Inside Workflow DevKit: How framework integrations work

Vercel's post explains the two-phase pattern (build-time and runtime) behind the Workflow DevKit (WDK) framework integrations, which now support eight frameworks including SvelteKit, Astro, Express, and Hono, with TanStack Start and React Router in active development.

The WDK uses an SWC compiler plugin to transform the same input file into three outputs (client, step, and workflow modes) and handles framework-specific request object conversion via injected helper functions.