[!todo] Seed note. A starting point, not a finished note yet.
An Architecture Decision Record (ADR) is a small file, one per decision, recording what was chosen, the context that forced the choice, the alternatives, and the consequences. The format (popularized by Michael Nygard) exists so a team can answer “why is it this way” years later without archaeology. It is having a revival in the AI era for a sharp reason: when agents generate code faster than anyone documents intent, recorded decisions become load-bearing infrastructure, otherwise an agent re-decides settled questions inconsistently across the codebase. ADRs record; agent context files like AGENTS.md enforce. Seeded from Upfront Planning in the AI Era - PRDs, Design Docs, and Specs.