foundation-models-on-device

# FoundationModels: On-Device LLM (iOS 26) Patterns for integrating Apple's on-device language model into apps using the FoundationModels framework. Covers text generation, structured output with `@Generable`, custom tool calling, and snapshot streaming — all running on-device for privacy and offline support. ## When to Activate - Building AI-powered features using Apple Intelligence on-device - Generating or summarizing text without cloud dependency - Extracting structured data from natural language input - Implementing custom tool calling for domain-specific AI actions - Streaming structured responses for real-time UI updates - Need privacy-preserving AI (no data leaves the device) ## Core Pattern — Availability Check Always check model availability before creating a session: ```swift struct GenerativeView: View { private var model = SystemLanguageModel.default var body: some View { switch model.availability { case .available: ContentView() case .unavailable(.deviceNotEligible): Text("Device not eligible for Apple Intelligence") case .unavailable(.appleIntelligenceNotEnabled): Text("Please enable Apple Intelligence in Settings") case .unavailable(.modelNotReady): Text("Model is downloading or not ready") case .unavailable(let other): Text("Model unavailable: \(other)") } } } ``` ## Core Pattern — Basic Session ```swift // Single-turn: crea...