[dashboard] Close WebSocket after process exit to prevent zombie connections (#13834)

esphome/dashboard/web_server.py

@@ -317,6 +317,7 @@ class EsphomeCommandWebSocket(CheckOriginMixin, tornado.websocket.WebSocketHandl
             # Check if the proc was not forcibly closed
             _LOGGER.info("Process exited with return code %s", returncode)
             self.write_message({"event": "exit", "code": returncode})
+            self.close()
 
     def on_close(self) -> None:
         # Check if proc exists (if 'start' has been run)

tests/dashboard/test_web_server.py

@@ -29,7 +29,7 @@ from esphome.dashboard.entries import (
     bool_to_entry_state,
 )
 from esphome.dashboard.models import build_importable_device_dict
-from esphome.dashboard.web_server import DashboardSubscriber
+from esphome.dashboard.web_server import DashboardSubscriber, EsphomeCommandWebSocket
 from esphome.zeroconf import DiscoveredImport
 
 from .common import get_fixture_path
@@ -1654,3 +1654,25 @@ async def test_websocket_check_origin_multiple_trusted_domains(
             assert data["event"] == "initial_state"
         finally:
             ws.close()
+
+
+def test_proc_on_exit_calls_close() -> None:
+    """Test _proc_on_exit sends exit event and closes the WebSocket."""
+    handler = Mock(spec=EsphomeCommandWebSocket)
+    handler._is_closed = False
+
+    EsphomeCommandWebSocket._proc_on_exit(handler, 0)
+
+    handler.write_message.assert_called_once_with({"event": "exit", "code": 0})
+    handler.close.assert_called_once()
+
+
+def test_proc_on_exit_skips_when_already_closed() -> None:
+    """Test _proc_on_exit does nothing when WebSocket is already closed."""
+    handler = Mock(spec=EsphomeCommandWebSocket)
+    handler._is_closed = True
+
+    EsphomeCommandWebSocket._proc_on_exit(handler, 0)
+
+    handler.write_message.assert_not_called()
+    handler.close.assert_not_called()