Plugin Settings

# Plugin Settings Pattern for Claude Code Plugins

## Overview

Plugins can store user-configurable settings and state in `.claude/plugin-name.local.md` files within the project directory. This pattern uses YAML frontmatter for structured configuration and markdown content for prompts or additional context.

**Key characteristics:**
- File location: `.claude/plugin-name.local.md` in project root
- Structure: YAML frontmatter + markdown body
- Purpose: Per-project plugin configuration and state
- Usage: Read from hooks, commands, and agents
- Lifecycle: User-managed (not in git, should be in `.gitignore`)

## File Structure

### Basic Template

```markdown
---
enabled: true
setting1: value1
setting2: value2
numeric_setting: 42
list_setting: ["item1", "item2"]
---

# Additional Context

This markdown body can contain:
- Task descriptions
- Additional instructions
- Prompts to feed back to Claude
- Documentation or notes
```

### Example: Plugin State File

**.claude/my-plugin.local.md:**
```markdown
---
enabled: true
strict_mode: false
max_retries: 3
notification_level: info
coordinator_session: team-leader
---

# Plugin Configuration

This plugin is configured for standard validation mode.
Contact @team-lead with questions.
```

## Reading Settings Files

### From Hooks (Bash Scripts)

**Pattern: Check existence and parse frontmatter**

```bash
#!/bin/bash
set -euo pipefail

# Define state file path
STATE_FILE=".claude/my-plugin.local.md"

# Quick exit if file doesn't exist
if [[ ! -f "$STATE_FILE" ]]; then
  exit 0  # Plugin not configured, skip
fi

# Parse YAML frontmatter (between --- markers)
FRONTMATTER=$(sed -n '/^---$/,/^---$/{ /^---$/d; p; }' "$STATE_FILE")

# Extract individual fields
ENABLED=$(echo "$FRONTMATTER" | grep '^enabled:' | sed 's/enabled: *//' | sed 's/^"\(.*\)"$/\1/')
STRICT_MODE=$(echo "$FRONTMATTER" | grep '^strict_mode:' | sed 's/strict_mode: *//' | sed 's/^"\(.*\)"$/\1/')

# Check if enabled
if [[ "$ENABLED" != "true" ]]; then
  exit 0  # Disabled
fi

# Use configuration in hook logic
if [[ "$STRICT_MODE" == "true" ]]; then
  # Apply strict validation
  # ...
fi
```

See `examples/read-settings-hook.sh` for complete working example.

### From Commands

Commands can read settings files to customize behavior:

```markdown
---
description: Process data with plugin
allowed-tools: ["Read", "Bash"]
---

# Process Command

Steps:
1. Check if settings exist at `.claude/my-plugin.local.md`
2. Read configuration using Read tool
3. Parse YAML frontmatter to extract settings
4. Apply settings to processing logic
5. Execute with configured behavior
```

### From Agents

Agents can reference settings in their instructions:

```markdown
---
name: configured-agent
description: Agent that adapts to project settings
---

Check for plugin settings at `.claude/my-plugin.local.md`.
If present, parse YAML frontmatter and adapt behavior according to:
- enabled: Whether plugin is active
- mode: Processing mode (strict, standard, lenient)
- Additional configuration fields
```

## Parsing Techniques

### Extract Frontmatter

```bash
# Extract everything between --- markers
FRONTMATTER=$(sed -n '/^---$/,/^---$/{ /^---$/d; p; }' "$FILE")
```

### Read Individual Fields

**String fields:**
```bash
VALUE=$(echo "$FRONTMATTER" | grep '^field_name:' | sed 's/field_name: *//' | sed 's/^"\(.*\)"$/\1/')
```

**Boolean fields:**
```bash
ENABLED=$(echo "$FRONTMATTER" | grep '^enabled:' | sed 's/enabled: *//')
# Compare: if [[ "$ENABLED" == "true" ]]; then
```

**Numeric fields:**
```bash
MAX=$(echo "$FRONTMATTER" | grep '^max_value:' | sed 's/max_value: *//')
# Use: if [[ $MAX -gt 100 ]]; then
```

### Read Markdown Body

Extract content after second `---`:

```bash
# Get everything after closing ---
BODY=$(awk '/^---$/{i++; next} i>=2' "$FILE")
```

## Common Patterns

### Pattern 1: Temporarily Active Hooks

Use settings file to control hook activation:

```bash
#!/bin/bash
STATE_FILE=".claude/security-scan.local.md"

# Quick exit if not configured
if [[ ! -f "$STATE_FILE" ]]; then
  exit 0
fi

# Read enabled flag
FRONTMATTER=$(sed -n '/^---$/,/^---$/{ /^---$/d; p; }' "$STATE_FILE")
ENABLED=$(echo "$FRONTMATTER" | grep '^enabled:' | sed 's/enabled: *//')

if [[ "$ENABLED" != "true" ]]; then
  exit 0  # Disabled
fi

# Run hook logic
# ...
```

**Use case:** Enable/disable hooks without editing hooks.json (requires restart).

### Pattern 2: Agent State Management

Store agent-specific state and configuration:

**.claude/multi-agent-swarm.local.md:**
```markdown
---
agent_name: auth-agent
task_number: 3.5
pr_number: 1234
coordinator_session: team-leader
enabled: true
dependencies: ["Task 3.4"]
---

# Task Assignment

Implement JWT authentication for the API.

**Success Criteria:**
- Authentication endpoints created
- Tests passing
- PR created and CI green
```

Read from hooks to coordinate agents:

```bash
AGENT_NAME=$(echo "$FRONTMATTER" | grep '^agent_name:' | sed 's/agent_name: *//')
COORDINATOR=$(echo "$FRONTMATTER" | grep '^coordinator_session:' | sed 's/coordinator_session: *//')

# Send notification to coordinator
tmux send-keys -t "$COORDINATOR" "Agent $AGENT_NAME completed task" Enter
```

### Pattern 3: Configuration-Driven Behavior

**.claude/my-plugin.local.md:**
```markdown
---
validation_level: strict
max_file_size: 1000000
allowed_extensions: [".js", ".ts", ".tsx"]
enable_logging: true
---

# Validation Configuration

Strict mode enabled for this project.
All writes validated against security policies.
```

Use in hooks or commands:

```bash
LEVEL=$(echo "$FRONTMATTER" | grep '^validation_level:' | sed 's/validation_level: *//')

case "$LEVEL" in
  strict)
    # Apply strict validation
    ;;
  standard)
    # Apply standard validation
    ;;
  lenient)
    # Apply lenient validation
    ;;
esac
```

## Creating Settings Files

### From Commands

Commands can create settings files:

```markdown
# Setup Command

Steps:
1. Ask user for configuration preferences
2. Create `.claude/my-plugin.local.md` with YAML frontmatter
3. Set appropriate values based on user input
4. Inform user that settings are saved
5. Remind user to restart Claude Code for hooks to recognize changes
```

### Template Generation

Provide template in plugin README:

```markdown
## Configuration

Create `.claude/my-plugin.local.md` in your project:

\`\`\`markdown
---
enabled: true
mode: standard
max_retries: 3
---

# Plugin Configuration

Your settings are active.
\`\`\`

After creating or editing, restart Claude Code for changes to take effect.
```

## Best Practices

### File Naming

✅ **DO:**
- Use `.claude/plugin-name.local.md` format
- Match plugin name exactly
- Use `.local.md` suffix for user-local files

❌ **DON'T:**
- Use different directory (not `.claude/`)
- Use inconsistent naming
- Use `.md` without `.local` (might be committed)

### Gitignore

Always add to `.gitignore`:

```gitignore
.claude/*.local.md
.claude/*.local.json
```

Document this in plugin README.

### Defaults

Provide sensible defaults when settings file doesn't exist:

```bash
if [[ ! -f "$STATE_FILE" ]]; then
  # Use defaults
  ENABLED=true
  MODE=standard
else
  # Read from file
  # ...
fi
```

### Validation

Validate settings values:

```bash
MAX=$(echo "$FRONTMATTER" | grep '^max_value:' | sed 's/max_value: *//')

# Validate numeric range
if ! [[ "$MAX" =~ ^[0-9]+$ ]] || [[ $MAX -lt 1 ]] || [[ $MAX -gt 100 ]]; then
  echo "⚠️  Invalid max_value in settings (must be 1-100)" >&2
  MAX=10  # Use default
fi
```

### Restart Requirement

**Important:** Settings changes require Claude Code restart.

Document in your README:

```markdown
## Changing Settings

After editing `.claude/my-plugin.local.md`:
1. Save the file
2. Exit Claude Code
3. Restart: `claude` or `cc`
4. New settings will be loaded
```

Hooks cannot be hot-swapped within a session.

## Security Considerations

### Sanitize User Input

When writing settings files from user input:

```bash
# Escape quotes in user input
SAFE_VALUE=$(echo "$USER_INPUT" | sed 's/"/\\"/g')

# Write to file
cat > "$STATE_FILE" <<EOF
---
user_setting: "$SAFE_VALUE"
---
EOF
```

### Validate File Paths

If settings contain file paths:

```bash
FILE_PATH=$(echo "$FRONTMATTER" | grep '^data_file:' | sed 's/data_file: *//')

# Check for path traversal
if [[ "$FILE_PATH" == *".."* ]]; then
  echo "⚠️  Invalid path in settings (path traversal)" >&2
  exit 2
fi
```

### Permissions

Settings files should be:
- Readable by user only (`chmod 600`)
- Not committed to git
- Not shared between users

## Real-World Examples

### multi-agent-swarm Plugin

**.claude/multi-agent-swarm.local.md:**
```markdown
---
agent_name: auth-implementation
task_number: 3.5
pr_number: 1234
coordinator_session: team-leader
enabled: true
dependencies: ["Task 3.4"]
additional_instructions: Use JWT tokens, not sessions
---

# Task: Implement Authentication

Build JWT-based authentication for the REST API.
Coordinate with auth-agent on shared types.
```

**Hook usage (agent-stop-notification.sh):**
- Checks if file exists (line 15-18: quick exit if not)
- Parses frontmatter to get coordinator_session, agent_name, enabled
- Sends notifications to coordinator if enabled
- Allows quick activation/deactivation via `enabled: true/false`

### ralph-wiggum Plugin

**.claude/ralph-loop.local.md:**
```markdown
---
iteration: 1
max_iterations: 10
completion_promise: "All tests passing and build successful"
---

Fix all the linting errors in the project.
Make sure tests pass after each fix.
```

**Hook usage (stop-hook.sh):**
- Checks if file exists (line 15-18: quick exit if not active)
- Reads iteration count and max_iterations
- Extracts completion_promise for loop termination
- Reads body as the prompt to feed back
- Updates iteration count on each loop

## Quick Reference

### File Location

```
project-root/
└── .claude/
    └── plugin-name.local.md
```

### Frontmatter Parsing

```bash
# Extract frontmatter
FRONTMATTER=$(sed -n '/^---$/,/^---$/{ /^---$/d; p; }' "$FILE")

# Read field
VALUE=$(echo "$FRONTMATTER" | grep '^field:' | sed 's/field: *//' | sed 's/^"\(.*\)"$/\1/')
```

### Body Parsing

```bash
# Extract body (after second ---)
BODY=$(awk '/^---$/{i++; next} i>=2' "$FILE")
```

### Quick Exit Pattern

```bash
if [[ ! -f ".claude/my-plugin.local.md" ]]; then
  exit 0  # Not configured
fi
```

## Additional Resources

### Reference Files

For detailed implementation patterns:

- **`references/parsing-techniques.md`** - Complete guide to parsing YAML frontmatter and markdown bodies
- **`references/real-world-examples.md`** - Deep dive into multi-agent-swarm and ralph-wiggum implementations

### Example Files

Working examples in `examples/`:

- **`read-settings-hook.sh`** - Hook that reads and uses settings
- **`create-settings-command.md`** - Command that creates settings file
- **`example-settings.md`** - Template settings file

### Utility Scripts

Development tools in `scripts/`:

- **`validate-settings.sh`** - Validate settings file structure
- **`parse-frontmatter.sh`** - Extract frontmatter fields

## Implementation Workflow

To add settings to a plugin:

1. Design settings schema (which fields, types, defaults)
2. Create template file in plugin documentation
3. Add gitignore entry for `.claude/*.local.md`
4. Implement settings parsing in hooks/commands
5. Use quick-exit pattern (check file exists, check enabled field)
6. Document settings in plugin README with template
7. Remind users that changes require Claude Code restart

Focus on keeping settings simple and providing good defaults when settings file doesn't exist.