Mastering Claude Hooks

Picture this: It's 6 AM, you're in the flow with Claude Code, and suddenly your AI assistant decides that "the best code is no code" and starts deleting your entire codebase with rm -rf commands. Sound terrifying? This exact scenario is what Claude hooks were designed to prevent.

Claude hooks transform your AI coding assistant from a reactive tool into a proactive development partner that:

• Automatically runs tests and formatters
• Blocks dangerous operations before they execute
• Provides voice notifications for long-running tasks
• Generates comprehensive logs for debugging
• Coordinates parallel agent workflows

Why Hooks Matter

Traditional AI assistants write code, but then leave you to handle all the housekeeping:

• Running linters and formatters
• Executing test suites
• Checking for type errors
• Monitoring what the AI actually did
• Preventing dangerous operations

Hooks automate all of this and more, letting you focus on solving problems instead of babysitting your AI.

Claude Code provides five powerful hook events that fire at specific points in the AI's lifecycle:

1. PreToolUse - Your Safety Guardian

This hook fires before any tool runs, giving you the power to inspect and potentially block operations.

Basic PreToolUse Hook

Common Use Cases:

• Block dangerous commands (rm -rf, sudo, etc.)
• Require approval for sensitive operations
• Validate inputs before execution
• Set up environment prerequisites

2. PostToolUse - The Observer

Fires after a tool completes, perfect for logging and monitoring.

Logging with PostToolUse

Common Use Cases:

• Log all file modifications
• Track tool execution times
• Generate audit trails
• Trigger follow-up actions

3. Notification - Interactive Moments

Triggers when Claude needs your input or wants to notify you of something important.

Voice Notification Hook

4. Stop - Session Complete

Executes when Claude finishes responding, ideal for cleanup and final actions.

Save Chat Log on Stop

5. SubagentStop - Parallel Processing

Fires when sub-agents complete their tasks in parallel workflows.

One of the most critical uses of hooks is preventing disasters before they happen. Let's build a comprehensive safety system.

Basic Command Blocking

Start with a simple Python script that checks for dangerous commands:

scripts/safety_check.py

Advanced Safety with Allowlists

For production environments, use an allowlist approach:

Advanced Safety Configuration

Observability is crucial for understanding and improving your agent's behavior. Let's build a comprehensive logging system.

Structured Logging

Create detailed, structured logs that capture everything your agent does:

Comprehensive Logging System

Analyzing Agent Behavior

Use the logs to understand patterns and optimize workflows:

Log Analysis Script

Transform your development experience with audio feedback:

Complete Voice Integration

Parallel Agent Coordination

Handle multiple agents working simultaneously:

Parallel Agent Monitoring

Integration with External Tools

Connect Claude to your existing development ecosystem:

Slack Integration

Let's put it all together by building a complete hook configuration for a production environment.

Exercise: Build Your Safety Net

Create a comprehensive hook setup that:

1. Prevents disasters with PreToolUse safety checks
2. Logs everything with PostToolUse monitoring
3. Notifies on completion with voice alerts
4. Saves chat context for analysis
5. Handles parallel agents gracefully

Complete Hook Configuration

Challenge Tasks

1. Add Custom Matchers: Instead of ".*", create specific matchers for different file types
2. Build a Dashboard: Create a real-time dashboard that visualizes your agent's activity
3. Implement Rollback: Add a hook that can automatically rollback changes if tests fail
4. Create Team Notifications: Build hooks that notify your team channel when important milestones are reached