Hello all, I just wanted to chime in here. I've been working on updating my project to library evolution support for about 2 weeks now. It's been grueling. I've been building iPhone apps for 14 years, quite knowledgeable with Xcode, and this has been one of the most painful processes I've encountered. It may be because I had sub-libraries that are static libraries inside my framework, but nevertheless I am ending up with frozen compilers, when interpreting .swiftinterface and related files. Compiler just hangs. Reason I am leaving this message is to give my opinion as well that forwards and backwards compatibility is what is being implied around the marketing of this. As a developer, that is what I assumed as well from watching the Apple WWDC video. Namely, because there are no directions anywhere on how and why someone should switch to an older version of Xcode or xcodebuild tools in order to correctly build something that supports multiple swift versions (as in, only forwards compatibility). There are no indications or even hints that one should do this. So I think it's a very confused subject, probably inside and outside of Apple. I'm currently filing another ticket because in my case compiler hangs forever when trying to build on a different version of swift than XCFramework was created in, even with build libraries for distribution, and there is no way to debug it even with xcodebuild as there are no details around, it just never returns from the '/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend' command. I am not even sure if it supports static libraries inside the framework at all at this point because I've done everything I can think of. Perhaps, just as they are hiding the fact that it's only forward compatible they are also hiding the fact that it does not support embedded static libraries? In any case, no way to tell as a developer, the parsing code for the swiftinterface files is done behind the scenes and there is no way for us to correct the problems.