Python 3.14 adds InterpreterPoolExecutor, a subclass of ThreadPoolExecutor that runs tasks in isolated subinterpreters.
The Temporal Python SDK appears to assume ThreadPoolExecutor-like behavior in worker/_activity.py, which doesn’t hold for InterpreterPoolExecutor. Using it as an activity executor leads to the following errors:
concurrent.interpreters.NotShareableError: (Queue(2), <built-in method run of _contextvars.Context object at 0x1015fec00>, (<function _execute_sync_activity at 0x1014171c0>, Info(activity_id='61', activity_type='task', attempt=3, current_attempt_scheduled_time=datetime.datetime(2025, 10, 13, 9, 32, 51, 324811, tzinfo=datetime.timezone.utc), heartbeat_details=[], heartbeat_timeout=None, is_local=False, schedule_to_close_timeout=None, scheduled_time=datetime.datetime(2025, 10, 13, 9, 32, 47, 122424, tzinfo=datetime.timezone.utc), start_to_close_timeout=datetime.timedelta(seconds=36000), started_time=datetime.datetime(2025, 10, 13, 9, 32, 51, 692224, tzinfo=datetime.timezone.utc), task_queue='hello-task-queue', task_token=b'\n$0199c8e3-3716-7223-b18b-3a720150440f\x1231906eac1-8e34-4119-b7d5-0da5e8ffefd4-hello-workflow\x1a$0199dcea-4e2f-7cb2-bf9b-ef9859498ab6 A(\x032\x0261B\x04taskJ\x08\x08\x01\x10\x93\xb4A\x18\x01', workflow_id='1906eac1-8e34-4119-b7d5-0da5e8ffefd4-hello-workflow', workflow_namespace='default', workflow_run_id='0199dcea-4e2f-7cb2-bf9b-ef9859498ab6', workflow_type='GreetingWorkflow', priority=Priority(priority_key=None, fairness_key=None, fairness_weight=None), retry_policy=RetryPolicy(initial_interval=datetime.timedelta(seconds=1), backoff_coefficient=2.0, maximum_interval=datetime.timedelta(seconds=100), maximum_attempts=0, non_retryable_error_types=None)), <function _ActivityInboundImpl.execute_activity.<locals>.<lambda> at 0x1016381a0>, <temporalio.worker._activity._ThreadExceptionRaiser object at 0x10161df60>, <threading.Event at 0x101620fb0: unset>, <threading.Event at 0x10152d810: unset>, <temporalio.converter.DefaultPayloadConverter object at 0x1010e4c20>, <temporalio.common._NoopMetricMeter object at 0x100d9be00>, _ActivityCancellationDetailsHolder(details=None), <function task at 0x101529430>), {}) does not support cross-interpreter data
Python 3.14 adds InterpreterPoolExecutor, a subclass of ThreadPoolExecutor that runs tasks in isolated subinterpreters.
The Temporal Python SDK appears to assume ThreadPoolExecutor-like behavior in worker/_activity.py, which doesn’t hold for InterpreterPoolExecutor. Using it as an activity executor leads to the following errors: