diff --git a/app/api/themes/[name]/route.ts b/app/api/themes/[name]/route.ts
new file mode 100644
index 000000000..5db73f2fe
--- /dev/null
+++ b/app/api/themes/[name]/route.ts
@@ -0,0 +1,33 @@
+import { NextRequest, NextResponse } from "next/server";
+import { resolveTheme, type ThemeVariant } from "@/lib/theme";
+
+export async function GET(
+  request: NextRequest,
+  { params }: { params: Promise<{ name: string }> },
+) {
+  try {
+    const { name } = await params;
+    const { searchParams } = new URL(request.url);
+    const mode = (searchParams.get("mode") || "dark") as ThemeVariant;
+
+    const resolved = resolveTheme(
+      decodeURIComponent(name),
+      mode === "light" ? "light" : "dark",
+    );
+
+    if (!resolved) {
+      return NextResponse.json(
+        { error: `Theme "${name}" variant "${mode}" not found` },
+        { status: 404 },
+      );
+    }
+
+    return NextResponse.json(resolved);
+  } catch (error) {
+    console.error("Failed to resolve theme:", error);
+    return NextResponse.json(
+      { error: "Failed to resolve theme" },
+      { status: 500 },
+    );
+  }
+}
diff --git a/app/api/themes/route.ts b/app/api/themes/route.ts
new file mode 100644
index 000000000..8e2829d70
--- /dev/null
+++ b/app/api/themes/route.ts
@@ -0,0 +1,16 @@
+import { NextResponse } from "next/server";
+import { listThemeSets } from "@/lib/theme";
+
+export async function GET() {
+  try {
+    const themeSets = listThemeSets();
+
+    return NextResponse.json({ themeSets });
+  } catch (error) {
+    console.error("Failed to list themes:", error);
+    return NextResponse.json(
+      { error: "Failed to list themes" },
+      { status: 500 },
+    );
+  }
+}
diff --git a/app/globals.css b/app/globals.css
index 1c0e917bd..df4f55e05 100644
--- a/app/globals.css
+++ b/app/globals.css
@@ -23,12 +23,18 @@
   --bg-panel: #f5f5f5;
   --bg-hover: #eeeeee;
   --bg-selected: #e8e8e8;
+  --bg-sidebar: #eeeeee;
   --border: #e0e0e0;
   --text: #1a1a1a;
   --text-muted: #6b7280;
   --text-dim: #9ca3af;
   --accent: #2563eb;
   --accent-hover: #1d4ed8;
+  /* 语法高亮语义色（prism-theme 引用；主题 JSON 映射会覆盖） */
+  --accent-blue: #2563eb;
+  --accent-red: #dc2626;
+  --accent-green: #16a34a;
+  --accent-orange: #d97706;
   --user-bg: #eff6ff;
   --assistant-bg: #ffffff;
   --tool-bg: #f9fafb;
@@ -40,12 +46,18 @@ html.dark {
   --bg-panel: #242424;
   --bg-hover: #2e2e2e;
   --bg-selected: #383838;
+  --bg-sidebar: #2e2e2e;
   --border: #3a3a3a;
   --text: #e8e8e8;
   --text-muted: #9ca3af;
   --text-dim: #6b7280;
   --accent: #60a5fa;
   --accent-hover: #93c5fd;
+  /* 语法高亮语义色（prism-theme 引用；主题 JSON 映射会覆盖） */
+  --accent-blue: #60a5fa;
+  --accent-red: #f87171;
+  --accent-green: #4ade80;
+  --accent-orange: #fb923c;
   --user-bg: #1e293b;
   --assistant-bg: #1a1a1a;
   --tool-bg: #1f2937;
diff --git a/app/layout.tsx b/app/layout.tsx
index 054989f56..60ed55931 100644
--- a/app/layout.tsx
+++ b/app/layout.tsx
@@ -63,7 +63,7 @@ export default function RootLayout({
         <meta name="google" content="notranslate" />
         <script
           dangerouslySetInnerHTML={{
-            __html: `(function(){try{var t=localStorage.getItem("pi-theme");if(t==="dark")document.documentElement.classList.add("dark")}catch(e){}})();`,
+            __html: `(function(){try{var h=document.documentElement,t=localStorage.getItem("pi-theme");if(t==="dark"){h.classList.add("dark")}else if(t&&t!=="light"){h.dataset.theme=t;if(window.matchMedia&&window.matchMedia("(prefers-color-scheme: dark)").matches)h.classList.add("dark")}}catch(e){}})();`,
           }}
         />
       </head>
diff --git a/components/AppShell.tsx b/components/AppShell.tsx
index d4d827fa7..d76523351 100644
--- a/components/AppShell.tsx
+++ b/components/AppShell.tsx
@@ -36,6 +36,7 @@ import type { SessionInfo, SessionTreeNode } from "@/lib/types";
 import type { ProjectTrustStatus } from "@/lib/api-types";
 import type { ChatInputHandle } from "./ChatInput";
 import type { SessionStatsInfo } from "@/lib/pi-types";
+import type { ThemeSetInfo } from "@/lib/theme";
 
 type SessionCopyField = "file" | "id";
 type AutoNameStatus =
@@ -46,12 +47,13 @@ type AutoNameStatus =
 
 const TOP_BAR_ICON_BUTTON_SIZE = 36;
 const LANGUAGE_MENU_WIDTH = 176;
+const THEME_MENU_WIDTH = 200;
 
 export function AppShell() {
   const router = useRouter();
   const searchParams = useSearchParams();
   const [initialNavigation] = useState(() => getInitialNavigation(searchParams));
-  const { isDark, toggleTheme } = useTheme();
+  const { isDark, toggleTheme, themeName, setTheme } = useTheme();
   const { locale, setLocale, t: translate, supportedLocales } = useI18n();
   const isMobile = useIsMobile();
   useViewportHeight();
@@ -145,6 +147,24 @@ export function AppShell() {
   const chatInputRef = useRef<ChatInputHandle | null>(null);
   const topBarRef = useRef<HTMLDivElement>(null);
   const languageBtnRef = useRef<HTMLButtonElement>(null);
+  const themeBtnRef = useRef<HTMLButtonElement>(null);
+
+  // 主题集列表（来自 ~/.pi/agent/themes/ 的 pi theme JSON，经 /api/themes 发现）
+  const [themeSets, setThemeSets] = useState<ThemeSetInfo[]>([]);
+  useEffect(() => {
+    let cancelled = false;
+    fetch("/api/themes")
+      .then((resp) => (resp.ok ? resp.json() : null))
+      .then((data: { themeSets?: ThemeSetInfo[] } | null) => {
+        if (!cancelled && data?.themeSets) setThemeSets(data.themeSets);
+      })
+      .catch(() => {
+        // 主题列表加载失败时面板只显示默认主题，不阻塞主流程
+      });
+    return () => {
+      cancelled = true;
+    };
+  }, []);
 
   // Branch navigator state — populated by ChatWindow via onBranchDataChange
   const [branchTree, setBranchTree] = useState<SessionTreeNode[]>([]);
@@ -201,10 +221,10 @@ export function AppShell() {
   }, []);
 
   // Single active panel — only one dropdown open at a time
-  const [activeTopPanel, setActiveTopPanel] = useState<"branches" | "system" | "session" | "language" | null>(null);
+  const [activeTopPanel, setActiveTopPanel] = useState<"branches" | "system" | "session" | "language" | "theme" | null>(null);
   const [topPanelPos, setTopPanelPos] = useState<{ top: number; left: number; width: number } | null>(null);
 
-  const toggleTopPanel = useCallback((panel: "branches" | "system" | "session" | "language") => {
+  const toggleTopPanel = useCallback((panel: "branches" | "system" | "session" | "language" | "theme") => {
     if (isMobile) setSidebarOpen(false);
     setActiveTopPanel((cur) => cur === panel ? null : panel);
   }, [isMobile]);
@@ -223,15 +243,22 @@ export function AppShell() {
     if (!activeTopPanel || !topBarRef.current) return;
     const update = () => {
       const topBarRect = topBarRef.current!.getBoundingClientRect();
-      if (activeTopPanel === "language" && !isMobile && languageBtnRef.current) {
-        const buttonRect = languageBtnRef.current.getBoundingClientRect();
-        const width = Math.min(LANGUAGE_MENU_WIDTH, topBarRect.width);
-        const left = Math.min(
-          buttonRect.left - 1,
-          Math.max(topBarRect.left, topBarRect.right - width),
-        );
-        setTopPanelPos({ top: topBarRect.bottom, left, width });
-        return;
+      // 语言 / 主题面板锚定在对应按钮下方，其余面板铺满顶栏宽
+      if ((activeTopPanel === "language" || activeTopPanel === "theme") && !isMobile) {
+        const anchorBtn = activeTopPanel === "language" ? languageBtnRef.current : themeBtnRef.current;
+        if (anchorBtn) {
+          const buttonRect = anchorBtn.getBoundingClientRect();
+          const width = Math.min(
+            activeTopPanel === "language" ? LANGUAGE_MENU_WIDTH : THEME_MENU_WIDTH,
+            topBarRect.width,
+          );
+          const left = Math.min(
+            buttonRect.left - 1,
+            Math.max(topBarRect.left, topBarRect.right - width),
+          );
+          setTopPanelPos({ top: topBarRect.bottom, left, width });
+          return;
+        }
       }
       setTopPanelPos({ top: topBarRect.bottom, left: topBarRect.left, width: topBarRect.width });
     };
@@ -239,6 +266,7 @@ export function AppShell() {
     const ro = new ResizeObserver(update);
     ro.observe(topBarRef.current);
     if (languageBtnRef.current) ro.observe(languageBtnRef.current);
+    if (themeBtnRef.current) ro.observe(themeBtnRef.current);
     return () => ro.disconnect();
   }, [activeTopPanel, isMobile]);
 
@@ -803,7 +831,7 @@ export function AppShell() {
         className={`sidebar-container${sidebarOpen ? " sidebar-open" : " sidebar-closed"}${mobileSidebarReady ? "" : " sidebar-mobile-pending"}${sidebarResizer.isResizing ? " sidebar-resizing" : ""}`}
         style={{
           "--sidebar-width": `${sidebarResizer.width}px`,
-          background: "var(--bg-panel)",
+          background: "var(--bg-sidebar)",
           borderRight: "1px solid var(--border)",
           display: "flex",
           flexDirection: "column",
@@ -883,6 +911,32 @@ export function AppShell() {
               </svg>
             )}
            </button>
+           <button
+             ref={themeBtnRef}
+             type="button"
+             onClick={() => toggleTopPanel("theme")}
+             title={translate("theme.select")}
+             aria-label={translate("theme.select")}
+             aria-haspopup="menu"
+             aria-expanded={activeTopPanel === "theme"}
+             aria-pressed={activeTopPanel === "theme"}
+             style={{
+               display: "flex", alignItems: "center", justifyContent: "center",
+               width: TOP_BAR_ICON_BUTTON_SIZE, height: TOP_BAR_ICON_BUTTON_SIZE, padding: 0,
+               background: activeTopPanel === "theme" ? "var(--bg-selected)" : "none",
+               border: "none", borderRight: "1px solid var(--border)",
+               color: activeTopPanel === "theme" ? "var(--text)" : "var(--text-muted)",
+               cursor: "pointer", flexShrink: 0, transition: "color 0.12s",
+             }}
+             onMouseEnter={(e) => { e.currentTarget.style.color = "var(--text)"; }}
+             onMouseLeave={(e) => { e.currentTarget.style.color = activeTopPanel === "theme" ? "var(--text)" : "var(--text-muted)"; }}
+           >
+             {/* 调色板图标：主题集选择入口 */}
+             <svg width="16" height="16" viewBox="0 0 24 24" fill="none" stroke="currentColor" strokeWidth="2" strokeLinecap="round" strokeLinejoin="round">
+               <path d="M12 22a10 10 0 1 1 10-10c0 1.66-1.34 3-3 3h-2.5a2.5 2.5 0 0 0-1.9 4.1c.4.5.2 1.4-.6 1.9-.8.4-1.5.8-2 1Z" />
+               <circle cx="7.5" cy="11.5" r="1" fill="currentColor" /><circle cx="11" cy="7.5" r="1" fill="currentColor" /><circle cx="16" cy="9.5" r="1" fill="currentColor" />
+             </svg>
+           </button>
            <button
              ref={languageBtnRef}
              type="button"
@@ -1288,6 +1342,80 @@ export function AppShell() {
                   ))}
                 </div>
               )}
+              {activeTopPanel === "theme" && (
+                <div
+                  role="menu"
+                  aria-label={translate("theme.select")}
+                  style={{
+                    background: "var(--bg-panel)",
+                    borderLeft: "1px solid var(--border)",
+                    borderRight: "1px solid var(--border)",
+                    borderBottom: "1px solid var(--border)",
+                    overflow: "hidden",
+                    padding: 4,
+                  }}
+                >
+                  <button
+                    type="button"
+                    onClick={() => {
+                      setTheme("");
+                      setActiveTopPanel(null);
+                    }}
+                    role="menuitemradio"
+                    aria-checked={themeName === ""}
+                    style={{
+                      display: "flex", alignItems: "center", width: "100%", height: 34, padding: "0 10px",
+                      border: "none", borderRadius: 4,
+                      background: themeName === "" ? "var(--bg-selected)" : "transparent",
+                      color: "var(--text)", cursor: "pointer", textAlign: "left", fontSize: 12,
+                      transition: "background 0.1s",
+                    }}
+                    onMouseEnter={(e) => {
+                      if (themeName !== "") e.currentTarget.style.background = "var(--bg-hover)";
+                    }}
+                    onMouseLeave={(e) => {
+                      if (themeName !== "") e.currentTarget.style.background = "transparent";
+                    }}
+                  >
+                    <span>{translate("theme.default")}</span>
+                    {themeName === "" && <span style={{ marginLeft: "auto", color: "var(--accent)" }}>✓</span>}
+                  </button>
+                  {themeSets.length === 0 ? (
+                    <div style={{ padding: "8px 10px", fontSize: 12, color: "var(--text-dim)" }}>
+                      {translate("theme.loading")}
+                    </div>
+                  ) : (
+                    themeSets.map((ts) => (
+                      <button
+                        key={ts.name}
+                        type="button"
+                        onClick={() => {
+                          setTheme(ts.name);
+                          setActiveTopPanel(null);
+                        }}
+                        role="menuitemradio"
+                        aria-checked={themeName === ts.name}
+                        style={{
+                          display: "flex", alignItems: "center", width: "100%", height: 34, padding: "0 10px",
+                          border: "none", borderRadius: 4,
+                          background: themeName === ts.name ? "var(--bg-selected)" : "transparent",
+                          color: "var(--text)", cursor: "pointer", textAlign: "left", fontSize: 12,
+                          transition: "background 0.1s",
+                        }}
+                        onMouseEnter={(e) => {
+                          if (themeName !== ts.name) e.currentTarget.style.background = "var(--bg-hover)";
+                        }}
+                        onMouseLeave={(e) => {
+                          if (themeName !== ts.name) e.currentTarget.style.background = "transparent";
+                        }}
+                      >
+                        <span>{ts.displayName}</span>
+                        {themeName === ts.name && <span style={{ marginLeft: "auto", color: "var(--accent)" }}>✓</span>}
+                      </button>
+                    ))
+                  )}
+                </div>
+              )}
               {activeTopPanel === "system" && (
                 <div style={{
                   background: "var(--bg-panel)",
diff --git a/components/FileExplorer.tsx b/components/FileExplorer.tsx
index 6803f21c5..e0101946f 100644
--- a/components/FileExplorer.tsx
+++ b/components/FileExplorer.tsx
@@ -332,7 +332,7 @@ function TreeNode({
             aria-label={t("files.newlyUploaded")}
             style={{ width: 14, height: 14, flexShrink: 0, display: "flex", alignItems: "center", justifyContent: "center" }}
           >
-            <span style={{ width: 6, height: 6, borderRadius: "50%", background: "#3b82f6" }} />
+            <span style={{ width: 6, height: 6, borderRadius: "50%", background: "var(--accent)" }} />
           </span>
         )}
         {!hovered && !node.isDir && gitStatus && (
diff --git a/components/FileViewer.tsx b/components/FileViewer.tsx
index 9635b4c6d..74d3d0300 100644
--- a/components/FileViewer.tsx
+++ b/components/FileViewer.tsx
@@ -6,10 +6,8 @@ import {
   createElement as renderSyntaxNode,
   type SyntaxHighlighterProps,
 } from "react-syntax-highlighter";
-import { vs } from "react-syntax-highlighter/dist/cjs/styles/prism";
-import { vscDarkPlus } from "react-syntax-highlighter/dist/cjs/styles/prism";
+import { prismTheme } from "@/lib/prism-theme";
 import ReactMarkdown from "react-markdown";
-import { useTheme } from "@/hooks/useTheme";
 import {
   DOCX_PREVIEW_MAX_BYTES,
   getFileExt,
@@ -797,7 +795,6 @@ export function FileViewer({ filePath, cwd, sourceSessionId, onOpenFile, onMenti
 }
 
 function TextFileViewer({ filePath, cwd, sourceSessionId, onOpenFile, onMentionLines, gitRefreshKey, initialDisplayMode }: Props) {
-  const { isDark } = useTheme();
   const { t } = useI18n();
   const [data, setData] = useState<FileData | null>(null);
   const [gitDiff, setGitDiff] = useState<GitFileDiffResponse | null>(null);
@@ -1206,7 +1203,7 @@ function TextFileViewer({ filePath, cwd, sourceSessionId, onOpenFile, onMentionL
           <SyntaxHighlighter
             className={wrapLines ? "file-source-view is-wrapped" : "file-source-view"}
             language={language === "text" ? "plaintext" : language}
-            style={isDark ? vscDarkPlus : vs}
+            style={prismTheme}
             showLineNumbers
             lineNumberStyle={{
               ...FILE_LINE_NUMBER_STYLE,
diff --git a/components/MermaidBlock.tsx b/components/MermaidBlock.tsx
index 0efd3db95..6f734774b 100644
--- a/components/MermaidBlock.tsx
+++ b/components/MermaidBlock.tsx
@@ -2,8 +2,7 @@
 
 import { useEffect, useRef, useState, type ReactNode } from "react";
 import { Prism as SyntaxHighlighter } from "react-syntax-highlighter";
-import { vs } from "react-syntax-highlighter/dist/cjs/styles/prism";
-import { vscDarkPlus } from "react-syntax-highlighter/dist/cjs/styles/prism";
+import { prismTheme } from "@/lib/prism-theme";
 import { useTheme } from "@/hooks/useTheme";
 import { useI18n } from "@/hooks/useI18n";
 import { copyText } from "@/lib/clipboard";
@@ -231,7 +230,6 @@ interface CodeBlockProps {
  * Used as the "source" view for mermaid blocks and for all non-mermaid code fences.
  */
 export function CodeBlock({ code, lang, headerAction }: CodeBlockProps) {
-  const { isDark } = useTheme();
   const { t } = useI18n();
   const [copied, setCopied] = useState(false);
 
@@ -258,7 +256,7 @@ export function CodeBlock({ code, lang, headerAction }: CodeBlockProps) {
       </div>
       <SyntaxHighlighter
         language={lang || "text"}
-        style={isDark ? vscDarkPlus : vs}
+        style={prismTheme}
         showLineNumbers
         lineNumberStyle={{ color: "var(--text-dim)", fontStyle: "normal" }}
         customStyle={{
diff --git a/components/MessageView.tsx b/components/MessageView.tsx
index d73bee37f..f158ba702 100644
--- a/components/MessageView.tsx
+++ b/components/MessageView.tsx
@@ -188,7 +188,7 @@ function UserMessageView({ message, cwd, onOpenFile, entryId, onFork, forking, o
             flex: 1,
             minWidth: 0,
             background: "var(--user-bg)",
-            border: "1px solid rgba(59,130,246,0.2)",
+            border: "1px solid color-mix(in srgb, var(--accent) 22%, transparent)",
             borderRadius: 12,
             padding: "8px 12px",
             fontSize: 14,
@@ -216,7 +216,7 @@ function UserMessageView({ message, cwd, onOpenFile, entryId, onFork, forking, o
                     key={i}
                     src={src}
                     alt=""
-                    style={{ maxWidth: 240, maxHeight: 240, borderRadius: 6, objectFit: "contain", display: "block", border: "1px solid rgba(59,130,246,0.15)" }}
+                    style={{ maxWidth: 240, maxHeight: 240, borderRadius: 6, objectFit: "contain", display: "block", border: "1px solid color-mix(in srgb, var(--accent) 18%, transparent)" }}
                   />
                 );
               })}
diff --git a/hooks/useTheme.ts b/hooks/useTheme.ts
index 9000f4699..e063249a6 100644
--- a/hooks/useTheme.ts
+++ b/hooks/useTheme.ts
@@ -1,6 +1,6 @@
 "use client";
 
-import { useCallback, useSyncExternalStore } from "react";
+import { useCallback, useEffect, useSyncExternalStore } from "react";
 
 type Theme = "light" | "dark";
 
@@ -22,11 +22,108 @@ function getServerSnapshot(): Theme {
   return "light";
 }
 
+// ─── 主题名（pi theme JSON 集，如 gruvbox / solarized）──────────────────────
+//
+// localStorage "pi-theme" 同时承载历史明暗值，兼容映射：
+//   "light" / "dark" → 默认主题（空字符串，globals.css 硬编码变量）
+//   其他值（如 "gruvbox"）→ pi theme JSON 主题集名
+// 主题名持久化后，明暗偏好不单独存储：切回默认主题前，明暗随系统偏好（bootstrap 处理）。
+
+function readStoredTheme(): string {
+  try {
+    const v = localStorage.getItem("pi-theme");
+    if (v && v !== "light" && v !== "dark") return v;
+  } catch {
+    // 忽略存储错误（隐私模式、配额等）
+  }
+  return "";
+}
+
+function getThemeSnapshot(): string {
+  if (typeof document === "undefined") return "";
+  const dt = document.documentElement.dataset.theme;
+  if (dt !== undefined) return dt;
+  return readStoredTheme();
+}
+
+// ─── CSS 变量应用 ────────────────────────────────────────────────────────────
+//
+// 与 lib/theme.ts mapToCssVars 输出严格一一对应（20 个），均为当前 UI
+// 实际消费的变量。--composer-focus-bg 为 Kabochar 独有，由 mapToCssVars
+// 从主题面板色派生（聚焦态与主题协调）。
+
+const THEME_CSS_VARS = [
+  "--bg", "--bg-panel", "--bg-hover", "--bg-selected", "--bg-sidebar", "--bg-subtle",
+  "--border",
+  "--text", "--text-muted", "--text-dim",
+  "--accent", "--accent-hover", "--accent-blue", "--accent-red", "--accent-green", "--accent-orange",
+  "--user-bg", "--assistant-bg", "--tool-bg",
+  "--composer-focus-bg",
+];
+
+function applyCssVars(vars: Record<string, string>) {
+  const el = document.documentElement;
+  for (const k of THEME_CSS_VARS) {
+    if (vars[k]) el.style.setProperty(k, vars[k]);
+    else el.style.removeProperty(k);
+  }
+}
+
+function clearCssVars() {
+  const el = document.documentElement;
+  for (const k of THEME_CSS_VARS) el.style.removeProperty(k);
+}
+
+/** 解析缓存按 `name::mode` 键控，避免重复 fetch 同一变体。 */
+const themeCache = new Map<string, Record<string, string> | null>();
+
+async function fetchThemeVars(name: string, mode: Theme): Promise<Record<string, string> | null> {
+  const cacheKey = `${name}::${mode}`;
+  if (themeCache.has(cacheKey)) return themeCache.get(cacheKey)!;
+  try {
+    const resp = await fetch(`/api/themes/${encodeURIComponent(name)}?mode=${mode}`);
+    if (!resp.ok) return null;
+    const data: { cssVars: Record<string, string> } = await resp.json();
+    themeCache.set(cacheKey, data.cssVars);
+    return data.cssVars;
+  } catch {
+    return null;
+  }
+}
+
+/** 应用主题集指定变体的 CSS 变量；name 为空时清空回落到 globals.css 默认。 */
+async function applyTheme(name: string, mode: Theme) {
+  const el = document.documentElement;
+  if (name) {
+    el.dataset.theme = name;
+    const vars = await fetchThemeVars(name, mode);
+    if (vars) {
+      applyCssVars(vars);
+    } else {
+      console.warn(`Theme "${name}" variant "${mode}" not found, using defaults`);
+      clearCssVars();
+    }
+  } else {
+    delete el.dataset.theme;
+    clearCssVars();
+  }
+}
+
 type ToggleOrigin = { x: number; y: number };
 
 export function useTheme() {
   const theme = useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot);
 
+  const setTheme = useCallback(async (name: string) => {
+    await applyTheme(name, getSnapshot());
+    try {
+      localStorage.setItem("pi-theme", name);
+    } catch {
+      // 忽略存储错误
+    }
+    listeners.forEach((cb) => cb());
+  }, []);
+
   const toggleTheme = useCallback((origin?: ToggleOrigin) => {
     const next: Theme = getSnapshot() === "dark" ? "light" : "dark";
 
@@ -36,10 +133,10 @@ export function useTheme() {
       } else {
         document.documentElement.classList.remove("dark");
       }
-      try {
-        localStorage.setItem("pi-theme", next);
-      } catch {
-        // ignore storage errors (private mode, quota, etc.)
+      // 明暗切换后重新解析当前主题的对应变体（gruvbox → gruvbox-light 等）
+      const tn = getThemeSnapshot();
+      if (tn) {
+        applyTheme(tn, next);
       }
       listeners.forEach((cb) => cb());
     };
@@ -81,5 +178,22 @@ export function useTheme() {
       });
   }, []);
 
-  return { theme, toggleTheme, isDark: theme === "dark" };
+  // 挂载时应用持久化主题：bootstrap 脚本已同步设置 data-theme 与 dark class，
+  // 此处补齐 CSS 变量（本地 API fetch，毫秒级）。
+  useEffect(() => {
+    const tn = getThemeSnapshot();
+    if (tn) {
+      applyTheme(tn, getSnapshot());
+    }
+  }, []);
+
+  return {
+    theme,
+    /** 当前主题集名（"" = 默认主题）。 */
+    themeName: getThemeSnapshot(),
+    /** 切换主题集（如 "gruvbox"），传 "" 恢复默认。 */
+    setTheme,
+    toggleTheme,
+    isDark: theme === "dark",
+  };
 }
diff --git a/lib/i18n/messages/en.ts b/lib/i18n/messages/en.ts
index 156cb961c..4f00fb1e1 100644
--- a/lib/i18n/messages/en.ts
+++ b/lib/i18n/messages/en.ts
@@ -14,6 +14,9 @@ export const enLocale: LocalePlugin = {
     "sidebar.show": "Show sidebar",
     "theme.light": "Switch to light mode",
     "theme.dark": "Switch to dark mode",
+    "theme.select": "Theme",
+    "theme.default": "Default",
+    "theme.loading": "Loading themes...",
     "history.full": "Full history",
     "history.unsaved": "Full history is available after the session is saved",
     "history.label": "Full history",
diff --git a/lib/i18n/messages/zh-CN.ts b/lib/i18n/messages/zh-CN.ts
index 7854f8142..72fd8b8d8 100644
--- a/lib/i18n/messages/zh-CN.ts
+++ b/lib/i18n/messages/zh-CN.ts
@@ -14,6 +14,9 @@ export const zhCNLocale: LocalePlugin = {
     "sidebar.show": "显示侧边栏",
     "theme.light": "切换到浅色模式",
     "theme.dark": "切换到深色模式",
+    "theme.select": "主题",
+    "theme.default": "默认",
+    "theme.loading": "正在加载主题...",
     "history.full": "完整历史",
     "history.unsaved": "会话保存后才能查看完整历史",
     "history.label": "完整历史",
diff --git a/lib/prism-theme.ts b/lib/prism-theme.ts
new file mode 100644
index 000000000..fcdbb15ca
--- /dev/null
+++ b/lib/prism-theme.ts
@@ -0,0 +1,50 @@
+import type { CSSProperties } from "react";
+
+/**
+ * Prism emits token colors as inline styles. These must stay tied to the same
+ * CSS variables as the surrounding surface: selecting a separate static dark
+ * or light Prism theme makes code text lag one React render behind a View
+ * Transition's CSS-variable update.
+ */
+export const prismTheme: Record<string, CSSProperties> = {
+  'pre[class*="language-"]': {
+    color: "var(--text)",
+    background: "transparent",
+  },
+  'code[class*="language-"]': {
+    color: "var(--text)",
+    background: "transparent",
+  },
+  comment: { color: "var(--text-dim)", fontStyle: "italic" },
+  prolog: { color: "var(--text-dim)", fontStyle: "italic" },
+  doctype: { color: "var(--text-dim)", fontStyle: "italic" },
+  cdata: { color: "var(--text-dim)" },
+  punctuation: { color: "var(--text-muted)" },
+  operator: { color: "var(--text-muted)" },
+  string: { color: "var(--accent-orange)" },
+  char: { color: "var(--accent-orange)" },
+  builtin: { color: "var(--accent-orange)" },
+  'attr-value': { color: "var(--accent-orange)" },
+  keyword: { color: "var(--accent)" },
+  atrule: { color: "var(--accent)" },
+  property: { color: "var(--accent-blue)" },
+  'attr-name': { color: "var(--accent-blue)" },
+  variable: { color: "var(--accent-blue)" },
+  parameter: { color: "var(--accent-blue)" },
+  constant: { color: "var(--accent-blue)" },
+  number: { color: "var(--accent-blue)" },
+  boolean: { color: "var(--accent-blue)" },
+  symbol: { color: "var(--accent-blue)" },
+  function: { color: "var(--accent-green)" },
+  'class-name': { color: "var(--accent-green)" },
+  'maybe-class-name': { color: "var(--accent-green)" },
+  tag: { color: "var(--accent-red)" },
+  selector: { color: "var(--accent-red)" },
+  regex: { color: "var(--accent-red)" },
+  entity: { color: "var(--accent-red)" },
+  deleted: { color: "var(--accent-red)" },
+  inserted: { color: "var(--accent-green)" },
+  important: { color: "var(--accent-orange)", fontWeight: "bold" },
+  bold: { fontWeight: "bold" },
+  italic: { fontStyle: "italic" },
+};
diff --git a/lib/theme.test.mjs b/lib/theme.test.mjs
new file mode 100644
index 000000000..e24336181
--- /dev/null
+++ b/lib/theme.test.mjs
@@ -0,0 +1,215 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import { mkdtempSync, mkdirSync, writeFileSync, rmSync } from "node:fs";
+import { join } from "node:path";
+import { tmpdir } from "node:os";
+
+// ─── 隔离 ───────────────────────────────────────────────────────────────────
+//
+// lib/theme.ts 的全局主题目录是 join(os.homedir(), ".pi", "agent", "themes")。
+// 将 USERPROFILE 指向临时目录并动态 import，避免测试耦合真实 ~/.pi/agent/themes/。
+// os.homedir() 每次调用读取环境变量（无模块级缓存），动态 import 后即生效。
+
+const baseDir = mkdtempSync(join(tmpdir(), "piweb-theme-test-"));
+const globalThemesDir = join(baseDir, ".pi", "agent", "themes");
+mkdirSync(globalThemesDir, { recursive: true });
+
+process.env.USERPROFILE = baseDir;
+
+const { listThemeSets, resolveTheme } = await import("./theme.ts");
+
+// ─── Fixture ────────────────────────────────────────────────────────────────
+//
+// pi CLI theme JSON（与官方文件名约定一致：base-dark.json / base-light.json）。
+
+const GRUVBOX_DARK = {
+  name: "gruvbox-dark",
+  vars: { bg0: "#282828", bg1: "#3c3836", bg2: "#504945", bg3: "#665c54", bg4: "#7c6f64", fg0: "#fbf1c7", fg3: "#bdae93", fg4: "#a89984", orange: "#d65d0e" },
+  colors: { accent: "orange", border: "bg4", text: "", muted: "fg4", dim: "fg4", selectedBg: "bg1" },
+};
+
+const GRUVBOX_LIGHT = {
+  name: "gruvbox-light",
+  vars: { bg0: "#fbf1c7", bg1: "#ebdbb2", bg2: "#d5c4a1", bg3: "#bdae93", bg4: "#a89984", fg0: "#282828", fg3: "#665c54", fg4: "#7c6f64", orange: "#d65d0e" },
+  colors: { accent: "orange", border: "bg4", text: "", muted: "fg4", dim: "fg4", selectedBg: "bg1" },
+};
+
+const SOLARIZED_DARK = {
+  name: "solarized-dark",
+  vars: { bg0: "#002b36", bg1: "#073642", bg2: "#094250", bg3: "#586e75", bg4: "#657b83", fg0: "#839496", fg3: "#586e75", fg4: "#657b83", blue: "#268bd2" },
+  colors: { accent: "blue", border: "bg3", text: "", muted: "fg4", dim: "fg4", selectedBg: "bg1" },
+};
+
+// 单文件主题（无 -dark/-light 后缀），验证文件名约定外的回退路径
+const MONOKAI = {
+  name: "monokai",
+  vars: { bg0: "#272822", bg1: "#2e2e2e", bg3: "#3e3d32", fg0: "#f8f8f2", fg3: "#75715e", fg4: "#555555", green: "#a6e22e" },
+  colors: { accent: "green", border: "bg3", text: "", muted: "fg4", dim: "fg4", selectedBg: "bg1" },
+};
+
+const write = (name, body) => writeFileSync(join(globalThemesDir, `${name}.json`), JSON.stringify(body));
+write("gruvbox-dark", GRUVBOX_DARK);
+write("gruvbox-light", GRUVBOX_LIGHT);
+write("solarized-dark", SOLARIZED_DARK);
+write("monokai", MONOKAI);
+
+test.after(() => {
+  rmSync(baseDir, { recursive: true, force: true });
+});
+
+// ─── 对比度工具（WCAG 相对亮度） ────────────────────────────────────────────
+
+function relativeLuminance(hex) {
+  const match = /^#([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/.exec(hex);
+  if (!match) return 0.5;
+  const [r, g, b] = [1, 2, 3].map((index) => {
+    const channel = parseInt(match[index], 16) / 255;
+    return channel <= 0.03928 ? channel / 12.92 : Math.pow((channel + 0.055) / 1.055, 2.4);
+  });
+  return 0.2126 * r + 0.7152 * g + 0.0722 * b;
+}
+
+function contrastRatio(foreground, background) {
+  const a = relativeLuminance(foreground);
+  const b = relativeLuminance(background);
+  return (Math.max(a, b) + 0.05) / (Math.min(a, b) + 0.05);
+}
+
+// ─── listThemeSets ──────────────────────────────────────────────────────────
+
+test("listThemeSets 按 base 名聚合 dark/light 变体为 set", () => {
+  const sets = listThemeSets();
+  const byName = new Map(sets.map((s) => [s.name, s]));
+
+  assert.ok(byName.has("gruvbox"), "gruvbox set 应存在");
+  assert.equal(byName.get("gruvbox").hasDark, true);
+  assert.equal(byName.get("gruvbox").hasLight, true);
+
+  assert.ok(byName.has("solarized"), "solarized set 应存在");
+  assert.equal(byName.get("solarized").hasDark, true);
+  assert.equal(byName.get("solarized").hasLight, false);
+
+  // 单文件主题也成 set
+  assert.ok(byName.has("monokai"));
+});
+
+// ─── resolveTheme：配对变体 ─────────────────────────────────────────────────
+
+test("resolveTheme 解析 gruvbox dark 变体（vars 引用 + 亮度推断）", () => {
+  const t = resolveTheme("gruvbox", "dark");
+  assert.ok(t, "应解析成功");
+  assert.equal(t.isDark, true);
+  assert.equal(t.cssVars["--bg"], "#282828");
+  // colors 里的 var 引用解析：accent: "orange" → vars.orange（经对比度保障 ≥4.5:1）
+  assert.ok(contrastRatio(t.cssVars["--accent"], t.cssVars["--bg"]) >= 4.5);
+  // border: "bg4" → vars.bg4（#7c6f64 在 bg 上 3.03:1，过 3.0 保障后不变）
+  assert.equal(t.cssVars["--border"], "#7c6f64");
+  // colors.text 为空串 → 回落 vars.fg0
+  assert.equal(t.cssVars["--text"], "#fbf1c7");
+});
+
+test("resolveTheme 解析 gruvbox light 变体", () => {
+  const t = resolveTheme("gruvbox", "light");
+  assert.ok(t);
+  assert.equal(t.isDark, false);
+  assert.equal(t.cssVars["--bg"], "#fbf1c7");
+  assert.equal(t.cssVars["--text"], "#282828");
+});
+
+test("resolveTheme 派生 --composer-focus-bg（聚焦态与主题协调）", () => {
+  const dark = resolveTheme("gruvbox", "dark");
+  const light = resolveTheme("gruvbox", "light");
+  assert.ok(dark);
+  assert.ok(light);
+  // dark 变体：聚焦背景 = 面板色提亮（#3c3836 向白方向）
+  const darkFocus = dark.cssVars["--composer-focus-bg"];
+  const darkPanel = dark.cssVars["--bg-panel"];
+  assert.ok(darkFocus.startsWith("#"), "dark 聚焦背景应为 hex");
+  assert.ok(darkFocus > darkPanel, "dark 聚焦背景应亮于面板色");
+  // light 变体：聚焦背景 = 面板色向白混合
+  const lightFocus = light.cssVars["--composer-focus-bg"];
+  const lightPanel = light.cssVars["--bg-panel"];
+  assert.ok(lightFocus.startsWith("#"), "light 聚焦背景应为 hex");
+  assert.ok(lightFocus > lightPanel, "light 聚焦背景应亮于面板色");
+});
+
+test("resolveTheme 缺失变体时回退到相反变体", () => {
+  // solarized 只有 dark 文件：请求 light 应回退 dark 文件，极性由内容决定
+  const t = resolveTheme("solarized", "light");
+  assert.ok(t);
+  assert.equal(t.isDark, true);
+  assert.equal(t.cssVars["--bg"], "#002b36");
+});
+
+// ─── resolveTheme：单文件主题 ──────────────────────────────────────────────
+
+test("resolveTheme 单文件主题（无后缀）优先于相反变体回退", () => {
+  // monokai.json 存在且 monokai-dark.json 不存在：dark/light 请求都走单文件
+  const dark = resolveTheme("monokai", "dark");
+  const light = resolveTheme("monokai", "light");
+  assert.ok(dark);
+  assert.ok(light);
+  assert.equal(dark.cssVars["--bg"], "#272822");
+  assert.equal(light.cssVars["--bg"], "#272822");
+});
+
+// ─── resolveTheme：不存在与非法输入 ─────────────────────────────────────────
+
+test("resolveTheme 不存在的主题返回 null", () => {
+  assert.equal(resolveTheme("nonexistent", "dark"), null);
+  assert.equal(resolveTheme("", "dark"), null);
+});
+
+// ─── 文字对比度保障（web 可读性） ─────────────────────────────────────────────
+
+test("文字层级对比度保障：muted ≥ 4.5、dim ≥ 3、dim 弱于 muted", () => {
+  // solarized dark 原版 muted/dim 对比不足（2.79/3.37），映射层应提升 muted；
+  // gruvbox light 原版 dim 3.24 接近下限，应保持或微调。
+  const solarizedDark = resolveTheme("solarized", "dark");
+  const gruvboxLight = resolveTheme("gruvbox", "light");
+  assert.ok(solarizedDark);
+  assert.ok(gruvboxLight);
+
+  for (const resolved of [solarizedDark, gruvboxLight]) {
+    const bg = resolved.cssVars["--bg"];
+    const textRatio = contrastRatio(resolved.cssVars["--text"], bg);
+    const mutedRatio = contrastRatio(resolved.cssVars["--text-muted"], bg);
+    const dimRatio = contrastRatio(resolved.cssVars["--text-dim"], bg);
+    assert.ok(textRatio >= 4.5, `text 对比度应 ≥4.5（实际 ${textRatio.toFixed(2)}）`);
+    assert.ok(mutedRatio >= 4.5, `muted 对比度应 ≥4.5（实际 ${mutedRatio.toFixed(2)}）`);
+    assert.ok(dimRatio >= 3.0, `dim 对比度应 ≥3.0（实际 ${dimRatio.toFixed(2)}）`);
+    assert.ok(dimRatio < mutedRatio, "dim 应弱于 muted（层级递减）");
+  }
+});
+
+// ─── 层级适配（高级 UI 评审整改项） ──────────────────────────────────────────
+
+test("层级适配：accent 系 ≥4.5、border ≥3、气泡/侧边栏/选中态分层", () => {
+  for (const [name, mode] of [
+    ["gruvbox", "dark"],
+    ["gruvbox", "light"],
+    ["solarized", "dark"],
+    ["solarized", "light"],
+  ]) {
+    const resolved = resolveTheme(name, mode);
+    assert.ok(resolved, `${name}/${mode} 应解析成功`);
+    const vars = resolved.cssVars;
+    const bg = vars["--bg"];
+
+    // 静止态 accent 与语法高亮语义色：全部 ≥4.5:1
+    for (const key of ["--accent", "--accent-blue", "--accent-green", "--accent-orange", "--accent-red"]) {
+      assert.ok(contrastRatio(vars[key], bg) >= 4.5, `${name}/${mode} ${key} ≥4.5（实际 ${contrastRatio(vars[key], bg).toFixed(2)}）`);
+    }
+    // 边框分隔线可见性：≥3:1
+    assert.ok(contrastRatio(vars["--border"], bg) >= 3.0, `${name}/${mode} border ≥3.0`);
+    // 用户气泡与面板分层（不再同色，可辨层级 ≥1.25:1）
+    const userVsPanel = contrastRatio(vars["--user-bg"], vars["--bg-panel"]);
+    assert.ok(userVsPanel >= 1.25, `${name}/${mode} 气泡与面板对比 ≥1.25（实际 ${userVsPanel.toFixed(2)}）`);
+    // 侧边栏表面色存在且与主背景可辨（≥1.5:1）
+    assert.ok(vars["--bg-sidebar"], `${name}/${mode} 应有侧边栏色`);
+    const sidebarVsBg = contrastRatio(vars["--bg-sidebar"], bg);
+    assert.ok(sidebarVsBg >= 1.5, `${name}/${mode} 侧边栏与主背景对比 ≥1.5（实际 ${sidebarVsBg.toFixed(2)}）`);
+    // 选中态与 hover 区分（accent 微染）
+    assert.notEqual(vars["--bg-selected"], vars["--bg-hover"], `${name}/${mode} 选中态应异于 hover`);
+  }
+});
diff --git a/lib/theme.ts b/lib/theme.ts
new file mode 100644
index 000000000..16e7bfc30
--- /dev/null
+++ b/lib/theme.ts
@@ -0,0 +1,541 @@
+/**
+ * Theme system for pi-web.
+ *
+ * Loads pi CLI theme JSON files (from ~/.pi/agent/themes/, .pi/themes/, etc.),
+ * resolves `vars` references, and maps the 51 pi CLI color tokens to pi-web's
+ * ~23 CSS custom properties.
+ *
+ * Themes are organized as **sets** — each set pairs a dark and a light variant
+ * (e.g. "gruvbox" → gruvbox-dark.json + gruvbox-light.json). A set may also
+ * contain only one variant (single-file theme).
+ *
+ * pi CLI theme format:
+ *   { name, vars: { key: hex|number, ... }, colors: { token: hex|number|varRef|"", ... } }
+ *
+ * Color values can be:
+ *   - Hex string: "#ff0000"
+ *   - 256-color index: 242
+ *   - Variable reference: "primary" (resolved from vars)
+ *   - Empty string "": terminal default (we derive from palette)
+ */
+
+import { readFileSync, readdirSync, existsSync, statSync } from "fs";
+import { join, basename, extname } from "path";
+import { homedir } from "os";
+
+// ─── Types ───────────────────────────────────────────────────────────────────
+
+export interface PiTheme {
+  name: string;
+  vars?: Record<string, string | number>;
+  colors: Record<string, string | number>;
+}
+
+/** Represents a paired theme set (e.g. "gruvbox" with dark + light variants). */
+export interface ThemeSetInfo {
+  /** Base name (e.g. "gruvbox") — used as the stable identifier. */
+  name: string;
+  /** Human-readable display name. */
+  displayName: string;
+  /** Whether this set has a dark variant. */
+  hasDark: boolean;
+  /** Whether this set has a light variant. */
+  hasLight: boolean;
+}
+
+/** A resolved, ready-to-use theme (one variant of a set). */
+export interface ResolvedTheme {
+  /** Base theme-set name. */
+  name: string;
+  /** Whether this specific variant is dark. */
+  isDark: boolean;
+  /** CSS variable name → hex value (e.g. "--bg" → "#282828") */
+  cssVars: Record<string, string>;
+}
+
+export type ThemeVariant = "dark" | "light";
+
+// ─── 256-color palette → hex ────────────────────────────────────────────────
+
+// Standard xterm 256-color palette. 0-15: ANSI, 16-231: 6x6x6 cube, 232-255: grayscale.
+function ansiToHex(code: number): string {
+  // 0-15: basic ANSI colors
+  const ansi: Record<number, string> = {
+    0: "#000000", 1: "#800000", 2: "#008000", 3: "#808000",
+    4: "#000080", 5: "#800080", 6: "#008080", 7: "#c0c0c0",
+    8: "#808080", 9: "#ff0000", 10: "#00ff00", 11: "#ffff00",
+    12: "#0000ff", 13: "#ff00ff", 14: "#00ffff", 15: "#ffffff",
+  };
+  if (code in ansi) return ansi[code];
+
+  // 16-231: 6×6×6 RGB cube
+  if (code >= 16 && code <= 231) {
+    const n = code - 16;
+    const r = Math.round((Math.floor(n / 36) % 6) * (255 / 5));
+    const g = Math.round((Math.floor(n / 6) % 6) * (255 / 5));
+    const b = Math.round((n % 6) * (255 / 5));
+    return `#${r.toString(16).padStart(2, "0")}${g.toString(16).padStart(2, "0")}${b.toString(16).padStart(2, "0")}`;
+  }
+
+  // 232-255: grayscale ramp
+  if (code >= 232 && code <= 255) {
+    const v = Math.round(((code - 232) / 23) * 255);
+    const h = v.toString(16).padStart(2, "0");
+    return `#${h}${h}${h}`;
+  }
+
+  return "#000000";
+}
+
+// ─── Color resolution ───────────────────────────────────────────────────────
+
+/**
+ * Resolve a single color value to a hex string.
+ * - Hex string: returned as-is (lowercased)
+ * - Number: treated as 256-color index, converted to hex
+ * - String matching a var name: resolved from vars
+ * - Empty string: returns empty (caller should substitute default)
+ */
+function resolveColor(
+  value: string | number | undefined,
+  vars: Record<string, string>,
+): string {
+  if (value === undefined || value === null) return "";
+  if (typeof value === "number") return ansiToHex(value);
+  if (typeof value === "string") {
+    const trimmed = value.trim();
+    if (trimmed === "") return "";
+    if (trimmed.startsWith("#")) return trimmed.toLowerCase();
+    // Variable reference
+    if (vars[trimmed]) return vars[trimmed].toLowerCase();
+    // Could be a raw number-as-string: "242"
+    const num = Number(trimmed);
+    if (!isNaN(num) && trimmed === String(num)) return ansiToHex(num);
+    // Unknown reference — return as-is (may be valid hex without #)
+    if (/^[0-9a-fA-F]{6}$/.test(trimmed)) return `#${trimmed.toLowerCase()}`;
+    return trimmed.toLowerCase();
+  }
+  return "";
+}
+
+/** Resolve all `vars` entries to hex strings. */
+function resolveVars(vars: Record<string, string | number> | undefined): Record<string, string> {
+  const resolved: Record<string, string> = {};
+  if (!vars) return resolved;
+  for (const [key, value] of Object.entries(vars)) {
+    resolved[key] = resolveColor(value, {});
+  }
+  return resolved;
+}
+
+/** Resolve all `colors` entries, expanding var references. */
+function resolveColors(
+  colors: Record<string, string | number>,
+  vars: Record<string, string>,
+): Record<string, string> {
+  const resolved: Record<string, string> = {};
+  for (const [key, value] of Object.entries(colors)) {
+    resolved[key] = resolveColor(value, vars);
+  }
+  return resolved;
+}
+
+// ─── Color manipulation helpers ─────────────────────────────────────────────
+
+function hexToRgb(hex: string): [number, number, number] | null {
+  const m = /^#([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})$/.exec(hex);
+  if (!m) return null;
+  return [parseInt(m[1], 16), parseInt(m[2], 16), parseInt(m[3], 16)];
+}
+
+function rgbToHex(r: number, g: number, b: number): string {
+  return `#${r.toString(16).padStart(2, "0")}${g.toString(16).padStart(2, "0")}${b.toString(16).padStart(2, "0")}`;
+}
+
+/** Lighten a hex color by mixing with white. factor 0 = no change, 1 = white. */
+function lighten(hex: string, factor: number): string {
+  const rgb = hexToRgb(hex);
+  if (!rgb) return hex;
+  const [r, g, b] = rgb;
+  return rgbToHex(
+    Math.round(r + (255 - r) * factor),
+    Math.round(g + (255 - g) * factor),
+    Math.round(b + (255 - b) * factor),
+  );
+}
+
+/** Darken a hex color by mixing with black. factor 0 = no change, 1 = black. */
+function darken(hex: string, factor: number): string {
+  const rgb = hexToRgb(hex);
+  if (!rgb) return hex;
+  const [r, g, b] = rgb;
+  return rgbToHex(
+    Math.round(r * (1 - factor)),
+    Math.round(g * (1 - factor)),
+    Math.round(b * (1 - factor)),
+  );
+}
+
+/** Mix two hex colors. factor 0 = all a, factor 1 = all b. */
+function mix(a: string, b: string, factor: number): string {
+  const ra = hexToRgb(a);
+  const rb = hexToRgb(b);
+  if (!ra || !rb) return a;
+  return rgbToHex(
+    Math.round(ra[0] + (rb[0] - ra[0]) * factor),
+    Math.round(ra[1] + (rb[1] - ra[1]) * factor),
+    Math.round(ra[2] + (rb[2] - ra[2]) * factor),
+  );
+}
+
+/** Calculate relative luminance (0-1). Used to determine dark vs light. */
+function relativeLuminance(hex: string): number {
+  const rgb = hexToRgb(hex);
+  if (!rgb) return 0.5;
+  const [rs, gs, bs] = rgb.map((c) => {
+    const s = c / 255;
+    return s <= 0.03928 ? s / 12.92 : Math.pow((s + 0.055) / 1.055, 2.4);
+  });
+  return 0.2126 * rs + 0.7152 * gs + 0.0722 * bs;
+}
+
+function contrastRatio(foreground: string, background: string): number {
+  const foregroundLum = relativeLuminance(foreground);
+  const backgroundLum = relativeLuminance(background);
+  return (Math.max(foregroundLum, backgroundLum) + 0.05) / (Math.min(foregroundLum, backgroundLum) + 0.05);
+}
+
+/**
+ * Preserve a theme status color's hue while making a modest contrast adjustment.
+ * Git status has redundant text, dot, and capsule-background signals, so 3:1
+ * keeps green and yellow distinguishable in light themes better than forcing
+ * every status color to normal-text 4.5:1 contrast.
+ */
+function ensureContrast(color: string, background: string, minimum = 3): string {
+  if (!hexToRgb(color) || !hexToRgb(background) || contrastRatio(color, background) >= minimum) {
+    return color;
+  }
+
+  const darkenForContrast = relativeLuminance(background) > relativeLuminance(color);
+  for (let step = 1; step <= 20; step += 1) {
+    const candidate = darkenForContrast
+      ? darken(color, step * 0.05)
+      : lighten(color, step * 0.05);
+    if (contrastRatio(candidate, background) >= minimum) return candidate;
+  }
+  return darkenForContrast ? "#000000" : "#ffffff";
+}
+
+// ─── pi CLI token → CSS variable mapping ────────────────────────────────────
+
+/**
+ * Maps resolved pi CLI theme colors + vars to pi-web CSS custom properties.
+ */
+function mapToCssVars(
+  colors: Record<string, string>,
+  vars: Record<string, string>,
+): Record<string, string> {
+  // ── Extract base palette from vars ──
+  const bg0 = vars.bg0 || "#1a1a1a";
+  const bg1 = vars.bg1 || "#242424";
+  const bg2 = vars.bg2 || "#2e2e2e";
+  const bg3 = vars.bg3 || "#383838";
+  const fg0 = vars.fg0 || "#e8e8e8";
+  const fg3 = vars.fg3 || "#888888";
+  const fg4 = vars.fg4 || "#555555";
+
+  // Semantic palette colors
+  const red = vars.red || "#dc2626";
+  const green = vars.green || "#16a34a";
+  const orange = vars.orange || "#d97706";
+
+  // ── Resolve key pi CLI tokens ──
+  const accent = colors.accent || orange;
+  const text = colors.text || fg0;
+  const muted = colors.muted || fg3;
+  const dim = colors.dim || fg4;
+  const border = colors.border || bg3;
+  const success = colors.success || green;
+  const error = colors.error || red;
+  const warning = colors.warning || orange;
+  const toolSuccessBg = colors.toolSuccessBg || bg1;
+
+  // Determine if dark theme
+  const isDark = relativeLuminance(bg0) < 0.5;
+
+  // ── Web 适配：强调色 / 边框对比度保障 ──
+  // 静止态 accent（链接/图标/按钮）与语法高亮共用 --accent-*，全部过
+  // ensureContrast（≥4.5:1），保留色相只调深浅；边框分隔线 ≥3:1。
+  const accentSafe = ensureContrast(accent, bg0, 4.5);
+  const borderSafe = ensureContrast(border, bg0, 3.0);
+
+  // ── Build CSS variables ──
+  const css: Record<string, string> = {};
+
+  // Core backgrounds
+  css["--bg"] = bg0;
+  css["--bg-panel"] = bg1;
+  css["--bg-hover"] = bg2;
+  // 选中态：bg2 微染 accent 色相（低浓度），与 hover 区分且带主题气质
+  css["--bg-selected"] = mix(bg2, accentSafe, 0.06);
+  // 侧边栏专用表面色：向 bg3 加深半档，避免与主区"融为一片"
+  // （实测 bg2 与主背景仅 1.3:1，人眼难辨，需 ~1.7:1+）
+  css["--bg-sidebar"] = mix(bg2, bg3, 0.5);
+  css["--bg-subtle"] = isDark
+    ? `rgba(255,255,255,0.035)`
+    : `rgba(15,23,42,0.035)`;
+
+  // Borders
+  css["--border"] = borderSafe;
+
+  // Text — web 可读性保障：主题色对比度不足时向正确方向微调，
+  // 正文/次级 ≥ 4.5:1、弱化层 ≥ 3:1，且层级严格递减（dim < muted < text）。
+  // 终端主题（如 solarized）的低对比哲学在小字号 UI 上不适用，这里做适配。
+  css["--text"] = ensureContrast(text, bg0, 4.5);
+  css["--text-muted"] = ensureContrast(muted, bg0, 4.5);
+  css["--text-dim"] = ensureContrast(dim, bg0, 3.0);
+
+  // Accent — 静止态与语法高亮共用，全部保障 ≥4.5:1
+  css["--accent"] = accentSafe;
+  css["--accent-hover"] = isDark ? lighten(accentSafe, 0.2) : darken(accentSafe, 0.15);
+  css["--accent-blue"] = ensureContrast(vars.blue || accent, bg0, 4.5);
+
+  // Semantic colors
+  css["--accent-red"] = ensureContrast(error, bg0, 4.5);
+  css["--accent-green"] = ensureContrast(success, bg0, 4.5);
+  css["--accent-orange"] = ensureContrast(warning, bg0, 4.5);
+
+  // Message bubbles — 用户气泡向 bg3 加深半档（~1.3:1），配 accent 描边，
+  // 与面板拉开可辨层级，消息归属清晰
+  css["--user-bg"] = mix(bg2, bg3, 0.5);
+  css["--assistant-bg"] = bg0;
+  css["--tool-bg"] = toolSuccessBg;
+
+  // Kabochar 特有：输入框聚焦背景（.chat-composer:focus-within）。
+  // light 从主背景向白派生（聚焦更亮），dark 从面板提亮。
+  css["--composer-focus-bg"] = isDark
+    ? lighten(bg1, 0.08)
+    : mix(bg0, "#ffffff", 0.35);
+
+  return css;
+}
+
+// ─── Theme loading ──────────────────────────────────────────────────────────
+
+/** All required pi CLI color tokens (51 tokens). */
+const ALL_COLOR_TOKENS = [
+  "accent", "border", "borderAccent", "borderMuted",
+  "success", "error", "warning", "muted", "dim", "text", "thinkingText",
+  "selectedBg", "userMessageBg", "userMessageText",
+  "customMessageBg", "customMessageText", "customMessageLabel",
+  "toolPendingBg", "toolSuccessBg", "toolErrorBg", "toolTitle", "toolOutput",
+  "mdHeading", "mdLink", "mdLinkUrl", "mdCode", "mdCodeBlock",
+  "mdCodeBlockBorder", "mdQuote", "mdQuoteBorder", "mdHr", "mdListBullet",
+  "toolDiffAdded", "toolDiffRemoved", "toolDiffContext",
+  "syntaxComment", "syntaxKeyword", "syntaxFunction", "syntaxVariable",
+  "syntaxString", "syntaxNumber", "syntaxType", "syntaxOperator", "syntaxPunctuation",
+  "thinkingOff", "thinkingMinimal", "thinkingLow", "thinkingMedium",
+  "thinkingHigh", "thinkingXhigh", "thinkingMax",
+  "bashMode",
+];
+
+/**
+ * Parse a pi CLI theme JSON file.
+ * Validates required fields and fills in missing color tokens with empty strings.
+ */
+function parseThemeFile(path: string): PiTheme | null {
+  try {
+    const raw = readFileSync(path, "utf-8");
+    const json = JSON.parse(raw);
+
+    if (!json.name || typeof json.name !== "string") return null;
+    if (!json.colors || typeof json.colors !== "object") return null;
+
+    // Fill missing tokens with empty strings
+    const colors: Record<string, string | number> = {};
+    for (const token of ALL_COLOR_TOKENS) {
+      colors[token] = json.colors[token] ?? "";
+    }
+
+    return {
+      name: json.name,
+      vars: json.vars,
+      colors,
+    };
+  } catch {
+    return null;
+  }
+}
+
+// ─── File-name convention helpers ───────────────────────────────────────────
+
+/**
+ * Detect the base name and variant from a theme filename.
+ *
+ * Convention:
+ *   gruvbox-dark.json  → { base: "gruvbox", variant: "dark" }
+ *   gruvbox-light.json → { base: "gruvbox", variant: "light" }
+ *   monokai.json       → { base: "monokai", variant: null }
+ */
+function parseThemeFilename(
+  filename: string,
+): { base: string; variant: ThemeVariant | null } {
+  const stem = basename(filename, extname(filename));
+
+  // Try "-dark" / "-light" suffix (case-insensitive)
+  const darkMatch = /^(.+)-dark$/i.exec(stem);
+  if (darkMatch) return { base: darkMatch[1], variant: "dark" };
+
+  const lightMatch = /^(.+)-light$/i.exec(stem);
+  if (lightMatch) return { base: lightMatch[1], variant: "light" };
+
+  // Single-file theme — variant determined from content later
+  return { base: stem, variant: null };
+}
+
+/**
+ * Scan a directory for pi CLI theme JSON files.
+ * Returns an array of { path, base, variant, isDark } records.
+ */
+interface ScannedFile {
+  path: string;
+  base: string;
+  variant: ThemeVariant | null;
+  isDark: boolean;
+}
+
+function scanThemeDir(dir: string): ScannedFile[] {
+  const results: ScannedFile[] = [];
+  try {
+    if (!existsSync(dir)) return results;
+    const entries = readdirSync(dir);
+    for (const entry of entries) {
+      if (extname(entry) !== ".json") continue;
+      const fullPath = join(dir, entry);
+      try {
+        if (!statSync(fullPath).isFile()) continue;
+      } catch {
+        continue;
+      }
+      const parsed = parseThemeFilename(entry);
+      // Determine actual polarity from file content
+      const theme = parseThemeFile(fullPath);
+      if (!theme) continue;
+      const vars = resolveVars(theme.vars);
+      const bg0 = vars.bg0 || "#1a1a1a";
+      const isDark = relativeLuminance(bg0) < 0.5;
+      // If variant wasn't detected from filename, infer from content
+      const variant = parsed.variant ?? (isDark ? "dark" : "light");
+
+      results.push({ path: fullPath, base: parsed.base, variant, isDark });
+    }
+  } catch {
+    // Permission errors, etc.
+  }
+  return results;
+}
+
+// ─── Public API ─────────────────────────────────────────────────────────────
+
+/** List all available theme sets from the global theme directory. */
+export function listThemeSets(): ThemeSetInfo[] {
+  const result: ThemeSetInfo[] = [];
+  const seen = new Set<string>();
+
+  // Collect all scanned files
+  const allFiles: ScannedFile[] = [];
+
+  // Global themes: ~/.pi/agent/themes/
+  const globalDir = join(homedir(), ".pi", "agent", "themes");
+  allFiles.push(...scanThemeDir(globalDir));
+
+  // Group by base name
+  const groups = new Map<string, ScannedFile[]>();
+  for (const f of allFiles) {
+    const list = groups.get(f.base) || [];
+    list.push(f);
+    groups.set(f.base, list);
+  }
+
+  // Build ThemeSetInfo for each group
+  for (const [base, files] of groups) {
+    if (seen.has(base)) continue;
+    seen.add(base);
+
+    let hasDark = false;
+    let hasLight = false;
+    for (const f of files) {
+      if (f.variant === "dark") hasDark = true;
+      if (f.variant === "light") hasLight = true;
+    }
+
+    result.push({
+      name: base,
+      displayName: themeNameToDisplay(base),
+      hasDark,
+      hasLight,
+    });
+  }
+
+  return result;
+}
+
+/** Convert a kebab-case theme name to a display-friendly title. */
+function themeNameToDisplay(name: string): string {
+  return name
+    .split(/[-_]/)
+    .map((w) => w.charAt(0).toUpperCase() + w.slice(1))
+    .join(" ");
+}
+
+/**
+ * Resolve a specific variant of a theme set.
+ *
+ * Lookup order:
+ *   1. `{base}-{variant}.json` (e.g. `gruvbox-dark.json`)
+ *   2. `{base}.json` (single-file fallback)
+ *   3. The opposite variant (if only one variant exists and user requests the other)
+ *
+ * @param name  Base theme-set name (e.g. "gruvbox").
+ * @param variant  Which variant to load ("dark" or "light").
+ */
+export function resolveTheme(
+  name: string,
+  variant: ThemeVariant,
+): ResolvedTheme | null {
+  if (!name) return null;
+
+  // Global themes: ~/.pi/agent/themes/
+  const dirs: string[] = [
+    join(homedir(), ".pi", "agent", "themes"),
+  ];
+
+  // Candidate filenames in priority order
+  const candidates = [
+    `${name}-${variant}.json`,  // e.g. gruvbox-dark.json
+    `${name}.json`,             // e.g. monokai.json (single-file)
+    `${name}-${variant === "dark" ? "light" : "dark"}.json`, // opposite variant fallback
+  ];
+
+  for (const dir of dirs) {
+    for (const candidate of candidates) {
+      const fullPath = join(dir, candidate);
+      if (!existsSync(fullPath)) continue;
+      const theme = parseThemeFile(fullPath);
+      if (!theme) continue;
+
+      const vars = resolveVars(theme.vars);
+      const colors = resolveColors(theme.colors, vars);
+      const cssVars = mapToCssVars(colors, vars);
+      const bg0 = vars.bg0 || "#1a1a1a";
+
+      return {
+        name, // Use the base name, not the file's internal name
+        isDark: relativeLuminance(bg0) < 0.5,
+        cssVars,
+      };
+    }
+  }
+
+  return null;
+}