Writing Hookify Rules

Overview

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 .gemini/egc-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 Gemini when this rule triggers.
Can include markdown formatting, warnings, suggestions, etc.

Frontmatter Fields

Field	Required	Values	Description
name	Yes	kebab-case string	Unique identifier (verb-first: warn-, block-, require-*)
enabled	Yes	true/false	Toggle without deleting
event	Yes	bash/file/stop/prompt/all	Which hook event triggers this
action	No	warn/block	warn (default) shows message; block prevents operation
pattern	Yes*	regex string	Pattern to match (*or use conditions for complex rules)

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'))"

File Organization

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

Commands

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

Quick Reference

Minimum viable rule:

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