Better multicolumn marks: Pre-release of LaTeX 2025-06-01 is available for testing

We submitted the first pre-release version for the 2025-06-01 LaTeX kernel to CTAN recently. It should have made its way into TeX Live for everyone by now, so it’s ready for users to try.

As the first pre-release, this contains only some of the ideas we are planning for the next release. However, there are significant changes in the marks code, particularly for multicolumn content, which are ready for testing.

Marks and multiple columns

A few releases ago, we introduced a new marks mechanism into LaTeX: the older approach knew only a very limited amount of information, and a much more flexible system was needed. At the time, we retained the old mechanism in parallel, and this was still used by the multicol package.

We have now updated multicol to use the new approach, which means we have been able to retire the old one fully. The legacy commands \markboth, \markright, \leftmark, and \rightmark are now simple wrappers around \InsertMark, etc., which should work transparently with current document classes.

We anticipate that everything should work smoothly with the move to a new approach, but it would be useful for interested users to check this is true in real-world documents. We are particularly keen to hear of any issues with multicol, which uses the full range of features in the new marks system.

Outlook

Code improvements across the kernel continue: this pre-release sees changes to case changing and in some aspects of verbatim handling. We are also continuing to extend automated tagging, handling more mathematics without user intervention.

We anticipate that there will be at least a couple of development releases in the new year as more features are added. So there is plenty of time to get testing done for the next LaTeX release.

Meanwhile, a hotfix kernel release

As well as getting the first pre-release out for 2025-06-01, we also sent CTAN a kernel hotfix (2024-11-01 patch level 1) this week. There were two issues that came up. First, \DeclareEncodingSubset couldn’t be used in the document body, which was an issue as we’d encouraged font package authors to use it in .fd files - which can be loaded after \begin{document}. Second, there was a timing issue with defining \tag_if_active:TF which showed up with tabulars. Both of these problems are fixed in the patch level 1 release. Naturally, these changes are in the 2025-06-01 pre-release too.

Enjoy — Joseph