What is plugin-subsystem-claim?

A plugin installation check that compares the subsystem-extension claims declared by a staged plugin with claims made by installed plugins. A claim represents an extension area, such as a test-runner.

Use it before installing or upgrading a plugin to detect duplicate declared subsystem claims in the workspace.

It prevents two plugins from registering the same extension area and conflicting with each other.

plugin-subsystem-claim — Skill 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.

agentmods

npx agentmods add skills/cintia09/codenook/plugin-subsystem-claim

Any agent

npx skills add cintia09/CodeNook --skill plugin-subsystem-claim

Clone the repo

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

Made for: Claude Code, Codex.

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

When invoked 210 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

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	$0.00000	$0.00210
Opus 5	$0.00000	$0.00105
Sonnet 5	$0.00000	$0.00042
Haiku 4.5	$0.00000	$0.00021

Measured 2d ago against content hash 4c1cee9cc618, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

plugin-subsystem-claim 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 2d ago.

The scan reads SKILL.md. This mod also ships 2 executable files (_subsystem_claim.py, subsystem-claim.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-subsystem-claim/SKILL.md · 23 lines

What it actually says

plugin-subsystem-claim — Install gate G07

Each plugin declares a list of free-form subsystem-extension claims in plugin.yaml.declared_subsystems. Two plugins may not claim the same string (e.g. both registering skills/test-runner).

CLI

subsystem-claim.sh --src <dir> [--workspace <dir>] [--upgrade] [--json]

Behaviour

If no --workspace, no peers exist → pass.
Walk <workspace>/.codenook/plugins/*/plugin.yaml; collect each peer's declared_subsystems set.
For every claim in the staged plugin: if any peer plugin (other than --upgrade self) already owns the same string → fail.
Without --upgrade, the same-id peer is treated like any other peer (so re-installing a plugin is itself a collision; G03 will also catch this, but G07 makes the message specific).

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.

2d ago First seen · 23 lines · 0 tokens per session scan A 4c1cee9cc618

Subscribe to this mod's changes

plugin-subsystem-claim is a skill published in the GitHub repository cintia09/CodeNook (5 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 210 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.

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