diff --git a/frontend/index.html b/frontend/index.html
index 7c3f092..0fdd40d 100644
--- a/frontend/index.html
+++ b/frontend/index.html
@@ -3,8 +3,17 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <meta name="theme-color" content="#0c0a09" />
+    <meta name="theme-color" content="#fafaf9" />
     <link rel="icon" href="/icon.svg" type="image/svg+xml" />
+    <script>
+      (() => {
+        try {
+          const t = localStorage.getItem("ui.theme") ?? "system";
+          if (t === "dark" || (t === "system" && matchMedia("(prefers-color-scheme: dark)").matches))
+            document.documentElement.classList.add("dark");
+        } catch {}
+      })();
+    </script>
     <title>BookLib — 个人书库</title>
   </head>
   <body>
diff --git a/frontend/src/App.tsx b/frontend/src/App.tsx
index b7224f8..dc4ff58 100644
--- a/frontend/src/App.tsx
+++ b/frontend/src/App.tsx
@@ -2,6 +2,7 @@ import { Navigate, Route, Routes } from "react-router-dom";
 import { AuthProvider, RequireAdmin, RequireAuth } from "./auth/AuthContext";
 import { ErrorBoundary } from "./components/ErrorBoundary";
 import { Toaster } from "./components/Toaster";
+import { ThemeProvider } from "./components/theme";
 import Login from "./pages/Login";
 import Reader from "./pages/Reader";
 import Shelf from "./pages/Shelf";
@@ -11,49 +12,51 @@ import AdminUsers from "./pages/admin/Users";
 export default function App() {
   return (
     <ErrorBoundary>
-      <AuthProvider>
-        <Routes>
-          <Route path="/login" element={<Login />} />
-          <Route
-            path="/"
-            element={
-              <RequireAuth>
-                <Shelf />
-              </RequireAuth>
-            }
-          />
-          <Route
-            path="/book/:id"
-            element={
-              <RequireAuth>
-                <Reader />
-              </RequireAuth>
-            }
-          />
-          <Route
-            path="/admin/users"
-            element={
-              <RequireAuth>
-                <RequireAdmin>
-                  <AdminUsers />
-                </RequireAdmin>
-              </RequireAuth>
-            }
-          />
-          <Route
-            path="/admin/libraries"
-            element={
-              <RequireAuth>
-                <RequireAdmin>
-                  <AdminLibraries />
-                </RequireAdmin>
-              </RequireAuth>
-            }
-          />
-          <Route path="*" element={<Navigate to="/" replace />} />
-        </Routes>
-        <Toaster />
-      </AuthProvider>
+      <ThemeProvider>
+        <AuthProvider>
+          <Routes>
+            <Route path="/login" element={<Login />} />
+            <Route
+              path="/"
+              element={
+                <RequireAuth>
+                  <Shelf />
+                </RequireAuth>
+              }
+            />
+            <Route
+              path="/book/:id"
+              element={
+                <RequireAuth>
+                  <Reader />
+                </RequireAuth>
+              }
+            />
+            <Route
+              path="/admin/users"
+              element={
+                <RequireAuth>
+                  <RequireAdmin>
+                    <AdminUsers />
+                  </RequireAdmin>
+                </RequireAuth>
+              }
+            />
+            <Route
+              path="/admin/libraries"
+              element={
+                <RequireAuth>
+                  <RequireAdmin>
+                    <AdminLibraries />
+                  </RequireAdmin>
+                </RequireAuth>
+              }
+            />
+            <Route path="*" element={<Navigate to="/" replace />} />
+          </Routes>
+          <Toaster />
+        </AuthProvider>
+      </ThemeProvider>
     </ErrorBoundary>
   );
 }
diff --git a/frontend/src/components/Cover.tsx b/frontend/src/components/Cover.tsx
index 81a5cc1..8472df0 100644
--- a/frontend/src/components/Cover.tsx
+++ b/frontend/src/components/Cover.tsx
@@ -2,7 +2,7 @@ import { useEffect, useState } from "react";
 import type { Book } from "../api/types";
 import { fetchObjectUrl } from "../lib/authImage";
 import { btn, formatBadge } from "./ui";
-import { IconAlert } from "./icons";
+import { TriangleAlert } from "lucide-react";
 
 export function useAuthedImage(url: string | undefined): { src: string; failed: boolean; retry: () => void } {
   const [state, setState] = useState<{ key: string; src: string; failed: boolean }>({ key: "", src: "", failed: false });
@@ -31,26 +31,26 @@ export function Cover({ book, className }: { book: Book; className?: string }) {
   if (!book.cover_url || failed) {
     return (
       <div
-        className={`relative grid place-items-center overflow-hidden bg-linear-to-br from-stone-800 to-stone-900 ${className ?? ""}`}
+        className={`relative grid place-items-center overflow-hidden bg-muted ${className ?? ""}`}
       >
-        <span className="select-none font-serif text-4xl text-stone-500">{Array.from(book.title)[0] ?? "?"}</span>
+        <span className="select-none font-serif text-4xl text-muted-foreground">{Array.from(book.title)[0] ?? "?"}</span>
         <span className={formatBadge(book.format, "absolute bottom-1.5 right-1.5")}>{book.format}</span>
         {failed && (
           <button className={btn + " absolute left-1/2 top-1/2 -translate-x-1/2 -translate-y-1/2"} onClick={retry}>
-            <IconAlert className="size-4" />
+            <TriangleAlert className="size-4" />
             封面重试
           </button>
         )}
       </div>
     );
   }
-  if (!src) return <div className={`animate-pulse bg-stone-800/80 ${className ?? ""}`} role="presentation" />;
+  if (!src) return <div className={`animate-pulse bg-muted ${className ?? ""}`} role="presentation" />;
   return (
     <img
       src={src}
       alt={`《${book.title}》封面`}
       loading="lazy"
-      className={`bg-stone-900 object-cover ${className ?? ""}`}
+      className={`bg-muted object-cover ${className ?? ""}`}
     />
   );
 }
diff --git a/frontend/src/components/Toaster.tsx b/frontend/src/components/Toaster.tsx
index d5e29af..9678fad 100644
--- a/frontend/src/components/Toaster.tsx
+++ b/frontend/src/components/Toaster.tsx
@@ -1,5 +1,5 @@
 import { useEffect, useState, type ReactNode } from "react";
-import { IconAlert, IconCheck } from "./icons";
+import { CheckCircle2, XCircle } from "lucide-react";
 
 type Toast = { id: number; kind: "ok" | "err"; text: ReactNode };
 
@@ -32,13 +32,11 @@ export function Toaster() {
         <div
           key={t.id}
           role="status"
-          className={`fx-rise flex max-w-sm items-center gap-2 rounded-xl px-4 py-2.5 text-sm shadow-xl ring-1 backdrop-blur-md ${
-            t.kind === "ok"
-              ? "bg-emerald-950/90 text-emerald-100 ring-emerald-500/25"
-              : "bg-red-950/90 text-red-100 ring-red-500/30"
+          className={`fx-rise flex max-w-sm items-center gap-2 rounded-lg border bg-card px-4 py-2.5 text-sm text-card-foreground shadow-lg ${
+            t.kind === "ok" ? "border-border" : "border-destructive/40"
           }`}
         >
-          {t.kind === "ok" ? <IconCheck className="size-4 shrink-0 text-emerald-400" /> : <IconAlert className="size-4 shrink-0 text-red-400" />}
+          {t.kind === "ok" ? <CheckCircle2 className="size-4 shrink-0 text-accent" /> : <XCircle className="size-4 shrink-0 text-destructive" />}
           {t.text}
         </div>
       ))}
diff --git a/frontend/src/components/theme.tsx b/frontend/src/components/theme.tsx
new file mode 100644
index 0000000..343bbdd
--- /dev/null
+++ b/frontend/src/components/theme.tsx
@@ -0,0 +1,47 @@
+import { createContext, useCallback, useContext, useEffect, useMemo, useState, type ReactNode } from "react";
+
+export type Theme = "system" | "light" | "dark";
+const KEY = "ui.theme";
+const SYS = "(prefers-color-scheme: dark)";
+
+function read(): Theme {
+  try {
+    const v = localStorage.getItem(KEY);
+    return v === "light" || v === "dark" || v === "system" ? v : "system";
+  } catch {
+    return "system";
+  }
+}
+
+function apply(t: Theme) {
+  const dark = t === "dark" || (t === "system" && matchMedia(SYS).matches);
+  document.documentElement.classList.toggle("dark", dark);
+}
+
+const Ctx = createContext<{ theme: Theme; setTheme: (t: Theme) => void } | null>(null);
+
+export function ThemeProvider({ children }: { children: ReactNode }) {
+  const [theme, set] = useState<Theme>(read);
+  useEffect(() => {
+    apply(theme);
+    try {
+      localStorage.setItem(KEY, theme);
+    } catch {
+      /* 隐私模式:仅本次会话生效 */
+    }
+    if (theme !== "system") return;
+    const mq = matchMedia(SYS);
+    const on = () => apply("system");
+    mq.addEventListener("change", on);
+    return () => mq.removeEventListener("change", on);
+  }, [theme]);
+  const setTheme = useCallback((t: Theme) => set(t), []);
+  const value = useMemo(() => ({ theme, setTheme }), [theme, setTheme]);
+  return <Ctx.Provider value={value}>{children}</Ctx.Provider>;
+}
+
+export function useTheme() {
+  const v = useContext(Ctx);
+  if (!v) throw new Error("useTheme outside ThemeProvider");
+  return v;
+}
diff --git a/frontend/src/index.css b/frontend/src/index.css
index d5fc3b1..6d2e7c7 100644
--- a/frontend/src/index.css
+++ b/frontend/src/index.css
@@ -1,4 +1,74 @@
 @import "tailwindcss";
+@import "tw-animate-css";
+
+@custom-variant dark (&:is(.dark *));
+
+:root {
+  --radius: 0.65rem;
+  --background: oklch(0.985 0.001 80);
+  --foreground: oklch(0.22 0.01 70);
+  --card: oklch(0.995 0 0);
+  --card-foreground: oklch(0.22 0.01 70);
+  --popover: oklch(1 0 0);
+  --popover-foreground: oklch(0.22 0.01 70);
+  --primary: oklch(0.25 0.012 70);
+  --primary-foreground: oklch(0.98 0.002 80);
+  --secondary: oklch(0.95 0.003 80);
+  --secondary-foreground: oklch(0.32 0.01 70);
+  --muted: oklch(0.95 0.003 80);
+  --muted-foreground: oklch(0.55 0.008 70);
+  --accent: oklch(0.68 0.16 46);
+  --accent-foreground: oklch(0.985 0.002 80);
+  --destructive: oklch(0.58 0.21 27);
+  --border: oklch(0.91 0.004 80);
+  --input: oklch(0.91 0.004 80);
+  --ring: oklch(0.62 0.01 70);
+}
+.dark {
+  --background: oklch(0.19 0.006 80);
+  --foreground: oklch(0.95 0.003 80);
+  --card: oklch(0.23 0.006 80);
+  --card-foreground: oklch(0.95 0.003 80);
+  --popover: oklch(0.23 0.006 80);
+  --popover-foreground: oklch(0.95 0.003 80);
+  --primary: oklch(0.95 0.003 80);
+  --primary-foreground: oklch(0.22 0.01 70);
+  --secondary: oklch(0.28 0.006 80);
+  --secondary-foreground: oklch(0.95 0.003 80);
+  --muted: oklch(0.28 0.006 80);
+  --muted-foreground: oklch(0.68 0.006 80);
+  --accent: oklch(0.7 0.16 46);
+  --accent-foreground: oklch(0.19 0.006 80);
+  --destructive: oklch(0.65 0.19 25);
+  --border: oklch(1 0 0 / 10%);
+  --input: oklch(1 0 0 / 14%);
+  --ring: oklch(0.6 0.01 70);
+}
+
+@theme inline {
+  --radius-sm: calc(var(--radius) - 4px);
+  --radius-md: calc(var(--radius) - 2px);
+  --radius-lg: var(--radius);
+  --radius-xl: calc(var(--radius) + 4px);
+  --color-background: var(--background);
+  --color-foreground: var(--foreground);
+  --color-card: var(--card);
+  --color-card-foreground: var(--card-foreground);
+  --color-popover: var(--popover);
+  --color-popover-foreground: var(--popover-foreground);
+  --color-primary: var(--primary);
+  --color-primary-foreground: var(--primary-foreground);
+  --color-secondary: var(--secondary);
+  --color-secondary-foreground: var(--secondary-foreground);
+  --color-muted: var(--muted);
+  --color-muted-foreground: var(--muted-foreground);
+  --color-accent: var(--accent);
+  --color-accent-foreground: var(--accent-foreground);
+  --color-destructive: var(--destructive);
+  --color-border: var(--border);
+  --color-input: var(--input);
+  --color-ring: var(--ring);
+}
 
 html,
 body,
@@ -6,10 +76,23 @@ body,
   height: 100%;
 }
 body {
-  @apply bg-stone-950 text-stone-100 antialiased;
-  /* 顶部一抹极淡的琥珀氛围光,避免大面积纯黑的"朴素感" */
-  background-image: radial-gradient(60rem 28rem at 50% -8rem, rgb(217 119 6 / 0.07), transparent 70%);
-  background-repeat: no-repeat;
+  @apply bg-background text-foreground antialiased;
+  color-scheme: light;
+}
+.dark body {
+  color-scheme: dark;
+}
+
+::-webkit-scrollbar {
+  width: 10px;
+  height: 10px;
+}
+::-webkit-scrollbar-thumb {
+  @apply rounded-full border-2 border-transparent bg-clip-padding;
+  background-color: color-mix(in oklab, var(--foreground) 22%, transparent);
+}
+::-webkit-scrollbar-thumb:hover {
+  background-color: color-mix(in oklab, var(--foreground) 34%, transparent);
 }
 
 /* 入场:卡片/区块轻微上浮淡入(列表 stagger 用 style.animationDelay) */
@@ -18,16 +101,6 @@ body {
   to { opacity: 1; transform: none; }
 }
 .fx-rise { animation: fx-rise 0.35s cubic-bezier(0.22, 1, 0.36, 1) both; }
-::-webkit-scrollbar {
-  width: 10px;
-  height: 10px;
-}
-::-webkit-scrollbar-thumb {
-  @apply rounded-full border-2 border-transparent bg-clip-padding bg-stone-700/70;
-}
-::-webkit-scrollbar-thumb:hover {
-  @apply bg-stone-600;
-}
 
 /* 阅读页主题:纸/米/夜,文本类阅读器共用 —— 见 lib/readerPrefs.ts */
 [data-rd="paper"] { --rd-bg: #faf8f4; --rd-fg: #292524; --rd-link: #9a3412; }
diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index 5ba74d3..ebf7d01 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -15,8 +15,8 @@ export default defineConfig({
         name: "BookLib 个人书库",
         short_name: "BookLib",
         description: "个人书库/漫画库在线阅读",
-        theme_color: "#0c0a09",
-        background_color: "#0c0a09",
+        theme_color: "#fafaf9",
+        background_color: "#fafaf9",
         display: "standalone",
         icons: [{ src: "icon.svg", sizes: "any", type: "image/svg+xml", purpose: "any" }],
       },