Chat agent is a way to build durable AI chat experiences that run on a machine with no timeouts and keep streaming through refreshes and crashes. The machine sleeps when nobody's typing and wakes where it left off, without you managing any state. Keep the AI SDK you already use: streamText on the server, useChat on the client. chat.agent slots in underneath as a transport and the API route between them goes away. Every turn is traced: prompts, tool calls, latency and cost.