hook.define

hook.define

Overview

hook.define is a Betty skill that creates and registers validation hooks for Claude Code. Hooks enable automatic validation and policy enforcement by triggering skills on events like file edits, commits, and pushes.

Purpose

Transform manual validation into automatic safety rails:

• Before: Developers must remember to run validation
• After: Validation happens automatically on every file edit

Usage

Basic Usage

python skills/hook.define/hook_define.py <event> <command> [options]

Parameters

Parameter	Required	Description	Example
event	Yes	Hook event trigger	on_file_edit
command	Yes	Command to execute	api.validate {file_path} zalando
--pattern	No	File pattern to match	*.openapi.yaml
--blocking	No	Block on failure (default: true)	true
--timeout	No	Timeout in ms (default: 30000)	10000
--description	No	Human-readable description	Validate OpenAPI specs

Valid Events

Event	Triggers When	Use Case
on_file_edit	File is edited in editor	Syntax validation
on_file_save	File is saved	Code generation
on_commit	Git commit attempted	Breaking change detection
on_push	Git push attempted	Full validation suite
on_tool_use	Any tool is used	Audit logging
on_agent_start	Agent begins execution	Context injection
on_workflow_end	Workflow completes	Cleanup/notification

Examples

Example 1: Validate OpenAPI Specs on Edit

python skills/hook.define/hook_define.py \
  on_file_edit \
  "python betty/skills/api.validate/api_validate.py {file_path} zalando" \
  --pattern="*.openapi.yaml" \
  --blocking=true \
  --timeout=10000 \
  --description="Validate OpenAPI specs against Zalando guidelines"

Result: Every time a *.openapi.yaml file is edited, it's automatically validated against Zalando guidelines. If validation fails, the edit is blocked.

Example 2: Check Breaking Changes on Commit

python skills/hook.define/hook_define.py \
  on_commit \
  "python betty/skills/api.compatibility/check_breaking_changes.py {file_path}" \
  --pattern="specs/**/*.yaml" \
  --blocking=true \
  --description="Prevent commits with breaking API changes"

Result: Commits are blocked if they contain breaking API changes.

Example 3: Regenerate Models on Save

python skills/hook.define/hook_define.py \
  on_file_save \
  "python betty/skills/api.generate-models/auto_generate.py {file_path}" \
  --pattern="specs/*.openapi.yaml" \
  --blocking=false \
  --description="Auto-regenerate models when specs change"

Result: When an OpenAPI spec is saved, models are regenerated automatically (non-blocking).

Example 4: Audit Trail for All Tool Use

python skills/hook.define/hook_define.py \
  on_tool_use \
  "python betty/skills/audit.log/log_api_change.py {tool_name}" \
  --blocking=false \
  --description="Log all tool usage for compliance"

Result: All tool usage is logged for audit trails (non-blocking).

Output

Success Response

{
  "status": "success",
  "data": {
    "hook_config": {
      "name": "api-validate-all-openapi-yaml",
      "command": "python betty/skills/api.validate/api_validate.py {file_path} zalando",
      "blocking": true,
      "timeout": 10000,
      "when": {
        "pattern": "*.openapi.yaml"
      },
      "description": "Validate OpenAPI specs against Zalando guidelines"
    },
    "hooks_file_path": "/home/user/betty/.claude/hooks.yaml",
    "event": "on_file_edit",
    "total_hooks": 1
  }
}

Generated Hooks File

The skill creates/updates .claude/hooks.yaml:

hooks:
  on_file_edit:
    - name: api-validate-all-openapi-yaml
      command: python betty/skills/api.validate/api_validate.py {file_path} zalando
      blocking: true
      timeout: 10000
      when:
        pattern: "*.openapi.yaml"
      description: Validate OpenAPI specs against Zalando guidelines

How It Works

1. Load Existing Hooks: Reads .claude/hooks.yaml if it exists
2. Create Hook Config: Builds configuration from parameters
3. Add or Update: Adds new hook or updates existing one with same name
4. Save: Writes updated configuration back to .claude/hooks.yaml

Benefits

For Developers

• ✅ Instant feedback: Errors caught immediately, not at commit time
• ✅ No discipline required: Validation happens automatically
• ✅ Consistent quality: Standards enforced, not suggested

For Teams

• ✅ Enforced standards: Can't save non-compliant code
• ✅ Reduced review time: Automated checks before human review
• ✅ Onboarding: New developers can't accidentally break standards

For Organizations

• ✅ Compliance: Policies enforced at tool level
• ✅ Audit trail: Every validation is logged
• ✅ Risk reduction: Catch issues early, not in production

Integration with Betty

Use in Workflows

# workflows/setup_api_validation.yaml
steps:
  - skill: hook.define
    args:
      - "on_file_edit"
      - "api.validate {file_path} zalando"
      - "--pattern=*.openapi.yaml"
      - "--blocking=true"

Use in Agents

Agents can dynamically create hooks based on project needs:

# Agent detects OpenAPI specs in project
# Automatically sets up validation hooks

File Pattern Examples

Pattern	Matches
*.openapi.yaml	All OpenAPI files in current directory
*.asyncapi.yaml	All AsyncAPI files in current directory
specs/**/*.yaml	All YAML files in specs/ and subdirectories
src/**/*.ts	All TypeScript files in src/ and subdirectories
**/*.py	All Python files anywhere

Blocking vs Non-Blocking

Blocking Hooks (blocking: true)

• Operation is paused until hook completes
• If hook fails, operation is aborted
• Use for: Validation, compliance checks, breaking change detection

Non-Blocking Hooks (blocking: false)

• Hook runs asynchronously
• Operation continues regardless of hook result
• Use for: Logging, notifications, background tasks

Timeout Considerations

Operation	Suggested Timeout	Reasoning
Syntax validation	5,000 - 10,000 ms	Fast, local checks
Zally API call	10,000 - 30,000 ms	Network latency
Model generation	30,000 - 60,000 ms	Compilation time
Full test suite	300,000 ms (5 min)	Comprehensive testing

Error Handling

Hook Execution Failed

If a blocking hook fails:

❌ Hook 'validate-openapi' failed:
   - Missing required field: info.x-api-id
   - Property 'userId' should use snake_case

Operation blocked. Fix errors and try again.

Hook Timeout

If a hook exceeds timeout:

⚠️ Hook 'validate-openapi' timed out after 10000ms
Operation blocked for safety.

Dependencies

• PyYAML: Required for YAML file handling

  pip install pyyaml
  

• context.schema: For validation rule definitions

Files Created

• .claude/hooks.yaml - Hook configurations for Claude Code

See Also

• api.validate - API validation skill
• Betty Architecture - Five-layer model
• API-Driven Development - Complete guide
• Claude Code Hooks Documentation

Version

0.1.0 - Initial implementation with basic hook definition support