diff --git a/.gitignore b/.gitignore
index efc7d5c..f6ed60d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,6 +30,7 @@ app
 *.tar
 
 dist_backend
+dist_backend_node
 .pilot
 
 verify_font_baseline
diff --git a/backend/app.ts b/backend/app.ts
index c052016..959c77d 100644
--- a/backend/app.ts
+++ b/backend/app.ts
@@ -1,3 +1,10 @@
+/** 首先加载 fs 适配层，必须在所有其他导入之前！仅在 LLRT 运行时引入 */
+(() => {
+  if (typeof __RUNTIME__ !== "undefined" && __RUNTIME__ === "llrt") {
+    require("./server/llrt");
+  }
+})();
+
 import { mimeTypes } from "./server/mime_type";
 import type { cMiddleware } from "./server/req_res";
 import { SimpleHttpServer } from "./server/server";
@@ -15,8 +22,6 @@ import { handleFontMeta } from "./routes/font_meta";
 import { startTempCleaner } from "./temp_cleaner";
 import { initMemoryGate } from "./subset_queue";
 import { subsetConcurrency } from "./config";
-import "./server/node";
-import "./server/llrt";
 
 const ROOT_DIR = "dist";
 
diff --git a/backend/global.d.ts b/backend/global.d.ts
new file mode 100644
index 0000000..8872c3e
--- /dev/null
+++ b/backend/global.d.ts
@@ -0,0 +1,2 @@
+/** 构建时由 tsdown 注入的运行时标识 */
+declare const __RUNTIME__: "llrt" | "node";
\ No newline at end of file
diff --git a/backend/interface.ts b/backend/interface.ts
index fbd5ea5..c0bd98b 100644
--- a/backend/interface.ts
+++ b/backend/interface.ts
@@ -18,20 +18,34 @@ export let mkdir: (path: string) => Promise<void>;
 
 export let unlink: (path: string) => Promise<void>;
 
+/** LLRT 专用：保存 rm 函数引用，避免闭包问题 */
+let llrtRm: ((path: string) => Promise<void>) | undefined;
+
 export const implInterface = (options: {
   stat: typeof stat;
   readFile: typeof readFile;
   writeFile: typeof writeFile;
   readdir: typeof readdir;
   mkdir: typeof mkdir;
-  unlink: typeof unlink;
+  unlink?: typeof unlink;
+  /** LLRT 没有 unlink，提供 rm 作为替代 */
+  rm?: (path: string) => Promise<void>;
 }) => {
   stat = options.stat;
   readFile = options.readFile;
   writeFile = options.writeFile;
   readdir = options.readdir;
   mkdir = options.mkdir;
-  unlink = options.unlink;
+  // 保存 rm 引用到模块级变量
+  llrtRm = options.rm;
+  /** LLRT 的 fs/promises 没有 unlink，需要用 rm 代替 */
+  unlink = async (path) => {
+    if (options.unlink) {
+      await options.unlink(path);
+    } else if (llrtRm) {
+      await llrtRm(path);
+    }
+  };
 };
 
 export function path_join(...paths: string[]) {
diff --git a/backend/server/llrt.ts b/backend/server/llrt.ts
index 3c6ddc1..2c18982 100644
--- a/backend/server/llrt.ts
+++ b/backend/server/llrt.ts
@@ -1 +1,27 @@
 import "web-streams-polyfill/polyfill";
+import { implInterface } from "../interface";
+import * as fs from "fs/promises";
+
+/**
+ * LLRT 的 fs 适配层
+ *
+ * LLRT 的 fs.readdir 返回字符串数组，需要转换为 { name, isFile } 对象。
+ * LLRT 的 fs/promises 没有 unlink 方法，implInterface 中会自动用 rm 代替。
+ */
+implInterface({
+  stat: fs.stat,
+  readFile: fs.readFile,
+  writeFile: fs.writeFile,
+  async readdir(path) {
+    const names = await fs.readdir(path);
+    return Promise.all(
+      names.map(async (name) => {
+        const s = await fs.stat(`${path}/${name}`);
+        return { name, isFile: () => s.isFile() };
+      })
+    );
+  },
+  mkdir: (path) => fs.mkdir(path, { recursive: true }),
+  /** LLRT 没有 unlink，用箭头函数包装 rm 避免 this 问题 */
+  rm: (path: string) => fs.rm(path),
+});
diff --git a/scripts/build-backend.ts b/scripts/build-backend.ts
index c1524bc..280c38e 100644
--- a/scripts/build-backend.ts
+++ b/scripts/build-backend.ts
@@ -102,9 +102,9 @@ function runTsdown() {
 
 /** woff2 已使用纯 JS 实现（vendor/fonteditor-core/woff2/index.js），无需复制 wasm */
 
-/** 使用 LLRT compile 生成 .lrt 文件 */
+/** 使用 LLRT compile 生成 .lrt 文件（仅 LLRT 构建需要） */
 function runLlrtCompile() {
-  console.log("\n--- Running LLRT compile ---");
+  console.log("\n--- Running LLRT compile (LLRT only) ---");
   execSync(`${LLRT_BIN} compile ./dist_backend/app.cjs ./dist_backend/app.lrt`, {
     stdio: "inherit",
     cwd: ROOT_DIR,
diff --git a/tsconfig.node.json b/tsconfig.node.json
index 51cc05e..a2cf0a6 100644
--- a/tsconfig.node.json
+++ b/tsconfig.node.json
@@ -16,7 +16,8 @@
     "strict": true,
     "noUnusedLocals": true,
     "noUnusedParameters": true,
-    "noFallthroughCasesInSwitch": true
+    "noFallthroughCasesInSwitch": true,
+    "types": ["node"]
   },
   "include": [
     "vite.config.ts",
diff --git a/tsdown.config.ts b/tsdown.config.ts
index d951bd8..dc51339 100644
--- a/tsdown.config.ts
+++ b/tsdown.config.ts
@@ -5,12 +5,10 @@ import { readFileSync } from "node:fs";
 const packageVersion = JSON.parse(readFileSync(new URL("./package.json", import.meta.url), "utf8")).version;
 
 const shared = {
-  format: ["cjs"],
+  format: "cjs",
   clean: true,
   sourcemap: true,
   outDir: "dist_backend",
-  /** 构建期把 PACKAGE_VERSION 替换为字面量字符串，运行时无任何文件读取 */
-  define: { PACKAGE_VERSION: JSON.stringify(packageVersion) },
   outputOptions: {
     /** 禁用代码拆分，确保单文件输出（tsdown 默认会拆分大依赖为 chunk） */
     codeSplitting: false,
@@ -19,13 +17,30 @@ const shared = {
     /** 所有依赖都打进 bundle（LLRT scratch 镜像无 node_modules） */
     alwaysBundle: [/.*/],
   },
-};
+} as const;
 
 export default [
   defineConfig({
     ...shared,
+    /** LLRT 构建 */
+    define: {
+      PACKAGE_VERSION: JSON.stringify(packageVersion),
+      __RUNTIME__: JSON.stringify("llrt"),
+    },
     entry: ["backend/app.ts"],
   }),
+  defineConfig({
+    ...shared,
+    /** Node.js 构建（用于本地开发测试） */
+    define: {
+      PACKAGE_VERSION: JSON.stringify(packageVersion),
+      __RUNTIME__: JSON.stringify("node"),
+    },
+    /** 第二个配置不 clean，避免清掉第一个的输出 */
+    clean: false,
+    entry: ["backend/app.ts"],
+    outDir: "dist_backend_node",
+  }),
   defineConfig({
     ...shared,
     /** 第二个配置不 clean，避免清掉第一个的输出 */