What is plugin-signature?

An optional installation check for a plugin's detached signature. It currently compares a recorded SHA-256 digest with the plugin's plugin.yaml file; full GPG or minisign signing is deferred.

Use it as an install gate to check plugin signatures, allow unsigned plugins when checks are optional, and return machine-readable results.

It lets an installer require an authenticity check or detect when the plugin metadata differs from the expected file.

plugin-signature — Skill for Claude Code and Codex by cintia09

Install

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.

Any agent

npx skills add cintia09/CodeNook --skill plugin-signature

Clone the repo

git clone --depth 1 https://github.com/cintia09/CodeNook

Made for: Claude Code, Codex.

Wrote 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.

README.md

[![agentmods](https://agentmods.dev/badge/skills/cintia09/codenook/plugin-signature/github.svg)](https://agentmods.dev/skills/cintia09/codenook/plugin-signature)

Your own site

<a href="https://agentmods.dev/skills/cintia09/codenook/plugin-signature"><img src="https://agentmods.dev/badge/skills/cintia09/codenook/plugin-signature/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.

Your own site · 80×15

<a href="https://agentmods.dev/skills/cintia09/codenook/plugin-signature"><img src="https://agentmods.dev/badge/skills/cintia09/codenook/plugin-signature.svg" alt="Reviewed on agentmods" width="80" height="20"></a>

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 176 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.

Origin original No closer match found in the catalogue.

Token cost

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	$0.00000	$0.00176
Opus 5.5	$0.00000	$0.00070
Sonnet 5.5	$0.00000	$0.00035
Haiku 4.5	$0.00000	$0.00018

Measured 2mo ago against content hash 2bea3dc8f483, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

plugin-signature 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 2mo ago.

The scan reads SKILL.md. This mod also ships 2 executable files (_signature_check.py, signature-check.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

skills/codenook-core/skills/builtin/plugin-signature/SKILL.md · 24 lines

What it actually says

plugin-signature — Install gate G05

Optional detached-signature check. Real cryptographic signing (GPG / minisign) is deferred to M5; M2 ships the hook with a self-contained sha256 baseline so the orchestrator and packaging tool can pin authenticity intent today.

CLI

signature-check.sh --src <dir> [--json]

Behaviour

`plugin.yaml.sig`	`CODENOOK_REQUIRE_SIG`	result
missing	unset / `0`	pass (signatures are opt-in)
missing	`1`	fail (G05)
present	any	digest must equal `sha256(plugin.yaml)`

The signature file may contain leading/trailing whitespace; only the first non-blank token is consumed.

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

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.

2mo ago First seen · 24 lines · 0 tokens per session scan A 2bea3dc8f483

Subscribe to this mod's changes

plugin-signature is a skill published in the GitHub repository cintia09/CodeNook (5 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 176 tokens. 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 2026-08-31.