Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add ilyautov/cordon --skill cordon-installgit clone --depth 1 https://github.com/ilyautov/cordonWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/ilyautov/cordon/cordon-install)<a href="https://agentmods.dev/skills/ilyautov/cordon/cordon-install"><img src="https://agentmods.dev/badge/skills/ilyautov/cordon/cordon-install/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/ilyautov/cordon/cordon-install"><img src="https://agentmods.dev/badge/skills/ilyautov/cordon/cordon-install.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00156 | $0.00907 |
| Opus 5 | $0.00078 | $0.00453 |
| Sonnet 5 | $0.00031 | $0.00181 |
| Haiku 4.5 | $0.00016 | $0.00091 |
Grade A, and why
cordon-install scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured today.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 76 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Installing Cordon
Cordon stands between untrusted text and what the agent does with it. It ships as a Claude Code plugin bound to four harness events: the user's message, a tool call, a tool result, the display of the answer.
Node 22 or newer. No keys, no tokens, no network access: there are no network requests and no model calls on the hot path.
Install
/plugin marketplace add ilyautov/cordon
/plugin install cordon@cordon
No build step. plugin/dist/cli.js ships ready to run, because an installed
plugin has neither node_modules nor package.json beside it, and a file with
external imports would crash node on the first event. The harness reads a
crashed hook as «pass», so the defence would switch off silently.
Verify, and do not confuse the two questions
/hooks answers «is it registered». It does not answer «does it work».
cordon doctor answers the second one: it reads the effective policy, runs a
built-in attack sample through the whole path, and names the dangerous parts of
the configuration. The plugin path carries the marketplace name and the version,
so it changes on every update. Ask the harness instead of hard-coding it:
CORDON=$(node -e "
const p = require(process.env.HOME + '/.claude/plugins/installed_plugins.json')
const key = Object.keys(p.plugins).find(k => k.startsWith('cordon@'))
if (!key) { console.error('plugin is not installed'); process.exit(1) }
console.log(p.plugins[key][0].installPath + '/dist/cli.js')
")
node "$CORDON" doctor
self-check: ok means the hidden layer is stripped, a call outside the
certificate is refused, and a call inside it goes through. A hook that is never
called looks, from outside, exactly like a hook that had no reason to fire.
What to tell the user honestly
Say how far this has been proven, and do not round it up. The wiring was
exercised on a live Claude Code session, 2.1.236: all four events fire, the
certificate refuses, provenance refuses, the footer is drawn, argument
quarantine is applied. The Gemini CLI adapter, the MCP gateway and the LangChain
middleware have not been run live. Their install guides are
docs/install-gemini.md, docs/install-mcp.md, docs/install-langchain.md.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- today First seen · 76 lines · 156 tokens per session scan A a493232d9627
cordon-install is a skill published in the GitHub repository ilyautov/cordon (2 stars, last pushed today), licensed MIT. It adds 156 tokens to every session and 907 once invoked, about $0.0008 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-12.
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