Update engine

app/main.py

@@ -24,7 +24,6 @@ from core.transports import SocketTransport, WebRtcTransport, BaseTransport
 from core.session import Session
 from processors.tracks import Resampled16kTrack
 from core.events import get_event_bus, reset_event_bus
-from models.ws_v1 import ev
 
 # Check interval for heartbeat/timeout (seconds)
 _HEARTBEAT_CHECK_INTERVAL_SEC = 5
@@ -54,9 +53,7 @@ async def heartbeat_and_timeout_task(
             break
         if now - last_heartbeat_at[0] >= heartbeat_interval_sec:
             try:
-                await transport.send_event({
-                    **ev("heartbeat"),
-                })
+                await session.send_heartbeat()
                 last_heartbeat_at[0] = now
             except Exception as e:
                 logger.debug(f"Session {session_id}: heartbeat send failed: {e}")