Issues with Python Environment Activation in Codex Tasks (uv, .venv, poe, Python 3.12)

Codex
1

Description

I’m working in OpenAI Codex and having trouble getting my Python environment to behave consistently across the “Environments > Edit” preview and actual task execution. Below are the key details and symptoms:

:laptop: Environment Setup

  • Using Python 3.12
  • Environment defined in a Devcontainer
  • Project dependencies managed using:
    • pyproject.toml + uv for fast installs
    • poethepoet for CLI tasks
  • Two installation attempts:
    1. uv sync
    2. pip install .

:red_exclamation_mark:Problems Encountered

1. .venv disappears in Codex tasks
  • After uv sync, a .venv is created and visible in the “Environments > Edit” preview.
  • However, in a new Codex task, that .venv is not present anymore — resulting in failed imports or missing commands.
2. poe commands not found during execution
  • When installing with pip install ., my poe commands (e.g., poe lint) are available and listed in the preview.
  • But when running a Codex task like poe lint, it errors with:
bash: poe: command not found

→ Indicates that the actual task shell isn’t picking up the environment.

3. Wrong Python version when running tasks
  • Despite setting Python 3.12 explicitly and it showing correctly in “Environments > Edit”, a task asking for the Python version with:
python --version

Returns:

Python 3.11.12

→ Suggests either the environment isn’t being activated or an internal fallback is being used.

:magnifying_glass_tilted_left: What I Tried

  • Switching between uv sync and pip install .
  • Ensuring .venv is committed and available
  • Manually adding .venv/bin to $PATH via postCreateCommand
  • Confirming poe works inside the container manually, but not inside Codex tasks
  • Using "Use This" on the configured environment

:red_question_mark: My Questions

  • Any steps to activate the environment for tasks that I forgot to execute?
  • What’s the underlying cause to have the Python version mismatch and how to fix this?
  • How to properly build an environment based on uv in Codex?
  • Is there a way to enforce environment activation like source .venv/bin/activate? Adding this explicitly in the environment setup didn’t work either.

I assume issues like this would be resolved by allowing custom image uploads, but since that’s not yet possible, Codex is currently unusable for my work (:cry:).

2

No problems here with py 3.13 here . Except for models writing code with syntax errors..