diff --git a/web/ui/app.js b/web/ui/app.js
index bcff449d..93f71ee8 100644
--- a/web/ui/app.js
+++ b/web/ui/app.js
@@ -1,4 +1,12 @@
 const collapsedWorkspacesStorageKey = "openpi.collapsed-workspaces";
+const languageStorageKey = "openpi.language";
+function readLanguage() {
+  try {
+    const value = localStorage.getItem(languageStorageKey);
+    if (value === "en" || value === "zh") return value;
+  } catch {}
+  return navigator.language?.toLowerCase().startsWith("zh") ? "zh" : "en";
+}
 function readCollapsedWorkspaces() {
   try {
     const value = JSON.parse(sessionStorage.getItem(collapsedWorkspacesStorageKey) || "[]");
@@ -32,7 +40,7 @@ const state = {
   liveRetry: null,
   query: "",
   selectedWorkspace: null,
-  language: navigator.language?.toLowerCase().startsWith("zh") ? "zh" : "en",
+  language: readLanguage(),
 };
 
 const translations = {
@@ -125,6 +133,12 @@ function applyLanguage() {
   }
 }
 
+function toggleLanguage() {
+  state.language = state.language === "zh" ? "en" : "zh";
+  try { localStorage.setItem(languageStorageKey, state.language); } catch {}
+  applyLanguage();
+}
+
 const $ = (id) => document.getElementById(id);
 const tokenStorageKey = "openpi.web.token";
 const fragmentToken = new URLSearchParams(location.hash.slice(1)).get("token");
@@ -1395,4 +1409,5 @@ $("prompt-input")?.addEventListener("keydown", (event) => {
 });
 
 applyLanguage();
+$("language-toggle")?.addEventListener("click", toggleLanguage);
 void connectEvents();
diff --git a/web/ui/index.html b/web/ui/index.html
index 7aa60047..cbc4799f 100644
--- a/web/ui/index.html
+++ b/web/ui/index.html
@@ -85,6 +85,7 @@
             <strong data-i18n="newSession">New session</strong>
             <small data-i18n="chooseWorkspaceHint">Choose a workspace and describe the work</small>
           </div>
+          <button id="language-toggle" class="icon-button" type="button" aria-label="切换语言" title="切换语言">文</button>
           <span id="connection-state" class="connection-state" aria-live="polite">Connecting</span>
         </header>