I’m getting the BLZBNTAGT00001389 “Whoops look like something broke. You can try restarting Battle.Net.” message. Of course restarting Battle.net, restarting the Mac, scanning/repairing SC1, doesn’t work. What to do?
Same story. MacOS 15.1.1
I just reinstalled the game and it helps.
I can confirm that reinstall helps!
While normally I have suspected firewall, it turned out the change to Sequoia updated some ownership. Battle.net client probably runs as you - the thing is, that probably /Applications/Starcraft folder has ownership list (you can see that with get info on Starcraft folder, scroll down, click >) that theoretically includes everyone - but despite that not your user name 
Adding your username (with propagate!) and Read/Write should solve the issue.
Myself I need to understand the Everyone security group in MacOsX better after the latest updates 