design-doc

Design Doc

Write a lightweight architecture design doc for a decision that deserves thinking before code. Use this when the problem has real ambiguity, tradeoffs, cross-cutting concerns, or future maintenance risk. If the solution is obvious and the doc would only become an implementation manual, say so and recommend spec or implement instead.

Workflow

1. Ground

• Treat the full argument as the design brief unless the user names a feature or path.
• Derive a kebab-case slug if no name is given.
• Read referenced docs, code, specs, plans, and architecture notes so the design fits the system as it exists.
• Identify stakeholders, goals, non-goals, constraints, cross-cutting concerns, and decisions that need human review.
• Ask only when a missing fact would materially change the design. Ask one question at a time with your recommended answer.

2. Write

Write docs/<design-slug>/design.md using the sections below. Keep solo-developer docs short: prefer 1-3 pages unless the architecture genuinely needs more.

• Status: Draft, In Review, Approved, or Superseded.
• Summary: the problem and recommended direction in a few sentences.
• Context and Scope: objective background, current system, and what this doc covers.
• Goals: outcomes this design must achieve.
• Non-Goals: reasonable adjacent outcomes this design deliberately excludes.
• Constraints: technical, product, migration, compatibility, operational, cost, or time constraints.
• Proposed Design: the chosen architecture, starting high-level before details.
• Architecture Views (when useful): system context, data flow, runtime, deployment, or component diagrams.
• Interfaces and Data (when relevant): API, event, schema, storage, or contract changes that affect the design.
• Alternatives Considered: plausible options and why they lose under the stated goals and constraints.
• Tradeoffs: what the chosen design gains, gives up, risks, or postpones.
• Cross-Cutting Concerns: security, privacy, observability, reliability, performance, cost, and operations where relevant.
• Rollout and Migration (when relevant): how to ship, migrate, verify, and back out safely.
• Open Questions: decisions or facts still unresolved.
• Decision: the recommendation, assumptions, and who needs to review or approve it.

3. Pause

Stop after writing. Do not continue into spec, plan, or implementation until the human confirms the design.

Rules

• The document exists to make reasoning reviewable, not to document every implementation step.
• Focus on tradeoffs, alternatives, and constraints code will not explain later.
• Use diagrams only when they clarify relationships, flows, or deployment.
• Do not copy full schemas, APIs, or code unless the exact shape is central to the decision.
• Write for a future maintainer who needs to understand why this design was chosen.