Cloudflare is opening up its Agents SDK as a base runtime layer that any agent harness or framework can build on. The post introduces a three-layer stack for production AI agents: a framework (Flue, built by the Astro team), a harness (Pi, Project Think), and the runtime platform (Cloudflare Agents SDK). Flue 1.0 Beta ships with declarative agent definitions, multi-platform support, and deep Cloudflare integration via Durable Objects. Key SDK primitives covered include durable execution via Fibers (runFiber/stash/onFiberRecovered), sandboxed code execution via Dynamic Workers (@cloudflare/codemode), a durable virtual filesystem backed by SQLite (@cloudflare/shell), and dynamic multi-step workflows. The post explains how each primitive solves a specific distributed systems problem agents face in production: crash recovery, secure code execution, persistent filesystems, and long-running orchestration.
