diff --git a/package.json b/package.json
index cc26a59..f9dbef2 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@appwrite.io/synapse",
-  "version": "0.4.0",
+  "version": "0.4.1",
   "description": "Operating system gateway for remote serverless environments",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/src/synapse.ts b/src/synapse.ts
index 9fa1729..16b7c4d 100644
--- a/src/synapse.ts
+++ b/src/synapse.ts
@@ -22,7 +22,16 @@ export type MessageHandler = (
   message: MessagePayload,
   connectionId: string,
 ) => void;
+
 export type ConnectionCallback = (connectionId: string) => void;
+
+export type ConnectionCloseCallback = (
+  connectionId: string,
+  code?: number,
+  reason?: string,
+  wasClean?: boolean,
+) => void;
+
 export type ErrorCallback = (error: Error, connectionId: string) => void;
 export type ServerConnectionCallback = (connectionId: string) => void;
 export type Logger = (message: string) => void;
@@ -33,7 +42,7 @@ class Synapse {
   private messageHandlers: Record<string, MessageHandler> = {};
   private connectionListeners = {
     onOpen: (() => {}) as ConnectionCallback,
-    onClose: (() => {}) as ConnectionCallback,
+    onClose: (() => {}) as ConnectionCloseCallback,
     onError: (() => {}) as ErrorCallback,
   };
 
@@ -112,8 +121,13 @@ class Synapse {
 
     ws.onmessage = (event) => this.handleMessage(event, connectionId);
 
-    ws.onclose = () => {
-      this.connectionListeners.onClose(connectionId);
+    ws.onclose = (event) => {
+      this.connectionListeners.onClose(
+        connectionId,
+        event.code,
+        event.reason,
+        event.wasClean,
+      );
       this.attemptReconnect(connectionId);
     };
 
@@ -440,10 +454,10 @@ class Synapse {
 
   /**
    * Registers a callback for when a WebSocket connection is closed
-   * @param callback - Function to be called when connection closes
+   * @param callback - Function to be called when connection closes. Receives (connectionId, code, reason)
    * @returns The Synapse instance for method chaining
    */
-  onClose(callback: ConnectionCallback): Synapse {
+  onClose(callback: ConnectionCloseCallback): Synapse {
     this.connectionListeners.onClose = callback;
     return this;
   }
diff --git a/tests/synapse.test.ts b/tests/synapse.test.ts
index cb6f0ca..33c9056 100644
--- a/tests/synapse.test.ts
+++ b/tests/synapse.test.ts
@@ -62,6 +62,28 @@ describe("Synapse", () => {
 
       await expect(connectPromise).rejects.toThrow("WebSocket error");
     });
+
+    it("should call onClose with code, reason, and wasClean", () => {
+      const mockWs = createMockWebSocket();
+      (WebSocket as unknown as jest.Mock).mockImplementation(() => mockWs);
+
+      const onCloseMock = jest.fn();
+      synapse.onClose(onCloseMock);
+
+      // Use the real setup method so event handlers are set
+      (synapse as any).setupWebSocket(mockWs, { url: "/" }, "conn1");
+
+      // Simulate close event
+      const closeEvent = { code: 4001, reason: "Test reason", wasClean: true };
+      mockWs.onclose && mockWs.onclose(closeEvent as any);
+
+      expect(onCloseMock).toHaveBeenCalledWith(
+        "conn1",
+        4001,
+        "Test reason",
+        true,
+      );
+    });
   });
 
   describe("message handling", () => {