Workflows

A WorkflowEntrypoint class whose run(event, step) is made of durable steps (step.do, step.sleep, step.waitForEvent), and a binding to create and inspect instances. CellB runs celld’s own workflow engine (vendored unchanged), so an instance’s state is celld’s and a running or sleeping instance can move between celld and CellB.

{
  "name": "workflow",
  "main": "index.js",
  "compatibility_date": "2026-08-18",
  "workflows": [
    {
      "binding": "REPORTS",
      "name": "report-builder",
      "class_name": "ReportBuilder"
    }
  ]
}

import { WorkflowEntrypoint } from "cloudflare:workers";

export class ReportBuilder extends WorkflowEntrypoint {
  async run(event, step) {
    // A completed step returns its stored result when the Workflow resumes.
    return await step.do("build report", async () => {
      const response = await fetch(event.payload.url);
      if (!response.ok) throw new Error(`source answered ${response.status}`);
      const text = await response.text();
      return { bytes: text.length, lines: text.split("\n").length };
    });
  }
}

export default {
  async fetch(request, env) {
    const url = new URL(request.url);
    const id = url.searchParams.get("id");

    if (url.pathname === "/create") {
      const instance = await env.REPORTS.create({
        params: { url: url.searchParams.get("url") ?? "https://example.com" },
      });
      return Response.json({ id: instance.id });
    }

    if (url.pathname === "/status" && id) {
      const instance = await env.REPORTS.get(id);
      return Response.json(await instance.status());
    }

    return new Response("Use /create?url=URL or /status?id=ID.", {
      status: 404,
    });
  },
};

This is celld’s workflow example (conformance/celld-examples/workflow), copied unchanged and run by the conformance suite on Node and in Chromium.

An instance is a cell with an alarm

Each instance is a cell __Workflow.<script>:<id> holding celld’s records (__wf.meta, one record per completed step, V8-serialized) and an alarm that wakes it for its next step. A completed step’s result is stored, so a resumed instance does not run it again.

e2e/p11f-celld-one-bucket.test.ts takes one instance across three runtimes through one bucket: its first step runs on celld, the step after its sleep on CellB, the step after its event on celld again, and none runs twice.

How it is checked

celld’s workflow example and CellB’s workflow-api project, on Node and in Chromium, and the celld → CellB → celld trip above.