---
name: writing-hookify-rules
description: Guides creation of hookify rules in .claude/hookify.{name}.local.md files, including YAML frontmatter fields (name, enabled, event, pattern, action, conditions), event types (bash, file, stop, prompt, all), regex pattern writing, condition operators, and rule organization. Activates when the user asks to create a hookify rule, write a hook rule, configure hookify, or add pattern-based automation rules.
---

# 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 `.claude/hookify.{rule-name}.local.md` files.

## Rule File Format

### Basic Structure

```markdown
---
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:**
```yaml
event: bash
pattern: rm\s+-rf
```

### Advanced Format (Multiple Conditions)

For complex rules with multiple conditions:

```markdown
---
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

**All conditions must match for rule to trigger.**

## Message Body

The markdown content after frontmatter is shown to Claude when the rule triggers.

**Good messages:**
- Explain what was detected
- Explain why it's problematic
- Suggest alternatives or best practices
- Use formatting for clarity (bold, lists, etc.)

**Example:**
```markdown
⚠️ **Console.log detected!**

You're adding console.log to production code.

**Why this matters:**
- Debug logs shouldn't ship to production
- Console.log can expose sensitive data
- Impacts browser performance

**Alternatives:**
- Use a proper logging library
- Remove before committing
- Use conditional debug builds
```

## Event Type Guide

### bash Events

Match Bash command patterns:

```markdown
---
event: bash
pattern: sudo\s+|rm\s+-rf|chmod\s+777
---

Dangerous command detected!
```

**Common patterns:**
- Dangerous commands: `rm\s+-rf`, `dd\s+if=`, `mkfs`
- Privilege escalation: `sudo\s+`, `su\s+`
- Permission issues: `chmod\s+777`, `chown\s+root`

### file Events

Match Edit/Write/MultiEdit operations:

```markdown
---
event: file
pattern: console\.log\(|eval\(|innerHTML\s*=
---

Potentially problematic code pattern detected!
```

**Match on different fields:**
```markdown
---
event: file
conditions:
  - field: file_path
    operator: regex_match
    pattern: \.tsx?$
  - field: new_text
    operator: regex_match
    pattern: console\.log\(
---

Console.log in TypeScript file!
```

**Common patterns:**
- Debug code: `console\.log\(`, `debugger`, `print\(`
- Security risks: `eval\(`, `innerHTML\s*=`, `dangerouslySetInnerHTML`
- Sensitive files: `\.env$`, `credentials`, `\.pem$`
- Generated files: `node_modules/`, `dist/`, `build/`

### stop Events

Match when agent wants to stop (completion checks):

```markdown
---
event: stop
pattern: .*
---

Before stopping, verify:
- [ ] Tests were run
- [ ] Build succeeded
- [ ] Documentation updated
```

**Use for:**
- Reminders about required steps
- Completion checklists
- Process enforcement

### prompt Events

Match user prompt content (advanced):

```markdown
---
event: prompt
conditions:
  - field: user_prompt
    operator: contains
    pattern: deploy to production
---

Production deployment checklist:
- [ ] Tests passing?
- [ ] Reviewed by team?
- [ ] Monitoring ready?
```

## Pattern Writing Tips

### Regex Basics

**Literal characters:** Most characters match themselves
- `rm` matches "rm"
- `console.log` matches "console.log"

**Special characters need escaping:**
- `.` (any char) → `\.` (literal dot)
- `(` `)` → `\(` `\)` (literal parens)
- `[` `]` → `\[` `\]` (literal brackets)

**Common metacharacters:**
- `\s` - whitespace (space, tab, newline)
- `\d` - digit (0-9)
- `\w` - word character (a-z, A-Z, 0-9, _)
- `.` - any character
- `+` - one or more
- `*` - zero or more
- `?` - zero or one
- `|` - OR

**Examples:**
```
rm\s+-rf         Matches: rm -rf, rm  -rf
console\.log\(   Matches: console.log(
(eval|exec)\(    Matches: eval( or exec(
chmod\s+777      Matches: chmod 777, chmod  777
API_KEY\s*=      Matches: API_KEY=, API_KEY =
```

### Testing Patterns

Test regex patterns before using:

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

Or use online regex testers (regex101.com with Python flavor).

### Common Pitfalls

**Too broad:**
```yaml
pattern: log    # Matches "log", "login", "dialog", "catalog"
```
Better: `console\.log\(|logger\.`

**Too specific:**
```yaml
pattern: rm -rf /tmp  # Only matches exact path
```
Better: `rm\s+-rf`

**Escaping issues:**
- YAML quoted strings: `"pattern"` requires double backslashes `\\s`
- YAML unquoted: `pattern: \s` works as-is
- **Recommendation**: Use unquoted patterns in YAML

## File Organization

**Location:** All rules in `.claude/` directory
**Naming:** `.claude/hookify.{descriptive-name}.local.md`
**Gitignore:** Add `.claude/*.local.md` to `.gitignore`

**Good names:**
- `hookify.dangerous-rm.local.md`
- `hookify.console-log.local.md`
- `hookify.require-tests.local.md`
- `hookify.sensitive-files.local.md`

**Bad names:**
- `hookify.rule1.local.md` (not descriptive)
- `hookify.md` (missing .local)
- `danger.local.md` (missing hookify prefix)

## Workflow

### Creating a Rule

1. Identify unwanted behavior
2. Determine which tool is involved (Bash, Edit, etc.)
3. Choose event type (bash, file, stop, etc.)
4. Write regex pattern
5. Create `.claude/hookify.{name}.local.md` file in project root
6. Test immediately - rules are read dynamically on next tool use

### Refining a Rule

1. Edit the `.local.md` file
2. Adjust pattern or message
3. Test immediately - changes take effect on next tool use

### Disabling a Rule

**Temporary:** Set `enabled: false` in frontmatter
**Permanent:** Delete the `.local.md` file

## Examples

See `${CLAUDE_PLUGIN_ROOT}/examples/` for complete examples:
- `dangerous-rm.local.md` - Block dangerous rm commands
- `console-log-warning.local.md` - Warn about console.log
- `sensitive-files-warning.local.md` - Warn about editing .env files

## Quick Reference

**Minimum viable rule:**
```markdown
---
name: my-rule
enabled: true
event: bash
pattern: dangerous_command
---

Warning message here
```

**Rule with conditions:**
```markdown
---
name: my-rule
enabled: true
event: file
conditions:
  - field: file_path
    operator: regex_match
    pattern: \.ts$
  - field: new_text
    operator: contains
    pattern: any
---

Warning message
```

**Event types:**
- `bash` - Bash commands
- `file` - File edits
- `stop` - Completion checks
- `prompt` - User input
- `all` - All events

**Field options:**
- Bash: `command`
- File: `file_path`, `new_text`, `old_text`, `content`
- Prompt: `user_prompt`

**Operators:**
- `regex_match`, `contains`, `equals`, `not_contains`, `starts_with`, `ends_with`