diff --git a/apps/lightcraft-web/index.html b/apps/lightcraft-web/index.html
index b088ad1..fa66781 100644
--- a/apps/lightcraft-web/index.html
+++ b/apps/lightcraft-web/index.html
@@ -22,23 +22,37 @@
   <div id="lightcraft_loading">Loading LightCraft…</div>
   <div id="lightcraft_status" aria-live="polite"></div>
   <script type="module">
-    import init, { start, command } from "./lightcraft_web.js";
+    import init, { start, command, install_chinese_font } from "./lightcraft_web.js";
     (async () => {
       // The Chinese font is a separate file: embedding it would exceed the host's WASM size limit.
       // Font-free development builds can still run, with the same missing-glyph warning as before.
-      const chineseFont = fetch("./lightcraft_zh_hans.otf")
-        .then(async response => response.ok ? new Uint8Array(await response.arrayBuffer()) : new Uint8Array())
-        .catch(() => new Uint8Array());
-      // Compile once; the render workers (worker.js) instantiate the same compiled module.
-      const [module, font] = await Promise.all([
-        WebAssembly.compileStreaming(fetch("./lightcraft_web_bg.wasm")),
-        chineseFont,
-      ]);
+      // The external CJK face is installed after the first usable UI frame.
+      const module = await WebAssembly.compileStreaming(fetch("./lightcraft_web_bg.wasm"));
       globalThis.lightcraftModule = module;
       await init({ module_or_path: module });
       // automation: `await lightcraft.command("library.info", "{}")` → JSON text
       globalThis.lightcraft = { command };
-      start(font);
+      start(new Uint8Array());
+      const fontStatus = document.createElement('div');
+      fontStatus.id = 'font-load-status';fontStatus.setAttribute('aria-live','polite');
+      fontStatus.style.cssText = 'position:fixed;right:12px;bottom:12px;font:12px system-ui;color:#ddd;background:#222;padding:6px 10px;border-radius:5px;z-index:20';
+      async function loadFont(){
+        document.body.append(fontStatus);fontStatus.textContent='Loading additional characters…';
+        try{
+          const response=await fetch('./lightcraft_zh_hans.otf',{priority:'low'});
+          if(!response.ok)throw new Error('font download failed');
+          install_chinese_font(new Uint8Array(await response.arrayBuffer()));
+          fontStatus.remove();document.documentElement.dataset.extraFont='ready';
+        }catch{
+          fontStatus.textContent='Additional font unavailable. ';
+          const retry=document.createElement('button');retry.textContent='Retry';retry.onclick=()=>loadFont();fontStatus.append(retry);
+        }
+      }
+      const readyTimer=setInterval(()=>{
+        if(document.getElementById('lightcraft_loading'))return;
+        clearInterval(readyTimer);
+        if('requestIdleCallback' in window)requestIdleCallback(loadFont,{timeout:1500});else setTimeout(loadFont,200);
+      },100);
     })().catch((e) => {
       console.error(e);
       const el = document.getElementById("lightcraft_loading");
diff --git a/apps/lightcraft-web/src/web.rs b/apps/lightcraft-web/src/web.rs
index 18c8963..1623c44 100644
--- a/apps/lightcraft-web/src/web.rs
+++ b/apps/lightcraft-web/src/web.rs
@@ -575,9 +575,21 @@ type Reply = (js_sys::Function, js_sys::Function);
 thread_local! {
     /// Commands from JavaScript ([`command`]), run on the next frame.
     static INBOX: std::cell::RefCell<Vec<(String, String, Reply)>> = const { std::cell::RefCell::new(Vec::new()) };
+    static LATE_FONT: std::cell::RefCell<Option<Vec<u8>>> = const { std::cell::RefCell::new(None) };
     static CTX: std::cell::RefCell<Option<egui::Context>> = const { std::cell::RefCell::new(None) };
 }
 
+/// Supply the optional font after startup. No document/library command is executed.
+#[wasm_bindgen]
+pub fn install_chinese_font(bytes: Vec<u8>) -> Result<(), JsValue> {
+    if bytes.len() > 24 * 1024 * 1024 || !bytes.starts_with(b"OTTO") {
+        return Err(JsValue::from_str("Invalid Chinese font asset"));
+    }
+    LATE_FONT.with(|font| *font.borrow_mut() = Some(bytes));
+    request_repaint();
+    Ok(())
+}
+
 /// Run a command by id from JavaScript (automation, tests): `await command("library.info", "{}")`
 /// resolves to the result as JSON text, or rejects with the error. Besides every engine/UI
 /// command, `web.stats` reports the browser host's state (storage, workers, originals in memory).
@@ -627,6 +639,9 @@ impl eframe::App for WebApp {
             let now = ctx.input(|i| i.time);
             self.app.ui.toast = Some((text, now + NOTICE_SECS, None));
         }
+        if let Some(bytes) = LATE_FONT.with(|font| font.borrow_mut().take()) {
+            self.app.install_web_chinese_font(bytes, ctx);
+        }
         self.run_inbox();
         self.import_dropped(ctx);
         self.load_originals(ctx);
@@ -672,7 +687,7 @@ pub fn start(chinese_font: Vec<u8>) {
     safety::install_panic_hook();
     log::info!("lightcraft: wasm instantiated at {:.0} ms", perf_now());
     if chinese_font.is_empty() {
-        log::warn!("lightcraft: no Simplified Chinese font supplied; Chinese-only glyphs will show as boxes");
+        log::warn!("lightcraft: Simplified Chinese font will be installed after startup");
     }
     let opts = Options::from_url();
     wasm_bindgen_futures::spawn_local(async move {
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 37fb86d..bdaecee 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -503,6 +503,18 @@ impl LightcraftApp {
         self
     }
 
+    /// Install the optional web CJK face without restarting or replacing the library.
+    pub fn install_web_chinese_font(&mut self, bytes: Vec<u8>, ctx: &egui::Context) {
+        if bytes.is_empty() {
+            return;
+        }
+        self.chinese_font = Some(std::sync::Arc::new(egui::FontData::from_owned(bytes)));
+        theme::install_fonts_with_chinese(ctx, self.chinese_font.as_ref());
+        self.font_language = self.ui.language;
+        self.fonts_ready = false;
+        ctx.request_repaint();
+    }
+
     pub fn with_control(mut self, rx: Receiver<ControlRequest>) -> Self {
         self.control_rx = Some(rx);
         // keep CPU copies of photo textures so `ui.screenshot {"headless": true}` can draw them