# CAFE names the Cloudflare, Alchemy, Foldkit and Effect stack > For agents: start with the [agent guide](https://ratstack.sh/llms.txt). Every page is Markdown by default; add `Accept: text/html` for HTML. Free workshop: [how to burn a trillion tokens and get good results](/tokenmaxx#interested). CAFE is a named stack. Each letter has one job. Read the [CAFE news](/news) and browse the [project directory](/directory). [Maxwell Brown](https://github.com/IMax153) coined the name; [Justin Bennett](https://github.com/just-be-dev) spread it with his template on 8 October 2026. That day, [Devin Jameson](https://github.com/devinjameson), Maxwell and [Sam Goodwin](https://github.com/sam-goodwin) streamed a CAFE build, and [Sebastian Lorenz](https://github.com/fubhy) wrote the explainer people share. | Letter | Part | Job | | ------ | ---------- | --------------------------------------------------------------- | | C | Cloudflare | Runs the app: Workers, Durable Objects, storage, static assets. | | A | Alchemy | Declares the cloud resources as an Effect program. | | F | Foldkit | Draws the UI with the Elm Architecture on Effect. | | E | Effect | Does the typed work between the UI and the cloud. | A request follows one path. The [Alchemy](/skills/learn-alchemy) Stack declares every box on it. ```text ┌─ Alchemy Stack ──────────────────────────────────┐ │ │ │ Foldkit app (browser) │ │ │ HTTP or RPC, typed by a shared schema │ │ ▼ │ │ Worker (Effect) │ │ │ │ │ ▼ │ │ Durable Object or storage │ │ │ └──────────────────────────────────────────────────┘ ``` The browser and the Worker import the same schemas. Alchemy reads the same program to deploy and to test. ## The canonical example [Effect-TS/cafe](https://github.com/Effect-TS/cafe) is a chat app from the Effect organization. Its README defines CAFE. [Sam Goodwin](/lore/sam-goodwin), who wrote Alchemy, built it. Maxwell Brown also commits to it. It shows these patterns: - `@cafe/api` holds the HTTP and [RPC](/skills/learn-rat-stack) schemas. It may import only `effect`, so the browser can import it safely. A lint rule enforces this. - The Worker serves an Effect `HttpApi`. [PR #6](https://github.com/Effect-TS/cafe/pull/6) moves chat events to Effect RPC over a `Cloudflare.RpcDurableObject`, one per chat. - The frontend is a Foldkit single-page app. Side effects are `Command.define` definitions. [PR #2](https://github.com/Effect-TS/cafe/pull/2) streamed socket frames with `Subscription.fromEvent`; PR #6 later replaced the socket with RPC. - Story tests check update, Messages, and Commands. Scene tests drive the rendered view. Both are pure. - Live tests deploy the Stack with `Test.make` from `alchemy/Test/Vitest`. The end-to-end test drives Chromium through Playwright. - CI deploys one stage per pull request and destroys it when the pull request closes. - `stacks/github.ts` is an Alchemy Stack that writes the CI Cloudflare credentials as repository secrets. - Configuration comes from `effect/Config`. Its `AGENTS.md` forbids `process.env`. - The repository carries the Foldkit agent skills. ## Other CAFE apps | App | What it shows | | ------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------- | | [just-be-dev/effect-cloudflare-foldkit-template](https://github.com/just-be-dev/effect-cloudflare-foldkit-template) | A template with tooling and guardrails for Effect 4, Foldkit, and Alchemy 2 on Cloudflare. | | [NigelThorne/foldkit-demo](https://github.com/NigelThorne/foldkit-demo) | Live shared sessions on Durable Objects with SQLite and hibernatable WebSockets. | | [mwarger/corefour](https://github.com/mwarger/corefour) | A poster app with an Effect `HttpApi` Worker, Foldkit server rendering, and KV and R2 storage. | | [Manzanita-Research/foldkit-dials](https://github.com/Manzanita-Research/foldkit-dials) | Live tuning controls for Foldkit apps. See the next section. | | [Manzanita-Research/pleat](https://github.com/Manzanita-Research/pleat) | Typed styles for Foldkit and Effect 4. MIT. | | [Effect-TS/slopcop](https://github.com/Effect-TS/slopcop) | Several Effect Workers with D1 and Queues, declared in one Alchemy Stack. | Pleat treats a style as a value: - Styles merge by fixed laws. - Every rule compiles to atomic CSS when its module loads. - Recipe variants are typed by Effect [Schema](/lore/schemas-define-the-boundary). - A model that generates UI can choose styles, but it can never write CSS. [Jem](https://github.com/jem-computer) at Manzanita Research builds actively in the CAFE space: Pleat, foldkit-dials, and [foldkit-native](https://github.com/Manzanita-Research/foldkit-native). ## foldkit-dials [Manzanita-Research/foldkit-dials](https://github.com/Manzanita-Research/foldkit-dials) gives a Foldkit app live tuning controls, after DialKit. It is MIT licensed, at version 0.1.0. - The dials are an Effect Schema. - Every dial edit is a Message. - Foldkit DevTools records each edit. - Time travel replays it. - Story and Scene tests can drive it. Its demo deploys with Alchemy. A `stacks/github.ts` Stack bootstraps its CI credentials, as in cafe. foldkit-dials is a clear example of the Foldkit rule that every change is a Message. A tool that follows the rule gets recording, replay, and tests from the runtime. ## Where rat-stack sits rat-stack is a CAFE stack with [the fence](/lore/the-fence) around it. The table compares it with cafe at rat-stack commit `3fb103b`. | Area | rat-stack | cafe | | -------------------- | --------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------- | | Alchemy Worker shape | Class form: `Cloudflare.Worker()`, `Cloudflare.Workers.RpcWorker`, `Cloudflare.Website.Foldkit` | `Cloudflare.Worker`, `Cloudflare.RpcDurableObject`, `Cloudflare.Website.Foldkit` | | Runtime tests | `alchemy/Test/Vitest` with fixture Workers in `apps/mischief/test/*-runtime.test.ts` | `Test.make` deploys the whole Stack; Playwright drives Chromium | | API surface | One contract projected to RPC, HTTP, MCP, and CLI by `packages/capability` | Hand-written `HttpApi` and `RpcGroup` | | Foldkit | `Runtime.makeApplication`, `Command.define`, `@foldkit/oxlint-plugin`, Story and Scene tests | The same, plus the Foldkit agent skills | | Config | varlock `.env.schema` into Effect `Config`; no `process.env` in source | `effect/Config`; no `process.env` | | Pull request stages | `scripts/deploy-preview.sh` deploys a Website and RpcBackend preview by hand; no live end-to-end test | CI deploys one stage per pull request, runs live tests, and destroys it on close | | Tracing | `Cloudflare.Telemetry`, opt-in, off by default | Not enabled | The largest difference is the API [surface](/lore/one-schema-three-surfaces). See [one capability, every surface](/lore/one-capability-every-surface) and [infrastructure as effects](/lore/infrastructure-as-effects). ## Sources - [Effect-TS/cafe](https://github.com/Effect-TS/cafe) - [foldhub/awesome-foldkit](https://github.com/foldhub/awesome-foldkit), Foldhub's community list for Foldkit, announced by Taras Kornichuk - [Foldkit](https://foldkit.dev) - [Alchemy](https://alchemy.run) - [Effect](https://effect.website) ## Sources 1. [Effect-TS/cafe · GitHub](https://github.com/Effect-TS/cafe) GitHub Effect-TS. README, AGENTS.md, package layout, CI workflows, and commit history; used for the canonical example. Accessed 2026-10-09. 2. [refactor: stream socket frames with Subscription.fromEvent · Effect-TS/cafe#2](https://github.com/Effect-TS/cafe/pull/2) GitHub Effect-TS. Used for the Subscription.fromEvent step. Accessed 2026-10-09. 3. [refactor: stream chat events over Effect RPC · Effect-TS/cafe#6](https://github.com/Effect-TS/cafe/pull/6) GitHub Effect-TS. Used for the move to Effect RPC over a Durable Object. Accessed 2026-10-09. 4. [Manzanita-Research/foldkit-dials · GitHub](https://github.com/Manzanita-Research/foldkit-dials) GitHub Manzanita-Research. README and package manifest; used for the foldkit-dials section. Accessed 2026-10-09. 5. [Manzanita-Research/pleat · GitHub](https://github.com/Manzanita-Research/pleat) GitHub Manzanita-Research. README; used for the Pleat row. Accessed 2026-10-09. 6. [Manzanita-Research/foldkit-native · GitHub](https://github.com/Manzanita-Research/foldkit-native) GitHub Manzanita-Research. Repository description; used for the Manzanita Research credit. Accessed 2026-10-09. 7. [just-be-dev/effect-cloudflare-foldkit-template · GitHub](https://github.com/just-be-dev/effect-cloudflare-foldkit-template) GitHub just-be-dev. Repository description; used for the other CAFE apps table. Accessed 2026-10-09. 8. [NigelThorne/foldkit-demo · GitHub](https://github.com/NigelThorne/foldkit-demo) GitHub NigelThorne. Repository description; used for the other CAFE apps table. Accessed 2026-10-09. 9. [mwarger/corefour · GitHub](https://github.com/mwarger/corefour) GitHub mwarger. README; used for the other CAFE apps table. Accessed 2026-10-09. 10. [Effect-TS/slopcop · GitHub](https://github.com/Effect-TS/slopcop) GitHub Effect-TS. alchemy.run.ts; used for the other CAFE apps table. Accessed 2026-10-09. 11. [foldhub/awesome-foldkit · GitHub](https://github.com/foldhub/awesome-foldkit) GitHub foldhub. Community list for Foldkit libraries and apps. Accessed 2026-10-09. ## Lore on this page - [One schema, three surfaces](/lore/one-schema-three-surfaces) ## Linked from - Agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms.txt) - Agent rules for rat-stack (AGENTS.md) → What you may change, which commands to run, and which changes need approval. → [Read page](https://ratstack.sh/AGENTS.md) - Change log → What changed in the files served here, newest first. → [Read page](https://ratstack.sh/log) - Full agent guide → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/llms-full.txt) - Infrastructure as effects → Sam Goodwin relates application operations to infrastructure requirements in one typed program. → [Read page](https://ratstack.sh/lore/infrastructure-as-effects) - Lint and type escape ledger (debt.md) → A source-linked count of repo-owned lint and type escapes. → [Read page](https://ratstack.sh/debt.md) - One prompt serves people and agents → Source-owned agent prompts with typed discovery and copyable browser pages. → [Read page](https://ratstack.sh/systems/prompts) - Rat Stack lore | rat-stack → Short, source-grounded notes on the ideas and decisions behind rat-stack. → [Read page](https://ratstack.sh/lore) - rat-stack → An Effect stack so pure (aspirational) Kit Langton will blush. → [Read page](https://ratstack.sh/) - Sam Goodwin → Sam Goodwin presents Alchemy as infrastructure built from Effect programs and typed requirements. → [Read page](https://ratstack.sh/lore/sam-goodwin) - Source change history (log.md) → The generated change log as Markdown. → [Read page](https://ratstack.sh/log.md)