What problem does it solve? It turns an approved change proposal and specs into a concrete technical design, documenting architecture decisions, data flow, file changes, and testing strategy so implementation work starts from a clear, reviewed plan instead of guesswork. ## Core Features & Use Cases - Design Document Generation: Produces a structured design.md covering technical approach, architecture decisions with rationale, data flow diagrams, file change tables, interfaces, and testing strategy. - Multi-Mode Persistence: Stores the design artifact via Engram topics, OpenSpec filesystem conventions, hybrid mode, or returns it inline depending on the artifact store mode. - 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-oauth-login" to this sub-agent, which reads the codebase and proposal, then writes a design.md documenting the auth flow, affected files, and test plan before task breakdown begins. ## Quick Start Ask the orchestrator to run the SDD design phase for your change, for example: "Create the technical design for the add-oauth-login change using the proposal and specs."
