Hi Anna,
Thanks for the report and the investigations you carried out.
We confirm that ROOT 6.38.04 works smoothly with XCode 26.4 as you could verify. I can also confirm I can reproduce the problem.
What I suspect, and here I agree with you, is that it could be that Brew did not move yet to the latest version. However, they traditionally have been very efficient with this and other kind of updates, and if what we think it’s true, it should not take long to fix.
In the mean time, I’ll open an issue to brew to see whether they have suggestions: ROOT does not work if XCode 26.4 is on the system on which the formula is installed · Issue #274363 · Homebrew/homebrew-core · GitHub
Cheers,
Danilo
PS
The compilation from sources works (thanks for mentioning it), as well as installing ROOT from CondaForge Anaconda.org