Workflow SDK now writes over WebSockets on Vercel

The Workflow SDK now sends event writes and stream writes to Vercel Workflows over a WebSocket by default, replacing one HTTP request per write, with no code change needed beyond upgrading to workflow@5.2.0 or later. In a benchmark replaying an AI agent's token stream, v5.2.0 delivered the full response 4.2× faster than v4.8.12, with no chunk delayed over a second. New runs use the WebSocket after deployment while in-flight runs finish on the deployment they started on, and users on 4.x must follow the upgrade guide because v5 is a major release.

The Workflow SDK https://workflow-sdk.dev now sends event writes and stream writes to Vercel Workflows https://vercel.com/workflows over a WebSocket by default, replacing one HTTP request per write, or per write group for streams. No code change is needed beyond upgrading to workflow@5.2.0 or later. Once you deploy the upgrade, new runs use it. In-flight runs finish on the deployment they started on. Existing streaming code works as is. A step that writes a burst of chunks, like AI tokens, sends them over the WebSocket once it opens: In a benchmark https://workflow-sdk.dev/docs/performance replaying an AI agent's token stream, v5.2.0, which writes streams over a WebSocket by default, delivered the full response 4.2× faster than v4.8.12, with no chunk delayed over a second. Every step start and completion is an event write, now sent over the WebSocket, so workflows with many steps make fewer HTTP requests. The added efficiency also improves performance and reduces costs. The queue handler opens the connection for every delivery. Read the Vercel World documentation https://workflow-sdk.dev/worlds/vercel to get started. If you're on 4.x, start with the upgrade guide https://workflow-sdk.dev/docs/whats-new , since v5 is a major release.