I had to fresh install the macOS to fix this. I don’t know if the RC has any changes regarding that.

Make sure you don't have other dependencies doing a method swizzling on the URLSessionConfiguration.default. I was having exactly the same crash on our app and found the Hyperconnectivity package was doing swizzling on URLSessionConfiguration.default like this: +(void)load { orig_defaultSessionConfiguration = (SessionConfigConstructor)HTTPStubsReplaceMethod(@selector(defaultSessionConfiguration), (IMP)HTTPStubs_defaultSessionConfiguration, [NSURLSessionConfiguration class], YES); orig_ephemeralSessionConfiguration = (SessionConfigConstructor)HTTPStubsReplaceMethod(@selector(ephemeralSessionConfiguration), (IMP)HTTPStubs_ephemeralSessionConfiguration, [NSURLSessionConfiguration class], YES); } I temporarily fixed the crash by disabling the package

@Frameworks Engineer for me it only crashed when I had another dependency doing method swizzling. I have a Feedback with the complete stack FB17891691

Here the crash stack Thread 2 Crashed: 0 ??? 0x1dee7618c ??? 1 ??? 0x1dee73d14 ??? 2 ??? 0x1dee73b8c ??? 3 ??? 0x1dee73b68 ??? 4 ??? 0x1dee73c98 ??? 5 ??? 0x1dee7d1bc ??? 6 ??? 0x1dee7d8e4 ??? 7 ??? 0x1dee73b8c ??? 8 ??? 0x1dee73b68 ??? 9 ??? 0x1dee7d888 ??? 10 ??? 0x19138fefc ??? 11 ??? 0x19139224c ??? 12 ??? 0x190918618 ??? 13 ??? 0x1909184b0 ??? 14 libdispatch.dylib 0x1802364b0 _dispatch_client_callout + 12 15 libdispatch.dylib 0x18021e3d4 _dispatch_once_callout + 28 16 ??? 0x19091b94c ??? 17 CFNetwork 0x180fe856c -[NSURLSessionConfiguration initWithDisposition:] + 356 18 CFNetwork 0x180fe8b04 __56+[NSURLSessionConfiguration defaultSessionConfiguration]_block_invoke + 36 19 libdispatch.dylib 0x1802364b0 _dispatch_client_callout + 12 20 libdispatch.dylib 0x18021e3d4 _dispatch_once_callout + 28 21 CFNetwork 0x180fe8818 +[NSURLSessionConfiguration defaultSessionConfiguration] + 64