That error is coming from the package parser when it encounters a semicolon in one of the entries you’ve put in

pip_packages

. In Prefect managed work pools (Prefect 3.x),

work_pool.job_variables.pip_packages

must be a list of simple, pip-installable specs (PEP 440) like

pandas

,

requests==2.31.0

,

numpy>=1.24

, etc. Environment markers (the

; ...

part from PEP 508) are not supported in

pip_packages

, which is why you’re seeing: Failed to parse:

;

Caused by: Expected package name starting with an alphanumeric character, found

;

Typical culprit examples: -

pandas; python_version >= "3.9"

-

s3fs; sys_platform == "linux"

How to fix - If you don’t need conditional installs, remove the

; ...

markers and keep plain specs:

work_pool:
    name: my-managed-pool
    job_variables:
      pip_packages:
        - pandas==2.2.1
        - requests>=2.31.0
        - numpy

- If you do need environment markers, move them into a requirements.txt and install via a pull step in your deployment: - requirements.txt

pandas>=2.0; python_version >= "3.9"
    s3fs; sys_platform == "linux"

- prefect.yaml

pull:
      - prefect.deployments.steps.git_clone:
          id: clone
          repository: <https://github.com/your-org/your-repo.git>
      - prefect.deployments.steps.pip_install_requirements:
          directory: "{{ clone.directory }}"
          requirements_file: requirements.txt
    deployments:
      - name: my-managed-deployment
        entrypoint: path/to/flow.py:my_flow
        work_pool:
          name: my-managed-pool
          # You can omit pip_packages here if requirements.txt covers everything

Also double-check that

pip_packages

is a YAML list (not a single string that starts with

[

): - Correct (YAML list):

pip_packages:
    - pandas
    - requests==2.31.0

- Incorrect (stringified JSON):

pip_packages: "[ 'pandas', 'requests==2.31.0' ]"

If you can, please paste the actual contents of your

pip_packages

and how you’re setting them (in prefect.yaml, via

.deploy(job_variables=...)

, or in the UI). I can pinpoint the exact line that’s causing the parse error. Docs for reference: - Managed work pools: https://docs.prefect.io/v3/how-to-guides/deployment_infra/managed - Customize job variables: https://docs.prefect.io/v3/how-to-guides/deployments/customize-job-variables - prefect.yaml reference: https://docs.prefect.io/v3/how-to-guides/deployments/prefect-yaml