Isabelle/661bf743296f is now on jdk-21.0.10 from the January 2026 Quarterly
Update from Azul, see also https://docs.azul.com/core/release-notes
I've browsed through the long list of changes for version "21", and did not
see anything of special concern for us. Java LTS updates are usually
rock-solid: I can't remember a problem with it in recent years.
Note that Java 21 LTS is actually the old LTS branch, while Java 25 LTS is
already available since Sep-2025.
It might become relevant for Isabelle2026 (October 2025), but it also requires
and update of Scala: We are presently lagging behind there, due to some
problems, notably with the Java Accessibility API that has become relevant to
use. The Scala guys have addressed my ticket for the scalac compiler already,
but the result has not been published yet.
I have also updated the cluster build manager to use Isabelle/661bf743296f
with jdk-21.0.10. We did have another out-of-memory kill in the pipeline, but
this is independent of Java versions. We need to sort out overly ambitious
Java heap usage on our side.
Makarius
