MRE of pixi issue https://github.com/prefix-dev/pixi/issues/1268

pyproject.toml

[project]
name = "my_project"
requires-python = ">=3.9"
dependencies = [
    "numpy",
]

[tool.pixi.project]
channels = ["conda-forge"]
platforms = ["linux-64", "osx-arm64", "osx-64", "win-64"]

[tool.pixi.dependencies]
numpy = "*"
numpy = "*"

[tool.pixi.tasks]
start = "echo"