Support for 2.13.0-M5 has been merged in Scala.js. We’ve started our own release train for 0.6.25 to make that support available. Assuming everything goes smoothly, jars will be available sometime tomorrow, although an official announcement will probably wait until Monday.
We’re not very happy about our process. The 2.13.x cycle has put enormous pressure on Scala.js to keep up and be released in a timely manner. We had to actively reduce our quality standards in terms of review process to make both M4 and M5. In both cases, changes merged in 2.13.x up to a few days or even the very same day as the release were source-breaking for Scala.js. Normally, we’re able to back-published already released versions of Scala.js when milestones of Scala show up, but that was far from being true for 2.13.0-M4 and M5.
I very much hope that the fast pace of 2.13.x is winding down, and that future milestones/RCs will be backward source compatible for Scala.js. In the future, I would like to ask for a bit more consideration for the ecosystem: allow for a few weeks between the last merges of source-breaking changes and the release of a milestones. That way, there is a chance that we don’t need to make changes, PR, review, merge, and deploy all within a few days, which is detrimental to our quality standards.