A Logger symbol missing on macOS 15 kept my Mac app from launching

I wrote up a launch crash that Yardlet, a macOS app, shipped for four days. Built with Xcode 27.1 for a macOS 15 deployment target, it called Logger.isEnabled(type:). The SDK's swiftinterface lists that method under Logger's @available(macOS 11.0, ...) with no availability of its own, but libswiftos.dylib on macOS 15.6.1 doesn't export it, so dyld stopped the app at launch. The post covers how I found it, the fix (OSLog.isEnabled(type:)), and a short script that compares an executable's strong ...