sdd-spec

Delta specifications document added, modified, and removed requirements for a proposed software change. They use ADDED, MODIFIED, and REMOVED sections with RFC 2119 strength keywords to remove ambiguity between product, design, and engineering teams.

Write Given/When/Then scenarios for each requirement by providing happy paths and edge cases within the delta spec. This scenario-driven approach enables automated testing and ensures requirements are testable and precise.

RFC 2119 keywords such as MUST, SHOULD, and MAY are used in delta specifications to define requirement strength and precision. They ensure specifications capture requirement changes with clear, testable intent across system domains.

OpenSpec supports engram and openspec persistence modes for artifact generation, or returns results only when persistence is disabled. The output adheres to the openspec persistence contract while generating delta spec files under the changes directory.

Delta specs can be applied to change proposals across system domains such as auth, payments, and UI. When a change touches multiple domains like auth and billing, per-domain delta specs are grouped and produced under openspec/changes/{change-name}/specs/.

The best way to document requirement changes is using delta specifications with separate ADDED, MODIFIED, and REMOVED sections. This approach uses RFC 2119 keywords and Given/When/Then scenarios to capture changes precisely and testably across domains.