Anthropic ships Claude for Apple Foundation Models
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- Anthropic released "Claude for Foundation Models," a Swift package that makes Claude available as a server-side language model in Apple's Foundation Models framework, conforming the model to the framework's LanguageModel protocol
- The package uses Apple's LanguageModelSession API identically to the on-device model, so respond(to:), streaming, guided generation, structured outputs via @Generable, and tool calling all work the same way
- Requests go directly from the app to the Claude API; Apple is not in the request path and does not see prompts or responses, and usage is billed to the developer's Anthropic account at standard API pricing
- Developers choose per session whether to use Claude or Apple's on-device model, with the docs recommending Apple's engine for fast, private, offline lightweight work and escalation to Claude for larger context, frontier reasoning, or server-side web search, web fetch, and code execution
- Authentication options include .apiKey (flagged as development-only because keys bundled into an app are extractable from the shipping binary) and .proxied, which routes traffic through the developer's own backend so no key ships in the app
- The release is a beta targeting the server-side language model API introduced in the OS 27 betas, and exposes five reasoning effort levels (low, medium, high, xhigh, max) — with xhigh and max only reachable through the package's fixedEffort option
- API errors map onto Apple's LanguageModelError cases (context overflow → .contextSizeExceeded, HTTP 429 → .rateLimited, timeouts → .timeout), with the docs explicitly suggesting a fallback to SystemLanguageModel for that turn when Claude is rate-limited
Why it matters: Apple-platform developers can now run a single LanguageModelSession that quietly routes lightweight, private tasks to Apple's on-device engine and escalates heavy reasoning, web search, and code execution to Claude — the same code path, same streaming and tool APIs, just a different model argument. The package is in beta against the OS 27 server-side API, so real-world adoption is gated on Apple's framework update landing first.
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