In Prefect 3.x, set a flow-level timeout with the

timeout_seconds

argument on the flow:

from prefect import flow
import time

@flow(timeout_seconds=300)
def my_flow():
    time.sleep(600)

If the run exceeds that threshold, Prefect marks the flow run as Failed with a timeout error. You can also override it on a copied flow with `with_options()`:

from prefect import flow

@flow(timeout_seconds=300)
def my_flow():
    pass

fast_fail_flow = my_flow.with_options(timeout_seconds=60)
fast_fail_flow()

A couple of important notes: -

timeout_seconds

is in seconds - You can set timeouts on tasks too, separately from the flow - In Prefect 3.x, this is configured in Python on the flow definition; it’s not typically set as a deployment-only knob Example with both flow and task timeouts:

from prefect import flow, task
import time

@task(timeout_seconds=30)
def slow_task():
    time.sleep(100)

@flow(timeout_seconds=120)
def my_flow():
    slow_task()

If you want, I can also show: - how this behaves in a deployment - how to cancel or retry long-running flows - how to enforce this for all flows in a project pattern-wise