diff --git a/core/huya/wss_client.py b/core/huya/wss_client.py
index 7b91b86..8fb9a6f 100644
--- a/core/huya/wss_client.py
+++ b/core/huya/wss_client.py
@@ -163,6 +163,19 @@ class HuyaWssClient:
             + HuyaWssClient._make_big_tail()
         )
 
+    @staticmethod
+    def _encode_activity_launch_body(wup_data: bytes) -> bytes:
+        """活动 wsLaunch 使用浏览器的固定大包头，即使包体小于 255B。"""
+        if len(wup_data) < 4:
+            return wup_data + TAIL_BYTES
+        packet_len = len(wup_data)
+        return (
+            bytes([packet_len & 0xFF])
+            + packet_len.to_bytes(4, "big")
+            + wup_data[4:]
+            + TAIL_BYTES
+        )
+
     @staticmethod
     def _normalize_biz_cookie(cookie: str) -> str:
         """业务 RPC 的 huya_ua Cookie 值按浏览器 WSS 抓包修正"""
@@ -398,7 +411,7 @@ class HuyaWssClient:
         wup.setRequestId(-1)
         wup.iTimeout = 0
         wup.newdata["tReq"] = os.get_bytes()
-        body = self._encode_rpc_body(wup.encode())
+        body = self._encode_activity_launch_body(wup.encode())
         msg = WssMessage(WssCommand.RPC_REQUEST, SEQ_ACTIVITY_WSLAUNCH, body)
         future = asyncio.Future()
         self.rpc_queue.append(future)