The official Isabelle2025-1 release is scheduled for mid December 2025. This blog entry is dynamically updated to follow the sequence of public release candidates. See also the isabelle-release repository.

• Isabelle2025-1-RC0 (07-Oct-2025): informal snapshot for experimentation, approx. 4 weeks before regular RC1. See also AFP/013063387a31.
• Isabelle2025-1-RC1 (05-Nov-2025): first official release candidate, approx. 6 weeks before final lift-off. Almost everything is ready for testing; some documentation and add-on components still require updates.. See also AFP/695d78dfa92a.