What is a Claude Code hook?

A hook is an event-driven script that runs at specific lifecycle points—like before or after a tool runs—to automate validations, checks, or repetitive tasks.

Will hooks slow down my Claude Code session?

Hooks should be designed to be fast, ideally executing in under one second. Using specific matchers for tools ensures hooks only run when relevant, minimizing overhead.

Can I block Claude from executing a tool if a check fails?

Yes, by returning a non-zero exit code from a PreToolUse hook, you can block the execution of the tool and provide an error message to the session.

What is the best way to parse the hook input data?

We recommend using 'jq' within your shell scripts to robustly parse the JSON input provided by Claude Code to the stdin of your hook scripts.

How do I ensure my hooks are portable across different machines?

Always use the $CLAUDE_PROJECT_DIR environment variable in your configuration to reference scripts relative to the project root rather than using relative or absolute paths.

Claude Code Lifecycle Hooks

Name: Claude Code Lifecycle Hooks
Author: jack-michaud

byjack-michaud

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Productivity & Workflow

Automates validation, environment checks, and workflow tasks using event-driven lifecycle hooks within Claude Code.

Enhance your AI development workflow by executing custom scripts at critical points in the Claude Code lifecycle. This skill provides a structured framework for validating tool inputs, checking environment states, and automating post-execution tasks like linting or formatting. By utilizing JSON-based session data and the $CLAUDE_PROJECT_DIR environment variable, developers can implement portable, reliable automation that maintains high code quality and consistency across various development environments.

Key Features

01Event-driven script execution for tool usage and session lifecycle events

02Pre-execution validation for tool inputs and environmental dependencies

03Post-execution automation for code formatting, linting, and side-effect logging

04Portable path resolution using the $CLAUDE_PROJECT_DIR environment variable

05Structured JSON input processing for robust script logic and state awareness

063 GitHub stars

Use Cases

01Automatically formatting source code with Black or Prettier after a file edit tool completes

02Validating system dependencies and environment variables during session initialization to prevent tool failures

03Checking git status before file operations to warn the user about uncommitted changes

What are Skills?·How to Install

Install with 🐟 Skill.Fish

npx skillfish add jack-michaud/faire creating-hooks

For use in Claude.ai and ChatGPT

Download Skill