Support for Pixi

New feature

Pixi is a package manager equivalent to Conda which is growing in popuarity recently.

Use case

Equivalent to Conda, Mamba, Spack, etc. We can use it to set environments per process using a Pixi TOML.

Suggested implementation

Here's a hacky version inspired by https://tiendu.github.io/2025/05/10/nextflow-pixi-eng.html. We could probably implement something similar inside a process.

main.nf:

process PIXI {

    debug true

    beforeScript '''
    [ -d .pixi ] && [ -f pixi.lock ] || pixi install
    eval "$(pixi shell-hook)"
    '''

    input:
        path pixi_lock

    output:
        stdout

    script:
    """
    cowpy "hello pixi"
    """
}

workflow {
    pixi_lock = Channel.fromPath("pixi.toml", checkIfExists: true)

    PIXI(pixi_lock)
}

pixi.toml

[project]
name = "test-pixi-env"

channels = ["conda-forge"]
platforms = ["linux-64", "osx-arm64", "win-64"]

[dependencies]
cowpy = "1.1.*"
python = "3.13.*"

N E X T F L O W   ~  version 25.04.1

Launching `./main.nf` [nauseous_hoover] DSL2 - revision: 8f2d7021a8

executor >  local (1)
[39/fcb524] PIXI (1) [100%] 1 of 1 ✔
 ______________________________________________________ 
< Cowacter, eyes:default, tongue:False, thoughts:False >
 ------------------------------------------------------ 
     \   ^__^
      \  (oo)\_______
         (__)\       )\/\
           ||----w |
           ||     ||

Start by reviewing the proposed implementation in main.nf and the pixi.toml example, then inspect closed pull requests #6157 and #6342 for existing work. Verify the intended process behavior against the shown Pixi installation, shell-hook, and cowpy output.