Workflow SDK now writes over WebSockets on Vercel
Vercel’s Workflow SDK now uses WebSockets by default for writes, reducing HTTP requests and improving performance for streaming and event-based workflows.
The Workflow SDK version 5.2.0 and later sends event writes and stream writes over a WebSocket by default, replacing individual HTTP requests. This change requires no code modifications beyond upgrading the SDK. Deployments automatically adopt the new behavior for new runs, while in-flight runs continue on their original deployment. Existing streaming implementations remain compatible without adjustments.
A benchmark comparing v5.2.0 to v4.8.12 showed a 4.2× speed improvement when streaming AI agent tokens via WebSocket. The upgrade ensures no chunk is delayed beyond one second, enhancing real-time responsiveness. Steps that generate bursts of data, such as AI token streams, benefit from reduced latency and fewer network overheads.
Every step start and completion generates an event write sent over the WebSocket, reducing the number of HTTP requests in workflows with many steps. This efficiency gain lowers operational costs and improves overall performance. The queue handler manages WebSocket connections for each delivery, streamlining the process.
Users on version 4.x must follow the upgrade guide to migrate to v5, as it introduces a major release. Documentation on Vercel World provides instructions for getting started with the updated SDK. Existing deployments are unaffected, and the transition is backward compatible for streaming code.