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Flue¶
Flue (flueframework.com) is an open-source declarative agent framework (1.0 Beta, June 2026) built by the team behind Astro. It sits at the framework layer of the three-layer agent platform stack (framework → harness → runtime), built on the Pi harness (same harness powering OpenClaw).
Architecture¶
Flue's core design principle: describe what an agent knows, not what it does. Define model, skills, sandbox, and instructions declaratively — the agent solves tasks autonomously with no orchestration loop to write.
Deployment targets¶
- Node.js: each agent runs as a long-lived process; deployable to any VM, container, or GitHub Actions.
- Cloudflare: each agent becomes a Durable Object with isolated storage and compute, automatic scaling, no server provisioning or sticky sessions.
Durable Streams¶
Flue achieves crash recovery via Durable Streams — an append-only event log where every prompt, tool response, and model choice is recorded as an immutable entry. On process death, a new instance replays the log from the exact interrupted step.
(Source: Agents platform post.)
Cloudflare integration¶
When targeting Cloudflare, Flue leverages:
runFiber()/stash()/onFiberRecovered()for durable execution@cloudflare/codemodefor sandboxed code execution via Code Mode@cloudflare/shellfor a durable virtual filesystem
Seen in¶
- sources/2026-06-17-cloudflare-bringing-more-agent-harnesses-and-frameworks-to-cloudflare — launch announcement with architectural decomposition
Related¶
- systems/pi-harness — underlying agentic-loop harness
- systems/cloudflare-agents-sdk — runtime layer Flue targets
- systems/project-think — Cloudflare's first-party harness (same SDK primitives)
- concepts/declarative-agent-definition — Flue's core design principle
- patterns/framework-harness-runtime-layering — the stack separation Flue exemplifies