diff --git a/extensions/Helloworld/ScbackendSDK.js b/extensions/Helloworld/ScbackendSDK.js
new file mode 100644
index 00000000..dfd38c54
--- /dev/null
+++ b/extensions/Helloworld/ScbackendSDK.js
@@ -0,0 +1,237 @@
+// Name: Scbackend SDK
+// ID: scbackendsdk
+// Description: SDK for Scbackend
+// By: XQYWorld
+// Original: FurryR
+// License: MPL-2.0
+
+(() => {
+  // src/l10n/index.js
+  var l10n_default = {
+    zh: {
+      "scbackendsdk.connect": "\u8FDE\u63A5\u5230 [remaddr] \u670D\u52A1\u5668\u4E0A\u7684 [instname] \u5B9E\u4F8B",
+      "scbackendsdk.connectwait": "\u8FDE\u63A5\u5230 [remaddr] \u670D\u52A1\u5668\u7684 [instname] \u5B9E\u4F8B \u5E76\u7B49\u5F85\u8FDE\u63A5\u5B8C\u6210",
+      "scbackendsdk.disconnect": "\u65AD\u5F00\u8FDE\u63A5",
+      "scbackendsdk.isconnected": "\u5DF2\u8FDE\u63A5\uFF1F",
+      "scbackendsdk.send": "\u53D1\u9001\u6D88\u606F [msg]",
+      "scbackendsdk.whenmessage": "\u5F53\u6536\u5230\u6D88\u606F",
+      "scbackendsdk.getmsg": "\u6536\u5230\u7684\u6D88\u606F",
+      "scbackendsdk.ping": "\u5EF6\u8FDF(\u6BEB\u79D2)"
+    },
+    en: {
+      "scbackendsdk.connect": "Connect to [remaddr] server [instname] instance",
+      "scbackendsdk.connectwait": "Connect to [remaddr] server [instname] instance and wait",
+      "scbackendsdk.disconnect": "Disconnect",
+      "scbackendsdk.isconnected": "Is connected?",
+      "scbackendsdk.send": "Send message [msg]",
+      "scbackendsdk.whenmessage": "When message received",
+      "scbackendsdk.getmsg": "Received message",
+      "scbackendsdk.ping": "Ping (ms)"
+    }
+  };
+
+  // src/index.js
+  (function(Scratch2) {
+    if (Scratch2.extensions.unsandboxed === false) {
+      throw new Error("Sandboxed mode is not supported");
+    }
+    const translate = function(key) {
+      const locale = globalThis.navigator.language.slice(0, 2);
+      if (l10n_default[locale] && l10n_default[locale][key]) {
+        return l10n_default[locale][key];
+      } else {
+        return l10n_default["en"][key] || key;
+      }
+    };
+    class ScbackendSDK {
+      constructor() {
+        this.ws = null;
+        this.isopened = false;
+        this.delay = -1;
+      }
+      getInfo() {
+        return {
+          id: "scbackendsdk",
+          name: "Scbackend SDK",
+          blocks: [
+            {
+              blockType: Scratch2.BlockType.COMMAND,
+              opcode: "connect",
+              text: translate("scbackendsdk.connect"),
+              arguments: {
+                remaddr: {
+                  type: Scratch2.ArgumentType.STRING,
+                  defaultValue: "ws://localhost:3031"
+                },
+                instname: {
+                  type: Scratch2.ArgumentType.STRING,
+                  defaultValue: "test"
+                }
+              }
+            },
+            {
+              blockType: Scratch2.BlockType.COMMAND,
+              opcode: "connectwait",
+              text: translate("scbackendsdk.connectwait"),
+              arguments: {
+                remaddr: {
+                  type: Scratch2.ArgumentType.STRING,
+                  defaultValue: "ws://localhost:3031"
+                },
+                instname: {
+                  type: Scratch2.ArgumentType.STRING,
+                  defaultValue: "test"
+                }
+              }
+            },
+            {
+              blockType: Scratch2.BlockType.COMMAND,
+              opcode: "disconnect",
+              text: translate("scbackendsdk.disconnect")
+            },
+            {
+              blockType: Scratch2.BlockType.BOOLEAN,
+              opcode: "isconnected",
+              text: translate("scbackendsdk.isconnected")
+            },
+            {
+              blockType: Scratch2.BlockType.REPORTER,
+              opcode: "ping",
+              text: translate("scbackendsdk.ping")
+            },
+            {
+              blockType: Scratch2.BlockType.COMMAND,
+              opcode: "send",
+              text: translate("scbackendsdk.send"),
+              arguments: {
+                msg: {
+                  type: Scratch2.ArgumentType.STRING,
+                  defaultValue: "Hello, world!"
+                }
+              }
+            },
+            {
+              blockType: Scratch2.BlockType.EVENT,
+              opcode: "whenmessage",
+              text: translate("scbackendsdk.whenmessage"),
+              isEdgeActivated: false
+            },
+            {
+              blockType: Scratch2.BlockType.REPORTER,
+              opcode: "getmsg",
+              text: translate("scbackendsdk.getmsg")
+            }
+          ]
+        };
+      }
+      _doconnect(remaddr, dst, util, resolve, reject) {
+        let attempts = 0;
+        const maxAttempts = 5;
+        const connectWS = () => {
+          if (this.isopened) return;
+          this.ws = new WebSocket(remaddr);
+          let interval;
+          this.ws.onopen = () => {
+            this.ws.send(JSON.stringify({ type: "handshake", dst: dst.toString() }));
+          };
+          this.ws.onmessage = (event) => {
+            const msg = event.data;
+            const data = JSON.parse(msg);
+            switch (data.type) {
+              case "handshake":
+                if (data.status === "ok") {
+                  this.isopened = true;
+                  this.sessionid = data.sessionId;
+                  interval = setInterval(() => {
+                    if (this.ws && this.isopened) {
+                      this.dtimer = Date.now();
+                      this.ws.send(JSON.stringify({ type: "ping" }));
+                    }
+                  }, 5e3);
+                  if (resolve) resolve();
+                } else {
+                  this.ws.close();
+                  this.ws = null;
+                  this.isopened = false;
+                  attempts++;
+                  if (attempts < maxAttempts) {
+                    setTimeout(connectWS, 1e3);
+                  } else {
+                    util.startHats("scbackendsdk_whenerror");
+                    if (reject) reject(new Error("Handshake failed"));
+                  }
+                }
+                break;
+              case "message":
+                util.startHats("scbackendsdk_whenmessage").forEach((t) => {
+                  t.initParams();
+                  t.pushParam("data", data.message);
+                });
+                break;
+              case "pong":
+                this.delay = Date.now() - this.dtimer;
+                break;
+            }
+          };
+          this.ws.onclose = (event) => {
+            let isopened = this.isopened;
+            this.ws = null;
+            this.isopened = false;
+            if (isopened) return;
+            attempts++;
+            if (attempts < maxAttempts) {
+              setTimeout(connectWS, 1e3);
+            } else {
+              util.startHats("scbackendsdk_whenerror");
+              if (reject) reject(event);
+            }
+          };
+          this.ws.onerror = (error) => {
+            attempts++;
+            if (attempts < maxAttempts) {
+              setTimeout(connectWS, 1e3);
+            } else {
+              util.startHats("scbackendsdk_whenerror");
+              if (reject) reject(error);
+            }
+          };
+        };
+        connectWS();
+      }
+      connect(args, util) {
+        if (this.ws) {
+          this.ws.close();
+          this.ws = null;
+          this.isopened = false;
+        }
+        this._doconnect(args.remaddr, args.instname, util);
+      }
+      connectwait(args, util) {
+        return new Promise((resolve, reject) => {
+          this._doconnect(args.remaddr, args.instname, util, resolve, reject);
+        });
+      }
+      disconnect() {
+        if (this.ws) {
+          this.ws.close();
+          this.ws = null;
+        }
+      }
+      isconnected() {
+        return this.isopened;
+      }
+      ping() {
+        return this.delay;
+      }
+      send(args) {
+        if (this.ws && this.isopened) {
+          this.ws.send(JSON.stringify({ type: "message", body: args.msg }));
+        }
+      }
+      getmsg(_args, util) {
+        return util.thread.getParam("data") || "";
+      }
+    }
+    Scratch2.extensions.register(new ScbackendSDK());
+  })(Scratch);
+})();