@Marvin How can make Prefect use uv instead of straight up python to run the function defined in my entrypoint? I want to make sure the venv is recreated before running

✅ thought for 459.1 seconds

what sort of worker are you using?

It's all set up in kubernetes. Our worker currently uses image

prefecthq/prefect:3.6.13-python3.11-kubernetes

. Is that what you were asking?

yep so each flow run executes on a pod, yea? ideally you should just use a custom

image

via deployment

job_variable

overrides of your k8s work pool

maybe it's because I don't know much about how Python resolves dependencies by I basically have the following repo structure:

if you have a claude at your disposal, you might have it use

tree

etc and poke around this repo: https://github.com/zzstoatzz/prefect-pack/tree/main with the

gh api

subgroup

project_root/
│
├── pyproject.toml
└── src/
    └── module_a/
    └── module_b/

and I need code in

module_a

to be used in

module_b

. I'm currently installing these when I build the image, but ideally I'd just get the most up-to-date code when I git clone as part of my usual Prefect workflow

are you using uv workspaces?

no, I'm not. Just doing

[tool.hatch.build.targets.wheel]
packages = [
    "...",
    "...",
]

Great question. In Prefect 3.x, the command that actually runs your flow is configurable per work pool or per deployment. To use uv instead of python, set the job variable

command

to run Prefect’s engine via uv, e.g.

uv run -m prefect.engine

. This makes the worker invoke uv, which can (re)create/refresh the environment before execution. Two common ways to do it: Option A — Set it at the work pool (affects all deployments on that pool) 1) Get and edit the base job template:

prefect work-pool get-default-base-job-template --type process --file process.json

In process.json, set the default for the command variable to:

"uv run -m prefect.engine"

Optionally add flags like

--refresh

or `--python 3.11`:

"uv run --refresh --python 3.11 -m prefect.engine"

Then update the pool:

prefect work-pool update my-process-pool --base-job-template process.json

Verify:

prefect work-pool inspect my-process-pool

Option B — Set it per deployment (no template editing) In your prefect.yaml:

deployments:
  - name: my-deployment
    entrypoint: flows/my_flow.py:my_flow
    work_pool:
      name: my-process-pool
      job_variables:
        command: "uv run --refresh -m prefect.engine"

Or in Python when deploying:

from prefect import flow

@flow
def my_flow():
    ...

my_flow.from_source(
    source="<https://github.com/your/repo.git>",
    entrypoint="flows/my_flow.py:my_flow"
).deploy(
    name="my-deployment",
    work_pool_name="my-process-pool",
    job_variables={"command": "uv run --refresh -m prefect.engine"}
)

Notes - Make sure

uv

is available on PATH wherever your worker runs. - The

command

string is executed as-is; Prefect defaults to

python -m prefect.engine

only when

command

is unset. - If you want to strictly re-resolve/install before every run, consider

--refresh

with uv. Adjust flags to your project’s setup (e.g.,

--python

, using a lockfile, etc.). Helpful docs: - Manage work pools - Customize job variables - Customize base job templates - Process worker API - Work pool CLI Quick question to confirm: are you using the Process worker, or another worker type (Docker/Kubernetes)? The same approach works for other workers via their base job template, but I can tailor the exact steps if you share which one you’re using.

omg I hope Marvin isn't hallucinating, this would be great

yea marvin is on the right track here

I couldn't get this to work 😔 but it's fine, I can work around it. The Prefect pack repo looks great! I'll compare with our usual workflows to see what we can copy.