I have a health app on the App Store that uses Foundation Models to generate brief narrative summaries from the user's own glucose and menstrual cycle data. No medical advice, just supportive summaries of their own numbers. This has been working reliably on iOS 26.x since early 2026. After updating to iOS 27 beta 2, every prompt is refused. The error is LanguageModelError ("The model refused to answer" / "May contain sensitive content"), not GenerationError.guardrailViolation. I've confirmed: Same device, same code, same prompts. Worked on iOS 26.x, fails on iOS 27 beta 2. Two independent features with different prompt structures and different service architectures are both affected. Using SystemLanguageModel(guardrails: .permissiveContentTransformations) does not help. The classifier passes. The model itself refuses. The prompts contain terms like "luteal phase," "progesterone," "glucose," "time in range," and "diabetes" in the system instructions. This appears to be a model-level sensitivity change in the iOS 27 on-device model that broadly blocks health/medical terminology, even when the use case is summarizing the user's own data. Filed as FB23513774 with the full prompt text, instructions, and source file attached. Is anyone else seeing model-level refusals (not guardrailViolation) on iOS 27 beta for health or medical content? Related threads from iOS 26 betas: Model Guardrails Too Restrictive? Model w/ Guardrails Disabled Still Refusing Using Past Versions of Foundation Models As They Progress

I've been successfully integrating the Foundation Models framework into my healthcare app using structured generation with @Generable schemas. While my initial testing (20-30 iterations) shows promising results, I need to validate consistency and reliability at scale before production deployment. Question Is there a recommended approach for automated, large-scale testing of Foundation Models responses? Specifically, I'm looking to: Automate 1000+ test iterations with consistent prompts and structured schemas Measure response consistency across identical inputs Validate structured output reliability (proper schema adherence, no generation failures) Collect performance metrics (TTFT, TPS) for optimization Specific Questions Framework Limitations: Are there any undocumented rate limits or thermal throttling considerations for rapid session creation/destruction? Performance Tools: Can Xcode's Foundation Models Instrument be used programmatically, or only through Instruments UI? Automation Integration: Any recommendations for integrating with testing frameworks? Session Reuse: Is it better to reuse a single LanguageModelSession or create fresh sessions for each test iteration? Use Case Context My wellness app provides medically safe activity recommendations based on user health profiles. The Foundation Models framework processes health context and generates structured recommendations for exercises, nutrition, and lifestyle activities. Given the safety implications of providing health-related guidance, I need rigorous validation to ensure the model consistently produces appropriate, well-formed recommendations across diverse user scenarios and health conditions. Has anyone in the community built similar large-scale testing infrastructure for Foundation Models? Any insights on best practices or potential pitfalls would be greatly appreciated.

Testing Foundation Models framework with a health-focused recipe generation app. The on-device approach is appealing but performance is rough. Taking 20+ seconds just to get recipe name and description. Same content from Claude API: 4 seconds. I know it's beta and on-device has different tradeoffs, but this is approaching unusable territory for real-time user experience. The streaming helps psychologically but doesn't mask the underlying latency.The privacy/cost benefits are compelling but not if users abandon the feature before it completes. Anyone else seeing similar performance? Is this expected for beta, or are there optimization techniques I'm missing?

I'm implementing a horizontal carousel in iOS 26 Beta 3 using SwiftUI ScrollView with LazyHStack. The goal is to programmatically scroll to a specific card on view load. What I'm trying to do: Display a horizontal carousel of cards using ScrollView + LazyHStack Automatically scroll to the "current" card when the view appears Use iOS 26's new ScrollPosition object for programmatic scrolling Current behavior: The ScrollPosition object receives scroll commands (confirmed via console logs) The scrollTo(id:anchor:) method executes without errors However, the ScrollView does not actually scroll - it remains at position 0 Manual scrolling and scrollTargetBehavior(.viewAligned) work perfectly Code snippet: @State private var scrollPositionObject = ScrollPosition() ScrollView(.horizontal) { LazyHStack(spacing: 16) { ForEach(cards, id: .id) { card in CardView(card: card) .id(card.id) } } .scrollTargetLayout() } .scrollPosition($scrollPositionObject) .scrollTargetBehavior(.viewAligned) .onAppear { let targetId = cards[currentIndex].id DispatchQueue.main.asyncAfter(deadline: .now() + 0.3) { scrollPositionObject.scrollTo(id: targetId, anchor: .center) } } Workaround that works: Using the iOS 17 scrollPosition(id:) binding instead of the ScrollPosition object: @State private var scrollPosition: UUID? .scrollPosition(id: $scrollPosition) .onAppear { scrollPosition = cards[currentIndex].id } Environment: iOS 26 Beta 3 Xcode 26 Beta 3 Physical device (iPhone 16 Pro Max) Is this a known issue with ScrollPosition in Beta 3, or am I missing something in the implementation? The older binding approach works fine, but I'd prefer to use the new ScrollPosition API if possible.