Thanks for the reply. I'm not actually doing number formatting, but rather locale-sensitive numeric expression evaluation. For example in the US: "123,456 + 10,000 = 133,456 " // Locale(identifier: "en_US") In Germany: "123.456 + 10.000 = 133.456" // Locale(identifier: "en_DE") Or with a custom grouping separator: "123’456 + 10’000 = 133’456" // How to create & test this locale programmatically? I have tests for standard locales, but a case was reported by a customer where number recognition was failing for a custom grouping separator. The only way for me to test this at the moment is to set this custom locale in my own macOS System Preferences, which is a bit fragile. I'd like for this test to be automated, like I have for the standard locales.

No luck - it still occurs in Version 13.3.1. I reported this to Apple last October (FB9726940). It also appears to affect Swift Package targets, and even occurs in Xcode Cloud test failures. The one interesting thing is that it only occurs if you set My Mac or My Mac Catalyst as the run destintation (which is obviously the default for a framework that only imports Foundation). If you choose an iOS simulator, the problem is resolved. Clearing the system log as discussed in the thread Quinn “The Eskimo!” linked to has no effect on the problem.

For any Apple engineers tracking this issue, it is still present on Ventura 13.0 Beta (22A5321d) and Xcode 14 (Version 14.0 beta 5 14A5294e).