Can I add custom context to every session automatically?

Yes, by using the SessionStart hook with a 'startup' or 'resume' matcher, you can trigger a script that outputs JSON with 'additionalContext' to be loaded immediately.

What is the difference between PreToolUse and PostToolUse?

PreToolUse runs before a tool executes, allowing you to validate, block, or modify input. PostToolUse runs after completion, useful for auditing results or triggering follow-up actions.

What are Claude Code hooks?

Hooks are event handlers that allow you to execute scripts or prompts at specific points in Claude's lifecycle, such as before a tool is used, when a session starts, or before the agent stops.

How do I block dangerous commands using hooks?

You can implement a PreToolUse hook with a command-type handler. The script validates the command input and returns exit code 2 to block the operation and notify Claude.

How do I debug my custom hooks?

You can run Claude with the --debug flag to see hook execution logs, or manually pipe test JSON data into your hook scripts via terminal to verify exit codes and outputs.

Claude Code Hooks Reference

Name: Claude Code Hooks Reference
Author: a-ariff

bya-ariff

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Productivity & Workflow

Provides comprehensive implementation patterns and event-driven automation guidance for Claude Code hooks.

About

The Hooks Reference Skill is a specialized documentation and implementation guide designed to help developers master Claude Code's event-driven hook system. It provides detailed technical specifications for lifecycle events—ranging from tool validation with PreToolUse to session initialization with SessionStart—enabling users to build production-grade automations. By leveraging this skill, developers can implement robust security checks, automate project context loading, and enforce custom workflow rules that transform Claude into a highly controlled and efficient autonomous development agent.

Key Features

Comprehensive guide to hook JSON structures, regex matcher patterns, and exit codes.
Patterns for injecting dynamic context into sessions and user prompts automatically.
1 GitHub stars
Detailed technical documentation for all 10+ hook events including PreToolUse and SessionStart.
Advanced techniques for structured decision control and environment variable persistence.
Production-ready bash script templates for file validation and bash command safety.

Use Cases

Enforcing security policies by blocking destructive shell commands or unauthorized sensitive file writes.
Automating project context loading from local documentation or git metadata at session startup.
Implementing custom verification steps to prevent Claude from exiting before specific tasks are complete.

About

Key Features

Comprehensive guide to hook JSON structures, regex matcher patterns, and exit codes.
Patterns for injecting dynamic context into sessions and user prompts automatically.
1 GitHub stars
Detailed technical documentation for all 10+ hook events including PreToolUse and SessionStart.
Advanced techniques for structured decision control and environment variable persistence.
Production-ready bash script templates for file validation and bash command safety.

Use Cases

Enforcing security policies by blocking destructive shell commands or unauthorized sensitive file writes.
Automating project context loading from local documentation or git metadata at session startup.
Implementing custom verification steps to prevent Claude from exiting before specific tasks are complete.