feat: Integrate WebSocket Gateway into API-based task launch

- Gateway now starts automatically when calling POST /runtime/start
- No need to run python backend/main.py separately
- Single service architecture: only FastAPI (port 8000) needed
- Gateway runs in background task and stops with pipeline
- Add error handling and logging for Gateway lifecycle

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/core/pipeline_runner.py

@@ -33,10 +33,33 @@ from backend.runtime.manager import (
 )
 from backend.services.market import MarketService
 from backend.services.storage import StorageService
+from backend.services.gateway import Gateway
 from backend.utils.settlement import SettlementCoordinator
 
 _prompt_loader = PromptLoader()
 
+# Global gateway reference for cleanup
+_gateway_instance: Optional[Gateway] = None
+
+
+def _set_gateway(gateway: Optional[Gateway]) -> None:
+    """Set global gateway reference."""
+    global _gateway_instance
+    _gateway_instance = gateway
+
+
+def stop_gateway() -> None:
+    """Stop the running gateway if exists."""
+    global _gateway_instance
+    if _gateway_instance is not None:
+        try:
+            _gateway_instance.stop()
+        except Exception as e:
+            import logging
+            logging.getLogger(__name__).error(f"Error stopping gateway: {e}")
+        finally:
+            _gateway_instance = None
+
 
 async def create_long_term_memory(agent_name: str, run_id: str, run_dir: Path):
     """Create ReMeTaskLongTermMemory for an agent."""
@@ -321,12 +344,45 @@ async def run_pipeline(
 
             scheduler_callback = scheduler_callback_fn
 
+        # Create Gateway for WebSocket connections (after pipeline and scheduler are ready)
+        gateway = Gateway(
+            market_service=market_service,
+            storage_service=storage_service,
+            pipeline=pipeline,
+            scheduler_callback=scheduler_callback,
+            config={
+                "mode": mode,
+                "mock_mode": is_mock,
+                "backtest_mode": is_backtest,
+                "tickers": tickers,
+                "config_name": run_id,
+                "schedule_mode": schedule_mode,
+                "interval_minutes": interval_minutes,
+                "trigger_time": trigger_time,
+                "initial_cash": initial_cash,
+                "margin_requirement": margin_requirement,
+                "max_comm_cycles": max_comm_cycles,
+                "enable_memory": enable_memory,
+            },
+            scheduler=live_scheduler,
+        )
+        _set_gateway(gateway)
+
         # Start pipeline execution
         async with AsyncExitStack() as stack:
             # Enter long-term memory contexts
             for memory in long_term_memories:
                 await stack.enter_async_context(memory)
 
+            # Start Gateway in background task
+            gateway_task = asyncio.create_task(
+                gateway.start(host="0.0.0.0", port=8765)
+            )
+            logger.info("[Pipeline] Gateway started on ws://localhost:8765")
+
+            # Give Gateway a moment to start
+            await asyncio.sleep(0.5)
+
             # Define the trading cycle callback
             async def trading_cycle(session_key: str) -> None:
                 """Execute one trading cycle."""
@@ -360,12 +416,30 @@ async def run_pipeline(
             while not stop_event.is_set():
                 await asyncio.sleep(1)
 
+            # Cancel gateway task
+            if not gateway_task.done():
+                gateway_task.cancel()
+                try:
+                    await gateway_task
+                except asyncio.CancelledError:
+                    pass
+
     except asyncio.CancelledError:
         # Handle cancellation gracefully
         raise
     finally:
         # Cleanup
+        logger.info("[Pipeline] Cleaning up...")
+
+        # Stop Gateway
+        try:
+            stop_gateway()
+            logger.info("[Pipeline] Gateway stopped")
+        except Exception as e:
+            logger.error(f"[Pipeline] Error stopping gateway: {e}")
+
         clear_shutdown_event()
         clear_global_runtime_manager()
         from backend.api.runtime import unregister_runtime_manager
         unregister_runtime_manager()
+        logger.info("[Pipeline] Cleanup complete")

backend/services/gateway.py

@@ -238,6 +238,8 @@ class Gateway:
             self.connected_clients.discard(websocket)
 
     async def _send_initial_state(self, websocket: ServerConnection):
+        try:
+            logger.info("[Gateway] Sending initial state to client...")
             state_payload = self.state_sync.get_initial_state_payload(
                 include_dashboard=True,
             )
@@ -262,6 +264,19 @@ class Gateway:
                     default=str,
                 ),
             )
+            logger.info("[Gateway] Initial state sent successfully")
+        except Exception as e:
+            logger.exception(f"[Gateway] Failed to send initial state: {e}")
+            # Send error response so client knows something went wrong
+            try:
+                await websocket.send(
+                    json.dumps(
+                        {"type": "error", "message": "Failed to load initial state"},
+                        ensure_ascii=False,
+                    ),
+                )
+            except Exception:
+                pass
 
     async def _handle_client_messages(
         self,