cellb.dev

The monorepo of cellb (@statewalker/cellb): an isomorphic Durable Objects runtime with a celld/Cloudflare-compatible surface. The same cells run in a browser (OPFS, ServiceWorker ingress), in Node, and alongside celld on one shared bucket.

What cellb does, next to celld

celld runs Cloudflare Workers projects on a fleet of servers that share one bucket. cellb runs the same projects unchanged, in Node and in browsers, answers the same requests the same way, and stores cells in celld's format, so one cell can be served by celld, then by cellb, then by celld again. celld is the judge: its examples, cellb's own probe projects and workerd's Durable Object tests run on the real celld, are recorded, and are replayed against cellb in Node and in Chromium (70 scenarios; 5 are judged by workerd instead, where cellb passes stubs by reference as workerd does, and 6 are known differences, listed in packages/cellb/docs/gaps.md).

Feature	celld 0.6.3	cellb, Node	cellb, browsers	How cellb is checked
Workers (stateless handlers)	supported	yes	yes	hello, webapi, router, body
Durable Objects / cells	supported	yes, same storage format	yes, same storage format	counter, rpc, alarm, workerd's tests; cells cross celld ↔ cellb
Durable Object facets	supported	yes	yes	facets, facets-api
KV	supported	yes (celld's code)	yes	kv, kv-values
Queues	supported	yes (celld's code)	yes	queues, queues-api
D1	supported	yes (Miniflare's simulator)	yes	d1, D1 migrations
R2	supported	yes, celld's bucket layout	yes	r2, r2-api, r2-advanced
Workflows	supported	yes (celld's engine)	yes	workflow, workflow-api
Cron triggers	supported	yes	yes	cron
Static assets	supported	yes (with Cloudflare's behaviour where celld has bugs)	yes	static-assets, assets-api
Dynamic Workers (Worker Loader)	supported	yes, a worker thread each	yes, a Dedicated Worker each	dynamic-worker-tails, the Worker Loader scenarios
WebSockets, hibernation	supported	yes	yes, over MessagePorts	wsecho, wsclient, wd-websocket-* (celld fails wd-websocket-hibernation, cellb passes it)
Vectorize-style search	example	yes	yes	vectordb
Workers AI (ai binding)	no binding	yes, on an OpenAI-compatible endpoint the host names	yes	p14-workers-ai, Flue's cloud agent
Python Workers (Pyodide)	supported	no, out of scope	no	not run
Containers	experimental (Docker or Podman)	no; reported in unsupported	no	not run
Agent frameworks: Flue, pi, opencode	examples (pi, opencode need the network)	yes, offline against a fake model	Flue	examples/flue, examples/agents

Where cellb follows Cloudflare or workerd instead of celld, and what still differs, is in packages/cellb/docs/celld-compatibility.md.

Layout

packages/cellb/        the runtime, its browser host, conformance corpus and docs (see its README)
examples/flue/         a Flue agent app (Cloudflare target, Agents SDK) on cellb, in Node and Chromium
examples/agents/       pi and opencode in Durable Objects on cellb, against the fake model
examples/fake-openai/  a scripted OpenAI-compatible model endpoint the examples test against
site/                  the cellb.dev website (Astro, Tailwind CSS, shadcn/ui tokens)
docs/superpowers/      plans for work on the repository
.github/workflows/     interop CI against the real celld and RustFS

packages/* are libraries; examples/* are private apps that use them, with the test tools only they use. Both are workspaces (pnpm-workspace.yaml), so an example depends on @statewalker/cellb and @statewalker/fake-openai through workspace:*.

How to run it

1. pnpm install
2. cd packages/cellb && pnpm test: the unit tests (test/) and the celld end-to-end tests (e2e/), which skip without CELLD_BIN.
3. pnpm exec playwright test: the Chromium end-to-end suite.
4. cd examples/flue && pnpm test: builds a Flue app with Flue's own Cloudflare build and runs it on cellb against a fake model endpoint; pnpm test:browser runs the same app in Chromium.
5. cd examples/agents && pnpm test: pi and opencode, each in a Durable Object on cellb, against the fake model.
6. pnpm --filter @statewalker/cellb-site dev: the website at http://localhost:4321; build writes it to site/dist/.
7. pnpm run interop: the celld interop suite. scripts/interop-env.sh downloads the pinned celld and RustFS releases and starts RustFS on 127.0.0.1:9200.

pnpm test at the root runs every workspace's tests, and stops at the first one that fails.

Why it is the way it is

• One package, three entry points. Callers differ by platform (isomorphic, Node, browser), not by internal module, so @statewalker/cellb, /node and /browser are the seams.
• CI runs against the real celld. celld is the conformance judge, so the interop workflow downloads the pinned celld and RustFS and runs the Node and Chromium interop suites on every pull request.
• Examples run offline. Agent frameworks need a model; the examples point theirs at @statewalker/fake-openai, so CI needs no key and no network beyond the package registry.

What will surprise you

• A green pnpm test without CELLD_BIN says nothing about celld compatibility: those tests skip.
• [cellb] …: unhandled rejection in Worker code lines on stderr during the conformance run are expected: workerd's vendored Durable Object tests leave assert.rejects(…) unawaited. A Worker's unhandled rejection is its own, as on workerd and celld; cellb reports it there and keeps it from the test runner and the process.
• The opencode example's first load takes about half a minute: its SDK bundles to about 430,000 lines.