Mastering Hooks

mastering-hooks

Contents

• Overview
• Decision Tree
• Capabilities
• When NOT to Use
• References

Overview

Claude Context Hooks (CCH) is a deterministic runtime engine that intercepts Claude Code events and executes configured actions.

User Prompt --> Claude Code --> CCH Binary --> [Match Rules] --> Execute Actions
                    |                              |
                    v                              v
              PreToolUse                    inject/run/block
              PostToolUse                   context/validation
              PermissionRequest

System components:

• CCH Binary (Rust): Fast, deterministic hook execution at runtime
• hooks.yaml: Declarative configuration defining rules, matchers, and actions
• This Skill: Intelligent assistant for setup, debugging, and optimization

Decision Tree

What do you need?
|
+-- New to CCH? --> [1. Install & Initialize]
|
+-- Have hooks.yaml but hooks not working? --> [4. Troubleshoot]
|
+-- Need to add new behavior? --> [2. Create Rules]
|
+-- Want to understand existing config? --> [3. Explain Configuration]
|
+-- Performance or complexity issues? --> [5. Optimize]

Capabilities

1. Install & Initialize CCH

Use when: Setting up CCH for the first time in a project or user-wide.

Checklist:

1. Verify CCH binary is installed: cch --version --json
2. Initialize configuration: cch init (creates .claude/hooks.yaml)
3. Register with Claude Code: cch install --project or cch install --user
4. Validate configuration: cch validate
5. Verify installation: Check .claude/settings.json for hook entries

Expected output from cch --version --json:

{"version": "1.1.0", "api_version": "1.1.0", "git_sha": "abc1234"}

Reference: cli-commands.md

2. Create Hook Rules

Use when: Adding new behaviors like context injection, command validation, or workflow automation.

Checklist:

1. Identify the event type (PreToolUse, PostToolUse, etc.)
2. Define matchers (tools, extensions, directories, patterns)
3. Choose action type (inject, run, block, require_fields)
4. Write the rule in hooks.yaml
5. Validate: cch validate
6. Test with: cch debug <event> --tool <tool_name>

Rule anatomy:

hooks:
  - name: rule-name           # kebab-case identifier
    event: PreToolUse         # When to trigger
    match:
      tools: [Write, Edit]    # What to match
      extensions: [.py]       # Optional: file filters
    action:
      type: inject            # What to do
      source: file            # file | inline | command
      path: .claude/context/python-standards.md

Reference: hooks-yaml-schema.md | rule-patterns.md

3. Explain Configuration

Use when: Understanding what existing hooks do, why they exist, or how they interact.

Checklist:

1. Run cch explain rule <rule-name> for specific rule analysis
2. Run cch explain config for full configuration overview
3. Check rule precedence (first match wins within same event)
4. Identify potential conflicts or overlaps

Example output from cch explain rule python-standards:

Rule: python-standards
Event: PreToolUse
Triggers when: Write or Edit tool used on .py files
Action: Injects content from .claude/context/python-standards.md

Reference: cli-commands.md

4. Troubleshoot Hook Issues

Use when: Hooks not firing, unexpected behavior, or error messages.

Diagnostic checklist:

1. Validate config: cch validate - catches YAML/schema errors
2. Check registration: cat .claude/settings.json | grep hooks
3. Enable debug logging: cch debug PreToolUse --tool Write --verbose
4. Check logs: cch logs --tail 20
5. Verify file paths: Ensure all path: references exist

Common issues:

Reference: troubleshooting-guide.md

5. Optimize Configuration

Use when: Too many rules, slow execution, or complex maintenance.

Optimization checklist:

1. Consolidate overlapping rules with broader matchers
2. Use enabled_when for conditional rules instead of duplicates
3. Move shared context to reusable markdown files
4. Order rules by frequency (most common first)
5. Use block early to short-circuit unnecessary processing

Reference: rule-patterns.md

When NOT to Use This Skill

• Simple Claude Code configuration: Use settings.json directly for basic permissions
• One-time context injection: Just paste into your prompt
• Non-Claude Code tools: CCH only works with Claude Code CLI
• Dynamic runtime decisions: CCH is deterministic; use MCP servers for complex logic

References

Example: Complete hooks.yaml

# .claude/hooks.yaml
version: "1"

hooks:
  # Inject Python standards before writing Python files
  - name: python-standards
    event: PreToolUse
    match:
      tools: [Write, Edit]
      extensions: [.py]
    action:
      type: inject
      source: file
      path: .claude/context/python-standards.md

  # Block dangerous git commands
  - name: block-force-push
    event: PreToolUse
    match:
      tools: [Bash]
      command_match: "git push.*--force"
    action:
      type: block
      reason: "Force push requires explicit approval."

  # Run security check before committing
  - name: pre-commit-security
    event: PreToolUse
    match:
      tools: [Bash]
      command_match: "git commit"
    action:
      type: run
      command: .claude/validators/check-secrets.sh
      timeout: 30