Inside Workflow DevKit: How framework integrations work

Vercel's Workflow Development Kit (WDK) now integrates with eight frameworks including SvelteKit, Astro, Express, and Hono, with TanStack Start and React Router in active development. All integrations follow a unified two-phase pattern: build-time compilation of workflows into handlers with framework-specific patches, and runtime HTTP exposure. The SWC compiler plugin transforms the same input into three outputs (client, step handler, workflow handler), enabling write-once deployment across frameworks.