Install Skarn.

Download the binary

Skarn is one static file with no runtime dependencies. Pick your platform from the release page and put it on your PATH - no installer, and on most machines no admin rights.

All assets, plus both license agreements, are on the Skarn release page. The container build-stage contract is on Containers and CI.

Guard plugin

Claude Code and Codex CLI can install the real-time guard through their own plugin systems, in two commands and with no checkout. This is an alternative to skarn setup, not a replacement: the plugin carries hook configuration only, so install the binary above first - the hooks call skarn guard on your PATH, so upgrading Skarn upgrades the detection engine without touching the plugin.

Both plugins ship in audit mode, which reports the verdict it would have reached and never changes what your agent does. Codex asks you to trust the hooks the first time you start it after installing; until you do, they do not run.

What is free, and what a license adds

The free tier is the full local product, not a trial: the whole detection engine and rule set, attack-chain correlation, the risk score, every session-recall command, the localhost web UI, text, JSON, SARIF and NDJSON output, redaction, CI gating, a personal baseline, custom rules, and the guard in audit mode. skarn check needs a free license, issued at getskarn.com/free after a one-time email confirmation; skarn assess and the recall commands need none; the license is verified offline. A license unlocks the org capabilities - policy as code, org-distributed baselines, a tamper-evident audit log, the maintained detection feed, and guard enforcement. A paid flag without a covering license refuses before any scan runs with exit 5; a missing license refuses with exit 7 and points you at the free registration. Nothing in the free scanner is time-limited or crippled to sell the paid tiers.

Common questions

Does installing Skarn require an account or a license key?

Installing needs no account: the tap, the npm packages, the binaries, and the image are public. Running differs by command. skarn assess scans with no account and no license; skarn check, the repeatable scriptable scan, needs a free license, issued at getskarn.com/free to anyone who registers and confirms their email, and verified offline. A paid license token additionally unlocks the Team and Enterprise features.

What should I run first?

Run skarn assess. It scans every AI coding session on the machine with no configuration and prints a redacted risk summary. It makes no network call and writes nothing to your session files.

Are the binaries signed?

The macOS binaries are Developer ID signed and Apple-notarized, so they run without a Gatekeeper warning. The Homebrew formula pins each platform's asset by sha256, and the npm packages carry the same binaries pinned by npm integrity hash. The install script verifies the Windows binary against the checksum GitHub computed for it, but the Windows binaries are not yet Authenticode-signed, so a first run may show a SmartScreen prompt. The container image is cosign-signed (Sigstore keyless) with an SPDX SBOM and SLSA build provenance.

Does Skarn phone home when I install or run it?

No. The binary sends nothing: no upload, no telemetry, no network call when it scans. skarn assess needs no account, and skarn check verifies its free license offline, so nothing leaves the machine either way. The one online feature is the opt-in maintained rule feed, a paid feature you invoke with a flag.

Which assistants does it read?

Claude Code, Gemini CLI, Codex CLI, Cursor, GitHub Copilot. Skarn finds their session stores automatically; no path configuration is needed for a standard install.