Rule Cascade

Write a business rule once, in YAML or JSON. Enforce it identically in the browser, in the API, in every programming language and on every operating system.

Rule Cascade is a rule engine built around a contract: a small, strict rule language, a compiler that checks rules before they ship, and engines for TypeScript, Java, Go and Python, a single-file command and a WebAssembly module. One conformance suite of more than 1,800 cases proves that every engine gives the same answer.

What it is

The model in one page: write, check, seal, evaluate.

Learn Rule Cascade

A short lesson for every feature of the rule language, each with an example to run in your browser and an exercise.

Try it in your browser

Edit a real ruleset and request, check and evaluate them on the page. Nothing to install.

Install rcas

One command on macOS, Linux or Windows, then rcas init for a new project or rcas init --from . for an existing one.

AI coding tools

Claude Code, Codex, Cursor, Copilot, Gemini CLI and Windsurf: agent instructions and an MCP server that proposes rules for review.

5-minute quickstart

Write a rule, check it with the command, evaluate a request.

Playbooks

Numbered procedures for real tasks: ship a rule change, enforce in a form or an API, deploy the rule server.

Usage by language

Install, load, evaluate and handle errors in TypeScript, Java, Go, Python, the command and the rule server.

Examples

One page per integration point, each pointing at code that CI builds and runs.

Reference

The specification, cookbook, authoring guidelines, naming conventions, decision records.

Where the pages come from

The reference section is rendered at build time from the Markdown files of the Rule Cascade source (docs/, spec/v1/SPECIFICATION.md, the package READMEs), so it always matches the specification and the code it was built with. The get-started pages, playbooks, usage pages and examples are written for this site.

Status

1.0.0-alpha.5. The specification is a draft and may change before 1.0; every change is in the changelog. Each release publishes the rcas command as signed downloads and on npm (@rules-cascade/cli), and the libraries on npm (@rules-cascade/*), PyPI (rcas), Maven Central (rules-cascade-core) and the Go module proxy (rulescascade.com/go). The packages are free to use under the Apache License 2.0; the source repository is private.