Cross-platform builds just became the default, not a setup project. swift 6.4, out september 15,…
cross-platform builds just became the default, not a setup project. swift 6.4, out september 15, makes swift build the default in the package manager so the same project builds identically on linux, macOS and windows.
the config file got smaller by omission.
Context
Swift.org's post of September 15, 2026 announces Swift 6.4 and says Swift Build is now the default in Swift Package Manager, so projects build the same way on Linux, macOS and Windows. The SwiftPM 6.4 docs describe a unified build experience across supported platforms, and list differences from the native engine: a different output location, stricter static stdlib validation, a test runner per test target, and resource rules matching xcodebuild on Apple platforms. The docs list known issues with Linux SDKs generated by the SDK generator, the explicit target dependency import check option, and swift-java projects with build tool plugins, and say users can fall back with swift build --build-system native.
The command is unchanged and the change is that it now uses the Swift Build engine by default in place of the native build system. Build the same way is the post's wording and the documented differences mean the outputs are not claimed to be bit-identical. A native fallback and known issues exist. The release also adds Android support through Swift Build and SBOM generation. The config file got smaller is not supported by anything read.
Watch next
- Resolution of the known issues.
Sources
- Swift.org: Swift 6.4 released (September 15, 2026)swift.org
- SwiftPM 6.4 documentationdocs.swift.org
Provenance
The note above is reproduced unedited from the original post, first published on Threads on 22 September 2026 at 13:38 IST. Sources are the papers and datasets the note draws on.
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