Vercel moves fx agent orchestration and model credentials onto the host

Vercel has updated the fx adapter for the AI SDK's HarnessAgent to run agent orchestration and model requests in the application's process. Model credentials now stay on the host instead of being forwarded into the sandbox, while built-in filesystem and shell operations remain isolated there. The adapter uses the TypeScript library libfx, removing the need to install fx inside the sandbox, run a sandbox bridge or expose a sandbox port. It also adds tool filtering, instructions during a running turn, schema-based responses and image results for models. Developers can save sessions and resume them in a new host process by updating @ai-sdk/harness-fx.