Unfortunately, even after a full re-install of Xcode 14.3 and Command Line Tools for 14.3, the compilation problem persists. :( Here's my clang++ `% clang++ --version **Apple clang version 14.0.3 (clang-1403.0.22.14.1) Target: arm64-apple-darwin22.4.0 Thread model: posix InstalledDir: /Library/Developer/CommandLineTools/usr/bin`**

Create a new user account - Great idea... I hadn't thought of that. I'm going to add that to my troubleshooting repertoire! Thanks also for the clarification on the xcode-select setting.