Cloudflare's Agents SDK adds PiHarness so a Pi Durable agent can pause mid-turn

Cloudflare’s 2 October 2026 changelog says the Agents SDK now has first-class support for the Pi harness. The new piece is a PiHarness class. Combined with Pi 1.0 and Pi Durable, it is meant to keep an agent’s work on a Durable Object when a turn is interrupted. Cloudflare calls this its first step toward first-class support for third-party agent harnesses, built with Earendil. It is a Cloudflare integration on top of Pi, not a new release of the Pi harness itself.

What is beta

The post labels PiHarness beta in the body. It says Pi Durable is a new, experimental package, and that the PiHarness API will likely change as Pi Durable matures. PiHarness is described as a “Lifecycle capability”. Pi Durable supplies the agent harness. The Lifecycle’s job is to keep that work running inside the Durable Object across restarts, crashes, and network failures. Cloudflare says it will explain Lifecycle capabilities more later.

How the sample is wired

Install, per the changelog, is agents@latest plus the optional peer dependencies @earendil-works/pi-durable and @earendil-works/pi-ai. They are optional peers, so a project that does not use Pi does not need them. The sample builds models with createModels() from @earendil-works/pi-ai/models, opens a Harness from @earendil-works/pi-durable against the Durable Object storage, and registers new PiHarness(...) with this.lifecycle.use(this.harness). The default model in the sample is this.ai("@cf/moonshotai/kimi-k2.7-code"), reached through agents/models/pi-ai, which the post says supports AI Gateway and Workers AI.

Tools and system-prompt sections go in through extensions. The sample registers a word_count tool with replay: "safe" and installs a skills bundle with registry.install(await skills(sources)) from agents/harness/pi. A prompt returns { text } from this.harness.prompt(prompt). The changelog links a fuller example with WebSockets, a browser UI, and a @cloudflare/computer Workspace.

Practical takeaway

If you already run an Agent on Cloudflare and want Pi’s harness, the supported path in this changelog is PiHarness plus the two Earendil packages, with the harness opened on the Durable Object’s storage. Plan for API changes: both the Cloudflare label and the Earendil package are marked experimental. Pin versions, and do not treat the sample model id as a requirement.