Vercel AI SDK Agent Builder Purpose Create streaming AI chat interfaces with minimal code using Vercel AI SDK and OpenRouter provider. When to Use - Building Next.js frontend with chat UI - Need streaming responses with SSE - Want type-safe tool calling in TypeScript - Switching between multiple AI providers - Building agentic loops with stopWhen/prepareStep Quick Start Installation Environment Variables Backend Setup (Route Handler) Basic Chat Endpoint With Tool Calling Frontend Integration Using useChat Hook With Tool Results Display Advanced Patterns Multi-Step Agentic Loop Custom Streamin…