Despite some minor issues, I had a pretty good impression of the previous beta versions of Xcode 26. Both the refreshing visual experience and the clearer annotations for AI-generated code were quite impressive. However, after recently updating to beta 4, these positive feelings quickly dissipated due to frequent Preview crashes.
In Xcode 26 beta 4, whenever I use the Preview feature, Xcode typically freezes within just a few seconds to tens of seconds. What’s even more terrifying is that this is immediately followed by an unexpected system crash and restart. I was truly shocked when I first encountered this—it was my first experience with an unexpected system crash on macOS 26. But when every single preview session inevitably triggers this scenario, I can be certain that Xcode’s preview functionality is the culprit.
After searching online, I discovered that this was actually a known issue before the release, which left me even more bewildered and amused. I have to say, the “power” of this bug is truly remarkable—even deliberately writing malicious code to crash the system might not be this “simple and direct.”
Since I started using Claude Code, I’ve almost completely switched back to Xcode from Cursor. Just when I was marveling at finally being able to have the best of both worlds (enjoying an excellent visual experience while having powerful AI assistance), the emergence of this issue is genuinely disheartening.
I hope beta 5 can fix this problem quickly, otherwise what crashes won’t just be Xcode and the system—but also our patience and confidence as developers.
The system crashes caused by Preview are more likely due to the iOS 26 simulator. Even when using Xcode 16.4 + macOS 26, setting the preview environment to iOS 26 will still cause crashes.
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Default Actor Isolation: New Problems from Good Intentions
While Swift’s strict concurrency checking has good intentions, it significantly increases the burden on developers in many single-threaded scenarios. Developers are forced to add unnecessary Sendable, @MainActor, and other declarations to their code just to satisfy the compiler’s requirements. Swift 6.2’s new Default Actor Isolation feature will greatly improve this situation and reduce unnecessary boilerplate code. This article will introduce the Default Actor Isolation feature and point out some situations to be aware of when using it.
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