Writing Hookify Rules

Overview

ECC evaluates project-local Hookify rules with its built-in Node runtime. No separate Hookify plugin or Python installation is required when ECC hooks are enabled.

Hookify rules are markdown files with YAML frontmatter that define patterns to watch for and messages to show when those patterns match. Rules are stored in .claude/hookify.{rule-name}.local.md files.

Rule File Format

Basic Structure

---
name: rule-identifier
enabled: true
event: bash|file|stop|prompt|all
pattern: regex-pattern-here
---

Message to show Claude when this rule triggers.
Can include markdown formatting, warnings, suggestions, etc.

Frontmatter Fields

Advanced Format (Multiple Conditions)

---
name: warn-env-api-keys
enabled: true
event: file
conditions:
  - field: file_path
    operator: regex_match
    pattern: \.env$
  - field: new_text
    operator: contains
    pattern: API_KEY
---

You're adding an API key to a .env file. Ensure this file is in .gitignore!

Condition fields by event:

• bash: command
• file: file_path, new_text, old_text, content
• prompt: user_prompt

Operators: regex_match, contains, equals, not_contains, starts_with, ends_with

All conditions must match for rule to trigger.

Event Type Guide

bash Events

Match Bash command patterns:

• Dangerous commands: rm\s+-rf, dd\s+if=, mkfs
• Privilege escalation: sudo\s+, su\s+
• Permission issues: chmod\s+777

file Events

Match Edit/Write/MultiEdit operations:

• Debug code: console\.log\(, debugger
• Security risks: eval\(, innerHTML\s*=
• Sensitive files: \.env$, credentials, \.pem$

stop Events

Completion checks and reminders. Pattern .* matches always.

prompt Events

Match user prompt content for workflow enforcement.

Pattern Writing Tips

Regex Basics

• Escape special chars: . to \., ( to \(
• \s whitespace, \d digit, \w word char
• + one or more, * zero or more, ? optional
• | OR operator

Common Pitfalls

• Too broad: log matches "login", "dialog" — use console\.log\(
• Too specific: rm -rf /tmp — use rm\s+-rf
• YAML escaping: Use unquoted patterns; quoted strings need \\s

Testing

python3 -c "import re; print(re.search(r'your_pattern', 'test text'))"

Avoid nested quantifiers such as (a+)+. The runtime rejects patterns with common catastrophic-backtracking shapes because rules run synchronously in the hook path, and every regex evaluation has a 25 ms hard timeout. Invalid, symlinked, or oversized local rules fail open and emit a diagnostic without disabling other Hookify rules.

Git-tracked local rules are disabled by default. Set ECC_HOOKIFY_ALLOW_TRACKED=1 only after reviewing those files; ordinary gitignored rules created locally remain active without that override.

Runtime Behavior

• warn injects the message as event-specific additional context and does not block.
• block denies matching Bash, PowerShell, Write, Edit, or MultiEdit calls before execution.
• On prompt, post-tool, and stop events, block uses Claude Code's structured block decision.
• Stop rules skip recursive stop_hook_active events to prevent infinite continuation loops.

File Organization

• Location: .claude/ directory in project root
• Naming: .claude/hookify.{descriptive-name}.local.md
• Gitignore: Add .claude/*.local.md to .gitignore

Commands

• /hookify [description] - Create new rules (auto-analyzes conversation if no args)
• /hookify-list - View all rules in table format
• /hookify-configure - Toggle rules on/off interactively
• /hookify-help - Full documentation

Quick Reference

Minimum viable rule:

---
name: my-rule
enabled: true
event: bash
pattern: dangerous_command
---
Warning message here