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UserPromptExpansion

UserPromptExpansion is a hook for Claude Code from GentBajko/capstone. Its token cost is not measured, scanned A, original, Apache-2.0.

An automatic prompt-expansion hook that runs a shell script when the agent handles capstone help requests. A hook is an action triggered by a matching event.

In plain words
What is it for?
It helps expand prompts for capstone:help tool calls by executing the specified help script.
Why use it?
It adds the script’s output before the agent processes matching requests, so those requests can receive extra prepared context.

Hook for Claude Code

Written for Claude Code: ${CLAUDE_PLUGIN_ROOT} variable.

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 capstone plugin — 16 skills, 2 hooks shipped together

One of 2 entries in hooks.json — they are configured in one file and arrive together.

not rated 3 +1 yesterday A scan tokens not measured original Apache-2.0
View the source file GentBajko/capstone capstone.sh
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 GentBajko/capstone
Claude Code
/plugin install capstone

Made for: Claude Code.

Or install capstone, the plugin that ships this one along with the rest of its 16 skills, 2 hooks.

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 UserPromptExpansion

README.md
[![agentmods](https://agentmods.dev/badge/hooks/gentbajko/capstone/user-prompt-expansion.svg)](https://agentmods.dev/hooks/gentbajko/capstone/user-prompt-expansion)
Your own site
<a href="https://agentmods.dev/hooks/gentbajko/capstone/user-prompt-expansion"><img src="https://agentmods.dev/badge/hooks/gentbajko/capstone/user-prompt-expansion.svg" alt="Measured on agentmods" height="20"></a>
Per session not measured What this adds to a session before it is invoked.
When invoked not measured Not applicable: nothing here is loaded into a session.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Security

Grade A, and why

UserPromptExpansion 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 6d ago.

A static scan of the commands this hook runs, not an audit. A hook is shell that executes on your machine at the event it names, which is why every command in it is printed with what was found.

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.

hooks/hooks.json · 13 lines

What it actually says

{
  "UserPromptExpansion": [
    {
      "matcher": "capstone:help",
      "hooks": [
        {
          "type": "command",
          "command": "bash \"${CLAUDE_PLUGIN_ROOT}\"/skills/core/scripts/help-hook.sh"
        }
      ]
    }
  ]
}
Same file

What else hooks.json configures

This page is one entry in a file that holds 2. Installing the file brings all of them; each is measured and scanned on its own page.

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. 6d ago First seen · 13 lines scan A ec10e02fc0e3

Subscribe to this mod's changes

UserPromptExpansion is a hook published in the GitHub repository GentBajko/capstone (3 stars, last pushed yesterday), licensed Apache-2.0. Its token cost is not measured: a hook is shell that never enters the context. 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.

agent-skillsagenticarchitectureclaude-codeclaude-code-plugindocumentation
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