diff --git a/tests/test_activity.py b/tests/test_activity.py
index a5682f221..53ffe835e 100644
--- a/tests/test_activity.py
+++ b/tests/test_activity.py
@@ -752,7 +752,7 @@ async def test_manual_completion(client: Client, env: WorkflowEnvironment):
         ActivityInput(event_workflow_id=event_workflow_id),
         id=activity_id,
         task_queue=task_queue,
-        start_to_close_timeout=timedelta(seconds=5),
+        start_to_close_timeout=timedelta(minutes=1),
     )
 
     async with Worker(
@@ -794,7 +794,7 @@ async def test_manual_cancellation(client: Client, env: WorkflowEnvironment):
         ActivityInput(event_workflow_id=event_workflow_id),
         id=activity_id,
         task_queue=task_queue,
-        start_to_close_timeout=timedelta(seconds=5),
+        start_to_close_timeout=timedelta(minutes=1),
     )
 
     async with Worker(
@@ -855,7 +855,7 @@ async def test_manual_failure(client: Client, env: WorkflowEnvironment):
         ActivityInput(event_workflow_id=event_workflow_id),
         id=activity_id,
         task_queue=task_queue,
-        start_to_close_timeout=timedelta(seconds=5),
+        start_to_close_timeout=timedelta(minutes=1),
     )
     async with Worker(
         client,
@@ -932,7 +932,7 @@ async def test_manual_heartbeat(client: Client, env: WorkflowEnvironment):
         ),
         id=activity_id,
         task_queue=task_queue,
-        start_to_close_timeout=timedelta(seconds=5),
+        start_to_close_timeout=timedelta(minutes=1),
     )
     wait_for_activity_start_wf_handle = await client.start_workflow(
         EventWorkflow.wait,
diff --git a/tests/worker/test_workflow.py b/tests/worker/test_workflow.py
index d751fdb8b..dcb71a231 100644
--- a/tests/worker/test_workflow.py
+++ b/tests/worker/test_workflow.py
@@ -947,7 +947,7 @@ async def run(self, params: CancelActivityWorkflowParams) -> None:
         if params.local:
             handle = workflow.start_local_activity_method(
                 ActivityWaitCancelNotify.wait_cancel,
-                schedule_to_close_timeout=timedelta(seconds=5),
+                schedule_to_close_timeout=timedelta(minutes=1),
                 cancellation_type=workflow.ActivityCancellationType[
                     params.cancellation_type
                 ],
@@ -956,7 +956,7 @@ async def run(self, params: CancelActivityWorkflowParams) -> None:
             handle = workflow.start_activity_method(
                 ActivityWaitCancelNotify.wait_cancel,
                 schedule_to_close_timeout=timedelta(seconds=5),
-                heartbeat_timeout=timedelta(seconds=1),
+                heartbeat_timeout=timedelta(seconds=5),
                 cancellation_type=workflow.ActivityCancellationType[
                     params.cancellation_type
                 ],
@@ -977,14 +977,24 @@ def activity_result(self) -> str:
 
 @pytest.mark.parametrize("local", [True, False])
 async def test_workflow_cancel_activity(client: Client, local: bool):
-    # Need short task timeout to timeout LA task and longer assert timeout
-    # so the task can timeout
-    task_timeout = timedelta(seconds=1)
-    assert_timeout = timedelta(seconds=10)
+    # Core completes the task holding a local activity at 80% of this timeout, and
+    # the cancel reaches the activity on the second such cycle (~8s), so the assert
+    # budget needs headroom beyond that on loaded runners
+    task_timeout = timedelta(seconds=5)
+    assert_timeout = timedelta(seconds=30)
     activity_inst = ActivityWaitCancelNotify()
 
+    async def wait_cancel_complete() -> None:
+        await asyncio.wait_for(
+            activity_inst.wait_cancel_complete.wait(), assert_timeout.total_seconds()
+        )
+        activity_inst.wait_cancel_complete.clear()
+
     async with new_worker(
-        client, CancelActivityWorkflow, activities=[activity_inst.wait_cancel]
+        client,
+        CancelActivityWorkflow,
+        activities=[activity_inst.wait_cancel],
+        max_heartbeat_throttle_interval=timedelta(milliseconds=300),
     ) as worker:
         # Try cancel - confirm error and activity was sent the cancel
         handle = await client.start_workflow(
@@ -1004,7 +1014,7 @@ async def activity_result() -> str:
         await assert_eq_eventually(
             "Error: CancelledError", activity_result, timeout=assert_timeout
         )
-        await activity_inst.wait_cancel_complete.wait()
+        await wait_cancel_complete()
         await handle.cancel()
 
         # Wait cancel - confirm no error due to graceful cancel handling
@@ -1023,7 +1033,7 @@ async def activity_result() -> str:
             activity_result,
             timeout=assert_timeout,
         )
-        await activity_inst.wait_cancel_complete.wait()
+        await wait_cancel_complete()
         await handle.cancel()
 
         # Abandon - confirm error and that activity stays running
@@ -1043,7 +1053,7 @@ async def activity_result() -> str:
         await asyncio.sleep(0.5)
         assert not activity_inst.wait_cancel_complete.is_set()
         await handle.cancel()
-        await activity_inst.wait_cancel_complete.wait()
+        await wait_cancel_complete()
 
 
 @workflow.defn