Cloudflare's Agents SDK becomes a shared runtime for agents — Flue is the first framework on board!

Hi everyone, it's Shii! Today I found a super exciting announcement: the whole foundation for building agents is being opened up! Cloudflare is turning the Agents SDK into a runtime that any agent framework can build on.

Cloudflare Blog blog.cloudflare.com

What was announced?

This comes from the Cloudflare Blog. The big point: the Agents SDK is no longer just one framework — it is being opened up as a runtime that many different agent frameworks can build on top of.

The first framework to arrive on it is Flue, a new open-source framework. And it comes from the team behind Astro! Cloudflare is also rolling out a way to run agents in the dashboard.

Why it matters

Cloudflare splits the agent world into three layers, from top to bottom:

• The framework (Flue) — the project structure, conventions, integrations, CLI, and developer experience for building agents.
• The harness (Pi, Project Think) — the agentic loop that calls tools, reads results, manages context, and keeps going until the task is done.
• The runtime/platform (the Cloudflare Agents SDK) — the compute, state, and storage primitives everything above depends on.

The nice thing about this split is that the framework, harness, and runtime are cleanly separated, so you can choose or swap each one on its own. Cloudflare takes care of the foundation, so framework authors can focus on the developer experience.

What changes

Until now, the Agents SDK leaned toward "the Cloudflare way" of building an agent. By opening up the primitives, outside frameworks can now choose the Agents SDK as their foundation.

The first real example is Flue. Its 1.0 Beta shipped this week, built on the Pi harness. Instead of scripting exactly what an agent should do, Flue uses a declarative style where you describe what it knows. It ships Channels to connect to existing tools like Slack, GitHub, Linear, and Discord, and @flue/react lets you stream agent state straight to your frontend.

Flue agents deploy as Durable Objects on Cloudflare, so storage and compute stay isolated while scaling automatically.

Dive Deep

Let's peek a little more at the Agents SDK primitives being opened up.

• Durable execution (Fibers): methods like runFiber(), stash(), and onFiberRecovered() checkpoint agent state to SQLite. If an agent is interrupted, it resumes from the exact step it left off, without losing context or wasting tokens.
• Code execution (@cloudflare/codemode): wraps Dynamic Workers to safely run LLM-generated TypeScript. Isolates start in under 10 ms and cost $0.002 per load.
• Durable filesystem (@cloudflare/shell): a virtual filesystem backed by SQLite, with typed operations like read, write, edit, search, grep, and diff inside Durable Objects.
• Dynamic workflows (@cloudflare/dynamic-workflows): agents can generate JavaScript workflows at runtime, with durable step execution, retries, and waiting for external events.

There is also @cloudflare/workspace, still under development. On top of that, the Agent class connects to AI Gateway for spend tracking and can run inference across 14+ model providers.

Wrap-up

• Cloudflare opened up the Agents SDK as a runtime that any agent framework can build on.
• The first framework is Flue, from the Astro team (1.0 Beta, built on the Pi harness).
• It organizes the agent world into three layers: framework / harness / runtime.
• The opened primitives include durable execution (Fibers), @cloudflare/codemode, @cloudflare/shell, and @cloudflare/dynamic-workflows.
• Flue agents deploy as Durable Objects and scale automatically.

If you build agent infrastructure from the ground up — or you author frameworks yourself — this one is for you. A great starting point is to try Flue and see how far Cloudflare's primitives carry you.