Claude Code Hooks Examples

A practical guide to using Claude Code hooks effectively.

Overview

This repository demonstrates how to implement and use all the Claude Code hook events to customize and control Claude's behavior in your development workflow.

What are Claude Code Hooks?

Claude Code hooks are user-defined shell commands that execute at specific points in Claude Code's lifecycle. They provide deterministic control over Claude's behavior, ensuring certain actions always happen rather than relying on the LLM to choose to run them.

Hook Events

This repo includes examples for all available hook events:

• PreToolUse - Runs before tool calls (can block them)
• PostToolUse - Runs after tool calls complete
• Notification - Runs when Claude Code sends notifications
• UserPromptSubmit - Runs when user submits a prompt
• Stop - Runs when Claude Code finishes responding
• SubagentStop - Runs when subagent tasks complete
• PreCompact - Runs before context compaction
• SessionStart - Runs when starting/resuming sessions

Current Examples

1. Block Database Deletions (PreToolUse)

Located in .claude/hooks/block-db-deletions.ts, this TypeScript hook prevents Claude from running dangerous database deletion commands by:

• Intercepting all Bash commands before execution
• Checking for dangerous patterns like DROP DATABASE, DROP TABLE, DELETE FROM, etc.
• Blocking execution with exit code 2 and providing feedback to Claude
• Supporting multiple database systems (PostgreSQL, MySQL, MongoDB, Redis)

2. Tool Memory with OTP Verification (PreToolUse)

Located in .claude/hooks/load-tool-memory.ts, this sophisticated hook:

• Loads instructions from tool-memory.txt that Claude must follow
• Requires Claude to acknowledge instructions by printing a specific sequence
• Generates a one-time password (OTP) that must be included in the command
• Clears the OTP after successful use to prevent replay
• Stores OTP state in .claude/hooks/clear-otp.ts for persistence

3. User Prompt Hook (UserPromptSubmit)

Located in .claude/hooks/user-prompt-hook.ts, this hook:

• Intercepts user prompts before Claude processes them
• Can inject additional instructions or requirements
• Currently configured to require Claude to print "1,2,3,4,5" before any action

Setup

1. Clone this repository
2. Make sure you have Bun installed (for TypeScript hooks)
3. Review .claude/settings.json to see the hook configurations
4. Customize the hooks for your needs

Security Note

Hooks execute with your system credentials. Always review hook commands before using them, as they can modify or access any files your user account can access.

Resources

• Claude Code Hooks Guide
• Claude Code Hooks Reference

Contributing

Feel free to add more hook examples by submitting a PR!