Update: I think I found the main reason. SystemLanguageModel.variant shows the iPhone 16 using .core3 with a 4K context, while the iPhone 17 Pro Max uses .coreAdvanced3 with 8K. Same OS, but not the same model. Apple says Core Advanced is a sparse 20B model that activates 1–4B parameters depending on the task. It was much more precise with tool calls in my tests: 98% completion versus 60% on Core. I couldn’t find an API showing which experts or how many parameters are active per request. Also, from what I've found is that Core Advanced isn’t limited to the 17 Pro Max, it seems like Apple lists iPhone Air and iPhone 17 Pro as supported too. Most other iPhones still use Core. Apple’s latest model overview

I think the issue is beta mismatch, I was able to solve it by updating the device, Command Line tools, XCode, MacOS and device OS to the latest beta and the issue doesn't appear. https://developer.apple.com/forums/thread/841805?page=1#901382022

It seems like the issue was caused by a beta-version mismatch. The device was on beta 4 while Xcode/macOS were on beta 5. After updating the device to the latest beta, the error disappeared and I could no longer reproduce it.

Same thing here on Tahoe 26.5.1 (25F80) and Xcode Version 26.5 (17F42) Takes around 5 minutes with fully white screen until finally opens the app. After some time the simulator just hangs and becomes unresponsive for couple of minutes and then revives again. Super weird thing, never experienced this before p.s. I have fullt re-installed Xcode and this issue persists.

Tell me if I am crazy, but the buttons on the left look like AppKit to me... Could be something related to that maybe?

If you’re set on using native views in iOS 26 (rather than custom LiquidContainers) and have encountered visual glitches, like shadow clipping or view hierarchy issues, when applying .glassEffect to Menu labels, this thread should be helpful. After some research, I found a useful suggestion on Stack Overflow. TLDR; Wrapping your label in .compositingGroup() significantly improves rendering, especially when using more complex labels inside a Menu. To achieve the cleanest appearance, I recommend combining .compositingGroup() with .glassEffect(.clear). Here’s a sample demonstrating this approach: Menu { Button("Duplicate", action: {}) Button("Rename", action: {}) Button("Delete…", action: {}) } label: { VStack(alignment: .leading) { Text("Title") .tint(.primary) Text("Subtitle") .tint(.secondary) } .frame(maxWidth: .infinity, alignment: .leading) .padding() .glassEffect(.clear) } .compositingGroup()

It seems like there are two ways of approaching this. One (bad one) is: Adding the padding on the label view to compensate the native shadow. Menu { Button("Duplicate", action: {}) Button("Rename", action: {}) Button("Delete…", action: {}) } label: { Label("PDF", systemImage: "doc.fill") .padding() .glassEffect(.regular) .padding(40) // <- Here } Another one, much better: Menu { Button("Duplicate", action: {}) Button("Rename", action: {}) Button("Delete…", action: {}) } label: { Label("PDF", systemImage: "doc.fill") .padding() .glassEffect(.clear) } Both have tradeoffs, one is a spatial one, since you have to provide space for it, but maybe useful for someone who is not constrained by space. Another one - visual, since the glass effect .clear, doesn't have a frost. I guess this could be improved by overlaying a white color with low opacity to simulate the same effect.

Even though this doesn’t provide a direct solution for cross-device real-time database persistence, it may simulate the behavior you’re looking for. If both devices are on the same network, you can leverage the MultipeerConnectivity framework to send data to other devices immediately and then persist it locally. This way you can achieve a “live update” experience within the Apple ecosystem, while still using SwiftData for storage.

I am also experiencing issues with tool calling. Not sure what is the issue yet, but what has been answered to you is checked on my code. It used to work perfectly before the change to the new tool output format.

I encounter the same issues. Also some strange haptics errors?

Hello Benjamin, I hope you’re doing well. Several posts by the developers, including myself, have raised concerns about an issue that seems to have arisen since installing iOS 26 Beta 3. Specifically, FoundationModels is intermittently throwing guardrail violations on otherwise harmless prompts. For example, Apple’s own sample app from the “Foundation Code-Along” session now fails with the same error. FoundationModels guardrailViolation on Beta 3 Community members on the forums have tested a variety of queries and found wildly inconsistent results—asking “What’s the population of New York?” succeeds, whereas “What’s the population of Sweden?” triggers a guardrailViolation or a GenerationError (see these threads for details): "FoundationModels GenerationError error 2" on iOS 26 beta 3 So far, the only official responses have been generic reminders about prompt safety, which don’t explain why simple factual questions are being blocked. Given Apple’s two-week beta cadence, I’m optimistic that this behavior will be addressed in the next release.

Fixed on Xcode beta 2

The issue seem to persist on the Tahoe Beta 3 @DTS Engineer I will submit the report shortly.

Also running the same exact code that runs fine on the mac simulator on iPhone simulators with iOS 26 result in this error: guardrailViolation(FoundationModels.LanguageModelSession.GenerationError.Context(debugDescription: "Safety guardrail was triggered after consecutive failures during streaming.", underlyingErrors: []))