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Overview

The cowboy CLI is a single Rust binary. Pick the method that fits your workflow, then verify with cowboy version before starting the Quickstart. What you’ll learn:
  • How to install cowboy (and optionally lasso) with Homebrew
  • How to download and verify a binary directly
  • How to install the Python SDK your actors import
  • How to enable shell completions
Cowboy publishes a public tap at cowboyinc/homebrew-tap:
Homebrew may trail the latest release by a version or two — the formula tracks whichever build the team has last validated for the tap, not every tag pushed to releases. If you need the newest binary immediately, use the direct download below.
If you use the interactive console, install it the same way:

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Direct download (macOS/Linux)

Grab your platform’s archive from the cowboy-cli releases page, verify its checksum, unpack it, and put the three binaries on your PATH. On Linux, run uname -m first: x86_64 needs the linux-x64 archive and aarch64 the linux-arm64 one.
Each release ships one .tar.xz archive per platform (cowboy-darwin-arm64.tar.xz, cowboy-linux-arm64.tar.xz, cowboy-linux-x64.tar.xz) and a SHA256SUMS file covering them. Each archive holds cowboy, the cowboy-dev-runner local simulator that cowboy run and cowboy test use, and lasso; keep them together in one directory. On Linux, tar needs xz (the xz-utils package on Debian and Ubuntu). There is no Intel macOS or Windows binary; on Windows, install inside WSL and follow the Linux instructions above.
Release binaries are ad-hoc signed, not notarized, so macOS Gatekeeper will refuse to run one downloaded through a browser (spctl reports it as rejected). If you hit “cannot be opened because the developer cannot be verified,” clear the quarantine flag before running it:

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Python SDK

Actors scaffolded by cowboy init import cowboy_sdk, published on PyPI as cowboy-sdk:
The scaffold’s pyproject.toml pins cowboy-sdk>=0.1.2, one version ahead of the 0.1.1 currently on PyPI. Projects created with cowboy init use uv, so uv sync will resolve the pin automatically once 0.1.2 is published — no action needed on your part in the meantime.

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Shell completions

cowboy completions <shell> prints a completion script for bash, zsh, fish, elvish, or powershell.
zsh
bash
Open a new shell afterward to pick up the completions.

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Verify

If you installed lasso, verify it separately:

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Upgrading

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Troubleshooting

The binary isn’t on your PATH. If you used Homebrew, run brew --prefix and confirm that directory’s bin/ is on your PATH. If you downloaded a binary directly, confirm you moved it to a directory already on your PATH (for example /usr/local/bin), then open a new terminal and run cowboy version.
Release binaries are ad-hoc signed rather than notarized. Clear the quarantine attribute Gatekeeper adds to browser-downloaded files: xattr -d com.apple.quarantine /usr/local/bin/cowboy /usr/local/bin/cowboy-dev-runner /usr/local/bin/lasso.