Use when authoring an Architecture Decision Record (ADR) — a short document that captures one significant, hard-to-reverse technical or architectural decision, its context, and its consequences. Triggered by the sdlc ADR pipeline (the knowledge-engineer agent behind /sdlc:docs seed adr and /sdlc:docs distill) when generating an ADR from a story, and by anyone hand-authoring an ADR under docs/adr/ today. Covers why ADRs are kept short and inverted-pyramid, the required sections (Title, Status, Decision, Context, Alternatives Considered, Consequences), the proposed→accepted→superseded (or →rejected) status lifecycle and the never-edit-only-supersede immutability rule, the NNNN-decision-slug.md filename convention, and the ADR frontmatter fields (status, agents, source-stories) the pipeline reads to route a generated ADR into docs/adr/index.md.