Hi Simon, Maybe I'm off the mark, but: > R 4.3.0 CRAN builds are using Xcode 14.2, macOS 11.3 SDK and targetting macOS 11 (Big Sur) AFAICT, Xcode 14.x includes an SDK for macOS 12.3 but not one for macOS 11.3. https://developer.apple.com/documentation/xcode-release-notes/xcode-14-release-notes Mikael