refactor: remove legacy assistant compatibility

backend/routes/voice_webrtc.py

@@ -63,24 +63,23 @@ async def _wait_for_pipeline_close(
 
 
 async def shutdown_active_sessions() -> None:
-    """Compatibility proxy; now drains RTVI and OpenAI Realtime sessions."""
+    """Drain RTVI and OpenAI Realtime sessions."""
     _http_peers.clear()
     await realtime_lifecycle.shutdown_active_sessions(
         timeout=PIPELINE_CLOSE_GRACE_SECONDS,
     )
 
 
-def _decode_client_tool_names(encoded: str | None) -> list[str] | None:
+def _decode_client_tool_names(encoded: str | None) -> list[str]:
     """Decode client capabilities carried outside the WebRTC SDP body.
 
     Pipecat's browser transport replaces the body of a ``Request`` endpoint
     with its SDP offer and drops ``APIRequest.requestData``. Request headers are
-    preserved, so they are the authoritative metadata channel for this path.
-    ``None`` means the header was absent and callers should use the legacy body.
+    preserved, so they are the single metadata channel for this path.
     """
 
     if encoded is None:
-        return None
+        return []
     try:
         padding = "=" * (-len(encoded) % 4)
         value = json.loads(
@@ -134,21 +133,16 @@ async def http_offer(request: Request, payload: dict = Body(...)):
         header_variables = json.loads(
             base64.urlsafe_b64decode(encoded_variables + padding).decode("utf-8")
         )
-    header_client_tools = _decode_client_tool_names(
+    client_tool_names = _decode_client_tool_names(
         request.headers.get("x-pipecat-client-tools")
     )
-    client_tool_names = (
-        header_client_tools
-        if header_client_tools is not None
-        else request_data.get("client_tool_names") or []
-    )
     logger.debug(f"WebRTC 客户端工具上报: {client_tool_names or '<none>'}")
     offer_payload = {
         **payload,
         "assistant_id": request.headers.get("x-pipecat-assistant-id"),
         "dynamic_variables": header_variables,
         **request_data,
-        # Keep header metadata authoritative when both paths are present.
+        # Client capabilities have one canonical transport: the request header.
         "client_tool_names": client_tool_names,
     }
     answer = await _handle_offer_payload(offer_payload, _http_peers)