diff --git a/web/src/js/editor/format.js b/web/src/js/editor/format.js
index 4fe0530..8a83840 100644
--- a/web/src/js/editor/format.js
+++ b/web/src/js/editor/format.js
@@ -4,9 +4,9 @@ const format = document.getElementById('format');
 
 format.addEventListener(
   'click',
-  (e) => {
+  async (e) => {
     e.preventDefault();
-    Command.format();
+    await Command.format();
   },
   false,
 );
diff --git a/web/src/js/editor/index.js b/web/src/js/editor/index.js
index 7f86c91..24be9d9 100644
--- a/web/src/js/editor/index.js
+++ b/web/src/js/editor/index.js
@@ -10,9 +10,8 @@ import './codemirror-kcl';
 import { load, invokeKCLRun, invokeKCLFmt } from "@kcl-lang/wasm-lib";
 
 const response = await fetch("kcl.wasm");
-const inst = await load({
-  data: await response.arrayBuffer(),
-});
+const wasm = await response.arrayBuffer();
+const inst = await load({ data: wasm });
 const source = document.getElementById('source');
 const run = document.getElementById('run');
 const outputContainer = document.getElementById('output-container');
@@ -29,41 +28,89 @@ const editor = CodeMirror.fromTextArea(source, {
   smartIndent: true,
 });
 
-const playgroundOptions = {
-  'compileURL': '/-/play/compile',
-  'fmtURL': '/-/play/fmt',
-};
+function generateRandomString(length = 10) {
+  const characters = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
+  let result = '';
+  for (let i = 0; i < length; i++) {
+    result += characters.charAt(Math.floor(Math.random() * characters.length));
+  }
+  return result;
+}
 
-function getBackendUrl() {
-  var backendUrl = window.plutoEnv.BACKEND_URL;
-  if (/http:\/\/0.0.0.0/g.test(backendUrl)) {
-    var parts = backendUrl.split(":");
-    var port = parts[parts.length - 1];
+class Mutex {
+  constructor() {
+    this.queue = [];
+    this.locked = false;
+  }
 
-    var protocol = window.location.protocol;
-    var host = window.location.hostname;
-    backendUrl = `${protocol}//${host}:${port}`;
+  async lock() {
+    return new Promise((resolve) => {
+      if (!this.locked) {
+        this.locked = true;
+        resolve();
+      } else {
+        this.queue.push(resolve);
+      }
+    });
   }
-  return backendUrl;
-}
 
+  unlock() {
+    if (this.queue.length > 0) {
+      const next = this.queue.shift();
+      next();
+    } else {
+      this.locked = false;
+    }
+  }
+}
+const mutex = new Mutex();
 export const Command = {
-  set: (value) => {
-    editor.setValue(value);
+  async run() {
+    await mutex.lock();
+    try {
+      const code = editor.getValue();
+      const result = invokeKCLRun(inst, {
+        filename: generateRandomString() + ".k",
+        source: code,
+      });
+      if (result.startsWith("ERROR:")) {
+        Command.clear();
+        Command.print(result.replace(/^ERROR:\s*/, ''));
+      } else {
+        Command.clear();
+        Command.print(result);
+      }
+    } finally {
+      mutex.unlock();
+    }
   },
 
-  run: () => {
-    const code = Command.getValue()
-    const result = invokeKCLRun(inst, {
-      filename: "test.k",
-      source: code,
-    });
-    if (result.startsWith("ERROR:")) {
-      Command.clear();
-      Command.print(result.replace(/^ERROR:\s*/, ''));
-    } else {
-      Command.clear();
-      Command.print(result);
+  async format() {
+    await mutex.lock();
+    try {
+      const inst = await load({ data: wasm });
+      const code = editor.getValue();
+      const result = invokeKCLFmt(inst, {
+        source: code,
+      });
+      if (result.startsWith("ERROR:")) {
+        Command.clear();
+        Command.print(result.replace(/^ERROR:\s*/, ''));
+      } else {
+        Command.clear();
+        Command.print(result);
+      }
+    } finally {
+      mutex.unlock();
+    }
+  },
+  
+  async set(value) {
+    await mutex.lock();
+    try {
+      editor.setValue(value);
+    } finally {
+      mutex.unlock();
     }
   },
 
@@ -88,22 +135,9 @@ export const Command = {
     output.innerHTML = '';
     outputContainer.scrollTop = 0;
   },
-
-  format: () => {
-    const code = Command.getValue()
-    const result = invokeKCLFmt(inst, {
-      source: code,
-    });
-    if (result.startsWith("ERROR:")) {
-      Command.clear();
-      Command.print(result.replace(/^ERROR:\s*/, ''));
-    } else {
-      Command.clear();
-      Command.print(result);
-    }
-  },
 };
 
+editor.on("change", Command.run)
 const query = new window.URLSearchParams(window.location.search);
 
 if (query.has(SHARE_QUERY_KEY)) {
@@ -145,9 +179,9 @@ document.addEventListener(
 
 run.addEventListener(
   'click',
-  (e) => {
+  async (e) => {
     e.preventDefault();
-    Command.run();
+    await Command.run();
   },
   false,
 );
diff --git a/web/webpack.config.js b/web/webpack.config.js
index c560728..e518f09 100644
--- a/web/webpack.config.js
+++ b/web/webpack.config.js
@@ -1,5 +1,5 @@
 const path = require('path');
-const webpack = require("webpack");
+const webpack = require('webpack');
 const HtmlWebpackPlugin = require('html-webpack-plugin');
 const MiniCssExtractPlugin = require('mini-css-extract-plugin');
 const CopyWebpackPlugin = require('copy-webpack-plugin');
@@ -12,7 +12,7 @@ module.exports = {
   mode: IS_PRODUCTION ? 'production' : 'development',
 
   entry: path.resolve(__dirname, 'src/js/index.js'),
-  target: "web",
+  target: 'web',
 
   output: {
     path: DIST_PATH,
@@ -31,13 +31,13 @@ module.exports = {
       },
       {
         resourceQuery: /raw/,
-        type: "asset/source",
+        type: 'asset/source',
       },
       {
         resourceQuery: /wasm/,
-        type: "asset/resource",
+        type: 'asset/resource',
         generator: {
-          filename: "wasm/[name][ext]",
+          filename: 'wasm/[name][ext]',
         },
       },
     ],
@@ -65,18 +65,18 @@ module.exports = {
     }),
     // needed by @wasmer/wasi
     new webpack.ProvidePlugin({
-      Buffer: ["buffer", "Buffer"],
+      Buffer: ['buffer', 'Buffer'],
     }),
   ],
   externals: {
     // needed by @wasmer/wasi
-    "wasmer_wasi_js_bg.wasm": true,
+    'wasmer_wasi_js_bg.wasm': true,
   },
   resolve: {
     fallback: {
       // needed by @wasmer/wasi
-      buffer: require.resolve("buffer/"),
-      path: require.resolve("path-browserify"),
+      buffer: require.resolve('buffer/'),
+      path: require.resolve('path-browserify'),
     },
   },
 };