---

name: mcaf-adr-writing description: "Create or update an ADR (Architecture Decision Record) under docs/ADR/ using docs/templates/ADR-Template.md: context, decision, alternatives, consequences, rollout, and verification. Use when changing architecture, boundaries, dependencies, data model, or cross-cutting patterns; ensure it is self-contained, has a Mermaid diagram, and defines testable invariants." compatibility: "Requires repository write access; produces Markdown docs with Mermaid diagrams."

MCAF: ADR Writing

Outputs

• docs/ADR/ADR-XXXX-<short-title>.md (create or update)
• Update docs/Architecture/Overview.md when boundaries/interactions change

Decision Quality (anti-guesswork checklist)

Before writing, make the ADR executable (no placeholders, no hand-waving):

• Decision: one sentence. If you can’t write it, you don’t have a decision yet.
• Scope: what changes / what does not + which module(s) are affected (match docs/Architecture/Overview.md names).
• No invented reality: every component you mention exists in the repo today, or is explicitly part of this change (named + where it will live).
• Invariants: write as MUST / MUST NOT statements and say how we prove each (test or static analysis).
• Verification: use exact commands from AGENTS.md and link scenarios → test IDs.
• Stakeholders: Product / Dev / DevOps / QA — what each role must know to execute safely.

Workflow

1. Confirm the decision scope:
   • what changes (and what does not)
   • what module(s) are affected
   • follow AGENTS.md scoping rules: Architecture map → linked ADR/Feature → entry points (do not scan everything)
2. Start from docs/templates/ADR-Template.md.
   • keep the ADR’s ## Implementation plan (step-by-step) updated while executing
3. Write the ADR as a decision record:
   • Context: constraints + why this is needed now
   • Decision: a short, direct statement
   • Diagram (mandatory): include at least one Mermaid diagram for the decision (boundaries/modules/interactions)
   • Alternatives: 1–3 realistic options with pros/cons
   • Consequences: trade-offs, risks, mitigations
4. Make it executable for the team:
   • follow AGENTS.md Task Delivery rules (analysis → plan → execute → verify)
   • include the invariants that must be proven by tests
   • include verification commands copied from AGENTS.md
   • include rollout/rollback and “how we know it’s safe”
5. Make impacts explicit:
   • code/modules affected
   • data/config changes (including migration/rollback)
   • backwards compatibility strategy
6. Add verification that proves the decision:
   • which tests must exist/change
   • which suites must stay green
7. If the decision changes boundaries, update docs/Architecture/Overview.md (diagram, modules table, dependency rules).

Guardrails

• ADRs are self-contained: no hidden context, no “as discussed”.
• ADRs justify why; feature docs describe what the system does.
• If you can’t state the decision in 1–2 sentences, the ADR is not ready.