Vercel's AI SDK has evolved beyond streaming text responses. The streamUI function now sends serialized React Server Components directly to the client, enabling AI to generate interactive dashboards, forms, and charts in real-time.
How It Works
The implementation relies on React 18's Server Components and Flight protocol. When an AI generates a response, the server wraps content in React components and streams them via Server-Sent Events. The client receives and hydrates these components immediately - users can interact with charts and buttons while the AI continues generating the rest of the response.
Server Actions enable bidirectional flow: streamed components can trigger secure server-side functions, which can spawn more AI generation and stream additional components. Think of it as overlaying interactive UI elements onto a live video feed, rather than just describing them in text.
Implementation Pattern
The server-side code uses streamUI with a text mapping function that wraps AI output in React components. A typical implementation might stream a <ReportComponent> with interactive buttons rather than JSON data. The client uses useCompletion to handle the stream, with the SDK deserializing the React tree.
The performance trade-offs matter here. RSCs eliminate client-side hydration for server-rendered components, cutting bundle sizes significantly. But mixing server and client component boundaries adds complexity - debugging becomes harder when some components render server-side while interactive elements require client boundaries.
The Real Test
This is Vercel's third major iteration of AI streaming patterns. The previous approaches (text-only, then structured JSON) taught them something about where developers hit limits. The question isn't whether streaming UI is technically impressive - it is. The question is whether enterprise teams will adopt a pattern that requires rethinking component architecture and server action security models.
Worth noting: RSCs remain experimental in React 18+. The Flight protocol underpinning this entire approach is still evolving. Teams shipping production features should weigh the performance gains against the debugging overhead and limited ecosystem tooling outside Next.js.