Finding Python in pixi environment

[AdaemmerP]

We are trying to set up Positron Server (2026.06.0-211) with an education license inside a Docker container. The Python environment is managed by pixi and lives at /opt/pixi/.pixi/envs/default.

The following environment variables are set in the container:

PATH=/opt/pixi/.pixi/envs/default/bin:...
CONDA_PREFIX=/opt/pixi/.pixi/envs/default
CONDA_DEFAULT_ENV=default

The integrated terminal correctly resolves Python:

$ which python
/opt/pixi/.pixi/envs/default/bin/python

What I tried

In settings.json:

{
"python.defaultInterpreterPath": "/opt/pixi/.pixi/envs/default/bin/python",
"python.interpreters.include": "/opt/pixi/.pixi/envs/default"
}

None of these work.

Is there a supported way to make Positron Server discover a pixi (conda-style) environment in a non-standard location?

[Lamg222]

A few things to check — the most likely culprit is the format of python.interpreters.include: it is declared as an array of strings in the extension's configuration schema (see extensions/positron-python/package.json, "type": "array", "items": {"type": "string"}), so a plain string value is silently ignored:

{
    "python.interpreters.include": ["/opt/pixi/.pixi/envs/default"]
}

If you want Positron to show only that environment, use python.interpreters.override instead (same array format).

A couple of related notes:

• python.defaultInterpreterPath only selects which already-discovered interpreter is the default — it does not add an undiscovered path to the list, so on its own it will not fix discovery.
• Pixi environments are picked up through the conda discovery path; in a headless container without a conda binary the automatic detection can fail, which is why the explicit include is the reliable route. If it still does not appear, try "python.locator": "js" as an alternative discovery mechanism.
• Discovery results are cached — after changing these settings in Positron Server, run Developer: Reload Window.

[AdaemmerP]

Thank you so much for your detailed response. There was one more piece to it in our case:

We build our image in two stages. In the first stage, we build the environment in /opt/pixi/.... In that folder, the environment—including the Python binary—lives in /opt/pixi/.pixi/envs/default/, while the pixi.toml and pixi.lock files are located in /opt/pixi/pixi.toml and /opt/pixi/pixi.lock. In the second build stage, we only copied the environment from /opt/pixi/.pixi/envs/default/, but not the pixi.toml and pixi.lock files.

It turns out that discovery wasn't the issue in our case as we found the environment under "Python: Select Interpreter" (but not the Session window). Yet selecting it did nothing. It turns out Positron also needs pixi.toml/pixi.lock to recognize /opt/pixi as a Pixi project and activate it. Once we copied over the pixi.toml and pixi.lock files as well, everything worked correctly.

[Lamg222]

Glad you got it working, and thanks for sharing the solution — this is a subtle gotcha with multi-stage Docker builds.

For future readers, the complete picture is:

• Copying only .pixi/envs/default/ into the final image is not enough. Positron can find the Python binary there (it shows up under "Python: Select Interpreter"), but selecting it does nothing.
• Positron needs pixi.toml and pixi.lock in the parent folder (/opt/pixi/ in this case) to recognize it as a pixi project and actually activate the environment in the Session pane.
• The fix: in the final build stage, also COPY the pixi.toml and pixi.lock files, keeping the same folder layout as the build stage.

A clearer error message when an interpreter is selectable but cannot be activated would help here — might be worth opening an issue.