Swift 6.4: what’s new for app developers

Two changes work together. Async code in a defer block is now awaited and runs to completion before the scope exits, and withTaskCancellationShield runs a closure shielded from the enclosing task’s cancellation. Combined, they let you guarantee cleanup work such as closing a session or flushing a cache, however the function returns. Foundation’s ProgressManager also gains async/await support.

Migrating to Swift Testing gets easier: XCTAssert works inside Swift Testing tests and #expect inside XCTests, CustomTestReflectable customizes values shown in failures, swift test can repeat test cases, and tests can record attachments that conform to Transferable on Apple platforms. SwiftPM now builds with Swift Build by default, so packages build the same way on Linux, macOS and Windows. Debugging is more robust, with LLDB importing modules through precise dependency tracking, and dSYM bundles shrink because binary Swift modules are no longer embedded. The Swift VS Code extension is now on the Open VSX Registry, so it works in Cursor, Antigravity and other editors too.

The Swift SDK for Android is built with the LTS NDK 30, and SwiftPM supports Android through Swift Build without a post-install script. Swift/Java interop extends async and throwing support to protocol and callback wrappers. For the browser, JavaScriptKit bridging is up to 40 times faster than earlier dynamic bridging, and the Wasm SDK installs from Swift.org. C++20 std::span bridges directly with Swift’s Span.

New types extend the work on non-copyable types: UniqueArray stores non-copyable elements without copy-on-write allocations, UniqueBox uniquely owns a heap value without reference counting, Ref and MutableRef borrow or mutate one value at a time, and the Iterable protocol loops over elements without copying them. Non-copyable types can conform to Equatable, Comparable and Hashable. Subprocess reaches 1.0 for running other programs from Swift.

Apple’s SDK table lists Swift 6.4 for Xcode 27.1 beta and Xcode 27.2 beta 2, both needing macOS Tahoe 26.6 or later, with Swift 6, 5, 4.2 and 4 language modes. For when App Store uploads must use the 27 SDKs, see the Xcode and SDK upload requirement; Apple’s on-device AI APIs are covered in Apple Foundation Models.

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