chanfana

chanfana (formerly itty-router-openapi) is a library that adds OpenAPI 3 and 3.1 schema generation and validation to any router, primarily targeting Hono and itty-router. Version 3.3.0, released by Cloudflare, emphasizes Cloudflare Workers but works on any runtime. Key differentiators: Zod v4 compatible with full TypeScript inference, class-based endpoints, CLI to extract schema, and extending existing apps without modifying old routes. Release cadence is active with frequent updates. Pairs with Hono, itty-router, and zod.