type-first-entity

name	type-first-entity
description	Start new domain entities from the type layer before repository, service, runtime, or UI code
metadata	{"type":"Playbook","origin":"harness-engineering/ch4","helpful":0,"harmful":0,"status":"active"}

Type-First Entity

When to use

• Adding a new domain entity or value object
• Adding a new API that introduces business vocabulary
• Refactoring stringly typed IDs or unvalidated payloads

Rules

1. Define the domain vocabulary in types, domain, or schema first.
2. Use schema-derived types where runtime validation is needed.
3. Keep UI, HTTP, ORM, and provider-specific shapes out of the domain type.
4. Use branded IDs when two IDs can be confused.

Checklist

• New vocabulary exists in the type layer
• No any / broad unknown leaks into inner layers
• Schema and type definitions are not duplicated
• Repository/service code accepts domain types, not UI or HTTP types