What problem does it solve? It turns an approved change proposal and specs into a concrete technical design, eliminating guesswork about architecture decisions, file changes, and testing strategy before implementation begins. ## Core Features & Use Cases - Design Document Generation: Produces a structured design.md covering technical approach, architecture decisions with rationale, data flow diagrams, file changes, interfaces, and testing strategy. - Multi-Mode Persistence: Supports engram, openspec, hybrid, and none artifact store modes, reading proposals and specs from the appropriate source and persisting the design accordingly. - Threat Matrix Integration: Applies an applicability-driven threat matrix for designs touching routing, shell commands, subprocesses, VCS/PR automation, or process integration, propagating applicable rows into tasks and RED tests. - Use Case: After a change proposal is approved, the orchestrator delegates to this sub-agent, which reads the actual codebase, documents each architecture decision with alternatives and rationale, and returns a summary ready for the task-planning phase. ## Quick Start Delegate the design phase for an approved change to the sdd-design sub-agent so it reads the codebase and produces the design artifact.
