# Build system priority for Apple platform projects

> Source: <https://gist.github.com/Kyome22/e4d4b211f7fbbcd1f81f7067489c0f4b>
> Published: 2026-07-18 04:30:15+00:00

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.