Thank you @GravityBytes for posting this. I bumped into this issue today and your tip turned out to be the solution for me too. The only difference in my setup was that the packages were part of a workspace. I removed their reference and added them back and the build started to work again. The delete + re-add of the package references to the workspace file resulted in a clean diff. I'd say this is some quirk in the way Xcode caches stuff. Some folks on StackOverflow suggested to reset the packages cache. I did that but it was no help because the issue was with a local package not a remote one.