You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.
synium was reported malicious
OSV:MAL-2025-192438 - Malicious code in synium (PyPI)

synium
1.0.0

This version was deleted from PyPI around 2025-12-12. Installing fails with:
$ pip3 install synium==1.0.0 ERROR: Could not find a version that satisfies the requirement synium==1.0.0
View other deleted versions of synium

Install through StableBuild

You can install this package from StableBuild's PyPI snapshots from before the version was deleted:
pip3 install \ -i https://YOUR_API_KEY.pypimirror.stablebuild.com/2025-12-11/ \ synium==1.0.0
Sign up for StableBuild to get an API key (it's free and takes <60 seconds!)

Or, download files manually

And install manually via pip:
synium-1.0.0-py3-none-any.whl (4.2KB)
synium-1.0.0.tar.gz (3.6KB)