Record and maintain Architecture Decision Records (ADRs) in Nygard format under docs/ADRs. Use this whenever the user wants to document an architecture or design decision, asks to "write an ADR", "record a decision", "document why we chose X", set up an ADR log, or backfill/catalog the decisions already baked into an existing codebase. Also use it when reusing this mechanism in another project. Three modes: scaffold the docs/ADRs directory, "new" (interview the user to capture one fresh decision), and "backfill" (mine existing docs and code to reconstruct past decisions). Prefer this skill over writing ad-hoc markdown so numbering, the index, and the Nygard structure stay consistent.
2026-06-28