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SkillSpec has two parts to install. The CLI binary (skillspec) handles everything you run from a terminal — Doctor reports, validation, porting, tracing, and local skill installs. The harness plugin wires those same commands into Claude Code or Codex so your agent can drive them from a chat prompt. You need the CLI regardless; the plugin is required only if you want in-harness invocation.

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CLI Install

The release installer is the fastest path on macOS and Linux. It detects your platform, downloads the right binary from the latest GitHub release, verifies the SHA256 checksum, and installs to ~/.local/bin by default.
To pin a specific version or choose a different install directory, pass environment variables inline:
If ~/.local/bin is not on your PATH, the installer will print a reminder. Add export PATH="$HOME/.local/bin:$PATH" to your shell profile to make skillspec available everywhere.

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Platform Notes

Prebuilt binaries are published for three platforms with every release: Every release artifact ships with a matching .sha256 checksum file. The release installer verifies the checksum automatically before extracting. For manual downloads, verify with:
On platforms not covered by the prebuilt binaries — such as Linux ARM — the installer will exit with an error and suggest cargo install skillspec as the fallback.

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Harness Plugin Install

The plugin adds SkillSpec commands to your agent harness. Once installed, you can ask your agent things like /skillspec run doctor on ./my-skill or /skillspec import ./my-skill, compile it, test it, and print the alignment summary.
Add the SkillSpec plugin from the marketplace, then install it into your active Claude Code session:
--sparse .claude-plugin plugins/skillspec fetches only the plugin directory from the repository instead of cloning the full tree.

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Local Dev Skill Install

For local development, you can install the SkillSpec skill folder directly into a harness without going through the plugin marketplace. The --retire-existing flag removes any previously installed version of the same skill before writing the new one.

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Verify the Install

If the binary is on your PATH and the install succeeded, this prints the version string. If the command is not found, confirm that the install directory is in $PATH.
Local development with the Justfile. The repository includes a Justfile that keeps the full local development workflow — build, install, harness skill wiring — in one place. Key recipes:
just preflight runs formatting, locked workspace checks, Clippy, tests, package file-list checks for every split crate, example validation, and conformance fixture checks — the same set of checks that run in CI.