use scope subprotocols

reflex/app.py

@@ -27,6 +27,7 @@ from typing import (
     Dict,
     Generic,
     List,
+    MutableMapping,
     Optional,
     Set,
     Type,
@@ -410,20 +411,16 @@ class App(MiddlewareMixin, LifespanMixin):
                 def __init__(self, app):
                     self.app = app
 
-                async def __call__(self, scope, receive, send):
+                async def __call__(
+                    self, scope: MutableMapping[str, Any], receive, send
+                ):
                     original_send = send
 
                     async def modified_send(message):
-                        headers = dict(scope["headers"])
-                        protocol_key = b"sec-websocket-protocol"
-                        if (
-                            message["type"] == "websocket.accept"
-                            and protocol_key in headers
-                            and isinstance(
-                                (subprotocol := headers[protocol_key]), bytes
-                            )
+                        if message["type"] == "websocket.accept" and (
+                            subprotocols := scope.get("subprotocols")
                         ):
-                            message["subprotocol"] = subprotocol.decode()
+                            message["subprotocol"] = subprotocols[0]
 
                         return await original_send(message)