CLI 

  brew install agent-ecosystem/tap/skillxp
  
  npm install -g skillxp
  
  pip install skillxp
  
  go install github.com/agent-ecosystem/skillxp/cmd/skillxp@latest

The npm and pip packages wrap the same prebuilt Go binary; nothing extra is downloaded at install time. Prebuilt static binaries are also on the releases page.

On Windows, use pip or a release binary: the npm package temporarily has no Windows support (a registry naming issue is being worked out with npm).

Verify any install with:

  skillxp version

Library 

  go get github.com/agent-ecosystem/skillxp

See Go Library for the API.

Harnesses

skillxp invokes real harnesses, so the harnesses you observe must be installed and authenticated: claude (Claude Code), codex (Codex CLI), and agy (Antigravity CLI). Sandboxed runs have one extra one-time auth step per harness; see Sandboxing.