Sorry for not using the template: I have observed the issue on my university cluster, and was unable to make a reliable reproducer. Specifically, I have observed that pixi on our university cluster has a problem with installing pypi packages.

[aakhmerov@login03 test21]$ pixi init
✔ Created /home/aakhmerov/test21/pixi.toml
[aakhmerov@login03 test21]$ pixi add python
✔ Added python >=3.14.0,<3.15
[aakhmerov@login03 test21]$ pixi add --pypi regex
Error: × File still doesn't exist
 ╰─▶ No such file or directory (os error 2)

I have figured out that the problem is somehow related to getting the conda-pypi mapping because the following two steps fix the issue:

mkdir -p ~/.config/pixi
echo '{}' > ~/.config/pixi/conda-forge-empty-mapping.json

and adding to pixi.toml

conda-pypi-map = { "conda-forge" = "/home/<username>/.config/pixi/conda-forge-empty-mapping.json" }

On the other hand, I have confirmed that there are no weird proxy settings, and that I can connect to both raw.githubusercontent.com and conda-mapping.prefix.dev (IIUC these are the places from which the mapping is obtained).

Adding verbose logging to pixi doesn't help resolve the problem, so I'd appreciate any pointers.