sdd-spec

name	sdd-spec
description	SDD (Specification-Driven Development) for Kotlin CA/FP projects. Produces precise, layer-aware spec files that drive tests and implementation. Use when planning a feature, designing the domain model, specifying API contracts, or writing acceptance criteria. Triggers on: spec writing, feature planning, domain model design, error hierarchy design.

SDD Spec

Save specs to .claude/specs/[feature-name].md.

See references/spec-template.md for the full format.

Core Rules

• Errors before happy path — list all error cases before describing success paths
• No implementation details — specify WHAT the system does, not HOW
• Testable criteria — every acceptance criterion must map to a concrete test case
• Layer ownership — for every error, identify which layer detects it (domain validation / application logic / infra)
• Ubiquitous language — use consistent domain terms throughout; the spec is the shared vocabulary

Spec Sections

1. Context — why this feature exists
2. Ubiquitous Language — term definitions
3. Domain Model — entities, value objects, errors, repository interface changes
4. Use Cases — input (primitive types), happy path, all error cases, application error types
5. Infrastructure — DB schema, migration file name
6. Presentation — REST/GraphQL contracts, HTTP status mapping per error variant
7. Acceptance Criteria — given/when/then, one per behavior

Error Hierarchy

• sealed interface XxxError : DomainError — domain validation failures, not found
• sealed interface XxxUseCaseError : ApplicationError — wraps domain errors per use case