What it is

Apple's Foundation Models framework (shipping in iOS 27 / macOS 27 this fall) is the standard Swift API for on-device AI — the same API Apple uses for their own small model. This package makes Claude plug into that same API as a drop-in swap.

  // Apple's on-device model
  let session = LanguageModelSession(model: SystemLanguageModel.default)

  // Claude — same API, just different model constructor
  let session = LanguageModelSession(model: ClaudeLanguageModel(name: .sonnet4_6, auth: auth))

You don't call the Anthropic API directly. Apple's framework handles streaming, tool calling, and structured output (@Generable) — you just get Claude's capability through it.