I built GPRBUILD 25.0.0 (20241103) (aarch64-apple-darwin23) because pre built ones I tried did not work running with Macos Sequoia 15.2.
When alr tries run gprbuild it returns the error message “ERROR: Not installed: gprbuild=18.0.0”.
This occurs with a pre build alr I downloaded and one I built from the latest sources.
Is there a way to tell alr what version of gprbuild is installed?
I think this is an old typo where newer GPRBuild versions did not have this error string update 
What is the output of which gprbuild when you run it? I am basically checking that you have it in your PATH.
There is a way to tell Alire to use the native (read system provided) toolchain. This can be done with alr toolchain and its different options, see alr help toolchain.
And just for good measure, let me ping our Mac expert here @simonjwright 
Best regards,
Fer
I get caught by this almost every time I build it. For how the issue occurs, see here; for why it’s done this way, you’ll have to ask AdaCore.
There’s a similar problem with libadalang-tools.
As it does for other tools, alr asks gprbuild for its version (who should know better?!)