What problem does it solve? It turns an approved change proposal and specs into a concrete technical design document, capturing architecture decisions, data flow, file changes, and testing strategy before implementation begins. ## Core Features & Use Cases - Structured design.md generation: Produces a design document with technical approach, architecture decisions with rationale, data flow diagrams, file change tables, interfaces, and testing strategy. - Multi-mode artifact persistence: Supports engram, openspec, hybrid, and none storage modes, reading proposals and specs from the appropriate source and persisting the design accordingly. - Applicability-driven threat matrix: Includes a security threat matrix for designs touching routing, shell commands, subprocesses, VCS/PR automation, or process integration, with planned RED tests. - Use Case: An orchestrator delegates a change named "add-journeymen-signing" to this sub-agent, which reads the codebase and proposal, then writes a design.md documenting decisions, affected files, and test plans. ## Quick Start Delegate the design phase for a named change to the sdd-design sub-agent so it reads the proposal and codebase and produces the design document.
