Drop support for Python versions 3.8 and 3.9?

[DavidVujic]

I can see Polylith users running Python versions 3.8 (few) and 3.9 (some) when looking at the download stats for the CLI and the Poetry plugin. The source I'm using is mainly https://clickpy.clickhouse.com/

Dropping these versions would be mostly a convenience currently (being able to implement PEP 621 internally, and bump outdated subdependencies). It's not an urgent task, but something that I plan to do during 2026.

This project is releasing new versions according to semantic versioning, and dropping support would be a breaking feature even if the versions are unsupported since quite a while. I hesitate how to approach this, because I don't want to cause disruptions in the flow of the teams out there. I know that the "big" tools in the Python community handle this in different ways.

Bumping the Major version (i.e. going from v1 to v2 in the CLI and Poetry plugin) could make teams miss out on new versions if they pin the poly tool to 1.*. I also know how I usually react to a new Major version: "Ok, what do we need to change on our end to make this new version of the library/tool work?"

Bumping the minor version would be breaking builds for Python 3.8 and 3.9 users unless they pin the poly tool to a specific minor version (such as 1.48.* or similar).

What do you think, what would be the best way to go forward here?