Defer schedule catchup window default to server

CHANGELOG.md

@@ -28,6 +28,9 @@ to include examples, links to docs, or any other relevant information.
 
 ### Fixed
 
+- Schedule policies now omit an unspecified catch-up window so the Temporal Server applies its
+  default (currently one year).
+
 ### Security
 
 ## [1.30.0] - 2026-07-01

temporalio/client/_schedule.py

@@ -956,9 +956,13 @@ class SchedulePolicy:
     """Controls what happens when an action is started while another is still
     running."""
 
-    catchup_window: timedelta = timedelta(days=365)
+    catchup_window: timedelta | None = None
     """After a Temporal server is unavailable, amount of time in the past to
-    execute missed actions."""
+    execute missed actions.
+
+    If unset, this is omitted so the Temporal Server applies its default
+    (currently one year).
+    """
 
     pause_on_failure: bool = False
     """Whether to pause the schedule if an action fails or times out.
@@ -971,20 +975,24 @@ class SchedulePolicy:
     def _from_proto(pol: temporalio.api.schedule.v1.SchedulePolicies) -> SchedulePolicy:
         return SchedulePolicy(
             overlap=ScheduleOverlapPolicy(int(pol.overlap_policy)),
-            catchup_window=pol.catchup_window.ToTimedelta(),
+            catchup_window=(
+                pol.catchup_window.ToTimedelta()
+                if pol.HasField("catchup_window")
+                else None
+            ),
             pause_on_failure=pol.pause_on_failure,
         )
 
     def _to_proto(self) -> temporalio.api.schedule.v1.SchedulePolicies:
-        catchup_window = google.protobuf.duration_pb2.Duration()
-        catchup_window.FromTimedelta(self.catchup_window)
-        return temporalio.api.schedule.v1.SchedulePolicies(
+        ret = temporalio.api.schedule.v1.SchedulePolicies(
             overlap_policy=temporalio.api.enums.v1.ScheduleOverlapPolicy.ValueType(
                 self.overlap
             ),
-            catchup_window=catchup_window,
             pause_on_failure=self.pause_on_failure,
         )
+        if self.catchup_window is not None:
+            ret.catchup_window.FromTimedelta(self.catchup_window)
+        return ret
 
 
 @dataclass
@@ -1060,8 +1068,6 @@ def _from_proto(sched: temporalio.api.schedule.v1.Schedule) -> Schedule:
         )
 
     async def _to_proto(self, client: Client) -> temporalio.api.schedule.v1.Schedule:
-        catchup_window = google.protobuf.duration_pb2.Duration()
-        catchup_window.FromTimedelta(self.policy.catchup_window)
         return temporalio.api.schedule.v1.Schedule(
             spec=self.spec._to_proto(),
             action=await self.action._to_proto(client),

tests/test_client.py

@@ -837,6 +837,15 @@ def test_history_from_json():
     )
 
 
+def test_schedule_policy_default_catchup_window_is_omitted():
+    policy = SchedulePolicy()
+    assert policy.catchup_window is None
+    assert not policy._to_proto().HasField("catchup_window")
+
+    policy.catchup_window = timedelta(minutes=5)
+    assert policy._to_proto().catchup_window.ToTimedelta() == timedelta(minutes=5)
+
+
 async def test_schedule_basics(
     client: Client, worker: ExternalWorker, env: WorkflowEnvironment
 ):
@@ -987,12 +996,15 @@ def update_fail(_input: ScheduleUpdateInput) -> ScheduleUpdate:
         state=ScheduleState(paused=True),
     )
     assert isinstance(new_schedule.action, ScheduleActionStartWorkflow)
+    assert new_schedule.policy.catchup_window is None
 
     async def update_schedule_basic(_input: ScheduleUpdateInput) -> ScheduleUpdate:
         return ScheduleUpdate(new_schedule)
 
     await handle.update(update_schedule_basic)
     desc = await handle.describe()
+    assert desc.schedule.policy.catchup_window == timedelta(days=365)
+    new_schedule.policy.catchup_window = timedelta(days=365)
     new_schedule.action.args = await DataConverter.default.encode(
         new_schedule.action.args
     )