Re: [DISCUSS] Should Maven 4 prioritize forward evolution over full Maven 3 compatibility?

Hi Romain,

Thank you. I agree that there needs to be a middle ground.

I have also experienced painful upgrades in real systems. Applications and
dependencies often evolve incrementally rather than being designed for
every future requirement from the beginning. Over time, they accumulate
assumptions, integrations, and behaviors that may only become visible when
an upgrade changes them.

Thinking more about Maven, I now better understand why this is especially
difficult here. Maven's plugin ecosystem has existed for more than twenty
years, and compatibility is not only about documented APIs. Plugins may
also come to rely on lifecycle ordering, classloading behavior,
model-building details, dependency resolution behavior, and other
assumptions that gradually become part of the practical contract.

Your point about stronger formal API boundaries in Maven 4 makes a lot of
sense in this context. At the same time, it is probably impossible to
predict every extension requirement for the next twenty years. What seems
particularly important is having clear and sustainable boundaries: what is
stable, what is experimental or incubating, what is internal, and how new
extension points can be added when future needs appear.

I am also starting to see Maven as more than just a build tool — it is also
a kind of protocol layer in the Java ecosystem. It connects project models,
plugins, repositories, dependency resolution, IDEs, CI systems, and many
other tools. Upgrading such a protocol is naturally much harder than
upgrading an ordinary application.

From that perspective, I understand much better why Maven 3 to Maven 4
requires so much care.

If the Maven 3 to Maven 4 transition is necessarily painful, one valuable
outcome could be a healthier boundary and extension model, making future
major-version transitions more localized, predictable, and easier to
migrate.

Thanks again for sharing your perspective. This discussion has helped me
understand the problem much better.

Best regards,
Josh