Thanks for the details. In Prefect 3.x there is no

prefect.engine

module — that was part of older Prefect internals. The error means something (your code or a dependency) is trying to import

prefect.engine

, which will fail on 3.4.18. Common causes and fixes: - You (or a library) have a 2.x-era import like

import prefect.engine

or

from prefect.engine...

. Remove or update these — user code in 3.x should not import engine internals. - Mixing environments (e.g., running

prefect server start

with one interpreter and running your flow with another) so the wrong set of packages is being used. - Old Prefect 2.x “collections” (prefect-aws, prefect-docker, etc.) still installed. In Prefect 3.x these moved into extras; older packages can import old paths. Quick checks 1) Verify what Prefect you’re importing when your script runs:

python -c "import prefect, sys; print(prefect.__version__, prefect.__file__, sys.executable)"

2) Make sure your flow code doesn’t import engine internals. A minimal working example in 3.x:

from prefect import flow, task, get_run_logger

@task
def say_hi(name: str):
    logger = get_run_logger()
    <http://logger.info|logger.info>(f"Hi, {name}!")

@flow
def my_flow():
    say_hi("world")

if __name__ == "__main__":
    my_flow.serve(name="demo")  # or my_flow()

3) Check for old packages and upgrade/uninstall as needed:

pip freeze | grep -i prefect
# If you see prefect-aws / prefect-docker / prefect-kubernetes, uninstall them:
pip uninstall -y prefect-aws prefect-docker prefect-kubernetes

# Ensure Prefect 3 is current
pip install -U "prefect>=3.4,<4"

# If you need integrations, install extras (example):
pip install -U "prefect[aws]" "prefect[docker]" "prefect[kubernetes]"

4) Make sure there’s no local shadowing: - No file/folder named

prefect

in your project. - Run

which prefect

(or

where prefect

on Windows) and confirm it’s from the same environment you use to run your script. If the error persists, could you paste the full traceback? That will show exactly which import is trying to load

prefect.engine

and we can pinpoint the source. References: - Prefect 3.x docs - Prefect 3 GA announcement