Xcode

Signing Issues

• "Automatic" signing still needs team selected — set in Signing & Capabilities
• Provisioning profile mismatch — bundle ID must match exactly, including case
• "No signing certificate" — open Keychain, check certificate is valid and not expired
• Device not registered — add UDID in developer portal, regenerate profile
• CI/CD needs manual signing — automatic doesn't work in headless builds

Derived Data Corruption

• Random build failures after Xcode update — delete ~/Library/Developer/Xcode/DerivedData
• "Module not found" but it exists — clean Derived Data, restart Xcode
• Stale cache symptoms — builds work, then fail, then work again
• xcodebuild clean not enough — sometimes must delete DerivedData manually

Build Settings Hierarchy

• Project → Target → xcconfig → command line — later overrides earlier
• $(inherited) to append not replace — forgetting it removes parent settings
• SWIFT_ACTIVE_COMPILATION_CONDITIONS for Swift flags — not OTHER_SWIFT_FLAGS
• GCC_PREPROCESSOR_DEFINITIONS for Obj-C — add to existing, don't replace