cpv-add-hook

cpv-add-hook is a skill for Claude Code from Emasoft/claude-plugins-validation. It costs 68 tokens per session (1,085 once invoked), scanned A, original, MIT.

A tool for adding an event handler to a plugin's hooks.json file. An event handler is a command that runs when a specified coding-agent event occurs.

In plain words
What is it for?
Use it to add a new cross-platform hook to an existing plugin. The hook can run a Python or Node.js command for a supported event.
Why use it?
It prevents duplicate entries when repeated and encourages commands that work on Linux, macOS, and Windows. Later validation catches commands that rely on shell-specific syntax.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter. Also seen: mentions .claude-plugin; mentions Claude Code.

Runs only inside its plugin — its command needs a path that Claude Code sets for a plugin’s own hooks and for nothing else. Install the plugin, not this.

Part of the claude-plugins-validation plugin — 52 skills, 14 commands, 14 agents shipped together

Good fit Use it to add a new cross-platform hook to an existing plugin. The hook can run a Python or Node.js command for a supported event.

Compare 6 skills from other repositories ↓
Install

Getting it into your agent

This one installs as part of its plugin. Adding the marketplace and installing the plugin brings it with everything else the plugin ships.

Claude Code
/plugin marketplace add Emasoft/claude-plugins-validation
Claude Code
/plugin install claude-plugins-validation

Made for: Claude Code.

Or install claude-plugins-validation, the plugin that ships this one along with the rest of its 52 skills, 14 commands, 14 agents.

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.

agentmods badge for cpv-add-hook

README.md
[![agentmods](https://agentmods.dev/badge/skills/emasoft/claude-plugins-validation/cpv-add-hook/github.svg)](https://agentmods.dev/skills/emasoft/claude-plugins-validation/cpv-add-hook)
Your own site
<a href="https://agentmods.dev/skills/emasoft/claude-plugins-validation/cpv-add-hook"><img src="https://agentmods.dev/badge/skills/emasoft/claude-plugins-validation/cpv-add-hook/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.

agentmods 80×15 button for cpv-add-hook

Your own site · 80×15
<a href="https://agentmods.dev/skills/emasoft/claude-plugins-validation/cpv-add-hook"><img src="https://agentmods.dev/badge/skills/emasoft/claude-plugins-validation/cpv-add-hook.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 68 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,085 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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00068 $0.01085
Opus 5.5 $0.00027 $0.00434
Sonnet 5.5 $0.00014 $0.00217
Haiku 4.5 $0.00007 $0.00109

Measured 1mo ago against content hash fa98ef003ef3, method: parsed. Prices are Anthropic first-party input rates as of 2026-10-07, from the pricing page.

Security

Grade A, and why

cpv-add-hook 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 1mo ago.

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/cpv-add-hook/SKILL.md · 83 lines

How it starts

The opening of the file, as written. The whole thing — 83 lines — stays where its author put it; the contents beside it link to each section on GitHub.

cpv-add-hook

Overview

Adds a new hook entry to a plugin's hooks/hooks.json. The scaffold is idempotent — re-running with the same event+command is a no-op. The new hook command MUST be cross-platform: prefer Python or Node.js delegation. Bash-only constructs (set -euo pipefail, [[ ]], $(<file), process substitution, brace expansion) will trigger validate_hook MAJOR findings. Loaded dynamically via cpv-the-skills-menu, reached via the Create → Add hook menu branch.

Prerequisites

  • uv on PATH
  • Target plugin path with .claude-plugin/plugin.json
  • A valid hook event name (see "Valid event names" below)
  • A cross-platform command string (delegate to Python/Node, NOT bash-isms)

Instructions

  1. Pick a valid hook event name from the canonical list.
  2. Write the command as a Python or Node delegation. add_component.py writes the command verbatim — it does NOT inspect or reject bash-only constructs at write time — so a bash-only command lands in hooks/hooks.json and is caught only later by validate_hook/validate_plugin --strict (step 5) as a MAJOR. Use Python/Node delegation up front to pass that re-validation.
  3. Run the underlying add_component.py --type hook invocation.
  4. The script creates hooks/hooks.json if missing or merges into the existing file.
  5. Re-validate via cpv-plugin-validation-skill to confirm cross-platform compliance.
  6. NEVER write runtime state to ${CLAUDE_PLUGIN_ROOT} (lost on every plugin update). Use ${CLAUDE_PLUGIN_DATA} instead.

Copy this checklist and track your progress:

  • Event name validated against canonical list
  • Command uses Python/Node delegation (no bash-isms)
  • add_component.py --type hook executed
  • hooks/hooks.json updated or created
  • validate_plugin --strict re-run

Output

  • A new entry in hooks/hooks.json keyed by event name.
  • Identical entries (same event + same command) are skipped — re-runs are no-ops.
  • The file is created if missing; existing entries are preserved.

Read the full file on GitHub · 83 lines

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.

  1. 1mo ago Changed fa98ef003ef3
  2. 1mo ago First seen · 83 lines · 68 tokens per session scan A 9b4b8be6ed01

Subscribe to this mod's changes

cpv-add-hook is a skill published in the GitHub repository Emasoft/claude-plugins-validation (4 stars, last pushed 3d ago), licensed MIT. It adds 68 tokens to every session and 1,085 once invoked, about $0.0003 per session on Opus 5.5. 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 2026-08-31.

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