Build system priority for Apple platform projects

A developer outlines a priority system for building Apple platform projects, recommending Xcode MCP Tools when Xcode is open, xcodebuild for CLI builds, and swift build/swift test only as a last resort for pure-Swift packages without resources. The post warns that swift build cannot compile bundled resources like .xcstrings or .xcassets, causing silent test failures.

For any Xcode project or Swift Package Manager package, use this order — pick the first option that fits the situation, do not skip down the list. - Xcode MCP Tools — use these when Xcode has the project open. They reuse the running Xcode's build state no duplicate DerivedData / build caches piling up , and open the door to workflows the CLI cannot reach — running screenshot / snapshot tests through the running IDE, driving simulators the user is already using, etc. - — for CLI builds and tests. Compiles bundled resources correctly: xcodebuild .xcstrings string catalogs become per-locale .strings inside the bundle, .xcassets are compiled, etc. Use this when Xcode is not open or when a headless build is needed. - — last resort. Only safe for pure-Swift packages with no resources. swift build / swift test They cannot resolve bundled resources. A .xcstrings file is copied into Bundle.module but never compiled into per-locale .strings , so at runtime String localized:bundle: returns the raw key and every test that asserts on translated text fails. .xcassets has the equivalent problem for image lookups. If a Package declares resources: .process "Resources" with anything more than plain data files, swift test will silently fail resource-dependent tests — reach for xcodebuild instead.