diff --git a/server/client_session.py b/server/client_session.py
index 399abec..f1e0e7b 100644
--- a/server/client_session.py
+++ b/server/client_session.py
@@ -5,10 +5,13 @@ import threading
 from dataclasses import dataclass, field
 from typing import Any
 
+from packet_codec import EncodedPacket
+from tcp_transport import send_message
+
 
 @dataclass
 class ClientSession:
-    connection: socket.socket
+    connection: Any
     address: tuple[str, int]
     player_id: int
     connected_at: float
@@ -61,6 +64,20 @@ class ClientSession:
         with self._send_lock:
             self.connection.sendall(payload)
 
+    def send_packet(self, encoded: EncodedPacket) -> None:
+        """Send one already-serialized protocol message through the active transport.
+
+        TCP compatibility adds its newline delimiter here. Message-oriented
+        transports can expose ``send_encoded`` and receive the raw JSON payload
+        plus its delivery policy without TCP framing leaking into the protocol.
+        """
+        with self._send_lock:
+            send_encoded = getattr(self.connection, "send_encoded", None)
+            if callable(send_encoded):
+                send_encoded(encoded)
+                return
+            send_message(self.connection, encoded.payload)
+
     def to_snapshot(self) -> dict[str, Any]:
         with self._lock:
             return {