fix: auto-start workers in TaskHandler context manager

src/conductor/client/automator/task_handler.py

@@ -331,9 +331,17 @@ def __init__(
         self._next_restart_at: List[float] = [0.0 for _ in self.workers]
         # Lock to protect process list during concurrent access (monitor thread vs main thread)
         self._process_lock = threading.Lock()
+        self._processes_started = False
         logger.info("TaskHandler initialized")
 
     def __enter__(self):
+        try:
+            self.start_processes()
+        except BaseException:
+            # __exit__ is not called if __enter__ raises, so clean up any
+            # partially-spawned workers here before propagating.
+            self.stop_processes()
+            raise
         return self
 
     def __exit__(self, exc_type, exc_value, traceback):
@@ -347,11 +355,14 @@ def stop_processes(self) -> None:
         with self._process_lock:
             self.__stop_task_runner_processes()
             self.__stop_metrics_provider_process()
+        self._processes_started = False
         logger.info("Stopped worker processes...")
         self.queue.put(None)
         self.logger_process.terminate()
 
     def start_processes(self) -> None:
+        if self._processes_started:
+            return
         logger.info("Starting worker processes...")
         freeze_support()
         self._monitor_stop_event.clear()
@@ -376,6 +387,7 @@ def start_processes(self) -> None:
             self.stop_processes()
             raise
         self.__start_monitor_thread()
+        self._processes_started = True
         logger.info("Started all processes")
 
     def join_processes(self) -> None:

tests/unit/automator/test_task_handler.py

@@ -57,8 +57,13 @@ def test_metrics_directory_cleaned_once_in_parent_init(self):
                 workers=[ClassWorker('task')],
                 metrics_settings=metrics_settings,
             )
-            with task_handler:
+            try:
+                # Assert before any processes are started — the mock on
+                # metrics_settings is not picklable, so we must not call
+                # start_processes() (which __enter__ now does automatically).
                 metrics_settings.clean_metrics_directory.assert_called_once_with()
+            finally:
+                task_handler.stop_processes()
 
 
 def _get_valid_task_handler():

tests/unit/automator/test_task_handler_coverage.py

@@ -663,12 +663,19 @@ def test_context_manager_enter(self, mock_process_class, mock_import, mock_loggi
 
     @patch('conductor.client.automator.task_handler._setup_logging_queue')
     @patch('importlib.import_module')
-    def test_context_manager_exit(self, mock_import, mock_logging):
+    @patch('conductor.client.automator.task_handler.Process')
+    def test_context_manager_exit(self, mock_process_class, mock_import, mock_logging):
         """Test context manager __exit__ method."""
         mock_queue = Mock()
         mock_logger_process = Mock()
         mock_logging.return_value = (mock_logger_process, mock_queue)
 
+        mock_process = Mock()
+        mock_process.terminate = Mock()
+        mock_process.kill = Mock()
+        mock_process.is_alive = Mock(return_value=False)
+        mock_process_class.return_value = mock_process
+
         worker = ClassWorker('test_task')
         handler = TaskHandler(
             workers=[worker],
@@ -679,10 +686,16 @@ def test_context_manager_exit(self, mock_import, mock_logging):
         # Override the queue and logger_process with fresh mocks
         handler.queue = Mock()
         handler.logger_process = Mock()
+        handler.logger_process.is_alive = Mock(return_value=False)
+        handler.metrics_provider_process = Mock()
+        handler.metrics_provider_process.terminate = Mock()
+        handler.metrics_provider_process.is_alive = Mock(return_value=False)
 
         # Mock terminate on all processes
         for process in handler.task_runner_processes:
             process.terminate = Mock()
+            process.kill = Mock()
+            process.is_alive = Mock(return_value=False)
 
         with handler:
             pass