I'm not sure that the conclusion, "You can't use willSet/didSet with @Observable" is correct any longer. With Xcode 16, the @Observable macro expands a simple String property as shown in the image below. Note that the "didSet" expression is copied to the newly-generated stored property "_name". Depending on exactly what you're doing in the property observers, they should just work.

Same here: apps built with the GM version of Xcode 16 crash on Intel Macs because the QuicklookUI framework is not loaded. It's really inexcusable that this made it to the production release of Xcode 16. It was reported (AND ACKNOWLEDGED!) in the beta period and nobody at Apple Engineering cared enough to do anything about it. We PAY for this. Apple loves to brag about how the 30% fee it collects goes to support APIs and the platforms. Really? Does it? Does anyone here feel supported? FIX THE BUG, Apple.

After you accept the latest developer agreement, there is a 5-10 minute delay before this error resolves. I've contacted Ken Orr directly to request a fix. I've reported this issue for years and the Radars are just getting ignored...like all Radars. Hopefully putting a spotlight on this with the head of Developer Tools will get it addressed.

In general, the only way to ensure that Xcode releases get fixed is to email Craig Federighi (head of software) or Ken Orr (head of developer tools) directly. Filing “feedback” or discussing the problem on these forums will have no effect—unless you catch Eskimo’s attention and he runs the issue up the chain on your behalf. I would encourage you all to email those executives. If they see enough noise, someone will force engineering to take a look. Otherwise, this issue will run for a year because Apple‘s feedback process is absolutely broken.

The issue is still present in the GM Release of Xcode 15. (This is my shocked face.) It manifests for me anytime I run a playground. @zettlunic - do you know what "-OS_ACTIVITY_MODE disable" does, precisely? @riccardo_p - do you have a link or a description of what, exactly, we're adding there? I'm a little hesitant to use these fixes without a better understanding of exactly what the changes are doing. Thanks!

The issue still manifests in Xcode 15 beta 2. It's now June of 2023. You guys must be new here. Apple Engineering never fixes ANYTHING in fewer than seven years and they maintain absolute radio silence the entire time. There are no updates. There will never BE any updates. The issue will continue until someone high enough in the organization is affected by it. See you in 2031.

Spoiler alert: it wasn't fixed soon. Still manifesting with Xcode 14.2 and Ventura 13.1

Details: I have already deleted Xcode's preferences, caches, and the entire ~/Library/Developer folder. No change. The issue happens on a BRAND-NEW project, so it's not a problem with a certain project's Xcode config file. I can reproduce the problem 100% of the time on two separate Macs. I am running Monterrey 12.4