If you run CI at a company with a long tail of platforms, you may know this one. I've worked on CI and Jenkins for years, and I keep seeing the same problem in the community and among peers.

The squeeze

A lot of enterprise software ships on many platforms. Besides mainstream Linux there is AIX, HP-UX, Solaris, and RHEL 6 machines (sometimes RHEL 5) that have been building releases for years and that nobody wants to touch. They are Jenkins agents, and every platform build comes from them.

On these systems, Java stops at 8:

AIX 7.1 tops out at IBM Java 8. IBM Semeru 17 and 21 need AIX 7.2 or 7.3.

HP-UX has HPE's JDK 8.

Solaris 10 has Java 8; Solaris 11 stops at JDK 11.

Current JDKs don't support RHEL 6 any more.

Jenkins, meanwhile, keeps raising its Java baseline, and the requirement covers agents, not only the controller :

Jenkins 2.361.1 LTS (2022): Java 11 for controller and agents.

2.479.1 LTS (2024): Java 17.

Today: Java 21 or 25.…