[R-SIG-Mac] macos 26 considerations

[Duncan Murdoch]

On 2026-02-22 10:40 a.m., Bill Evans via R-SIG-Mac wrote:
> I’ve been holding off upgrading to MacOS 26 for many reasons, most
> related to yet-unsubstantiated concerns about R. Because it’s a new ABI,
> I suspect the process would be similar to a major/minor release in R:
> update the compile chain then re-install all packages. Is there a strong
> recommendation for or against this upgrade? Are there safe or at least
> less-risky pathways for upgrading the OS? Is R-devel regularly tested
> against 26? Are there known unresolved problems, such as “package xyz
> does not currently work”?
> 
> FTR: I’m currently on macos 15.7.4 using R-4.5.2, and there is nothing
> inherently broken. I don’t have a /need/ to upgrade to 26 atm but fear
> at some point that some tool I use (be it Parallels or something else)
> may eventually require 26 for some or all of the desired functionality.
> I’m just planning ahead (and holding back two colleagues, also on
> macos-15.7).

I upgraded in the fall, and found that XQuartz didn't work, and its 
maintainer had stopped working on it.  Since I was planning some work on 
rgl that needed XQuartz, I downgraded and I'm still on Sequoia 15.7.2.

You should be aware that downgrading isn't easy:  you need to create a 
bootable external disk, reformat your main drive and restore from a 
backup.  I did it and didn't lose anything, but it wasted a day or so, 
during which I wondered whether my backups were really as complete as I 
hoped they were.

Duncan Murdoch