mpm-adr

Documents

Architecture Decision Records (ADRs) — opt-in convention for documenting significant, hard-to-reverse architectural decisions using the Nygard template.

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/mpm-adr

Architecture Decision Records (ADRs) are short, structured documents that capture why a significant architectural decision was made — not just what was decided. They live alongside the code so future contributors understand the constraints and trade-offs that shaped the system.

This skill is opt-in. Only use it for decisions that are architecturally significant AND costly to reverse. Over-forcing ADRs on routine work is the documented adoption-killer.

When to Write an ADR

Write an ADR only when all three conditions are true:

Architecturally significant — the decision shapes how major parts of the system are structured, constrain future options, or affect multiple teams/components.
Costly to reverse — undoing or changing the decision later would require substantial rework, data migration, or coordination.
Not obvious from the code — the rationale is not apparent from reading the implementation alone.

Write an ADR for:

Choosing a database engine or persistence strategy
Adopting an async framework or concurrency model
Selecting an authentication/authorization approach
Defining service boundaries or API contracts
Committing to a major dependency or platform
Establishing a cross-cutting pattern (error handling, logging format)
Deprecating a foundational component

Do NOT write an ADR for:

Routine bug fixes
Small features or minor enhancements
Style/formatting decisions (use a linter config)
Decisions already obvious from the codebase
Every library version bump

If you are unsure, ask: "Would a new team member in six months need to understand why this choice was made?" If no — skip it.

File Location Convention

Scope	Location
Workspace-wide decisions	`docs/adr/NNNN-kebab-title.md`
Component-specific decisions	`docs/<component>/decisions/NNNN-kebab-title.md`

Use docs/adr/ for decisions that span the whole project or affect architectural boundaries. Use docs/<component>/decisions/ for decisions scoped to a single service or library within a monorepo.

Numbering Convention

ADRs are numbered sequentially with zero-padded four-digit integers:

docs/adr/
  0000-template.md           ← master template (never a real decision)
  0001-use-postgres.md
  0002-adopt-async-framework.md
  0003-api-versioning-strategy.md

Pick the next available number by listing existing files:

ls docs/adr/ | sort | tail -5

Status Lifecycle

Every ADR carries a Status field with one of these values:

Status	Meaning
`Proposed`	Draft under discussion; not yet adopted
`Accepted`	Adopted — this is the current approach
`Deprecated`	No longer recommended; superseded or abandoned
`Superseded by [NNNN]`	Replaced by a later ADR (link to the new one)

When a decision changes, update the old ADR's status to Superseded by NNNN and create a new ADR for the replacement. Never delete old ADRs — the historical record is the point.

Nygard Template

# NNNN. Title (short, imperative: "Use X for Y")

Date: YYYY-MM-DD

## Status

Proposed | Accepted | Deprecated | Superseded by [NNNN](NNNN-replacement.md)

## Context

What is the issue that we are seeing that is motivating this decision?
Describe the forces at play: technical constraints, team constraints,
organizational constraints, product requirements. Be factual.

## Decision

The change that we are proposing or have agreed to implement.
State the decision clearly in active voice: "We will use X."

## Consequences

What becomes easier or more difficult as a result of this change?
List both positive and negative consequences. Include known risks.
Be honest about trade-offs — this section is the most valuable part.

Workflow

Creating a new ADR

Run /mpm-init on a new project — docs/adr/ is scaffolded with README.md and 0000-template.md.
Copy 0000-template.md to NNNN-your-title.md with the next number.
Fill in Context, Decision, and Consequences. Set Status to Proposed.
Submit for review. Once agreed, change Status to Accepted.
Commit with: docs: ADR-NNNN adopt X for Y

Superseding an ADR

Create a new ADR (MMMM-new-approach.md) with Status Accepted.
Edit the old ADR's Status to Superseded by [MMMM](MMMM-new-approach.md).
Commit both files together.

Follow-up (Stretch Goal)

A future documentation-agent hook could auto-draft ADRs from significant commits or conversation context. This is tracked as a follow-up to issue #562 and is not part of the current implementation.

References

Michael Nygard, "Documenting Architecture Decisions" (2011)
bobmatnyc/trusty-tools — prior art for this convention
docs/features/adr.md — trigger criteria and hybrid location guide