I know this thread is boring/meaningless to anybody not a Mac developer, but just to wrap it up for curious folks: it’s an issue that affects dyld library resolution of a helper app (my crash reporter), which doesn’t itself depend on Swift but depends on libraries that do.

Since it doesn’t depend on Swift, it doesn’t get a /usr/lib/swift LC_RPATH in its binary, so when a dependencies’ own Swift library is being resolved, it reverts to the versions bundled in the app. Or something.