Install
Install rcas, the Rule Cascade command, on macOS, Linux or Windows, with the install script, npm or Go, and the runtime library for your language.
rcas is the Rule Cascade command: one static binary with no dependencies, for Linux, macOS and
Windows on x86-64 and ARM64. It checks, compiles and evaluates rulesets, scaffolds projects, derives
rules from API schemas, and serves the Model Context Protocol to AI coding tools.
The install scripts also install it as rule-cascade, its earlier name, which behaves the same.
curl -fsSL https://rulescascade.com/install.sh | shWith options, put them after sh -s --:
curl -fsSL https://rulescascade.com/install.sh | sh -s -- --version 1.0.0 --install-dir ~/bin --verify cosignThen check it:
rcas version
rcas doctorOther ways to install
| Command | Installs | Needs |
|---|---|---|
npm install -g @rules-cascade/cli | rcas, the binary for your platform | Node.js 18+ |
npx -y @rules-cascade/cli <command> | nothing permanent: runs the command once (this is what AI tools use for the MCP server) | Node.js 18+ |
go install rulescascade.com/go/cmd/rcas@latest | rcas, built from source | Go 1.22+ |
| Download and verify | one file you choose, checked by hand with sha256sum and cosign | cosign 3+ for the signature |
docker run ghcr.io/yarlisaisolutions/rule-cascade-server | the rule server, not the command | Docker |
Installer options
| Flag (sh) | Parameter (PowerShell) | Environment | Default | Meaning |
|---|---|---|---|---|
--version <v> | -Version | RCAS_VERSION | the latest release | version to install, e.g. 1.0.0 |
--install-dir <dir> | -InstallDir | RCAS_INSTALL_DIR | ~/.local/bin; %LOCALAPPDATA%\Programs\rcas | where to put the binary |
--verify cosign | -Verify cosign | RCAS_VERIFY | off | also verify the Sigstore signatures; fails if cosign is missing |
--base-url <url> | -BaseUrl | RCAS_DOWNLOAD_BASE | https://rulescascade.com/download | a mirror of the download directory |
--dry-run | -DryRun | print what would happen; download and change nothing | ||
--no-alias | -NoAlias | do not create rule-cascade | ||
-AddToPath | add the directory to the user PATH |
What it installs, and where
| Path | What |
|---|---|
~/.local/bin/rcas (%LOCALAPPDATA%\Programs\rcas\rcas.exe) | the command |
~/.local/bin/rule-cascade (rule-cascade.cmd) | the same command under its earlier name |
Nothing else: no service, no configuration file, no telemetry. rcas doctor checks the
installation and, unless RCAS_NO_NETWORK is set, whether a newer version is published.
The library for your language
The command is enough to write, check and compile rules, and to evaluate them from any language over the engine protocol. To evaluate in process, add the runtime of your language. Every runtime loads the same bundle and gives the same answer.
| Language | Install | Guide |
|---|---|---|
| TypeScript, JavaScript (Node.js, browsers, React Native) | npm install @rules-cascade/core (and @rules-cascade/client for browsers) | TypeScript |
| Python 3.10+ | pip install rule-cascade | Python |
| Java 17+, Kotlin, Scala, Spring Boot | Maven com.rulescascade:rules-cascade-core | Java |
| Go 1.22+ | go get rulescascade.com/go | Go |
| C#, Rust, PHP, Ruby, Swift, C++ and others | rcas engine as a child process, or rcas.wasm in a WASI host | Command and WebAssembly |
| Any language over HTTP | the rule server image | Rule server |
Operating systems
| System | Command | Runtimes |
|---|---|---|
| macOS 11+, Intel and Apple silicon | rcas-darwin-amd64, rcas-darwin-arm64 | all four |
| Linux, x86-64 and ARM64 (static: any distribution, Alpine included) | rcas-linux-amd64, rcas-linux-arm64 | all four |
| Windows 10+ and Windows Server, x86-64 and ARM64 | rcas-windows-amd64.exe, rcas-windows-arm64.exe | all four |
| Any WASI preview 1 host | rcas.wasm | through the command |
CI runs every runtime and the command on Linux, macOS and Windows.
Upgrade and uninstall
Run the installer again to upgrade (or npm install -g @rules-cascade/cli@latest). To uninstall,
delete the two files above. rcas keeps no other state: proposals and reports live in each
project's .rcas/ directory.
Troubleshooting
| Symptom | Fix |
|---|---|
rcas: command not found after installing | The install directory is not on PATH: add ~/.local/bin (the installer prints the line), or on Windows rerun with -AddToPath and open a new terminal |
| The installer stops with "checksum mismatch" | The download was altered or truncated. Do not use it; run again, and report it if it repeats |
--verify cosign fails: cosign not found | Install cosign 3 or later, or drop the flag (the checksum is still verified) |
| Behind a proxy | Set HTTPS_PROXY; curl and PowerShell honour it. Or mirror /download/ and pass --base-url |
npx asks to install @rules-cascade/cli every time | Install it globally, or let your AI tool run npx -y (it does not ask) |
| macOS says the binary is from an unidentified developer | Only when downloaded with a browser: install with the script or npm, or run xattr -d com.apple.quarantine rcas |
Next: start a new project, or generate rules from an existing one.
What Rule Cascade is
One rule contract, compiled once and evaluated by the same pure function in the browser, the backend and any other language.
Start a new project
rcas init creates the project file, a first ruleset with golden tests, CI, and optionally the instructions and MCP configuration for your AI coding tools.