Writing Hookify Rules

Writing Hookify Rules

Define hookify rules as .github/hookify.{rule-name}.local.md files — markdown with YAML frontmatter specifying patterns to watch for and messages to display on match.

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

name (required): Unique identifier for the rule

• Use kebab-case: warn-dangerous-rm, block-console-log
• Be descriptive and action-oriented
• Start with verb: warn, prevent, block, require, check

enabled (required): Boolean to activate/deactivate

• true: Rule is active
• false: Rule is disabled (won't trigger)
• Can toggle without deleting rule

event (required): Which hook event to trigger on

• bash: Bash tool commands
• file: Edit, Write, MultiEdit tools
• stop: When agent wants to stop
• prompt: When user submits a prompt
• all: All events

action (optional): What to do when rule matches

• warn: Show message but allow operation (default)
• block: Prevent operation (PreToolUse) or stop session (Stop events)
• If omitted, defaults to warn

pattern (simple format): Regex pattern to match

• Used for simple single-condition rules
• Matches against command (bash) or new_text (file)
• Python regex syntax

Example:

event: bash
pattern: rm\s+-rf

Advanced Format (Multiple Conditions)

For complex rules with multiple conditions:

---
name: warn-env-file-edits
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:

• field: Which field to check
  • For bash: command
  • For file: file_path, new_text, old_text, content
• operator: How to match
  • regex_match: Regex pattern matching
  • contains: Substring check
  • equals: Exact match
  • not_contains: Substring must NOT be present
  • starts_with: Prefix check
  • ends_with: Suffix check
• pattern: Pattern or string to match