Registering Your First Feature

This guide shows you how to register a feature in the Sentinel feature registry, link its components, and set up tracking. After registration, Massu AI will monitor the feature's health and warn you before any changes that could break it.

What Is a Feature?

In Massu AI, a feature is a unit of business functionality that maps to specific files in your codebase:

• Components: UI elements that implement the feature
• Procedures: API endpoints that the feature depends on
• Pages: Routes where the feature is accessible

For example, an "Order Creation" feature might include a form component, a create mutation, and the /orders/new page.

Auto-Discovery

Before registering manually, run massu_sync to see what Massu AI discovers automatically:

> Run massu_sync

Massu AI auto-discovers features from:

• tRPC router names (each router becomes a feature group)
• Page routes (each page route registers as a feature)
• Component directory patterns

Manual Registration

For precise control, register a feature manually:

> Use massu_sentinel_register with:
  feature_key: "orders.create"
  title: "Order Creation Flow"
  domain: "orders"
  status: "active"
  priority: "P1"
  components: [
    {"file": "src/components/orders/CreateOrderForm.tsx", "role": "primary"},
    {"file": "src/components/orders/ProductSelector.tsx", "role": "supporting"},
    {"file": "src/components/orders/OrderSummary.tsx", "role": "supporting"}
  ]
  procedures: ["orders.create", "orders.validateDraft"]
  pages: ["/orders/new"]

Component Roles

Verifying Registration

Check that your feature was registered:

> Use massu_sentinel_detail with feature_key: "orders.create"

Testing Feature Protection

Try to see what would happen if you deleted a component:

> Use massu_sentinel_impact with files: ["src/components/orders/CreateOrderForm.tsx"]

You should see a warning that the feature would be orphaned.

Validating All Features

Run validation across all features:

> Use massu_sentinel_validate

This checks that all registered components, procedures, and pages still exist in the codebase.

Tips

• Register critical features with priority: "P1" to get stronger deletion protection
• Use primary role for the component that IS the feature (without it, the feature does not exist)
• Use supporting for components that enhance but are not essential
• Auto-discovery is a good starting point, but manually refine features for accuracy
• The pre-delete-check hook automatically runs impact analysis on file deletions