feat(desktop): add data-driven theme system

desktop/.gitignore

@@ -4,3 +4,6 @@ release/
 *.log
 .DS_Store
 Thumbs.db
+flavors/
+resources/app-config.json
+resources/themes/

desktop/package.json

@@ -15,7 +15,10 @@
     "build:renderer": "vite build",
     "dist": "npm run build && electron-builder",
     "dist:mac": "npm run build && electron-builder --mac",
-    "dist:win": "npm run build && electron-builder --win"
+    "dist:win": "npm run build && electron-builder --win",
+    "flavor:apply": "node scripts/apply-flavor.mjs",
+    "flavor:clear": "node scripts/apply-flavor.mjs --clear",
+    "dist:flavor": "node scripts/apply-flavor.mjs $FLAVOR && npm run build && electron-builder && node scripts/apply-flavor.mjs --clear"
   },
   "dependencies": {
     "electron-updater": "^6.8.9",
@@ -60,7 +63,9 @@
         "from": "resources",
         "to": ".",
         "filter": [
-          "icon.png"
+          "icon.png",
+          "app-config.json",
+          "themes/**"
         ]
       }
     ],

desktop/scripts/apply-flavor.mjs

@@ -0,0 +1,68 @@
+#!/usr/bin/env node
+// Stage or clear a flavor into resources/ before packaging.
+//
+// A flavor lives in flavors/<name>/ and may contain:
+//   app-config.json    → copied to resources/app-config.json
+//   themes/<id>/...     → copied to resources/themes/<id>/...
+//
+// Usage:
+//   node scripts/apply-flavor.mjs <name>   # stage flavors/<name> into resources/
+//   node scripts/apply-flavor.mjs --clear  # remove staged app-config.json + themes/
+//
+// The standard build ships neither app-config.json nor resources/themes, so it
+// keeps the default theme and free switching. Always --clear after a flavored
+// build so the repo's resources/ stays clean.
+
+import fs from 'node:fs'
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const here = path.dirname(fileURLToPath(import.meta.url))
+const root = path.resolve(here, '..')
+const resourcesDir = path.join(root, 'resources')
+const configFile = path.join(resourcesDir, 'app-config.json')
+const resThemesDir = path.join(resourcesDir, 'themes')
+
+function rimraf(target) {
+  fs.rmSync(target, { recursive: true, force: true })
+}
+
+function copyDir(src, dest) {
+  fs.mkdirSync(dest, { recursive: true })
+  for (const entry of fs.readdirSync(src, { withFileTypes: true })) {
+    const s = path.join(src, entry.name)
+    const d = path.join(dest, entry.name)
+    if (entry.isDirectory()) copyDir(s, d)
+    else fs.copyFileSync(s, d)
+  }
+}
+
+function clear() {
+  rimraf(configFile)
+  rimraf(resThemesDir)
+  console.log('[flavor] cleared resources/app-config.json and resources/themes')
+}
+
+function apply(name) {
+  const flavorDir = path.join(root, 'flavors', name)
+  if (!fs.existsSync(flavorDir)) {
+    console.error(`[flavor] no such flavor: flavors/${name}`)
+    process.exit(1)
+  }
+  clear()
+  const srcConfig = path.join(flavorDir, 'app-config.json')
+  if (fs.existsSync(srcConfig)) {
+    fs.mkdirSync(resourcesDir, { recursive: true })
+    fs.copyFileSync(srcConfig, configFile)
+    console.log(`[flavor] staged app-config.json from flavors/${name}`)
+  }
+  const srcThemes = path.join(flavorDir, 'themes')
+  if (fs.existsSync(srcThemes)) {
+    copyDir(srcThemes, resThemesDir)
+    console.log(`[flavor] staged themes from flavors/${name}`)
+  }
+}
+
+const arg = process.argv[2]
+if (!arg || arg === '--clear') clear()
+else apply(arg)

desktop/src/main/index.ts

@@ -6,6 +6,7 @@ import { PythonBackend } from './python-manager'
 import { buildAppMenu } from './menu'
 import { createTray, destroyTray } from './tray'
 import { initUpdater, checkForUpdates, startDownload, quitAndInstall, setUpdateLanguage } from './updater'
+import { setupThemeIPC } from './themes'
 
 // Force the product name so the Dock/menu shows "CowAgent" even in dev mode,
 // where the default Electron binary would otherwise report "Electron".
@@ -306,6 +307,7 @@ app.whenReady().then(async () => {
   }
 
   setupIPC()
+  setupThemeIPC()
   createWindow()
   buildAppMenu(() => mainWindow)
   // No menu-bar tray on macOS — the Dock + window controls are enough there.

desktop/src/main/preload.ts

@@ -43,6 +43,14 @@ contextBridge.exposeInMainWorld('electronAPI', {
   // Current app version (e.g. "0.0.5"), shown in the NavRail footer.
   getAppVersion: () => ipcRenderer.invoke('get-app-version'),
 
+  // Themes (bundled + user themes from ~/.cow/themes), assets inlined.
+  listThemes: () => ipcRenderer.invoke('themes-list') as Promise<Record<string, unknown>[]>,
+  getThemesDir: () => ipcRenderer.invoke('themes-dir') as Promise<string>,
+  // Optional app config (first-run default theme + display name). Null in
+  // the standard build.
+  getAppConfig: () =>
+    ipcRenderer.invoke('app-config-get') as Promise<{ defaultTheme?: string; appName?: string } | null>,
+
   // Auto-update: trigger checks/download/install and subscribe to status. The
   // optional lang routes installer downloads to the China CDN mirror (zh) or R2.
   checkForUpdate: (lang?: string) => ipcRenderer.invoke('update-check', lang),

desktop/src/main/themes.ts

@@ -0,0 +1,195 @@
+import { app, ipcMain } from 'electron'
+import path from 'path'
+import fs from 'fs'
+import os from 'os'
+
+// Themes come from two sources and are merged at load time:
+//
+//   1. Bundled themes — resources/themes/ shipped inside the app package
+//      (read-only). Present only in builds produced from a flavor; absent
+//      in the standard build.
+//   2. User themes — ~/.cow/themes/, the shared data dir users can add to
+//      (via a future in-app store/import). Each theme is its own folder:
+//
+//        <id>/
+//          ├── theme.json      (required)
+//          ├── wallpaper.jpg   (optional)
+//          └── logo.svg        (optional)
+//
+// An optional app config (resources/app-config.json) can set a first-run
+// default theme and a display name. When it's absent the app behaves exactly
+// as the standard build (default theme, free switching).
+
+const THEMES_DIRNAME = 'themes'
+// Max bytes for an inlined image (mirrors the theme spec limit).
+const MAX_IMAGE_BYTES = 16 * 1024 * 1024
+const IMAGE_MIME: Record<string, string> = {
+  '.jpg': 'image/jpeg',
+  '.jpeg': 'image/jpeg',
+  '.png': 'image/png',
+  '.webp': 'image/webp',
+  '.svg': 'image/svg+xml',
+  '.gif': 'image/gif',
+}
+
+function cowRoot(): string {
+  // Honor an explicit override, else default to ~/.cow to match the backend.
+  return process.env.COW_HOME || path.join(os.homedir(), '.cow')
+}
+
+export function themesDir(): string {
+  return path.join(cowRoot(), THEMES_DIRNAME)
+}
+
+// Directory holding themes bundled inside the app package (read-only). In dev
+// it maps to the repo's resources/; in a packaged app to process.resourcesPath.
+// Returns null when that folder doesn't exist (the standard build).
+function bundledThemesDir(): string | null {
+  const base = app.isPackaged
+    ? path.join(process.resourcesPath, THEMES_DIRNAME)
+    : path.resolve(__dirname, '../../resources', THEMES_DIRNAME)
+  try {
+    return fs.statSync(base).isDirectory() ? base : null
+  } catch {
+    return null
+  }
+}
+
+// Optional app config bundled with the app. Absent in the standard build.
+export interface AppConfig {
+  defaultTheme?: string
+  appName?: string
+}
+
+function appConfigPath(): string {
+  return app.isPackaged
+    ? path.join(process.resourcesPath, 'app-config.json')
+    : path.resolve(__dirname, '../../resources', 'app-config.json')
+}
+
+export function loadAppConfig(): AppConfig | null {
+  try {
+    const raw = fs.readFileSync(appConfigPath(), 'utf8')
+    const parsed = JSON.parse(raw) as AppConfig
+    if (!parsed || typeof parsed !== 'object') return null
+    return parsed
+  } catch {
+    return null // no app config → standard behavior
+  }
+}
+
+function ensureThemesDir(): string {
+  const dir = themesDir()
+  try {
+    fs.mkdirSync(dir, { recursive: true })
+  } catch {
+    // Non-fatal: scanning will simply return no themes.
+  }
+  return dir
+}
+
+// Read an image inside a theme folder and return a data: URL, or null. The
+// path is constrained to the theme folder to avoid escaping via '..'.
+function inlineImage(themeFolder: string, rel: string): string | null {
+  if (!rel || typeof rel !== 'string') return null
+  const resolved = path.resolve(themeFolder, rel)
+  if (resolved !== themeFolder && !resolved.startsWith(themeFolder + path.sep)) return null
+  let stat: fs.Stats
+  try {
+    stat = fs.statSync(resolved)
+  } catch {
+    return null
+  }
+  if (!stat.isFile() || stat.size === 0 || stat.size > MAX_IMAGE_BYTES) return null
+  const ext = path.extname(resolved).toLowerCase()
+  const mime = IMAGE_MIME[ext]
+  if (!mime) return null
+  try {
+    const buf = fs.readFileSync(resolved)
+    return `data:${mime};base64,${buf.toString('base64')}`
+  } catch {
+    return null
+  }
+}
+
+// Walk a theme object and replace any wallpaper/logo image *file references*
+// with inlined data URLs so the renderer can use them directly.
+function inlineThemeAssets(theme: Record<string, unknown>, themeFolder: string) {
+  for (const appearance of ['light', 'dark'] as const) {
+    const app_ = theme[appearance] as Record<string, unknown> | undefined
+    const wp = app_?.wallpaper as Record<string, unknown> | undefined
+    if (wp && typeof wp.image === 'string') {
+      const url = inlineImage(themeFolder, wp.image)
+      if (url) wp.image = url
+      else delete wp.image
+    }
+  }
+  const identity = theme.identity as Record<string, unknown> | undefined
+  if (identity && typeof identity.logo === 'string') {
+    const url = inlineImage(themeFolder, identity.logo)
+    if (url) identity.logo = url
+    else delete identity.logo
+  }
+}
+
+// Scan one directory for theme folders and return validated, asset-inlined themes.
+function scanDir(dir: string): Record<string, unknown>[] {
+  let entries: fs.Dirent[]
+  try {
+    entries = fs.readdirSync(dir, { withFileTypes: true })
+  } catch {
+    return []
+  }
+  const themes: Record<string, unknown>[] = []
+  for (const entry of entries) {
+    if (!entry.isDirectory()) continue
+    const folder = path.join(dir, entry.name)
+    const jsonPath = path.join(folder, 'theme.json')
+    let raw: string
+    try {
+      raw = fs.readFileSync(jsonPath, 'utf8')
+    } catch {
+      continue // no theme.json in this folder
+    }
+    let theme: Record<string, unknown>
+    try {
+      theme = JSON.parse(raw)
+    } catch (e) {
+      console.warn(`[themes] invalid theme.json in ${entry.name}:`, (e as Error).message)
+      continue
+    }
+    // Default the id to the folder name so it's always stable/unique.
+    if (!theme.id || typeof theme.id !== 'string') theme.id = entry.name
+    if (!theme.name || typeof theme.name !== 'string') theme.name = String(theme.id)
+    inlineThemeAssets(theme, folder)
+    themes.push(theme)
+  }
+  return themes
+}
+
+// Merge bundled themes (read-only, shipped in the package) with user themes
+// (~/.cow/themes). Bundled themes take precedence on id conflicts so a shipped
+// theme can't be shadowed by a user folder of the same id.
+export function loadThemes(): Record<string, unknown>[] {
+  ensureThemesDir()
+  const byId = new Map<string, Record<string, unknown>>()
+  for (const theme of scanDir(themesDir())) byId.set(String(theme.id), theme)
+  const bundled = bundledThemesDir()
+  if (bundled) {
+    for (const theme of scanDir(bundled)) byId.set(String(theme.id), theme)
+  }
+  return [...byId.values()]
+}
+
+export function setupThemeIPC() {
+  ipcMain.handle('themes-list', () => {
+    try {
+      return loadThemes()
+    } catch (e) {
+      console.warn('[themes] load failed:', (e as Error).message)
+      return []
+    }
+  })
+  ipcMain.handle('themes-dir', () => themesDir())
+  ipcMain.handle('app-config-get', () => loadAppConfig())
+}

desktop/src/renderer/src/hooks/useTheme.ts

@@ -1,57 +1,228 @@
 import { useState, useEffect, useCallback } from 'react'
+import {
+  COLOR_KEYS,
+  DEFAULT_THEME_ID,
+  getAllThemes,
+  getTheme,
+  registerRuntimeThemes,
+  SHAPE_KEYS,
+  tokenToCssVar,
+  type Theme,
+  type Wallpaper,
+} from '../theme/themes'
 
 export type ThemePref = 'light' | 'dark' | 'system'
 export type ResolvedTheme = 'light' | 'dark'
 
-const STORAGE_KEY = 'cow_theme'
+// Appearance preference (light/dark/system).
+const PREF_KEY = 'cow_theme'
+// Selected theme id (which visual theme is active).
+const THEME_ID_KEY = 'cow_theme_id'
 
 function getSystemTheme(): ResolvedTheme {
   return window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
 }
 
-function readStored(): ThemePref {
+function readStoredPref(): ThemePref {
-  const saved = localStorage.getItem(STORAGE_KEY)
+  const saved = localStorage.getItem(PREF_KEY)
   if (saved === 'dark' || saved === 'light' || saved === 'system') return saved
   // First run: follow the OS appearance rather than forcing a fixed theme.
   return 'system'
 }
 
-function applyTheme(resolved: ResolvedTheme) {
+function readStoredThemeId(): string {
+  return localStorage.getItem(THEME_ID_KEY) || DEFAULT_THEME_ID
+}
+
+// Whether the user has ever explicitly chosen a theme. Used so a bundled
+// first-run default only applies when the user hasn't made a choice yet.
+function hasStoredThemeId(): boolean {
+  return localStorage.getItem(THEME_ID_KEY) != null
+}
+
+// All CSS variables a theme may inject, so we can fully reset before
+// applying one (prevents stale overrides from leaking across switches).
+const WALLPAPER_VARS = [
+  '--wallpaper-image',
+  '--wallpaper-position',
+  '--wallpaper-overlay',
+  '--glass-fill',
+  '--glass-blur',
+  '--surface-alpha',
+] as const
+
+function hexToRgb(hex: string): [number, number, number] | null {
+  const m = /^#?([0-9a-f]{6})$/i.exec(hex.trim())
+  if (!m) return null
+  const n = parseInt(m[1], 16)
+  return [(n >> 16) & 255, (n >> 8) & 255, n & 255]
+}
+
+// Apply the resolved appearance (light/dark) as the .dark class, plus the
+// active theme's overrides. Themes are pure data: we only write contract
+// tokens as inline CSS variables on <html> (and toggle a wallpaper flag on
+// <body>), so components restyle without any code change.
+function applyAppearanceAndTheme(resolved: ResolvedTheme, themeId: string) {
   const root = document.documentElement
   root.classList.toggle('dark', resolved === 'dark')
+
+  const theme = getTheme(themeId)
+  if (theme.id === DEFAULT_THEME_ID) root.removeAttribute('data-theme')
+  else root.setAttribute('data-theme', theme.id)
+
+  activeSurface = {
+    light: theme.light?.colors?.bgSurface,
+    dark: theme.dark?.colors?.bgSurface,
+  }
+
+  // Reset everything a theme can touch, then re-apply the active one.
+  for (const key of COLOR_KEYS) root.style.removeProperty(tokenToCssVar(key))
+  for (const key of SHAPE_KEYS) root.style.removeProperty(tokenToCssVar(key))
+  for (const v of WALLPAPER_VARS) root.style.removeProperty(v)
+
+  // Shape tokens are appearance-independent.
+  if (theme.shape) {
+    for (const [k, v] of Object.entries(theme.shape)) {
+      if (v) root.style.setProperty(tokenToCssVar(k), v)
+    }
+  }
+
+  const appearance = resolved === 'dark' ? theme.dark : theme.light
+  if (appearance?.colors) {
+    for (const [k, v] of Object.entries(appearance.colors)) {
+      if (v) root.style.setProperty(tokenToCssVar(k), v)
+    }
+  }
+
+  applyWallpaper(resolved, appearance?.wallpaper)
+}
+
+// Render (or clear) the ambient wallpaper + frosted-glass panels.
+function applyWallpaper(resolved: ResolvedTheme, wp?: Wallpaper) {
+  const root = document.documentElement
+  const body = document.body
+  if (!wp?.image) {
+    body.removeAttribute('data-wallpaper')
+    return
+  }
+  body.setAttribute('data-wallpaper', 'on')
+  root.style.setProperty('--wallpaper-image', `url("${wp.image}")`)
+
+  const fx = clamp01(wp.focusX ?? 0.5) * 100
+  const fy = clamp01(wp.focusY ?? 0.5) * 100
+  root.style.setProperty('--wallpaper-position', `${fx}% ${fy}%`)
+
+  // Default scrim: darker in dark mode, lighter in light mode.
+  const opacity = clamp01(wp.overlayOpacity ?? (resolved === 'dark' ? 0.4 : 0.5))
+  const scrim = resolved === 'dark' ? '0, 0, 0' : '255, 255, 255'
+  root.style.setProperty('--wallpaper-overlay', `rgba(${scrim}, ${opacity})`)
+
+  if (wp.glass) {
+    // Frosted glass: surfaces become translucent (so the wallpaper shows
+    // through) + blurred. We derive the tint from the theme's own surface
+    // color so it stays on-palette, then drive alpha via --surface-alpha.
+    const themeSurface =
+      (resolved === 'dark' ? getThemeSurface('dark') : getThemeSurface('light')) ??
+      (resolved === 'dark' ? '#141416' : '#ffffff')
+    const rgb = hexToRgb(themeSurface) ?? (resolved === 'dark' ? [20, 20, 22] : [255, 255, 255])
+    const alpha = resolved === 'dark' ? 0.55 : 0.62
+    root.style.setProperty('--glass-fill', `rgba(${rgb[0]}, ${rgb[1]}, ${rgb[2]}, ${alpha})`)
+    root.style.setProperty('--glass-blur', '20px')
+    // Also make the generic surface tokens translucent so existing cards
+    // (bg-surface) read as glass without touching component code.
+    root.style.setProperty('--surface-alpha', String(alpha))
+  }
+}
+
+// Cache of the active theme's surface color for glass tinting.
+let activeSurface: { light?: string; dark?: string } = {}
+function getThemeSurface(mode: 'light' | 'dark'): string | undefined {
+  return activeSurface[mode]
+}
+
+function clamp01(n: number): number {
+  return Math.min(1, Math.max(0, n))
+}
+
+// Apply the persisted appearance + theme once, before React renders, so the
+// first paint already has the right colors (no flash of the default theme).
+export function initThemeEarly() {
+  const pref = readStoredPref()
+  const resolved: ResolvedTheme = pref === 'system' ? getSystemTheme() : pref
+  applyAppearanceAndTheme(resolved, readStoredThemeId())
 }
 
 export function useTheme() {
-  const [pref, setPref] = useState<ThemePref>(readStored)
+  const [pref, setPref] = useState<ThemePref>(readStoredPref)
+  const [themeId, setThemeIdState] = useState<string>(readStoredThemeId)
+  const [themes, setThemes] = useState<Theme[]>(getAllThemes)
   const [resolved, setResolved] = useState<ResolvedTheme>(() =>
-    readStored() === 'system' ? getSystemTheme() : (readStored() as ResolvedTheme)
+    readStoredPref() === 'system' ? getSystemTheme() : (readStoredPref() as ResolvedTheme)
   )
+  // Display name; a bundled app config may override the default.
+  const [appName, setAppName] = useState<string>('CowAgent')
+  // Snapshot before any effect persists a value, so we can tell a genuine
+  // first run (no prior choice) from a user who explicitly picked a theme.
+  const [firstRun] = useState(() => !hasStoredThemeId())
 
+  // Load themes (bundled + user) and the optional app config once on mount.
+  // On a genuine first run, apply the config's default theme if one is set;
+  // otherwise just re-apply the current selection now its definition is loaded.
+  useEffect(() => {
+    let cancelled = false
+    Promise.all([
+      window.electronAPI?.listThemes?.() ?? Promise.resolve([]),
+      window.electronAPI?.getAppConfig?.() ?? Promise.resolve(null),
+    ])
+      .then(([remote, config]) => {
+        if (cancelled) return
+        registerRuntimeThemes(remote)
+        setThemes(getAllThemes())
+        if (config?.appName) setAppName(config.appName)
+
+        // First-run default from the app config (if the theme exists).
+        if (firstRun && config?.defaultTheme && getTheme(config.defaultTheme).id === config.defaultTheme) {
+          setThemeIdState(config.defaultTheme) // triggers the apply effect below
+          return
+        }
+        // Re-apply the current selection now that its definition is loaded.
+        const next: ResolvedTheme = readStoredPref() === 'system' ? getSystemTheme() : (readStoredPref() as ResolvedTheme)
+        applyAppearanceAndTheme(next, readStoredThemeId())
+      })
+      .catch(() => {})
+    return () => {
+      cancelled = true
+    }
+  }, [firstRun])
+
+  // Re-apply whenever the appearance preference or theme changes.
   useEffect(() => {
     const next: ResolvedTheme = pref === 'system' ? getSystemTheme() : pref
     setResolved(next)
-    applyTheme(next)
+    applyAppearanceAndTheme(next, themeId)
-    localStorage.setItem(STORAGE_KEY, pref)
+    localStorage.setItem(PREF_KEY, pref)
-  }, [pref])
+    localStorage.setItem(THEME_ID_KEY, themeId)
+  }, [pref, themeId])
 
-  // Follow system changes only when preference is "system"
+  // Follow system changes only when preference is "system".
   useEffect(() => {
     if (pref !== 'system') return
     const mq = window.matchMedia('(prefers-color-scheme: dark)')
     const handler = () => {
       const next = getSystemTheme()
       setResolved(next)
-      applyTheme(next)
+      applyAppearanceAndTheme(next, themeId)
     }
     mq.addEventListener('change', handler)
     return () => mq.removeEventListener('change', handler)
-  }, [pref])
+  }, [pref, themeId])
 
   const toggleTheme = useCallback(() => {
     setPref(resolved === 'dark' ? 'light' : 'dark')
   }, [resolved])
 
   const setTheme = useCallback((next: ThemePref) => setPref(next), [])
+  const setThemeId = useCallback((next: string) => setThemeIdState(next), [])
 
-  return { theme: resolved, pref, toggleTheme, setTheme }
+  return { theme: resolved, pref, themeId, themes, appName, toggleTheme, setTheme, setThemeId }
 }

desktop/src/renderer/src/i18n.ts

@@ -85,6 +85,7 @@ const translations: Record<string, Record<string, string>> = {
     menu_more: '更多',
     menu_theme_light: '浅色模式',
     menu_theme_dark: '深色模式',
+    menu_theme_picker: '主题',
     menu_language: '语言',
     menu_website: '官网',
     menu_docs: '文档中心',
@@ -477,6 +478,7 @@ const translations: Record<string, Record<string, string>> = {
     menu_more: 'More',
     menu_theme_light: 'Light mode',
     menu_theme_dark: 'Dark mode',
+    menu_theme_picker: 'Theme',
     menu_language: 'Language',
     menu_website: 'Website',
     menu_docs: 'Documentation',

desktop/src/renderer/src/index.css

@@ -52,6 +52,27 @@
   --ai-bubble-bg: transparent;
   --message-gap: 16px;
 
+  /* Shape tokens — themable (radius / fonts). Kept as variables so a
+     theme can reshape the whole UI without touching components. */
+  --radius-card: 12px;
+  --radius-btn: 8px;
+  --radius-sm: 6px;
+  --font-sans: 'Inter', system-ui, -apple-system, 'PingFang SC', 'Hiragino Sans GB', 'Microsoft YaHei', sans-serif;
+  --font-mono: 'JetBrains Mono', 'Fira Code', Consolas, monospace;
+
+  /* Wallpaper layer — empty by default (solid theme). A theme sets these
+     to render an ambient background image behind the app. */
+  --wallpaper-image: none;
+  --wallpaper-position: 50% 50%;
+  --wallpaper-overlay: rgba(255, 255, 255, 0);
+  /* Panel fill used by .glass surfaces; opaque by default so non-glass
+     themes look identical to today. */
+  --glass-fill: var(--bg-surface);
+  --glass-blur: 0px;
+  /* 1 = fully opaque surfaces (default). A glass wallpaper theme lowers this
+     so bg-surface panels turn translucent and reveal the wallpaper. */
+  --surface-alpha: 1;
+
   color-scheme: light;
 }
 
@@ -107,6 +128,93 @@ body {
   text-rendering: optimizeLegibility;
 }
 
+body {
+  font-family: var(--font-sans);
+}
+
+/* ============================================================
+   Wallpaper layer — ambient background behind the whole app.
+   Rendered as a fixed pseudo-element so it never scrolls and
+   sits under all content. Invisible unless a theme sets
+   --wallpaper-image (default 'none').
+   ============================================================ */
+#root {
+  position: relative;
+  isolation: isolate;
+}
+
+body[data-wallpaper='on']::before {
+  content: '';
+  position: fixed;
+  inset: 0;
+  z-index: -2;
+  background-image: var(--wallpaper-image);
+  background-size: cover;
+  background-position: var(--wallpaper-position);
+  background-repeat: no-repeat;
+  pointer-events: none;
+}
+
+/* Scrim over the wallpaper to keep foreground readable. */
+body[data-wallpaper='on']::after {
+  content: '';
+  position: fixed;
+  inset: 0;
+  z-index: -1;
+  background: var(--wallpaper-overlay);
+  pointer-events: none;
+}
+
+/* When a wallpaper is active, let the app base show it through. The three
+   structural panels use bg-base; make that fill translucent so the ambient
+   image reads behind the UI. Surfaces/cards stay controlled by their own
+   tokens (or .glass) for readability. Zero component changes needed. */
+body[data-wallpaper='on'] {
+  background: transparent;
+}
+
+body[data-wallpaper='on'] .bg-base {
+  background-color: color-mix(in srgb, var(--bg-base) 45%, transparent);
+}
+
+/* Glass mode (wallpaper + glass theme): turn the common surface panels
+   translucent + blurred so the wallpaper reads behind the whole UI, with a
+   subtle top border-highlight for a premium, layered material feel. All via
+   CSS only — components keep using bg-surface / bg-elevated unchanged. */
+body[data-wallpaper='on'] .bg-surface,
+body[data-wallpaper='on'] .bg-elevated {
+  background-color: color-mix(in srgb, var(--bg-surface) calc(var(--surface-alpha) * 100%), transparent);
+  backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+}
+
+/* Slightly brighten default borders over a wallpaper so panels keep clean
+   edges against the artwork. Kept subtle — no inset shadows on every bordered
+   element (that would look noisy on inputs/dividers). */
+body[data-wallpaper='on'] .border-default {
+  border-color: color-mix(in srgb, var(--border-default) 78%, rgba(255, 255, 255, 0.12));
+}
+
+/* ---- New-chat home page under a wallpaper ------------------------
+   When a wallpaper is active, the empty chat home keeps its original
+   centered layout; the suggestion cards just get a premium frosted-glass
+   treatment so they read cleanly over the artwork. Only the empty state. */
+body[data-wallpaper='on'] .chat-home .bg-surface {
+  background-color: color-mix(in srgb, var(--bg-surface) calc(var(--surface-alpha) * 100%), transparent);
+  backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.18), inset 0 1px 0 0 rgba(255, 255, 255, 0.08);
+}
+
+/* Frosted-glass panel: translucent fill + blur so the wallpaper shows
+   through. Opt-in via the .glass class; a theme toggles the fill/blur
+   variables. Falls back to a solid surface when glass is off. */
+.glass {
+  background: var(--glass-fill);
+  backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(1.4);
+}
+
 /* Smooth theme transition (respect reduced motion) */
 body,
 body * {

desktop/src/renderer/src/layout/NavRail.tsx

@@ -21,8 +21,11 @@ import {
   FileText,
   Store,
   MessageSquareWarning,
+  Palette,
+  Check,
 } from 'lucide-react'
 import type { LucideIcon } from 'lucide-react'
+import type { Theme } from '../theme/themes'
 // The desktop app's own brand icon (transparent PNG), bundled by Vite.
 import brandLogo from '../assets/logo.png'
 import { t, getLang, setLang, Lang } from '../i18n'
@@ -76,7 +79,7 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
   const location = useLocation()
   const navigate = useNavigate()
   const { navCollapsed, toggleNav } = useUIStore()
-  const { theme, toggleTheme } = useTheme()
+  const { theme, toggleTheme, themeId, themes, appName, setThemeId } = useTheme()
   // On macOS the top-left is occupied by the native traffic lights, so the
   // brand mark is only shown on Windows/Linux where that corner is otherwise
   // empty (mirrors the web console's sidebar logo).
@@ -178,7 +181,7 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
           <div className="flex items-center gap-2 min-w-0 select-none">
             <BrandLogo />
             {!collapsed && (
-              <span className="text-[14px] font-semibold text-content truncate">CowAgent</span>
+              <span className="text-[14px] font-semibold text-content truncate">{appName}</span>
             )}
           </div>
         )}
@@ -230,6 +233,9 @@ const NavRail: React.FC<NavRailProps> = ({ onLangChange }) => {
               navigate('/logs')
             }}
             onTheme={toggleTheme}
+            themeId={themeId}
+            themes={themes}
+            onThemeId={setThemeId}
             onLanguage={toggleLanguage}
             onCheckUpdate={checkUpdate}
             onOpenLink={(url) => {
@@ -312,12 +318,16 @@ const FooterMenu: React.FC<{
   checking: boolean
   pendingUpdate: boolean
   upToDate: boolean
+  themeId: string
+  themes: Theme[]
+  onThemeId: (id: string) => void
   onLogs: () => void
   onTheme: () => void
   onLanguage: () => void
   onCheckUpdate: () => void
   onOpenLink: (url: string) => void
-}> = ({ theme, checking, pendingUpdate, upToDate, onLogs, onTheme, onLanguage, onCheckUpdate, onOpenLink }) => {
+}> = ({ theme, checking, pendingUpdate, upToDate, themeId, themes, onThemeId, onLogs, onTheme, onLanguage, onCheckUpdate, onOpenLink }) => {
+  const [themeMenuOpen, setThemeMenuOpen] = useState(false)
   const updateLabel = checking
     ? t('update_checking')
     : upToDate
@@ -350,6 +360,24 @@ const FooterMenu: React.FC<{
       label={theme === 'dark' ? t('menu_theme_light') : t('menu_theme_dark')}
       onClick={onTheme}
     />
+    <MenuItem
+      icon={<Palette size={16} />}
+      label={t('menu_theme_picker')}
+      trailing={themeMenuOpen ? '▾' : '▸'}
+      onClick={() => setThemeMenuOpen((o) => !o)}
+    />
+    {themeMenuOpen &&
+      themes.map((th) => (
+        <button
+          key={th.id}
+          onClick={() => onThemeId(th.id)}
+          className="w-full flex items-center gap-2.5 pl-8 pr-3 h-9 text-[13px] text-content-secondary hover:bg-surface-2 hover:text-content cursor-pointer transition-colors"
+        >
+          <ThemeSwatch preview={th.preview ?? { accent: '#4abe6e', bg: '#111', surface: '#1c1c1f' }} />
+          <span className="flex-1 text-left truncate">{th.name}</span>
+          {themeId === th.id && <Check size={14} className="flex-shrink-0 text-accent" />}
+        </button>
+      ))}
     <MenuItem
       icon={<Languages size={16} />}
       label={t('menu_language')}
@@ -361,6 +389,17 @@ const FooterMenu: React.FC<{
   )
 }
 
+// Tiny 3-color preview (bg / surface / accent) for the theme picker.
+const ThemeSwatch: React.FC<{ preview: { accent: string; bg: string; surface: string } }> = ({
+  preview,
+}) => (
+  <span className="flex-shrink-0 inline-flex h-4 w-4 rounded-full overflow-hidden border border-default">
+    <span className="w-1/3 h-full" style={{ background: preview.bg }} />
+    <span className="w-1/3 h-full" style={{ background: preview.surface }} />
+    <span className="w-1/3 h-full" style={{ background: preview.accent }} />
+  </span>
+)
+
 const MenuItem: React.FC<{
   icon: React.ReactNode
   label: string

desktop/src/renderer/src/main.tsx

@@ -2,8 +2,12 @@ import React from 'react'
 import ReactDOM from 'react-dom/client'
 import { HashRouter } from 'react-router-dom'
 import App from './App'
+import { initThemeEarly } from './hooks/useTheme'
 import './index.css'
 
+// Apply persisted appearance + theme before first paint to avoid a flash.
+initThemeEarly()
+
 ReactDOM.createRoot(document.getElementById('root')!).render(
   <React.StrictMode>
     <HashRouter>

desktop/src/renderer/src/pages/ChatPage.tsx

@@ -241,7 +241,7 @@ const ChatPage: React.FC<ChatPageProps> = ({ baseUrl }) => {
         )}
 
         {isEmpty ? (
-          <div className="flex flex-col items-center justify-center h-full px-6 py-12">
+          <div data-home className="chat-home flex flex-col items-center justify-center h-full px-6 py-12">
             <img src="./logo.jpg" alt="CowAgent" className="w-16 h-16 rounded-2xl mb-5 shadow-md" />
             <h1 className="text-xl font-semibold text-content mb-2">{t('chat_welcome')}</h1>
             <p className="text-content-tertiary text-sm text-center max-w-md mb-8 leading-relaxed whitespace-pre-line">

desktop/src/renderer/src/theme/themes.ts

@@ -0,0 +1,142 @@
+// ============================================================
+// Theme Contract — single source of truth for themes.
+//
+// A "theme" is pure data: it overrides semantic design tokens
+// (colors, radius, shadow, font) and an optional background
+// wallpaper. It never touches component code or DOM structure,
+// so themes stay stable across UI refactors — as long as
+// components keep consuming these tokens, old themes keep working.
+//
+// Contract rule: themes may ONLY set fields defined here. Adding a
+// new token is an additive, versioned change (bump THEME_SPEC_VERSION).
+//
+// Themes are NOT bundled into the app. They live in ~/.cow/themes/<id>/
+// (theme.json + images) and are loaded at runtime via the main process,
+// which inlines images as data URLs. The only built-in theme is 'default'
+// (a pure-color fallback that always works offline).
+// ============================================================
+
+// ---- Color tokens (per-appearance) -------------------------
+export const COLOR_KEYS = [
+  'accent',
+  'accentHover',
+  'accentActive',
+  'accentSoft',
+  'accentContrast',
+  'bgBase',
+  'bgSurface',
+  'bgSurface2',
+  'bgElevated',
+  'bgInset',
+  'textPrimary',
+  'textSecondary',
+  'textTertiary',
+  'textDisabled',
+  'borderDefault',
+  'borderStrong',
+  'borderSubtle',
+  'shadowSm',
+  'shadowMd',
+  'shadowLg',
+] as const
+export type ColorKey = (typeof COLOR_KEYS)[number]
+
+// ---- Shape tokens (appearance-independent) -----------------
+// Radius / font apply regardless of light or dark.
+export const SHAPE_KEYS = ['radiusCard', 'radiusBtn', 'radiusSm', 'fontSans', 'fontMono'] as const
+export type ShapeKey = (typeof SHAPE_KEYS)[number]
+
+// camelCase token -> --kebab-case CSS variable
+export function tokenToCssVar(key: string): string {
+  return '--' + key.replace(/[A-Z0-9]/g, (m) => '-' + m.toLowerCase())
+}
+
+// ---- Wallpaper (Codex-style ambient background) ------------
+export interface Wallpaper {
+  // Image URL (bundled asset path or data/file URL). Empty = solid color.
+  image?: string
+  focusX?: number // 0..1 horizontal focal point, default 0.5
+  focusY?: number // 0..1 vertical focal point, default 0.5
+  overlayOpacity?: number // 0..1 scrim strength over the image, default per-appearance
+  // Panels become translucent + blurred (frosted glass) so the wallpaper
+  // shows through. When false, panels stay solid (wallpaper only behind base).
+  glass?: boolean
+}
+
+export interface ThemeAppearance {
+  colors?: Partial<Record<ColorKey, string>>
+  wallpaper?: Wallpaper
+}
+
+// Optional per-theme identity overrides (logo + display name).
+export interface ThemeIdentity {
+  logo?: string // data URL (inlined by main) or asset URL
+  appName?: string
+}
+
+export interface Theme {
+  id: string
+  name: string
+  specVersion?: number
+  // Optional preview swatch; when absent it's derived from colors.
+  preview?: { accent: string; bg: string; surface: string }
+  identity?: ThemeIdentity
+  // Appearance-independent shape tokens.
+  shape?: Partial<Record<ShapeKey, string>>
+  // Per-appearance colors + wallpaper.
+  light?: ThemeAppearance
+  dark?: ThemeAppearance
+}
+
+// Bump when the contract changes in a breaking way. theme.json files declare
+// which version they target so imports can be validated.
+export const THEME_SPEC_VERSION = 1
+
+// 'default' uses the built-in :root / .dark values in index.css and
+// applies no data-theme attribute nor overrides.
+export const DEFAULT_THEME_ID = 'default'
+
+// The only built-in theme: 'default' maps to the base :root / .dark values in
+// index.css (no overrides). Everything else is loaded at runtime from
+// ~/.cow/themes. This keeps the app bundle free of theme assets.
+export const DEFAULT_THEME: Theme = {
+  id: DEFAULT_THEME_ID,
+  name: 'CowAgent',
+  preview: { accent: '#4abe6e', bg: '#f9fafb', surface: '#ffffff' },
+}
+
+// Runtime registry: default first, then whatever was loaded from ~/.cow.
+let runtimeThemes: Theme[] = [DEFAULT_THEME]
+
+// Basic shape validation so a malformed theme.json can't break the app.
+function isValidTheme(x: unknown): x is Theme {
+  if (!x || typeof x !== 'object') return false
+  const s = x as Record<string, unknown>
+  return typeof s.id === 'string' && s.id.length > 0
+}
+
+// Derive a preview swatch from a theme's colors when it didn't ship one.
+function derivePreview(theme: Theme): { accent: string; bg: string; surface: string } {
+  if (theme.preview) return theme.preview
+  const c = theme.dark?.colors ?? theme.light?.colors ?? {}
+  return {
+    accent: c.accent ?? '#4abe6e',
+    bg: c.bgBase ?? '#111111',
+    surface: c.bgSurface ?? '#1c1c1f',
+  }
+}
+
+// Replace the runtime theme list with default + validated remote themes.
+export function registerRuntimeThemes(themes: unknown[]): void {
+  const valid = (themes ?? []).filter(isValidTheme).filter((t) => t.id !== DEFAULT_THEME_ID)
+  for (const t of valid) t.preview = derivePreview(t)
+  runtimeThemes = [DEFAULT_THEME, ...valid]
+}
+
+export function getAllThemes(): Theme[] {
+  return runtimeThemes
+}
+
+export function getTheme(id: string): Theme {
+  return runtimeThemes.find((t) => t.id === id) ?? runtimeThemes[0]
+}

desktop/src/renderer/src/types.ts

@@ -21,6 +21,12 @@ export interface ElectronAPI {
   onMenuAction?: (callback: (action: string) => void) => () => void
   // Current app version string (e.g. "0.0.5").
   getAppVersion?: () => Promise<string>
+  // Themes (bundled + user themes from ~/.cow/themes), images inlined.
+  listThemes?: () => Promise<Record<string, unknown>[]>
+  getThemesDir?: () => Promise<string>
+  // Optional app config: first-run default theme + display name. Null when
+  // the build ships no app config (standard build).
+  getAppConfig?: () => Promise<{ defaultTheme?: string; appName?: string } | null>
   // Auto-update. lang (e.g. "zh") routes installer downloads to the China CDN.
   checkForUpdate?: (lang?: string) => Promise<void>
   downloadUpdate?: (lang?: string) => Promise<void>

desktop/tailwind.config.js

@@ -5,8 +5,9 @@ module.exports = {
   theme: {
     extend: {
       fontFamily: {
-        sans: ['Inter', 'system-ui', '-apple-system', '"PingFang SC"', '"Hiragino Sans GB"', '"Microsoft YaHei"', 'sans-serif'],
+        // Driven by CSS variables so a skin can restyle typography.
-        mono: ['"JetBrains Mono"', '"Fira Code"', 'Consolas', 'monospace'],
+        sans: 'var(--font-sans)',
+        mono: 'var(--font-mono)',
       },
       colors: {
         'danger-soft': 'var(--danger-soft)',
@@ -62,8 +63,9 @@ module.exports = {
         lg: 'var(--shadow-lg)',
       },
       borderRadius: {
-        card: '12px',
+        card: 'var(--radius-card)',
-        btn: '8px',
+        btn: 'var(--radius-btn)',
+        sm: 'var(--radius-sm)',
       },
       animation: {
         'pulse-dot': 'pulseDot 1.4s infinite ease-in-out both',