I was getting an exception with the same upgrade: java.lang.NoClassDefFoundError: org/eclipse/compare/internal/TabFolderLayout

I found that class in the previous eclipse version 2024-09 and as a workaround I copied the class to the jar in 2024-12 in which it was missing.

Copy the class org.eclipse.compare.internal.TabFolderLayout.class from plugins/org.eclipse.compare_3.11.100.xxxx.jar to plugins/org.eclipse.compare_3.11.200.xxxx.jar And restart Eclipse

I reported the problem as a bug in: subversive/issues/260