Xcode 26.4 -- Here Is What Actually Matters for Devs

Apple released Xcode 26.4 (build 17E192) on March 24, 2026. It ships with Swift 6.3, updated SDKs for iOS/iPadOS/tvOS/macOS/visionOS 26.4, and the largest Instruments update in the entire Xcode 26 cycle. This post cuts through the release notes and organizes everything by what will actually affect your day-to-day work. If You Read Nothing Else: The Sanitizer Regression Address Sanitizer and Thread Sanitizer hang indefinitely on any OS 26.4 target when you build with Xcode 26.3 or older. Not crash. Not fail. Hang. Your CI jobs will silently block without producing any error output. If your machines are running OS 26.4, upgrade Xcode to 26.4 immediately. There is no other workaround. This is the single most urgent item in the release. Instruments: Serious New Profiling Tools Instruments got three headline features that are worth learning before your next performance investigation. Run Comparison. You can now compare call trees across multiple profiling sessions. Open it from View > De