Try x-safari-https:, as in: x-safari-https://christiantietze.de/posts/2023/05/safari-for-mac-url-scheme Which incidentally is a blog post about this :)

We have no Headers built phase and I did the opposite of @ivayale's solution and disabled the new build system integration (which previously was enabled): defaults write com.apple.dt.XCBuild EnableSwiftBuildSystemIntegration 0 As always in Xcode, try toggling all toggles etc.; there seems to be neither sense nor reason behind the actual value. What matter is you change it :)

Same problem since I switched to an M1 Mac.