)).toThrow();
+        }
+    });
+});
diff --git a/packages/core/src/webui/server.ts b/packages/core/src/webui/server.ts
index 5fd9eb74..c3bc43a8 100644
--- a/packages/core/src/webui/server.ts
+++ b/packages/core/src/webui/server.ts
@@ -1,6 +1,7 @@
 import { APP_VERSION } from '@snowluma/common/version';
 import { serve } from '@hono/node-server';
-import { serveStatic } from '@hono/node-server/serve-static';
+import { resolveWebuiTarget } from '@snowluma/common/webui-target';
+import { registerStaticFrontend } from './static-frontend';
 import type { HookManager, HookProcessInfo } from '@snowluma/bridge';
 import { getRuntimeIntegrity, hasLowProcessIntegrity } from '@snowluma/bridge';
 import {
@@ -636,6 +637,15 @@ export async function initWebUI(
         updateRoot?: string;
     } = {},
 ): Promise<{ port: number; stop: () => Promise<void> }> {
+    const webuiTarget = resolveWebuiTarget(process.env.SNOWLUMA_WEBUI_TARGET);
+
+    if (webuiTarget) {
+        log.info(
+            'presentation target enabled: %s (runtime override; saved appearance is preserved)',
+            webuiTarget,
+        );
+    }
+
     const host = listener.host || '127.0.0.1';
     const tlsEnabled = listener.tlsEnabled === true;
     const bootCheck = checkListenerExposure({
@@ -2267,29 +2277,7 @@ export async function initWebUI(
     // Build path is relative to the bundled / dev __dirname. SPA fallback to
     // index.html so client-side routes (if any) keep working.
     const staticRoot = path.resolve(__dirname, 'client');
-    app.use('/*', serveStatic({ root: staticRoot }));
-
-    const indexHtmlPath = path.join(staticRoot, 'index.html');
-    app.get('*', (c) => {
-        // SPA fallback: only for navigations that didn't hit a static asset.
-        if (
-            c.req.path.startsWith('/api/') ||
-            c.req.path.startsWith('/avatar/') ||
-            c.req.path.startsWith('/ui-asset/')
-        ) {
-            return c.text('not found', 404);
-        }
-
-        if (existsSync(indexHtmlPath)) {
-            const html = readFileSync(indexHtmlPath, 'utf8');
-            return c.html(html);
-        }
-
-        return c.text(
-            'WebUI client bundle not found. Run `pnpm --filter webui build` (or use the dev server on :5178).',
-            404,
-        );
-    });
+    registerStaticFrontend(app, staticRoot, webuiTarget);
 
     const finalPort = await findAvailablePort(desiredPort, { host });
 
diff --git a/packages/core/src/webui/static-frontend.ts b/packages/core/src/webui/static-frontend.ts
new file mode 100644
index 00000000..da64f2bd
--- /dev/null
+++ b/packages/core/src/webui/static-frontend.ts
@@ -0,0 +1,34 @@
+import { existsSync, readFileSync } from 'node:fs';
+import path from 'node:path';
+import type { Hono, Context } from 'hono';
+import { serveStatic } from '@hono/node-server/serve-static';
+import { injectWebuiTarget, type WebuiTarget } from '@snowluma/common/webui-target';
+
+/** All document entry paths share runtime injection, including direct index.html requests. */
+export function registerStaticFrontend(app: Hono, root: string, target: WebuiTarget | null): void {
+    const indexPath = path.join(root, 'index.html');
+
+    const document = (c: Context) => {
+        if (!existsSync(indexPath)) {
+            return c.text(
+                'WebUI client bundle not found. Run `pnpm --filter webui build` (or use the dev server on :5178).',
+                404,
+            );
+        }
+
+        // A packaged frontend can be reused with a different deployment target on restart.
+        c.header('Cache-Control', 'no-store');
+        return c.html(injectWebuiTarget(readFileSync(indexPath, 'utf8'), target));
+    };
+
+    app.get('/', document);
+    app.get('/index.html', document);
+    app.use('/*', serveStatic({ root }));
+    app.get('*', (c) => {
+        if (['/api/', '/avatar/', '/ui-asset/'].some((prefix) => c.req.path.startsWith(prefix))) {
+            return c.text('not found', 404);
+        }
+
+        return document(c);
+    });
+}
diff --git a/packages/core/tests/webui-static-frontend.test.ts b/packages/core/tests/webui-static-frontend.test.ts
new file mode 100644
index 00000000..79fc522f
--- /dev/null
+++ b/packages/core/tests/webui-static-frontend.test.ts
@@ -0,0 +1,47 @@
+import { afterEach, beforeEach, describe, expect, it } from 'vitest';
+import { Hono } from 'hono';
+import { mkdtempSync, rmSync, writeFileSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import path from 'node:path';
+import { registerStaticFrontend } from '../src/webui/static-frontend';
+
+let root: string;
+const html = '<!doctype html><html><head><title>SnowLuma</title></head><body>app</body></html>';
+
+beforeEach(() => {
+    root = mkdtempSync(path.join(tmpdir(), 'snowluma-presentation-'));
+    writeFileSync(path.join(root, 'index.html'), html);
+    writeFileSync(path.join(root, 'asset.js'), 'window.asset = true;');
+});
+
+afterEach(() => rmSync(root, { recursive: true, force: true }));
+
+describe('runtime target document delivery', () => {
+    it.each(['/', '/index.html', '/settings?tab=appearance'])(
+        'injects on %s before authentication',
+        async (url) => {
+            const app = new Hono();
+            registerStaticFrontend(app, root, 'maibot');
+            const response = await app.request(url);
+            expect(response.status).toBe(200);
+            expect(response.headers.get('cache-control')).toBe('no-store');
+            expect(await response.text()).toContain('"target":"maibot"');
+        },
+    );
+
+    it('reuses the exact same built frontend for an unconfigured deployment', async () => {
+        const app = new Hono();
+        registerStaticFrontend(app, root, null);
+        expect(await (await app.request('/index.html')).text()).toBe(html);
+    });
+
+    it('does not inject into assets or API error responses', async () => {
+        const app = new Hono();
+        registerStaticFrontend(app, root, 'maibot');
+        expect(await (await app.request('/asset.js')).text()).toBe('window.asset = true;');
+
+        for (const url of ['/api/missing', '/avatar/missing', '/ui-asset/missing']) {
+            expect((await app.request(url)).status).toBe(404);
+        }
+    });
+});
diff --git a/packages/webui/INTEGRATIONS.md b/packages/webui/INTEGRATIONS.md
new file mode 100644
index 00000000..cb11cf85
--- /dev/null
+++ b/packages/webui/INTEGRATIONS.md
@@ -0,0 +1,111 @@
+# Host appearance overlays
+
+Set `SNOWLUMA_WEBUI_TARGET=maibot` on the **SnowLuma process** to use MaiBot's
+millennium appearance. The same release bundle supports standalone and embedded
+deployments. An unset or empty value keeps the existing SnowLuma experience;
+unknown values fail WebUI startup with an explicit diagnostic.
+
+This first adapter implements **millennium only**, in light and dark modes.
+Other MaiBot styles are not implemented. There is no new appearance selector in
+SnowLuma. The host owns theme changes; existing theme controls are unavailable
+while managed, and the settings page explains which preferences are preserved.
+
+## Runtime and ownership
+
+1. Core reads the environment at startup. [Static document delivery](../core/src/webui/static-frontend.ts)
+   injects a validated, public JSON bootstrap into `/`, `/index.html` and SPA
+   fallback documents. Documents use `Cache-Control: no-store`. No secrets or
+   arbitrary environment variables reach the browser.
+2. [Frontend bootstrap](src/appearance/runtime.ts) loads only the selected
+   target's assets before mounting React. Standalone deployments load no target
+   stylesheet, font or host listener. Vite development serves the same bootstrap
+   when its process has the environment variable; production builds remain neutral.
+3. [ThemeContext](src/contexts/ThemeContext.tsx) keeps `savedAppearance` separate
+   from effective `appearance`. Only saved preferences enter localStorage or
+   `config/ui.json`. Target updates never invoke the persistence API.
+4. The target owns colors, fonts, radius, wallpaper, CSS variable overrides,
+   custom CSS and custom cursor presentation. These saved values are preserved
+   but suspended. UI scale, density, motion/accessibility, navigation layout and
+   data preferences remain available. Safe-mode restrictions still apply when
+   returning to native appearance.
+5. A single layout effect applies effective appearance. Changes do not reload
+   the document, change React keys or restart sessions. All target rules are
+   scoped to `html[data-webui-target]`, including portals under `body`.
+
+## Host protocol, version 1
+
+The contract lives in [common/webui-target.ts](../common/src/webui-target.ts).
+The deployment environment is an opt-in, **not a live transport**. Existing
+launchers need to implement the sender below; merely setting the environment
+variable cannot convey another process's current theme.
+
+A same-document embedding bridge (for example Electron `executeJavaScript`)
+publishes the latest snapshot before dispatching the event:
+
+```js
+const appearance = {
+    version: 1,
+    target: 'maibot',
+    style: 'millennium',
+    mode: 'dark', // 'light' | 'dark' | 'system'
+};
+window.__SNOWLUMA_HOST_APPEARANCE__ = appearance;
+window.dispatchEvent(new CustomEvent('snowluma:host-appearance', { detail: appearance }));
+```
+
+The snapshot handles messages sent before React or the lazy asset loader is
+ready. Publish on each guest `dom-ready` and whenever the host's resolved
+brightness changes. A host that already follows MaiBot should forward its own
+resolved `light`/`dark` state; this avoids competing sources of truth. Validate
+the guest's expected origin before injecting, serialize values with
+`JSON.stringify`, and do not enable Node integration in the guest.
+
+Send `{ version: 1, target: null }` using the same mechanism to release the
+override for the current document. The original appearance returns immediately.
+The opted-in document keeps its host subscription so the host can reapply the
+target later. Listeners are released on provider unmount. This does not change
+the startup environment or enable a target in a standalone deployment.
+
+The current adapter starts with millennium and system brightness before a host
+snapshot arrives. The last valid snapshot remains active if the host stops
+sending. Snapshots are not persisted or shared across origins/tabs. A reload
+requires the host to publish again. Unsupported versions, targets, styles or
+modes are rejected with `[SnowLuma appearance]` console diagnostics; the previous
+valid snapshot remains. The host cannot supply CSS, URLs or executable content
+through this protocol. No unauthenticated HTTP write endpoint is introduced.
+
+## Adding a target
+
+- Add its identifier, styles and default style to `WEBUI_TARGETS` in the shared
+  contract. Keep validation at this boundary; do not accept arbitrary strings.
+- Add one lazy loader to the exhaustive [frontend registry](src/appearance/registry.ts).
+  Implement a pure saved-to-effective resolver and scoped stylesheet under
+  `src/appearance/targets`. Keep any fonts local with their redistribution license.
+- Use semantic color variables, shared component classes and neutral
+  `data-ui-surface` markers. Do not add target-name checks to business pages.
+- Never persist resolved overrides, mutate saved preferences, introduce a
+  second DOM theme writer, or remount the application to switch presentation.
+- Test default asset/listener isolation, initial document routes, malformed
+  messages, rapid updates, cleanup and exact restoration of saved preferences.
+  Verify forms, focus, scroll, portals and mobile layout with an isolated backend.
+  Electron integration needs a separate real-host check.
+
+## Sources and checks
+
+The adapter follows the main MaiBot repository's
+[millennium stylesheet](https://github.com/Mai-with-u/MaiBot/blob/5c7637e6913c84d1c3d5e742fa9e95a7e70d3501/dashboard/src/styles/millennium.css),
+not the archived standalone WebUI. Colors/materials also match the
+[OneKey shell](https://github.com/Mai-with-u/MaiBotOneKey/blob/e8073b0bce35c8c4da973b06156602e14c42fee5/src/renderer/src/styles/millennium.css).
+The bundled Jersey 20 font is from that MaiBot revision, copyright The Soft Type
+Project Authors, under the [SIL Open Font License](src/appearance/targets/assets/Jersey20-OFL.txt).
+Its license is emitted alongside the font in production assets.
+
+Focused checks (from the repository root):
+
+```sh
+pnpm --filter @snowluma/common exec vitest run tests/webui-target.test.ts
+pnpm --filter @snowluma/core exec vitest run tests/webui-static-frontend.test.ts
+pnpm --filter webui exec vitest run tests/target-appearance.test.ts
+```
+
+Run the normal workspace checks from `AGENTS.md` before handing off changes.
diff --git a/packages/webui/README.md b/packages/webui/README.md
index c6b7c9ef..d84dd902 100644
--- a/packages/webui/README.md
+++ b/packages/webui/README.md
@@ -3,6 +3,14 @@
 SnowLuma's browser console is a Vite + React application for managing runtime
 status, OneBot configuration, logs, storage, and server settings.
 
+## Host appearance integration
+
+`SNOWLUMA_WEBUI_TARGET=maibot` opts a deployment into a reversible millennium
+appearance overlay. Standalone defaults are unchanged. Hosts drive live light/dark
+updates without saving over personal preferences or adding another selector.
+See [the integration contract and extension guide](INTEGRATIONS.md) before changing
+target startup, theme ownership, host messaging or scoped styles.
+
 ## Interaction conventions
 
 - Destructive actions and second confirmations stay in modal dialogs.
diff --git a/packages/webui/index.html b/packages/webui/index.html
index 983febae..80cc5386 100644
--- a/packages/webui/index.html
+++ b/packages/webui/index.html
@@ -17,6 +17,9 @@
     <script>
       (function () {
         try {
+          // Deployment overlays are prepared before React mounts. Do not flash
+          // a saved palette/font underneath an opted-in host presentation.
+          if (document.getElementById('snowluma-webui-target')) return;
           var raw = localStorage.getItem('snowluma_ui_appearance');
           var a = raw ? JSON.parse(raw) : {};
           if (!a || typeof a !== 'object') a = {};
diff --git a/packages/webui/src/appearance/registry.ts b/packages/webui/src/appearance/registry.ts
new file mode 100644
index 00000000..84ae495b
--- /dev/null
+++ b/packages/webui/src/appearance/registry.ts
@@ -0,0 +1,29 @@
+import type { WebuiPresentation, WebuiTarget } from '@snowluma/common/webui-target';
+import type { UiAppearance } from '@/types';
+
+export interface TargetAppearance {
+    css: string;
+    licenseUrl?: string;
+    resolve: (saved: UiAppearance, presentation: WebuiPresentation) => UiAppearance;
+}
+
+export function resolveAppearance(
+    saved: UiAppearance,
+    presentation: WebuiPresentation | null,
+    target: TargetAppearance | null,
+): UiAppearance {
+    if (!presentation) {
+        return saved;
+    }
+
+    if (!target) {
+        throw new Error('Target appearance must be prepared before mounting ThemeProvider');
+    }
+
+    return target.resolve(saved, presentation);
+}
+
+// Exhaustive: adding a shared target requires a frontend implementation here.
+export const targetLoaders = {
+    maibot: () => import('./targets/maibot').then((module) => module.maibotAppearance),
+} satisfies Record<WebuiTarget, () => Promise<TargetAppearance>>;
diff --git a/packages/webui/src/appearance/runtime.ts b/packages/webui/src/appearance/runtime.ts
new file mode 100644
index 00000000..c9a9c0ce
--- /dev/null
+++ b/packages/webui/src/appearance/runtime.ts
@@ -0,0 +1,104 @@
+import {
+    parseWebuiPresentation,
+    WEBUI_PRESENTATION_EVENT,
+    WEBUI_TARGET_BOOTSTRAP_ID,
+    type WebuiPresentation,
+} from '@snowluma/common/webui-target';
+import { createPresentationStore, type PresentationStore } from './store';
+import { targetLoaders, type TargetAppearance } from './registry';
+
+declare global {
+    interface Window {
+        /** The embedding host sets this before dispatching WEBUI_PRESENTATION_EVENT. */
+        __SNOWLUMA_HOST_APPEARANCE__?: unknown;
+    }
+}
+
+const bootstrap =
+    typeof document === 'undefined' ? null : document.getElementById(WEBUI_TARGET_BOOTSTRAP_ID);
+const initial = bootstrap
+    ? parseWebuiPresentation(JSON.parse(bootstrap.textContent || 'null'))
+    : null;
+export const presentationStore = createPresentationStore(initial?.target ?? null);
+let targetAppearance: TargetAppearance | null = null;
+
+function acceptHostValue(store: PresentationStore, value: unknown): void {
+    try {
+        store.receive(value);
+    } catch (error) {
+        // Reject only the bad update; keep the last valid presentation and expose the failure.
+        console.error('[SnowLuma appearance] Rejected host update', error);
+    }
+}
+
+export function subscribeHostAppearance(host: Window, store: PresentationStore): () => void {
+    if (store.target === null) {
+        return () => {};
+    }
+
+    const receive = (event: Event) =>
+        acceptHostValue(store, (event as CustomEvent<unknown>).detail);
+    host.addEventListener(WEBUI_PRESENTATION_EVENT, receive);
+
+    // Covers messages sent before React subscribed, including while the lazy CSS was loading.
+    if (host.__SNOWLUMA_HOST_APPEARANCE__ !== undefined) {
+        acceptHostValue(store, host.__SNOWLUMA_HOST_APPEARANCE__);
+    }
+
+    return () => host.removeEventListener(WEBUI_PRESENTATION_EVENT, receive);
+}
+
+export function applyPresentationAttributes(presentation: WebuiPresentation | null): void {
+    const root = document.documentElement;
+
+    if (presentation) {
+        root.dataset.webuiTarget = presentation.target;
+        root.dataset.webuiStyle = presentation.style;
+    } else {
+        delete root.dataset.webuiTarget;
+        delete root.dataset.webuiStyle;
+    }
+}
+
+export function getTargetAppearance(): TargetAppearance | null {
+    return targetAppearance;
+}
+
+/** Called before mounting React; standalone deployments do not load any target assets. */
+export async function prepareTargetAppearance(): Promise<void> {
+    const target = presentationStore.target;
+
+    if (target === null) {
+        return;
+    }
+
+    targetAppearance = await targetLoaders[target]();
+    const style = document.createElement('style');
+    style.id = 'snowluma-target-styles';
+    style.textContent = targetAppearance.css;
+    document.head.appendChild(style);
+
+    if (targetAppearance.licenseUrl) {
+        const license = document.createElement('link');
+        license.rel = 'license';
+        license.href = targetAppearance.licenseUrl;
+        document.head.appendChild(license);
+    }
+
+    if (window.__SNOWLUMA_HOST_APPEARANCE__ !== undefined) {
+        acceptHostValue(presentationStore, window.__SNOWLUMA_HOST_APPEARANCE__);
+    }
+
+    const presentation = presentationStore.getSnapshot();
+    applyPresentationAttributes(presentation);
+
+    if (presentation) {
+        const dark =
+            presentation.mode === 'system'
+                ? window.matchMedia('(prefers-color-scheme: dark)').matches
+                : presentation.mode === 'dark';
+        document.documentElement.classList.toggle('dark', dark);
+        document.documentElement.classList.toggle('light', !dark);
+        document.documentElement.style.colorScheme = dark ? 'dark' : 'light';
+    }
+}
diff --git a/packages/webui/src/appearance/store.ts b/packages/webui/src/appearance/store.ts
new file mode 100644
index 00000000..8d6de3d8
--- /dev/null
+++ b/packages/webui/src/appearance/store.ts
@@ -0,0 +1,51 @@
+import {
+    defaultWebuiPresentation,
+    parseWebuiPresentation,
+    type WebuiPresentation,
+    type WebuiTarget,
+} from '@snowluma/common/webui-target';
+
+/** Synchronous snapshots avoid stale async style loads winning a rapid host theme change. */
+export function createPresentationStore(target: WebuiTarget | null) {
+    let snapshot: WebuiPresentation | null = target ? defaultWebuiPresentation(target) : null;
+    const listeners = new Set<() => void>();
+
+    return {
+        target,
+        getSnapshot: () => snapshot,
+        subscribe(listener: () => void) {
+            if (target) {
+                listeners.add(listener);
+            }
+
+            return () => {
+                listeners.delete(listener);
+            };
+        },
+        receive(value: unknown) {
+            // Host code cannot opt a standalone deployment into a target.
+            if (target === null) {
+                return;
+            }
+
+            const update = parseWebuiPresentation(value);
+
+            if (update.target !== null && update.target !== target) {
+                throw new Error(
+                    `Host appearance target does not match deployment target ${target}`,
+                );
+            }
+
+            const next = update.target === null ? null : update;
+
+            if (JSON.stringify(next) === JSON.stringify(snapshot)) {
+                return;
+            }
+
+            snapshot = next;
+            listeners.forEach((listener) => listener());
+        },
+    };
+}
+
+export type PresentationStore = ReturnType<typeof createPresentationStore>;
diff --git a/packages/webui/src/appearance/targets/assets/Jersey20-OFL.txt b/packages/webui/src/appearance/targets/assets/Jersey20-OFL.txt
new file mode 100644
index 00000000..0e2994d7
--- /dev/null
+++ b/packages/webui/src/appearance/targets/assets/Jersey20-OFL.txt
@@ -0,0 +1,93 @@
+Copyright 2023 The Soft Type Project Authors (https://github.com/scfried/soft-type-jersey)
+
+This Font Software is licensed under the SIL Open Font License, Version 1.1.
+This license is copied below, and is also available with a FAQ at:
+https://openfontlicense.org
+
+
+-----------------------------------------------------------
+SIL OPEN FONT LICENSE Version 1.1 - 26 February 2007
+-----------------------------------------------------------
+
+PREAMBLE
+The goals of the Open Font License (OFL) are to stimulate worldwide
+development of collaborative font projects, to support the font creation
+efforts of academic and linguistic communities, and to provide a free and
+open framework in which fonts may be shared and improved in partnership
+with others.
+
+The OFL allows the licensed fonts to be used, studied, modified and
+redistributed freely as long as they are not sold by themselves. The
+fonts, including any derivative works, can be bundled, embedded,
+redistributed and/or sold with any software provided that any reserved
+names are not used by derivative works. The fonts and derivatives,
+however, cannot be released under any other type of license. The
+requirement for fonts to remain under this license does not apply
+to any document created using the fonts or their derivatives.
+
+DEFINITIONS
+"Font Software" refers to the set of files released by the Copyright
+Holder(s) under this license and clearly marked as such. This may
+include source files, build scripts and documentation.
+
+"Reserved Font Name" refers to any names specified as such after the
+copyright statement(s).
+
+"Original Version" refers to the collection of Font Software components as
+distributed by the Copyright Holder(s).
+
+"Modified Version" refers to any derivative made by adding to, deleting,
+or substituting -- in part or in whole -- any of the components of the
+Original Version, by changing formats or by porting the Font Software to a
+new environment.
+
+"Author" refers to any designer, engineer, programmer, technical
+writer or other person who contributed to the Font Software.
+
+PERMISSION & CONDITIONS
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of the Font Software, to use, study, copy, merge, embed, modify,
+redistribute, and sell modified and unmodified copies of the Font
+Software, subject to the following conditions:
+
+1) Neither the Font Software nor any of its individual components,
+in Original or Modified Versions, may be sold by itself.
+
+2) Original or Modified Versions of the Font Software may be bundled,
+redistributed and/or sold with any software, provided that each copy
+contains the above copyright notice and this license. These can be
+included either as stand-alone text files, human-readable headers or
+in the appropriate machine-readable metadata fields within text or
+binary files as long as those fields can be easily viewed by the user.
+
+3) No Modified Version of the Font Software may use the Reserved Font
+Name(s) unless explicit written permission is granted by the corresponding
+Copyright Holder. This restriction only applies to the primary font name as
+presented to the users.
+
+4) The name(s) of the Copyright Holder(s) or the Author(s) of the Font
+Software shall not be used to promote, endorse or advertise any
+Modified Version, except to acknowledge the contribution(s) of the
+Copyright Holder(s) and the Author(s) or with their explicit written
+permission.
+
+5) The Font Software, modified or unmodified, in part or in whole,
+must be distributed entirely under this license, and must not be
+distributed under any other license. The requirement for fonts to
+remain under this license does not apply to any document created
+using the Font Software.
+
+TERMINATION
+This license becomes null and void if any of the above conditions are
+not met.
+
+DISCLAIMER
+THE FONT SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
+OF COPYRIGHT, PATENT, TRADEMARK, OR OTHER RIGHT. IN NO EVENT SHALL THE
+COPYRIGHT HOLDER BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+INCLUDING ANY GENERAL, SPECIAL, INDIRECT, INCIDENTAL, OR CONSEQUENTIAL
+DAMAGES, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF THE USE OR INABILITY TO USE THE FONT SOFTWARE OR FROM
+OTHER DEALINGS IN THE FONT SOFTWARE.
diff --git a/packages/webui/src/appearance/targets/assets/Jersey20-Regular.ttf b/packages/webui/src/appearance/targets/assets/Jersey20-Regular.ttf
new file mode 100644
index 00000000..8b4e0fef
Binary files /dev/null and b/packages/webui/src/appearance/targets/assets/Jersey20-Regular.ttf differ
diff --git a/packages/webui/src/appearance/targets/maibot.css b/packages/webui/src/appearance/targets/maibot.css
new file mode 100644
index 00000000..06063708
--- /dev/null
+++ b/packages/webui/src/appearance/targets/maibot.css
@@ -0,0 +1,233 @@
+/* MaiBot millennium: plastic case, recessed screen, raised keys.
+   Only loaded for this target; every rule remains scoped so release is reversible. */
+@font-face {
+  font-family: "SnowLuma Jersey 20";
+  src: url("./assets/Jersey20-Regular.ttf") format("truetype");
+  font-weight: 400;
+  font-style: normal;
+  font-display: swap;
+  size-adjust: 118%;
+  unicode-range: U+0000-024F;
+}
+
+html[data-webui-target="maibot"] {
+  --mil-shell: #ddd4bf;
+  --mil-panel: #ebe4d2;
+  --mil-hi: #f6f1e3;
+  --mil-lo: #bdb39c;
+  --mil-drop: #9c927b;
+  --mil-line: #5a544a;
+  --mil-ink: #4a443a;
+  --mil-print: #5f5849;
+  --mil-screen: #fbf9f0;
+  --mil-screen-ink: #3a3833;
+  --mil-key: #f3eee1;
+  --mil-key-side: #c2b8a1;
+  --mil-key-hi: #fffaf0;
+  --mil-key-hover: #fbf7ec;
+  --mil-on: #8fd6a0;
+  --mil-on-ink: #2f3a2b;
+  --mil-on-side: #5fa873;
+  --mil-accent-text: #236b43;
+
+  --background: var(--mil-shell);
+  --foreground: var(--mil-ink);
+  --card: var(--mil-panel);
+  --card-foreground: var(--mil-ink);
+  --popover: var(--mil-panel);
+  --popover-foreground: var(--mil-ink);
+  --primary: var(--mil-accent-text);
+  --primary-foreground: var(--mil-screen);
+  --secondary: var(--mil-key);
+  --secondary-foreground: var(--mil-ink);
+  --muted: var(--mil-shell);
+  --muted-foreground: var(--mil-print);
+  --accent: var(--mil-on);
+  --accent-foreground: var(--mil-on-ink);
+  --destructive: #b53724;
+  --destructive-foreground: #fffaf0;
+  --success: #2a7d50;
+  --warning: #8f4f18;
+  --log-info: #315b7c;
+  --log-success: #2a7d50;
+  --log-warn: #8f4f18;
+  --log-error: #b53724;
+  --border: var(--mil-lo);
+  --input: var(--mil-screen);
+  --ring: var(--mil-accent-text);
+  --sidebar: var(--mil-panel);
+  --sidebar-foreground: var(--mil-ink);
+  --sidebar-primary: var(--mil-accent-text);
+  --sidebar-primary-foreground: var(--mil-screen);
+  --sidebar-accent: var(--mil-on);
+  --sidebar-accent-foreground: var(--mil-on-ink);
+  --sidebar-border: var(--mil-lo);
+  --sidebar-ring: var(--mil-accent-text);
+  --shadow-card: inset 1px 1px var(--mil-hi), inset -1px -1px var(--mil-lo), 0 3px 0 var(--mil-drop);
+  --mil-key-shadow: inset 1px 1px var(--mil-key-hi), inset -1px -1px var(--mil-key-side), 0 2px 0 var(--mil-key-side);
+  --mil-screen-shadow: inset 1px 1px 2px var(--mil-lo), inset -1px -1px var(--mil-hi);
+  --radius-sm: 0px;
+  --radius-md: 0px;
+  --radius-lg: 0px;
+  --radius-xl: 0px;
+}
+
+html[data-webui-target="maibot"].dark {
+  --mil-shell: #2f2c28;
+  --mil-panel: #3a3631;
+  --mil-hi: #4a453f;
+  --mil-lo: #2a2723;
+  --mil-drop: #1d1b18;
+  --mil-line: #171513;
+  --mil-ink: #ebe4d2;
+  --mil-print: #b5ad9a;
+  --mil-screen: #1e221e;
+  --mil-screen-ink: #e8e2cf;
+  --mil-key: #4d4841;
+  --mil-key-side: #2e2b27;
+  --mil-key-hi: #60594f;
+  --mil-key-hover: #595249;
+  --mil-accent-text: #8fd6a0;
+  --primary-foreground: #2f3a2b;
+  --sidebar-primary-foreground: #2f3a2b;
+  --border: #746c5d;
+  --sidebar-border: #746c5d;
+  --destructive: #f08a77;
+  --destructive-foreground: #352019;
+  --success: #8fd6a0;
+  --warning: #e5b278;
+  --log-info: #99bdd8;
+  --log-success: #8fd6a0;
+  --log-warn: #e5b278;
+  --log-error: #f08a77;
+}
+
+/* Preserve accessibility preferences above both target palettes. */
+html[data-webui-target="maibot"][data-contrast="high"] {
+  --border: var(--mil-ink);
+  --sidebar-border: var(--mil-ink);
+  --muted-foreground: var(--mil-ink);
+}
+
+html[data-webui-target="maibot"] :is(.ui-card, [data-ui-surface="panel"], [role="dialog"], [role="alertdialog"], [role="menu"], [role="listbox"]) {
+  border: 1px solid var(--mil-line);
+  border-radius: 0;
+  background: var(--mil-panel);
+  color: var(--mil-ink);
+  box-shadow: var(--shadow-card);
+  backdrop-filter: none;
+}
+
+html[data-webui-target="maibot"] [data-ui-surface="chrome"] {
+  background: var(--mil-panel);
+  box-shadow: inset 1px 1px var(--mil-hi), inset -1px -1px var(--mil-lo);
+}
+
+html[data-webui-target="maibot"] [data-ui-surface="canvas"] {
+  border-radius: 0;
+  box-shadow: none;
+}
+
+/* The desktop rail clips a fixed-width inner sidebar. Its separator must
+   belong to the animated outer edge, not the clipped inner panel. */
+html[data-webui-target="maibot"] [data-ui-surface="sidebar"] {
+  border-inline-end: 1px solid var(--sidebar-border);
+}
+
+html[data-webui-target="maibot"] :is([data-ui-control], pre, table) {
+  border-radius: 0;
+  background: var(--mil-screen);
+  color: var(--mil-screen-ink);
+  box-shadow: var(--mil-screen-shadow);
+  caret-color: var(--mil-accent-text);
+}
+
+html[data-webui-target="maibot"] :is([data-ui-control], input, textarea):focus-visible {
+  outline: 2px solid var(--ring);
+  outline-offset: 2px;
+}
+
+html[data-webui-target="maibot"] :is(.ui-button, [role="tab"], .ui-nav-item) {
+  border: 1px solid var(--mil-line);
+  border-radius: 0;
+  background: var(--mil-key);
+  color: var(--mil-ink);
+  box-shadow: var(--mil-key-shadow);
+}
+
+html[data-webui-target="maibot"] :is(.ui-button, [role="tab"], .ui-nav-item):hover:not(:disabled) {
+  background: var(--mil-key-hover);
+}
+
+/* Keep the whole keycap inside the collapsed rail instead of cropping the
+   expanded key's right edge. Text stays mounted and retains its nowrap rules. */
+html[data-webui-target="maibot"] nav[data-collapsed="true"] .ui-nav-item {
+  width: 3rem;
+}
+
+html[data-webui-target="maibot"] :is(.ui-button[data-variant="default"], [role="tab"][aria-selected="true"], .ui-nav-item[aria-current="page"]) {
+  background: var(--mil-on);
+  color: var(--mil-on-ink);
+  box-shadow: inset 1px 1px #c1ebcb, inset -1px -1px var(--mil-on-side), 0 2px 0 var(--mil-on-side);
+}
+
+html[data-webui-target="maibot"] .ui-button[data-variant="destructive"] {
+  background: var(--destructive);
+  color: var(--destructive-foreground);
+}
+
+html[data-webui-target="maibot"] .ui-button[data-variant="default"]:hover:not(:disabled) {
+  background: color-mix(in srgb, var(--mil-on) 85%, var(--mil-key-hi));
+}
+
+html[data-webui-target="maibot"] .ui-button[data-variant="destructive"]:hover:not(:disabled) {
+  background: color-mix(in srgb, var(--destructive) 90%, var(--mil-ink));
+}
+
+html[data-webui-target="maibot"] .ui-button:is([data-variant="ghost"], [data-variant="link"]) {
+  background: transparent;
+  border-color: transparent;
+  box-shadow: none;
+}
+
+html[data-webui-target="maibot"] :is(.ui-button, [role="tab"], .ui-nav-item):active:not(:disabled) {
+  box-shadow: var(--mil-screen-shadow);
+  scale: 1;
+}
+
+html[data-webui-target="maibot"] .ui-nav-item[aria-current="page"] :is(svg, span) {
+  color: var(--mil-on-ink);
+}
+
+html[data-webui-target="maibot"] .ui-nav-highlight {
+  display: none;
+}
+
+html[data-webui-target="maibot"] .ui-segmented {
+  border-radius: 0;
+  background: var(--mil-screen);
+  box-shadow: var(--mil-screen-shadow);
+}
+
+html[data-webui-target="maibot"] .ui-segmented-thumb {
+  border-radius: 0;
+  background: var(--mil-on);
+  box-shadow: var(--mil-key-shadow);
+}
+
+html[data-webui-target="maibot"] .ui-segmented-thumb span {
+  color: var(--mil-on-ink);
+}
+
+html[data-webui-target="maibot"] [data-ui-decoration] {
+  display: none;
+}
+
+html[data-webui-target="maibot"] ::selection {
+  background: var(--mil-on);
+  color: var(--mil-on-ink);
+}
+
+html[data-webui-target="maibot"] * {
+  scrollbar-color: var(--mil-print) var(--mil-shell);
+}
diff --git a/packages/webui/src/appearance/targets/maibot.ts b/packages/webui/src/appearance/targets/maibot.ts
new file mode 100644
index 00000000..b425c786
--- /dev/null
+++ b/packages/webui/src/appearance/targets/maibot.ts
@@ -0,0 +1,27 @@
+import type { TargetAppearance } from '../registry';
+import css from './maibot.css?inline';
+import licenseUrl from './assets/Jersey20-OFL.txt?url';
+
+export const maibotAppearance: TargetAppearance = {
+    css,
+    licenseUrl,
+    resolve: (saved, presentation) => ({
+        ...saved,
+        mode: presentation.mode,
+        palette: 'default',
+        accentMode: 'preset',
+        accentScope: 'global',
+        darkIntensity: 'soft',
+        sidebarStyle: 'follow',
+        background: { ...saved.background, type: 'none' },
+        fontSans: 'custom',
+        fontSansCustom:
+            '"SnowLuma Jersey 20", system-ui, "PingFang SC", "Microsoft YaHei", sans-serif',
+        fontMono: 'default',
+        fontMonoCustom: '',
+        radius: 0,
+        customCss: '',
+        cssVars: {},
+        customPointerSystem: false,
+    }),
+};
diff --git a/packages/webui/src/components/interior/segmented-control.tsx b/packages/webui/src/components/interior/segmented-control.tsx
index 47f3d513..5d44df5b 100644
--- a/packages/webui/src/components/interior/segmented-control.tsx
+++ b/packages/webui/src/components/interior/segmented-control.tsx
@@ -126,7 +126,7 @@ export function SegmentedControl({
         <div
             role="radiogroup"
             aria-label={label}
-            className={`relative inline-block select-none rounded-[9px] border border-border bg-muted/70 p-[3px] shadow-[inset_0_1px_2px_rgb(0_0_0/0.07)] ${className}`}
+            className={`ui-segmented relative inline-block select-none rounded-[9px] border border-border bg-muted/70 p-[3px] shadow-[inset_0_1px_2px_rgb(0_0_0/0.07)] ${className}`}
         >
             <div
                 className="relative grid"
@@ -150,7 +150,7 @@ export function SegmentedControl({
 
                 <motion.div
                     aria-hidden
-                    className="pointer-events-none absolute inset-y-0 left-0 overflow-hidden rounded-[6px] bg-foreground text-background shadow-[0_1px_2px_rgb(0_0_0/0.28)]"
+                    className="ui-segmented-thumb pointer-events-none absolute inset-y-0 left-0 overflow-hidden rounded-[6px] bg-foreground text-background shadow-[0_1px_2px_rgb(0_0_0/0.28)]"
                     style={{ width: `${100 / count}%`, x: thumbX }}
                     initial={false}
                 >
diff --git a/packages/webui/src/components/layout/main-layout.tsx b/packages/webui/src/components/layout/main-layout.tsx
index 7c353416..50b7e808 100644
--- a/packages/webui/src/components/layout/main-layout.tsx
+++ b/packages/webui/src/components/layout/main-layout.tsx
@@ -55,6 +55,7 @@ export function MainLayout({ status, onLogout, notice, children }: MainLayoutPro
             {/* Desktop sidebar (hidden in kiosk) */}
             {!isMobile && !kiosk && (
                 <motion.aside
+                    data-ui-surface="sidebar"
                     initial={false}
                     animate={{ width: showCollapsed ? 64 : 248 }}
                     transition={
@@ -133,6 +134,7 @@ export function MainLayout({ status, onLogout, notice, children }: MainLayoutPro
           Depth comes from a soft shadow + the canvas tone sitting on the
           (sidebar-toned) chrome, not a border. */}
             <div
+                data-ui-surface="canvas"
                 className={cn(
                     'flex min-w-0 flex-1 flex-col overflow-hidden',
                     !isMobile && !kiosk && 'rounded-tl-2xl',
diff --git a/packages/webui/src/components/layout/sidebar.tsx b/packages/webui/src/components/layout/sidebar.tsx
index 4cc2db91..287973a7 100644
--- a/packages/webui/src/components/layout/sidebar.tsx
+++ b/packages/webui/src/components/layout/sidebar.tsx
@@ -137,7 +137,10 @@ export function Sidebar({ collapsed = false, onItemClick }: SidebarProps) {
         setNavItems(reconciled.map((i) => (i.id === id ? { ...i, visible: !i.visible } : i)));
 
     return (
-        <div className="flex h-full w-full flex-col overflow-hidden bg-sidebar text-sidebar-foreground">
+        <div
+            data-ui-surface="chrome"
+            className="flex h-full w-full flex-col overflow-hidden bg-sidebar text-sidebar-foreground"
+        >
             {/* Brand — logo sits in a fixed 48px column centred in the collapsed
           rail; the wordmark to its right is clipped (never unmounted) when the
           rail narrows. */}
@@ -206,7 +209,7 @@ export function Sidebar({ collapsed = false, onItemClick }: SidebarProps) {
                         </Reorder.Group>
                     </div>
                 ) : (
-                    <nav className="flex flex-col gap-1 px-2 py-2">
+                    <nav data-collapsed={collapsed} className="flex flex-col gap-1 px-2 py-2">
                         {orderedNav.map(({ to, label, icon: Icon, description }) => {
                             const isActive = pathname === to;
                             return (
@@ -217,7 +220,7 @@ export function Sidebar({ collapsed = false, onItemClick }: SidebarProps) {
                                     onClick={onItemClick}
                                     aria-current={isActive ? 'page' : undefined}
                                     className={cn(
-                                        'group relative flex items-center rounded-lg py-2.5 text-sm font-medium transition-colors cursor-pointer outline-none',
+                                        'ui-nav-item group relative flex items-center rounded-lg py-2.5 text-sm font-medium transition-colors cursor-pointer outline-none',
                                         isActive
                                             ? 'text-sidebar-accent-foreground'
                                             : 'text-muted-foreground hover:bg-sidebar-accent/40 hover:text-foreground',
@@ -232,7 +235,7 @@ export function Sidebar({ collapsed = false, onItemClick }: SidebarProps) {
                                             <motion.span
                                                 layoutId="sidebar-active-pill"
                                                 className={cn(
-                                                    'absolute inset-y-0 rounded-lg bg-sidebar-accent',
+                                                    'ui-nav-highlight absolute inset-y-0 rounded-lg bg-sidebar-accent',
                                                     collapsed ? 'left-0.5 w-11' : 'inset-x-0',
                                                 )}
                                                 transition={{
@@ -244,7 +247,7 @@ export function Sidebar({ collapsed = false, onItemClick }: SidebarProps) {
                                             {!collapsed && (
                                                 <motion.span
                                                     layoutId="sidebar-active-bar"
-                                                    className="absolute left-0 top-1/2 h-5 w-0.5 -translate-y-1/2 rounded-full bg-primary"
+                                                    className="ui-nav-highlight absolute left-0 top-1/2 h-5 w-0.5 -translate-y-1/2 rounded-full bg-primary"
                                                     transition={{
                                                         type: 'spring',
                                                         stiffness: 380,
diff --git a/packages/webui/src/components/layout/top-bar.tsx b/packages/webui/src/components/layout/top-bar.tsx
index 242447b4..36f2848a 100644
--- a/packages/webui/src/components/layout/top-bar.tsx
+++ b/packages/webui/src/components/layout/top-bar.tsx
@@ -54,7 +54,10 @@ export function TopBar({
     );
 
     return (
-        <header className="z-30 flex min-h-16 shrink-0 items-center gap-[4px] bg-background px-[max(10px,env(safe-area-inset-left))] pr-[max(1rem,env(safe-area-inset-right))] pt-[env(safe-area-inset-top)] md:gap-2 md:px-4">
+        <header
+            data-ui-surface="chrome"
+            className="z-30 flex min-h-16 shrink-0 items-center gap-[4px] bg-background px-[max(10px,env(safe-area-inset-left))] pr-[max(1rem,env(safe-area-inset-right))] pt-[env(safe-area-inset-top)] md:gap-2 md:px-4"
+        >
             {/* Mobile-only menu trigger. On desktop there's no collapse button — the
           sidebar auto-expands on hover/focus, and its boundary with the content
           is a soft surface-tone shift, not a hard border. */}
diff --git a/packages/webui/src/components/pages/login-page.tsx b/packages/webui/src/components/pages/login-page.tsx
index 02e85eb9..a1f01508 100644
--- a/packages/webui/src/components/pages/login-page.tsx
+++ b/packages/webui/src/components/pages/login-page.tsx
@@ -353,6 +353,7 @@ function LoginShell({
     wide?: boolean;
     children: ReactNode;
 }) {
+    const { managedBy } = useTheme();
     return (
         <div
             className={cn(
@@ -360,9 +361,10 @@ function LoginShell({
                 customBg ? 'bg-transparent' : 'bg-background',
             )}
         >
-            {fxOn && <LoginWaves />}
+            {fxOn && !managedBy && <LoginWaves />}
 
             <div
+                data-ui-decoration=""
                 className="pointer-events-none absolute inset-0"
                 style={{
                     background:
@@ -393,6 +395,7 @@ function LoginShell({
                 </Card>
 
                 <motion.button
+                    style={{ display: managedBy ? 'none' : undefined }}
                     type="button"
                     onClick={() => onHelpOpen(true)}
                     whileHover={reduce ? undefined : { scale: 1.04 }}
diff --git a/packages/webui/src/components/pages/settings-page.tsx b/packages/webui/src/components/pages/settings-page.tsx
index b643403a..e3d92240 100644
--- a/packages/webui/src/components/pages/settings-page.tsx
+++ b/packages/webui/src/components/pages/settings-page.tsx
@@ -189,6 +189,7 @@ export function SettingsPage() {
 function SettingsNav({ tab, onChange }: { tab: SettingsTab; onChange: (t: SettingsTab) => void }) {
     return (
         <nav
+            data-ui-surface="panel"
             aria-label="设置导航"
             className={cn(
                 'flex flex-wrap gap-1 rounded-xl border bg-card p-1.5',
@@ -518,7 +519,14 @@ function TopbarPanel() {
 
 function AppearancePanel() {
     const isDesktop = useDesktopSidebar();
-    const { appearance, setAppearance, uploadBackground, removeBackground, resolved } = useTheme();
+    const {
+        savedAppearance: appearance,
+        setAppearance,
+        uploadBackground,
+        removeBackground,
+        resolved,
+        managedBy,
+    } = useTheme();
     const a = appearance;
     // A Catppuccin flavor fixes its own light/dark + darkness, so the mode and
     // intensity controls are inert while one is active.
@@ -560,205 +568,234 @@ function AppearancePanel() {
 
     return (
         <div className="flex flex-col gap-5">
-            <Group
-                title="主题"
-                icon={Sun}
-                description="配色方案、明暗模式与深色风格。所有改动立即生效并保存到服务器，跨设备同步。"
-            >
-                <SettingRow
-                    label="配色方案"
-                    hint="“默认”跟随下方明暗模式；Catppuccin 为整套配色，会自行决定明暗。"
-                    layout="stack"
+            {managedBy && (
+                <p className="text-sm leading-relaxed text-muted-foreground" role="status">
+                    外观跟随{managedBy}
+                    。原有配色、字体和背景已保留，退出集成后恢复；缩放与无障碍设置仍可调整。
+                </p>
+            )}
+            <fieldset disabled={!!managedBy} className="contents" aria-label="主题、配色与背景">
+                <Group
+                    title="主题"
+                    icon={Sun}
+                    description={
+                        managedBy
+                            ? '下方显示已保留的个人设置；当前界面外观由宿主管理。'
+                            : '配色方案、明暗模式与深色风格。所有改动立即生效并保存到服务器，跨设备同步。'
+                    }
                 >
-                    <div className="flex flex-wrap gap-2.5" role="radiogroup" aria-label="配色方案">
-                        {PALETTE_OPTIONS.map((p) => {
-                            const active = a.palette === p.id;
-                            return (
-                                <button
-                                    key={p.id}
-                                    type="button"
-                                    role="radio"
-                                    aria-checked={active}
-                                    aria-label={p.label}
-                                    onClick={() => setAppearance({ palette: p.id })}
-                                    className={cn(
-                                        'flex w-[5.5rem] flex-col items-center gap-1.5 rounded-xl border p-1.5 transition-[border-color,box-shadow] duration-150 ease-out cursor-pointer outline-none focus-visible:ring-[3px] focus-visible:ring-ring/40',
-                                        active
-                                            ? 'border-primary ring-2 ring-primary/30'
-                                            : 'border-border hover:border-foreground/30',
-                                    )}
-                                >
-                                    <span
-                                        className="flex h-11 w-full items-center justify-center rounded-lg"
-                                        style={{ backgroundColor: p.preview.bg }}
+                    <SettingRow
+                        label="配色方案"
+                        hint="“默认”跟随下方明暗模式；Catppuccin 为整套配色，会自行决定明暗。"
+                        layout="stack"
+                    >
+                        <div
+                            className="flex flex-wrap gap-2.5"
+                            role="radiogroup"
+                            aria-label="配色方案"
+                        >
+                            {PALETTE_OPTIONS.map((p) => {
+                                const active = a.palette === p.id;
+                                return (
+                                    <button
+                                        key={p.id}
+                                        type="button"
+                                        role="radio"
+                                        aria-checked={active}
+                                        aria-label={p.label}
+                                        onClick={() => setAppearance({ palette: p.id })}
+                                        className={cn(
+                                            'flex w-[5.5rem] flex-col items-center gap-1.5 rounded-xl border p-1.5 transition-[border-color,box-shadow] duration-150 ease-out cursor-pointer outline-none focus-visible:ring-[3px] focus-visible:ring-ring/40',
+                                            active
+                                                ? 'border-primary ring-2 ring-primary/30'
+                                                : 'border-border hover:border-foreground/30',
+                                        )}
                                     >
                                         <span
-                                            className="flex gap-1 rounded-md px-1.5 py-1 shadow-sm"
-                                            style={{ backgroundColor: p.preview.surface }}
+                                            className="flex h-11 w-full items-center justify-center rounded-lg"
+                                            style={{ backgroundColor: p.preview.bg }}
                                         >
-                                            {p.preview.dots.map((d, i) => (
-                                                <span
-                                                    key={i}
-                                                    className="size-1.5 rounded-full"
-                                                    style={{ backgroundColor: d }}
-                                                />
-                                            ))}
+                                            <span
+                                                className="flex gap-1 rounded-md px-1.5 py-1 shadow-sm"
+                                                style={{ backgroundColor: p.preview.surface }}
+                                            >
+                                                {p.preview.dots.map((d, i) => (
+                                                    <span
+                                                        key={i}
+                                                        className="size-1.5 rounded-full"
+                                                        style={{ backgroundColor: d }}
+                                                    />
+                                                ))}
+                                            </span>
                                         </span>
-                                    </span>
-                                    <span className="text-xs font-medium">{p.label}</span>
-                                </button>
-                            );
-                        })}
-                    </div>
-                </SettingRow>
-                <SettingRow
-                    label="显示模式"
-                    hint={paletteFixed ? '当前由 Catppuccin 配色决定明暗。' : undefined}
-                >
-                    <Segmented
-                        value={a.mode}
-                        options={MODE_OPTIONS}
-                        onChange={(mode) => setAppearance({ mode })}
-                        disabled={paletteFixed}
-                    />
-                </SettingRow>
-                <SettingRow
-                    label="深色强度"
-                    hint={
-                        paletteFixed
-                            ? 'Catppuccin 配色自带明暗，无需调节。'
-                            : '“纯黑”将深色背景压到接近纯黑，适合 OLED 屏幕（仅深色模式下可见）。'
-                    }
-                    layout="stack"
-                >
-                    <Segmented
-                        value={a.darkIntensity}
-                        options={DARK_INTENSITY_OPTIONS}
-                        onChange={(darkIntensity) => setAppearance({ darkIntensity })}
-                        disabled={paletteFixed}
-                    />
-                </SettingRow>
-            </Group>
+                                        <span className="text-xs font-medium">{p.label}</span>
+                                    </button>
+                                );
+                            })}
+                        </div>
+                    </SettingRow>
+                    <SettingRow
+                        label="显示模式"
+                        hint={
+                            managedBy
+                                ? '明暗模式跟随宿主。'
+                                : paletteFixed
+                                  ? '当前由 Catppuccin 配色决定明暗。'
+                                  : undefined
+                        }
+                    >
+                        <Segmented
+                            value={a.mode}
+                            options={MODE_OPTIONS}
+                            onChange={(mode) => setAppearance({ mode })}
+                            disabled={paletteFixed}
+                        />
+                    </SettingRow>
+                    <SettingRow
+                        label="深色强度"
+                        hint={
+                            managedBy
+                                ? '深色材质由宿主外观决定。'
+                                : paletteFixed
+                                  ? 'Catppuccin 配色自带明暗，无需调节。'
+                                  : '“纯黑”将深色背景压到接近纯黑，适合 OLED 屏幕（仅深色模式下可见）。'
+                        }
+                        layout="stack"
+                    >
+                        <Segmented
+                            value={a.darkIntensity}
+                            options={DARK_INTENSITY_OPTIONS}
+                            onChange={(darkIntensity) => setAppearance({ darkIntensity })}
+                            disabled={paletteFixed}
+                        />
+                    </SettingRow>
+                </Group>
 
-            <Group title="强调色" icon={Palette} description="按钮、链接与高亮使用的主色调。">
-                <SettingRow label="预设色" layout="stack">
-                    <div className="flex flex-wrap items-center gap-2">
-                        {ACCENTS.map((spec) => {
-                            const active = a.accentMode === 'preset' && a.accentPreset === spec.id;
-                            return (
-                                <button
-                                    key={spec.id}
-                                    type="button"
-                                    onClick={() =>
-                                        setAppearance({
-                                            accentMode: 'preset',
-                                            accentPreset: spec.id,
-                                        })
-                                    }
-                                    title={spec.label}
-                                    aria-label={spec.label}
-                                    className={cn(
-                                        'relative flex size-9 items-center justify-center rounded-full border transition-transform cursor-pointer hover:scale-105',
-                                        active
-                                            ? 'border-foreground/30 ring-2 ring-primary'
-                                            : 'border-border',
-                                    )}
-                                    style={{ backgroundColor: spec.swatch }}
-                                >
-                                    {active && (
-                                        <Check
-                                            className="size-4 text-white drop-shadow-sm"
-                                            strokeWidth={3}
-                                        />
-                                    )}
-                                </button>
-                            );
-                        })}
-                        <label
-                            title="自定义颜色"
-                            className={cn(
-                                'relative flex size-9 cursor-pointer items-center justify-center overflow-hidden rounded-full border transition-transform hover:scale-105',
-                                a.accentMode === 'custom'
-                                    ? 'border-foreground/30 ring-2 ring-primary'
-                                    : 'border-border',
-                            )}
-                            style={{
-                                background:
+                <Group title="强调色" icon={Palette} description="按钮、链接与高亮使用的主色调。">
+                    <SettingRow label="预设色" layout="stack">
+                        <div className="flex flex-wrap items-center gap-2">
+                            {ACCENTS.map((spec) => {
+                                const active =
+                                    a.accentMode === 'preset' && a.accentPreset === spec.id;
+                                return (
+                                    <button
+                                        key={spec.id}
+                                        type="button"
+                                        onClick={() =>
+                                            setAppearance({
+                                                accentMode: 'preset',
+                                                accentPreset: spec.id,
+                                            })
+                                        }
+                                        title={spec.label}
+                                        aria-label={spec.label}
+                                        className={cn(
+                                            'relative flex size-9 items-center justify-center rounded-full border transition-transform cursor-pointer hover:scale-105',
+                                            active
+                                                ? 'border-foreground/30 ring-2 ring-primary'
+                                                : 'border-border',
+                                        )}
+                                        style={{ backgroundColor: spec.swatch }}
+                                    >
+                                        {active && (
+                                            <Check
+                                                className="size-4 text-white drop-shadow-sm"
+                                                strokeWidth={3}
+                                            />
+                                        )}
+                                    </button>
+                                );
+                            })}
+                            <label
+                                title="自定义颜色"
+                                className={cn(
+                                    'relative flex size-9 cursor-pointer items-center justify-center overflow-hidden rounded-full border transition-transform hover:scale-105',
                                     a.accentMode === 'custom'
-                                        ? a.accentCustom
-                                        : 'conic-gradient(from 0deg, #f43f5e, #f59e0b, #10b981, #0ea5e9, #8b5cf6, #f43f5e)',
-                            }}
-                        >
-                            <input
-                                type="color"
-                                value={toColorInputValue(a.accentCustom)}
-                                onChange={(e) => pickCustomAccent(e.target.value)}
-                                className="absolute inset-0 cursor-pointer opacity-0"
-                                aria-label="自定义强调色"
-                            />
-                            {a.accentMode === 'custom' && (
-                                <Check
-                                    className="pointer-events-none size-4 text-white drop-shadow-sm"
-                                    strokeWidth={3}
+                                        ? 'border-foreground/30 ring-2 ring-primary'
+                                        : 'border-border',
+                                )}
+                                style={{
+                                    background:
+                                        a.accentMode === 'custom'
+                                            ? a.accentCustom
+                                            : 'conic-gradient(from 0deg, #f43f5e, #f59e0b, #10b981, #0ea5e9, #8b5cf6, #f43f5e)',
+                                }}
+                            >
+                                <input
+                                    type="color"
+                                    value={toColorInputValue(a.accentCustom)}
+                                    onChange={(e) => pickCustomAccent(e.target.value)}
+                                    className="absolute inset-0 cursor-pointer opacity-0"
+                                    aria-label="自定义强调色"
                                 />
-                            )}
-                        </label>
-                    </div>
-                </SettingRow>
-                <SettingRow
-                    label="应用范围"
-                    hint="“仅侧栏”时，按钮等全局元素保持默认蓝，强调色只染侧栏选中项。"
-                >
-                    <Segmented
-                        value={a.accentScope}
-                        options={SCOPE_OPTIONS}
-                        onChange={(accentScope) => setAppearance({ accentScope })}
-                    />
-                </SettingRow>
-                <SettingRow label="侧栏样式">
-                    <Segmented
-                        value={a.sidebarStyle}
-                        options={SIDEBAR_STYLE_OPTIONS}
-                        onChange={(sidebarStyle) => setAppearance({ sidebarStyle })}
-                    />
-                </SettingRow>
-            </Group>
-
-            <BackgroundCard
-                appearance={a}
-                setAppearance={setAppearance}
-                uploadBackground={uploadBackground}
-                removeBackground={removeBackground}
-            />
+                                {a.accentMode === 'custom' && (
+                                    <Check
+                                        className="pointer-events-none size-4 text-white drop-shadow-sm"
+                                        strokeWidth={3}
+                                    />
+                                )}
+                            </label>
+                        </div>
+                    </SettingRow>
+                    <SettingRow
+                        label="应用范围"
+                        hint="“仅侧栏”时，按钮等全局元素保持默认蓝，强调色只染侧栏选中项。"
+                    >
+                        <Segmented
+                            value={a.accentScope}
+                            options={SCOPE_OPTIONS}
+                            onChange={(accentScope) => setAppearance({ accentScope })}
+                        />
+                    </SettingRow>
+                    <SettingRow label="侧栏样式">
+                        <Segmented
+                            value={a.sidebarStyle}
+                            options={SIDEBAR_STYLE_OPTIONS}
+                            onChange={(sidebarStyle) => setAppearance({ sidebarStyle })}
+                        />
+                    </SettingRow>
+                </Group>
 
+                <BackgroundCard
+                    appearance={a}
+                    setAppearance={setAppearance}
+                    uploadBackground={uploadBackground}
+                    removeBackground={removeBackground}
+                />
+            </fieldset>
             <Group title="排版与界面" icon={Palette} description="字体、圆角、缩放与密度。">
-                <SettingRow label="界面字体" layout="stack">
-                    <FontField
-                        value={a.fontSans}
-                        custom={a.fontSansCustom}
-                        presets={FONT_SANS_OPTIONS}
-                        onChange={(fontSans) => setAppearance({ fontSans })}
-                        onCustomChange={(fontSansCustom) => setAppearance({ fontSansCustom })}
-                        placeholder="例如：LXGW WenKai, PingFang SC"
-                    />
-                </SettingRow>
-                <SettingRow label="等宽字体" hint="用于日志与代码。" layout="stack">
-                    <FontField
-                        value={a.fontMono}
-                        custom={a.fontMonoCustom}
-                        presets={FONT_MONO_OPTIONS}
-                        onChange={(fontMono) => setAppearance({ fontMono })}
-                        onCustomChange={(fontMonoCustom) => setAppearance({ fontMonoCustom })}
-                        placeholder="例如：Cascadia Code, Sarasa Mono SC"
-                    />
-                </SettingRow>
-                <SettingRow label="圆角">
-                    <Segmented
-                        value={a.radius}
-                        options={RADIUS_OPTIONS.map((r) => ({ value: r.value, label: r.label }))}
-                        onChange={(radius) => setAppearance({ radius })}
-                    />
-                </SettingRow>
+                <fieldset disabled={!!managedBy} className="contents" aria-label="字体与圆角">
+                    <SettingRow label="界面字体" layout="stack">
+                        <FontField
+                            value={a.fontSans}
+                            custom={a.fontSansCustom}
+                            presets={FONT_SANS_OPTIONS}
+                            onChange={(fontSans) => setAppearance({ fontSans })}
+                            onCustomChange={(fontSansCustom) => setAppearance({ fontSansCustom })}
+                            placeholder="例如：LXGW WenKai, PingFang SC"
+                        />
+                    </SettingRow>
+                    <SettingRow label="等宽字体" hint="用于日志与代码。" layout="stack">
+                        <FontField
+                            value={a.fontMono}
+                            custom={a.fontMonoCustom}
+                            presets={FONT_MONO_OPTIONS}
+                            onChange={(fontMono) => setAppearance({ fontMono })}
+                            onCustomChange={(fontMonoCustom) => setAppearance({ fontMonoCustom })}
+                            placeholder="例如：Cascadia Code, Sarasa Mono SC"
+                        />
+                    </SettingRow>
+                    <SettingRow label="圆角">
+                        <Segmented
+                            value={a.radius}
+                            options={RADIUS_OPTIONS.map((r) => ({
+                                value: r.value,
+                                label: r.label,
+                            }))}
+                            onChange={(radius) => setAppearance({ radius })}
+                        />
+                    </SettingRow>
+                </fieldset>
                 <SliderSettingRow
                     label="界面缩放"
                     hint="整体放大或缩小界面，适合高分屏或视力需要。"
@@ -779,10 +816,12 @@ function AppearancePanel() {
                 </SettingRow>
             </Group>
 
-            <ThemeVarsPanel
-                cssVars={a.cssVars}
-                onChange={(cssVars) => setAppearance({ cssVars })}
-            />
+            <fieldset disabled={!!managedBy} className="contents" aria-label="主题变量">
+                <ThemeVarsPanel
+                    cssVars={a.cssVars}
+                    onChange={(cssVars) => setAppearance({ cssVars })}
+                />
+            </fieldset>
 
             <TopbarPanel />
 
@@ -816,6 +855,7 @@ function AppearancePanel() {
                 >
                     <ToggleSwitch
                         value={a.customPointerSystem}
+                        disabled={!!managedBy}
                         onChange={(customPointerSystem) => setAppearance({ customPointerSystem })}
                         ariaLabel="自定义光标"
                     />
@@ -1432,7 +1472,7 @@ function validateCss(css: string): string | null {
 }
 
 function AdvancedPanel() {
-    const { appearance, setAppearance } = useTheme();
+    const { savedAppearance: appearance, setAppearance, managedBy } = useTheme();
     const { runAction } = useActionFeedback();
     const cssRef = useRef<HTMLTextAreaElement>(null);
     const [cssWarn, setCssWarn] = useState<string | null>(null);
@@ -1572,77 +1612,83 @@ function AdvancedPanel() {
 
     return (
         <div className="flex flex-col gap-5">
-            <Card>
-                <CardHeader className="gap-1">
-                    <CardTitle className="flex items-center gap-2 text-[15px]">
-                        <Code2 className="size-4 text-primary" /> 自定义 CSS
-                    </CardTitle>
-                    <CardDescription className="text-[12px] leading-relaxed">
-                        高级用户可注入自定义样式，登录后全局生效（登录页不受影响）。
-                        若改坏了界面，在地址后加{' '}
-                        <code className="rounded bg-muted px-1 py-0.5 font-mono text-meta">
-                            ?safe-mode=1
-                        </code>{' '}
-                        可临时禁用自定义 CSS 进来修复。
-                    </CardDescription>
-                </CardHeader>
-                <CardContent className="flex flex-col gap-3">
-                    <div className="flex flex-wrap items-center gap-1.5">
-                        <span className="mr-1 text-xs text-muted-foreground">插入模板：</span>
-                        {CSS_SNIPPETS.map((s) => (
-                            <button
-                                key={s.label}
-                                type="button"
-                                onClick={() => insertSnippet(s.css)}
-                                className="inline-flex items-center gap-1 rounded-md border bg-muted/40 px-2 py-1 text-xs font-medium text-muted-foreground transition-colors cursor-pointer outline-none hover:text-foreground focus-visible:ring-[3px] focus-visible:ring-ring/40"
-                            >
-                                <Plus className="size-3" /> {s.label}
-                            </button>
-                        ))}
-                    </div>
-                    <Textarea
-                        ref={cssRef}
-                        value={appearance.customCss}
-                        onChange={(e) => {
-                            setAppearance({ customCss: e.target.value });
+            {managedBy && (
+                <p className="text-sm text-muted-foreground">
+                    自定义 CSS 已保留，跟随{managedBy}外观期间暂停应用。
+                </p>
+            )}
+            <fieldset disabled={!!managedBy} className="contents" aria-label="自定义 CSS">
+                <Card>
+                    <CardHeader className="gap-1">
+                        <CardTitle className="flex items-center gap-2 text-[15px]">
+                            <Code2 className="size-4 text-primary" /> 自定义 CSS
+                        </CardTitle>
+                        <CardDescription className="text-[12px] leading-relaxed">
+                            高级用户可注入自定义样式，登录后全局生效（登录页不受影响）。
+                            若改坏了界面，在地址后加{' '}
+                            <code className="rounded bg-muted px-1 py-0.5 font-mono text-meta">
+                                ?safe-mode=1
+                            </code>{' '}
+                            可临时禁用自定义 CSS 进来修复。
+                        </CardDescription>
+                    </CardHeader>
+                    <CardContent className="flex flex-col gap-3">
+                        <div className="flex flex-wrap items-center gap-1.5">
+                            <span className="mr-1 text-xs text-muted-foreground">插入模板：</span>
+                            {CSS_SNIPPETS.map((s) => (
+                                <button
+                                    key={s.label}
+                                    type="button"
+                                    onClick={() => insertSnippet(s.css)}
+                                    className="inline-flex items-center gap-1 rounded-md border bg-muted/40 px-2 py-1 text-xs font-medium text-muted-foreground transition-colors cursor-pointer outline-none hover:text-foreground focus-visible:ring-[3px] focus-visible:ring-ring/40"
+                                >
+                                    <Plus className="size-3" /> {s.label}
+                                </button>
+                            ))}
+                        </div>
+                        <Textarea
+                            ref={cssRef}
+                            value={appearance.customCss}
+                            onChange={(e) => {
+                                setAppearance({ customCss: e.target.value });
 
-                            if (cssWarn) {
-                                setCssWarn(null);
-                            }
-                        }}
-                        onBlur={(e) => setCssWarn(validateCss(e.target.value))}
-                        maxLength={50000}
-                        spellCheck={false}
-                        placeholder={
-                            '/* 例如：放大侧栏字号 */\n.text-sidebar-foreground { font-size: 1.05em; }'
-                        }
-                        className="h-64 resize-y rounded-lg bg-card/40 p-3 font-mono text-base leading-relaxed md:text-[12px]"
-                    />
-                    {cssWarn && (
-                        <p className="flex items-start gap-1.5 text-xs text-warning">
-                            <AlertTriangle className="mt-px size-3.5 shrink-0" /> {cssWarn}
-                        </p>
-                    )}
-                    <div className="flex items-center justify-between gap-2">
-                        <span className="text-meta text-muted-foreground">
-                            {appearance.customCss.length} / 50000 字符
-                        </span>
-                        <Button
-                            variant="ghost"
-                            size="sm"
-                            onClick={() => {
-                                setAppearance({ customCss: '' });
-                                setCssWarn(null);
+                                if (cssWarn) {
+                                    setCssWarn(null);
+                                }
                             }}
-                            disabled={!appearance.customCss}
-                            className="text-destructive hover:text-destructive"
-                        >
-                            <Trash2 className="size-4" /> 清空
-                        </Button>
-                    </div>
-                </CardContent>
-            </Card>
-
+                            onBlur={(e) => setCssWarn(validateCss(e.target.value))}
+                            maxLength={50000}
+                            spellCheck={false}
+                            placeholder={
+                                '/* 例如：放大侧栏字号 */\n.text-sidebar-foreground { font-size: 1.05em; }'
+                            }
+                            className="h-64 resize-y rounded-lg bg-card/40 p-3 font-mono text-base leading-relaxed md:text-[12px]"
+                        />
+                        {cssWarn && (
+                            <p className="flex items-start gap-1.5 text-xs text-warning">
+                                <AlertTriangle className="mt-px size-3.5 shrink-0" /> {cssWarn}
+                            </p>
+                        )}
+                        <div className="flex items-center justify-between gap-2">
+                            <span className="text-meta text-muted-foreground">
+                                {appearance.customCss.length} / 50000 字符
+                            </span>
+                            <Button
+                                variant="ghost"
+                                size="sm"
+                                onClick={() => {
+                                    setAppearance({ customCss: '' });
+                                    setCssWarn(null);
+                                }}
+                                disabled={!appearance.customCss}
+                                className="text-destructive hover:text-destructive"
+                            >
+                                <Trash2 className="size-4" /> 清空
+                            </Button>
+                        </div>
+                    </CardContent>
+                </Card>
+            </fieldset>
             <Card>
                 <CardHeader className="gap-1">
                     <CardTitle className="text-[15px]">备份与重置</CardTitle>
diff --git a/packages/webui/src/components/theme-toggle.tsx b/packages/webui/src/components/theme-toggle.tsx
index 107d703c..58026b26 100644
--- a/packages/webui/src/components/theme-toggle.tsx
+++ b/packages/webui/src/components/theme-toggle.tsx
@@ -10,12 +10,12 @@ const OPTIONS: { mode: ThemeMode; icon: typeof Sun; label: string }[] = [
 ];
 
 export function ThemeToggle({ className }: { className?: string }) {
-    const { appearance, mode, setMode } = useTheme();
+    const { appearance, mode, setMode, managedBy } = useTheme();
 
     // A Catppuccin flavor fixes light/dark, so this quick toggle would be inert
     // (and its pill would desync from the forced scheme) — hide it. Light/dark is
     // then changed by switching the palette back to “默认” in settings.
-    if (paletteResolved(appearance.palette)) {
+    if (managedBy || paletteResolved(appearance.palette)) {
         return null;
     }
 
diff --git a/packages/webui/src/components/ui/button.tsx b/packages/webui/src/components/ui/button.tsx
index e0c3a08f..ec5260db 100644
--- a/packages/webui/src/components/ui/button.tsx
+++ b/packages/webui/src/components/ui/button.tsx
@@ -50,6 +50,7 @@ const Button = React.forwardRef<HTMLButtonElement, ButtonProps>(
                 className={cn(buttonVariants({ variant, size, press: !isStatic }), className)}
                 ref={ref}
                 data-press-scale={isStatic ? undefined : ''}
+                data-variant={variant ?? 'default'}
                 {...props}
             />
         );
diff --git a/packages/webui/src/contexts/ThemeContext.tsx b/packages/webui/src/contexts/ThemeContext.tsx
index 961c1fb3..0b8a2106 100644
--- a/packages/webui/src/contexts/ThemeContext.tsx
+++ b/packages/webui/src/contexts/ThemeContext.tsx
@@ -7,6 +7,7 @@ import {
     useMemo,
     useRef,
     useState,
+    useSyncExternalStore,
     type ReactNode,
 } from 'react';
 import { flushSync } from 'react-dom';
@@ -14,6 +15,14 @@ import { MotionConfig } from 'motion/react';
 import { actionErrorMessage, useActionFeedback } from '@/contexts/ActionFeedbackContext';
 import { webuiSessionHeaders } from '@/lib/api/session-headers';
 import type { Palette, ThemeMode, UiAppearance, UiBackground } from '@/types';
+import { WEBUI_TARGETS, type WebuiPresentation } from '@snowluma/common/webui-target';
+import { resolveAppearance } from '@/appearance/registry';
+import {
+    applyPresentationAttributes,
+    getTargetAppearance,
+    presentationStore,
+    subscribeHostAppearance,
+} from '@/appearance/runtime';
 
 // Re-export the appearance value types so consumers (settings page etc.) can
 // import them straight from the context module.
@@ -745,8 +754,13 @@ function cssVarsCss(a: UiAppearance): string {
     return decls ? `:root{${decls}}` : '';
 }
 
-function applyAppearance(a: UiAppearance, resolved: 'light' | 'dark'): void {
+function applyAppearance(
+    a: UiAppearance,
+    resolved: 'light' | 'dark',
+    presentation: WebuiPresentation | null,
+): void {
     const root = document.documentElement;
+    applyPresentationAttributes(presentation);
 
     root.classList.remove('light', 'dark');
     root.classList.add(resolved);
@@ -811,7 +825,9 @@ function applyAppearance(a: UiAppearance, resolved: 'light' | 'dark'): void {
     // Palette (base/surface tokens) first, then accent (--primary/--ring) — a
     // disjoint var set, layered after so it composes with any flavor. The
     // operator's variable-panel overrides come last so they win over both.
-    el.textContent = `${paletteVarsCss(a)}\n${accentVarsCss(a)}\n${cssVarsCss(a)}`;
+    el.textContent = presentation
+        ? ''
+        : `${paletteVarsCss(a)}\n${accentVarsCss(a)}\n${cssVarsCss(a)}`;
 
     // Custom CSS — appended AFTER the accent block so it is the last style in
     // <head> and can override anything. Skipped under ?safe-mode=1 (escape
@@ -1078,7 +1094,12 @@ function writeCache(a: UiAppearance): void {
 // ─── Context ───────────────────────────────────────────────────────────────
 
 interface ThemeContextValue {
+    /** Effective presentation for components. Never persist this object. */
     appearance: UiAppearance;
+    /** User preferences underneath the deployment overlay. Only these are persisted. */
+    savedAppearance: UiAppearance;
+    presentation: WebuiPresentation | null;
+    managedBy: string | null;
     /** True once the first server load attempt has resolved. */
     ready: boolean;
     resolved: 'light' | 'dark';
@@ -1112,6 +1133,14 @@ function getSystemTheme(): 'light' | 'dark' {
 export function ThemeProvider({ children }: { children: ReactNode }) {
     const { runAction, startAction } = useActionFeedback();
     const [appearance, setAppearanceState] = useState<UiAppearance>(readCache);
+    const presentation = useSyncExternalStore(
+        presentationStore.subscribe,
+        presentationStore.getSnapshot,
+    );
+    const effectiveAppearance = useMemo(
+        () => resolveAppearance(appearance, presentation, getTargetAppearance()),
+        [appearance, presentation],
+    );
     const [systemTheme, setSystemTheme] = useState<'light' | 'dark'>(getSystemTheme);
     const [ready, setReady] = useState(false);
     const saveTimer = useRef<ReturnType<typeof setTimeout> | null>(null);
@@ -1123,8 +1152,10 @@ export function ThemeProvider({ children }: { children: ReactNode }) {
 
     // A Catppuccin flavor fixes light/dark; otherwise honor mode (+ system).
     const resolved: 'light' | 'dark' =
-        paletteResolved(appearance.palette) ??
-        (appearance.mode === 'system' ? systemTheme : appearance.mode);
+        paletteResolved(effectiveAppearance.palette) ??
+        (effectiveAppearance.mode === 'system' ? systemTheme : effectiveAppearance.mode);
+
+    useLayoutEffect(() => subscribeHostAppearance(window, presentationStore), []);
 
     // Track the OS theme for `mode: 'system'`.
     useEffect(() => {
@@ -1167,11 +1198,11 @@ export function ThemeProvider({ children }: { children: ReactNode }) {
     // application doesn't flash. The pre-mount flash is handled by the inline
     // bootstrap script in index.html.
     useLayoutEffect(() => {
-        applyAppearance(appearance, resolved);
-    }, [appearance, resolved]);
+        applyAppearance(effectiveAppearance, resolved, presentation);
+    }, [effectiveAppearance, resolved, presentation]);
     useLayoutEffect(() => {
-        applyBackgroundLayer(appearance);
-    }, [appearance]);
+        applyBackgroundLayer(effectiveAppearance);
+    }, [effectiveAppearance]);
 
     // Cancel a pending save when the provider unmounts.
     useEffect(
@@ -1358,7 +1389,10 @@ export function ThemeProvider({ children }: { children: ReactNode }) {
 
     const value = useMemo<ThemeContextValue>(
         () => ({
-            appearance,
+            appearance: effectiveAppearance,
+            savedAppearance: appearance,
+            presentation,
+            managedBy: presentation ? WEBUI_TARGETS[presentation.target].label : null,
             ready,
             resolved,
             setAppearance,
@@ -1366,12 +1400,14 @@ export function ThemeProvider({ children }: { children: ReactNode }) {
             removeBackground,
             formatClock,
             reloadAppearance,
-            mode: appearance.mode,
+            mode: effectiveAppearance.mode,
             setMode: (m: ThemeMode) => setAppearance({ mode: m }),
             pollInterval: appearance.pollInterval,
         }),
         [
             appearance,
+            effectiveAppearance,
+            presentation,
             ready,
             resolved,
             setAppearance,
diff --git a/packages/webui/src/main.tsx b/packages/webui/src/main.tsx
index 78250954..79c6aa67 100644
--- a/packages/webui/src/main.tsx
+++ b/packages/webui/src/main.tsx
@@ -2,9 +2,19 @@ import { StrictMode } from 'react';
 import { createRoot } from 'react-dom/client';
 import './index.css';
 import App from './App.tsx';
+import { prepareTargetAppearance } from './appearance/runtime';
 
-createRoot(document.getElementById('root')!).render(
-    <StrictMode>
-        <App />
-    </StrictMode>,
-);
+const root = document.getElementById('root')!;
+
+void prepareTargetAppearance()
+    .then(() => {
+        createRoot(root).render(
+            <StrictMode>
+                <App />
+            </StrictMode>,
+        );
+    })
+    .catch((error: unknown) => {
+        console.error('[SnowLuma appearance] Startup failed', error);
+        root.textContent = '界面外观加载失败，请刷新重试。详细原因见浏览器控制台。';
+    });
diff --git a/packages/webui/tests/target-appearance.test.ts b/packages/webui/tests/target-appearance.test.ts
new file mode 100644
index 00000000..7bafb32f
--- /dev/null
+++ b/packages/webui/tests/target-appearance.test.ts
@@ -0,0 +1,106 @@
+import { describe, expect, it, vi } from 'vitest';
+import { defaultWebuiPresentation, WEBUI_PRESENTATION_EVENT } from '@snowluma/common/webui-target';
+import { createPresentationStore } from '../src/appearance/store';
+import { subscribeHostAppearance } from '../src/appearance/runtime';
+import { resolveAppearance } from '../src/appearance/registry';
+import { maibotAppearance } from '../src/appearance/targets/maibot';
+import { DEFAULT_APPEARANCE } from '../src/contexts/ThemeContext';
+
+const initial = defaultWebuiPresentation('maibot');
+
+describe('reversible presentation overlay', () => {
+    it('retains saved appearance, wallpaper, custom CSS and accessibility preferences', () => {
+        const saved = structuredClone(DEFAULT_APPEARANCE);
+        Object.assign(saved, {
+            customCss: 'body { color: red; }',
+            palette: 'catppuccin-mocha',
+            radius: 1,
+            fontSansCustom: 'My Font',
+            customPointerSystem: true,
+            reduceMotion: true,
+            disableMotion: true,
+            highContrast: true,
+            uiScale: 1.2,
+        });
+        saved.background.type = 'image';
+        saved.background.hasImage = true;
+        const before = structuredClone(saved);
+
+        const effective = resolveAppearance(saved, { ...initial, mode: 'light' }, maibotAppearance);
+        expect(effective).toMatchObject({
+            mode: 'light',
+            palette: 'default',
+            radius: 0,
+            customCss: '',
+            background: { type: 'none' },
+            customPointerSystem: false,
+            reduceMotion: true,
+            disableMotion: true,
+            highContrast: true,
+            uiScale: 1.2,
+        });
+        expect(saved).toEqual(before);
+        expect(resolveAppearance(saved, null, maibotAppearance)).toBe(saved);
+        expect(resolveAppearance(saved, null, null)).toBe(saved);
+    });
+
+    it('cannot enable a target through host messages on a standalone deployment', () => {
+        const store = createPresentationStore(null);
+        const host = new EventTarget() as Window;
+        const add = vi.spyOn(host, 'addEventListener');
+        const cleanup = subscribeHostAppearance(host, store);
+        store.receive(initial);
+        expect(store.getSnapshot()).toBeNull();
+        expect(add).not.toHaveBeenCalled();
+        cleanup();
+    });
+
+    it('applies the latest of rapid updates synchronously, deduplicates, releases and restores', () => {
+        const store = createPresentationStore('maibot');
+        const notify = vi.fn();
+        const cleanup = store.subscribe(notify);
+        store.receive(initial);
+        expect(notify).not.toHaveBeenCalled();
+        store.receive({ ...initial, mode: 'dark' });
+        store.receive({ ...initial, mode: 'light' });
+        expect(store.getSnapshot()?.mode).toBe('light');
+        store.receive({ version: 1, target: null });
+        expect(store.getSnapshot()).toBeNull();
+        store.receive(initial);
+        expect(store.getSnapshot()).toEqual(initial);
+        cleanup();
+        store.receive({ ...initial, mode: 'dark' });
+        expect(notify).toHaveBeenCalledTimes(4);
+    });
+
+    it('reads pre-mount host state, reports invalid input and cleans up subscriptions', () => {
+        const store = createPresentationStore('maibot');
+        const host = new EventTarget() as Window;
+        host.__SNOWLUMA_HOST_APPEARANCE__ = { ...initial, mode: 'dark' };
+        const error = vi.spyOn(console, 'error').mockImplementation(() => {});
+        const cleanup = subscribeHostAppearance(host, store);
+
+        try {
+            expect(store.getSnapshot()?.mode).toBe('dark');
+            host.dispatchEvent(
+                new CustomEvent(WEBUI_PRESENTATION_EVENT, {
+                    detail: { ...initial, mode: 'invalid' },
+                }),
+            );
+            expect(error).toHaveBeenCalledOnce();
+            expect(store.getSnapshot()?.mode).toBe('dark');
+            host.dispatchEvent(
+                new CustomEvent(WEBUI_PRESENTATION_EVENT, {
+                    detail: { ...initial, mode: 'light' },
+                }),
+            );
+            expect(store.getSnapshot()?.mode).toBe('light');
+            cleanup();
+            host.dispatchEvent(new CustomEvent(WEBUI_PRESENTATION_EVENT, { detail: initial }));
+            expect(store.getSnapshot()?.mode).toBe('light');
+        } finally {
+            cleanup();
+            error.mockRestore();
+        }
+    });
+});
diff --git a/packages/webui/vite.config.ts b/packages/webui/vite.config.ts
index 7900db03..892bf921 100644
--- a/packages/webui/vite.config.ts
+++ b/packages/webui/vite.config.ts
@@ -3,11 +3,25 @@ import { fileURLToPath } from 'node:url';
 import { defineConfig } from 'vite';
 import react from '@vitejs/plugin-react';
 import tailwindcss from '@tailwindcss/vite';
+import { injectWebuiTarget, resolveWebuiTarget } from '@snowluma/common/webui-target';
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
 export default defineConfig({
-    plugins: [tailwindcss(), react()],
+    plugins: [
+        tailwindcss(),
+        react(),
+        {
+            name: 'webui-runtime-target',
+            // Production builds are target-neutral. Core injects the deployment at request time.
+            apply: 'serve',
+            transformIndexHtml: {
+                order: 'pre',
+                handler: (html) =>
+                    injectWebuiTarget(html, resolveWebuiTarget(process.env.SNOWLUMA_WEBUI_TARGET)),
+            },
+        },
+    ],
     resolve: {
         alias: {
             '@': path.resolve(__dirname, 'src'),