Tool Calling Comes to Apple On‑Device LLM for React Native

Callstack has released an update to their Apple provider for the Vercel AI SDK, adding tool calling support for Apple's on-device LLM in React Native apps. Developers can now define JavaScript functions using the AI SDK's tool() interface and have the on-device model invoke them directly. The release also supports structured output via experimental_output with Zod schemas. Notable caveats include that tools are executed natively by the Apple provider, so some AI SDK callbacks like onStepStart and maxSteps are not available. Upcoming work includes Android support and a stable release timed with iOS 26's public launch.