I started building a new app with Xcode 15, and I uploaded a few builds to TestFlight with it. Now I'm trying with 15b4, and I'm getting:
Invalid Toolchain. Your app was built with an unsupported SDK or version of Xcode. If you plan to submit this build to the App Store, make sure you are using the versions listed in https://help.apple.com/xcode/mac/current/#/devf16aefe3b or later. (ID: 0c544ce8-53ee-4122-b4a9-467a3d766349)
Is this a bug? They've always allowed TestFlight builds with pre-release toolchans, havn't they? How else can you ensure your app is ready for the new OS version if you can't test changes to it?