GitHub CodeQL breaks on macOS 27, Xcode 27 and Swift 6.4
Apple dropped Intel code from system binaries CodeQL relies on, so traced builds stop working on the new OS and Swift 6.4 is unsupported everywhere.
GitHub says CodeQL breaks on macOS 27 and Xcode 27, because Apple no longer ships Intel (x86_64) code in some of the system binaries and libraries CodeQL uses to trace builds. With Xcode 27 installed, traced extraction stops working for C/C++, C#, Go, Java, Kotlin and Swift. Separately, CodeQL doesn’t support Swift 6.4 at all, on any platform.
GitHub’s fix for now is to pin: if you scan Swift or rely on traced builds for other languages, pin your workflows to macOS 26 or earlier and Xcode 26 or earlier, and pin the runner image and toolchain explicitly rather than trusting “latest”. For C/C++, C# and Java projects, switching CodeQL to build mode none avoids tracing altogether. CodeQL support for Intel-based Macs is also being deprecated, in mid-December 2026.
Why it matters: this will bite silently. A workflow using macos-latest or the newest Xcode image can lose code scanning coverage the moment GitHub rolls the image forward, with no obvious error beyond gaps in results. Anyone running CodeQL on Apple platform code should pin their CI images now rather than find out after a quiet coverage drop.