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Adopt architecture decision records

contributing/decisions/2026-03-11-adopt-architecture-decision-records.md

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Adopt architecture decision records

Context and Problem Statement

Architecture decisions in this project are made implicitly — through code, conversations, and tribal knowledge. When a new contributor (human or AI agent) joins the codebase, there is no record of why things are built the way they are. This makes it hard to:

  • Understand whether a pattern is intentional or accidental
  • Know if a past decision still applies or has been superseded
  • Avoid relitigating decisions that were already carefully considered

We need a lightweight, version-controlled way to capture decisions where the code lives.

Decision

Adopt Architecture Decision Records (ADRs) using the MADR 4.0 format, stored in contributing/decisions/.

Conventions:

  • One ADR per file, named YYYY-MM-DD-title-with-dashes.md
  • New ADRs start as proposed, move to accepted or rejected
  • Superseded ADRs link to their replacement
  • ADRs are written to be self-contained — a coding agent should be able to read one and implement the decision without further context

Consequences

  • Good, because decisions are discoverable and version-controlled alongside the code
  • Good, because new contributors (human or agent) can understand the "why" behind architecture choices
  • Good, because the team builds a shared decision log that prevents relitigating settled questions
  • Bad, because writing ADRs takes time — though a good ADR saves more time than it costs
  • Neutral, because ADRs require periodic review to mark outdated decisions as deprecated or superseded

Alternatives Considered

  • No formal records: Continue making decisions in conversations and code comments. Rejected because context is lost and decisions get relitigated.
  • Wiki or Notion pages: Capture decisions outside the repo. Rejected because they drift out of sync with the code and are not version-controlled.
  • Lightweight RFCs: More heavyweight process with formal review cycles. Rejected as overkill for most decisions — ADRs can scale up to RFC-level detail when needed.

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