React for Agents: Astro Creator Brings Hooks to his Meta-Harness, Flue

Astro creator Fred Schott has released version 2 of Flue, an early-stage developer framework for building AI agents. In Flue, an agent is defined as a JavaScript function that re-renders on every turn before a model call. The new version introduces React-style Agent Hooks authored in TypeScript, allowing agents to dynamically manage state, respond to lifecycle events, and attach tools and skills at runtime. This capability enables agents to adapt in real time to complex workflows, such as support or triage bots.

A core concept in Flue is the agent harness, an environment providing the context and capabilities an agent needs to drive itself through problems rather than relying solely on scripts. Flue is built on top of Pi, a minimal open source harness, and uses Vite for building hosted agents. Schott moved away from file-based routing after early users showed that complex applications typically rely on a single, composable agent rather than multiple static route files.

Flue is designed to be completely headless and programmable, often set up with the assistance of AI coding agents like Claude Code. While it shares the foundational harness approach with Vercel’s eve framework, Flue distinguishes itself by remaining an open source framework designed for host portability across different platforms, rather than being tied to a single infrastructure provider like Cloudflare or Vercel. Schott remains focused on refining the harness rather than building managed agent products or a broader meta-harness API.