Hook Development for Claude Code Plugins
anthropics/claude-plugins-official
Explains how to write Claude Code plugin hooks, both prompt-based checks and bash commands, for events such as PreToolUse, Stop and SessionStart.
Helps write, debug and configure Crush hooks in crush.json that block, approve or rewrite tool calls before they run.
Install Crush Hook Writer
$ npx skills add charmbracelet/crush --skill crush-hooks -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install charmbracelet/crush crush-hooks --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .claude/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .claude/skills/crush-hooks && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .claude/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooksType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add charmbracelet/crush --skill crush-hooks -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install charmbracelet/crush crush-hooks --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .agents/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .agents/skills/crush-hooks && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .agents/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add charmbracelet/crush --skill crush-hooks -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install charmbracelet/crush crush-hooks --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .cursor/skills/crush-hooks && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .cursor/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/charmbracelet/crush.git --path internal/skills/builtin/crush-hooks--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add charmbracelet/crush --skill crush-hooks -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install charmbracelet/crush crush-hooks --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .gemini/skills/crush-hooks && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .gemini/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install charmbracelet/crush crush-hooksInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add charmbracelet/crush --skill crush-hooks -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .github/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .github/skills/crush-hooks && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .github/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add charmbracelet/crush --skill crush-hooks -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install charmbracelet/crush crush-hooks --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/charmbracelet/crush.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/internal/skills/builtin/crush-hooks .opencode/skills/crush-hooks && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "crush-hooks" agent skill from https://github.com/charmbracelet/crush/tree/main/internal/skills/builtin/crush-hooks into .opencode/skills/crush-hooks/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "crush-hooks", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
crush-hooks- GitHub stars
- 29k
- Token cost
- ~1.8k tokens
- SKILL.md length
- 677 words
- Files
- 1
- Skills in repo
- 5
- Repo updated
- First seen
- Licence
- Custom licence
At a glance
Helps write, debug and configure Crush hooks in crush.json that block, approve or rewrite tool calls before they run.
- Works in 5 steps: Add #!/usr/bin/env bash and set -euo… → chmod +x the script. → Add the entry under hooks.PreToolUse in… → …
- Blocking dangerous shell commands before Crush runs them
- SKILL.md covers Supported Events, Configuration, Language and Input, plus 6 more sections
- Calls jq, node and python3
What it does
Hooks in Crush are user-defined commands set in crush.json that fire at set points during execution and give deterministic control over tool behavior. They run before permission checks and only on the top-level agent's tool calls. Work done by sub-agents, such as the task tool, is not intercepted, though the call that starts the sub-agent is. Only the PreToolUse event is supported today, and event names are case-insensitive.
The skill explains the configuration layout (project hooks take precedence over global ones, and matching hooks are deduplicated by command, run in parallel and combined in config order), the inputs a hook receives as environment variables such as CRUSH_TOOL_NAME and as JSON on stdin, and the outputs. Exit code 0 means success with JSON on stdout, 2 blocks the call with the reason on stderr, and 49 halts the whole turn. Because the command is a shell command, hooks can be written in any language.
When your agent uses it
- Blocking dangerous shell commands before Crush runs them
- Approving or rewriting tool input before it executes
- Injecting extra context into a tool result
- Debugging a hook in crush.json that does not fire or misbehaves
Example prompts
- “Write a Crush hook that blocks any bash command containing rm -rf.”
- “My PreToolUse hook in crush.json never fires. Help me debug it.”
- “Add a hook that rewrites file paths in tool input so they stay inside the project directory.”
Requirements
- Crush with a crush.json configuration
Workflow steps
5 steps, taken from the first numbered list in SKILL.md.
- Add #!/usr/bin/env bash and set -euo pipefail (for shell scripts).
- chmod +x the script.
- Add the entry under hooks.PreToolUse in crush.json with the right matcher.
- Decide intent: inject context (omit decision), auto-approve ("allow"),
- If rewriting input, remember updated_input is a shallow merge — only
What it can do on your machine
Read from SKILL.md and the folder at commit 6e026b1. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
Shell commands in SKILL.md call:
jqnodepython3
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Crush Hook Writer loads about 1.8k tokens when it runs. Until then it costs about 63 tokens; SKILL.md has 677 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
Its licence (Custom licence) doesn't allow us to republish the file, so here is its outline and opening line. It has 677 words (~1,818 tokens).
“Hooks are user-defined commands in crush.json that fire at specific points during execution, giving deterministic control over tool behavior. They run before permission checks and only on the top-level agent's tool calls — sub-agent calls (task tool, agentic_fetch, etc.) are…”
- name
- crush-hooks
Files
Just SKILL.md in internal/skills/builtin/crush-hooks of charmbracelet/crush.
Open the folder on GitHubat commit 6e026b1
Compare with similar skills
Crush Hook Writer next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Crush Hook Writer this skillcharmbracelet/crush | 29k | — | ~1.8k | Automated safety check: Pass | Custom licence | |
| Hook Development for Claude Code Pluginsanthropics/claude-plugins-official | 38k | 10 repos | ~4.1k | Automated safety check: Notes | Apache-2.0 | |
| Claude Code Agent Developmentanthropics/claude-plugins-official | 38k | 7 repos | ~2.8k | Automated safety check: Pass | Apache-2.0 | |
| Claude Code Skill Developer Guidediet103/claude-code-infrastructure-showcase | 10k | 11 repos | ~3.5k | Automated safety check: Pass | MIT | |
| Plugin Settings Patternanthropics/claude-plugins-official | 38k | 7 repos | ~3k | Automated safety check: Pass | Apache-2.0 | |
| MCP Integration for Pluginsanthropics/claude-plugins-official | 38k | 11 repos | ~3.1k | Automated safety check: Pass | Apache-2.0 |
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Related
Categories
Questions about Crush Hook Writer
What does Crush Hook Writer do?
Helps write, debug and configure Crush hooks in crush.json that block, approve or rewrite tool calls before they run. json that fire at set points during execution and give deterministic control over tool behavior. They run before permission checks and only on the top-level agent's tool calls.
When should I use Crush Hook Writer?
Crush Hook Writer fits situations like: blocking dangerous shell commands before Crush runs them; approving or rewriting tool input before it executes; injecting extra context into a tool result; debugging a hook in crush.json that does not fire or misbehaves.
How do I install Crush Hook Writer in Claude Code?
Run `npx skills add charmbracelet/crush --skill crush-hooks -a claude-code`. Or copy the skill folder (internal/skills/builtin/crush-hooks in charmbracelet/crush) into .claude/skills/crush-hooks in your project. Claude Code loads it when a task matches its description.
How do I install Crush Hook Writer in Codex?
Run `npx skills add charmbracelet/crush --skill crush-hooks -a codex`. Or copy the skill folder (internal/skills/builtin/crush-hooks in charmbracelet/crush) into .agents/skills/crush-hooks in your project. Codex loads it when a task matches its description.
Can I use Crush Hook Writer in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add charmbracelet/crush --skill crush-hooks -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/crush-hooks, .gemini/skills/crush-hooks, .github/skills/crush-hooks and .opencode/skills/crush-hooks in your project.
What does Crush Hook Writer need to run?
Going by SKILL.md and its folder, Crush Hook Writer needs the command-line tools its instructions call (jq, node and python3). Our summary lists: Crush with a crush.json configuration.
Does Crush Hook Writer access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Crush Hook Writer safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Crush Hook Writer use?
Crush Hook Writer has a licence file (the repository's licence) that doesn't match a standard licence. Read it on GitHub before reusing the skill.
How many tokens does Crush Hook Writer use?
About 1.8k tokens (SKILL.md is roughly 7.3k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Crush Hook Writer?
Skills that share tags, products or a category with Crush Hook Writer: Hook Development for Claude Code Plugins (anthropics/claude-plugins-official, 38k stars), Claude Code Agent Development (anthropics/claude-plugins-official, 38k stars), Claude Code Skill Developer Guide (diet103/claude-code-infrastructure-showcase, 10k stars) and Plugin Settings Pattern (anthropics/claude-plugins-official, 38k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Crush Hook Writer?
charmbracelet (a GitHub organization) maintains it in charmbracelet/crush, which has 28,557 GitHub stars. The repository holds 5 skills in this directory. The repository was last updated on October 9, 2026.
Source: charmbracelet/crush on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.