Design Code Architecture

Design Code Architecture

Design the architecture for a new app: get the small number of expensive-to-reverse decisions right and stay aggressively simple everywhere else. This is an interactive, resumable journey of eight phases — the agent asks before every decision and records the outcome in your project's docs/ folder, so you can stop after any phase and resume later. It runs from the most foundational and hardest-to-reverse (boundaries, domain) through the tunable (data, resilience) to the cross-cutting disciplines (complexity, reversibility, scope) you apply throughout. A weekend project uses three phases lightly; a funded team building toward launch wants the whole stack.

Core Principle

Architecture is the set of decisions that are expensive to reverse: make exactly those deliberately, and defer everything cheap. This skill sequences the phases, asks the decision questions, and records every choice in docs/. The constituent skills carry the method — invoke them rather than improvising their frameworks. The whole strategy is to convert expensive decisions into cheap ones by putting a boundary in front of them, so the irreducibly expensive set stays small enough to get right with care.

Journey Map

Operating Rules

1. Resume first. Before anything else, read docs/DESIGN-CODE-ARCHITECTURE-PLAN.md and every artifact in the Journey Map. If the tracker exists, summarize the journey state in 3-5 lines and ask which phase to enter. Done when the user has confirmed an entry point. A journey with a tracker is resumed, never restarted.
2. Intake on first run only. No tracker: run the Intake below, then create docs/DESIGN-CODE-ARCHITECTURE-PLAN.md with every phase statused pending | in-progress | awaiting-evidence | done | deferred: reason | skipped: reason. Done when the tracker exists and the user has confirmed the phase plan.
3. Phase entry. Announce: what the phase does, the decision it forces, the artifact it produces, rough effort. Offer proceed / skip / defer — phases marked GATE may be deferred, never skipped. Mark the phase in-progress on proceed. Done when the user chose.
4. Skill invocation and fallback. Load the phase's skill and use it: each phase's Invoke line names the skill by slug — use that skill to run the phase. If it is not available, offer: npx skills add wondelai/skills/<slug> --global. If the user declines, run the phase from its Brief — the minimum viable method. State which mode you are in.
5. In-phase decisions. Ask every question under "Decide with the user" — with concrete options and your recommendation. Record the choice in the tracker's Key Decisions. A decision made silently is a defect.
6. Phase exit. Present the draft artifact content for sign-off before writing. On approval: write or extend the docs/ files, update the tracker (status, Key Decisions, Next Actions). Done when the files are written and the phase row shows done.
7. Artifact discipline. Read before writing; create a file only if missing, otherwise extend — add or update your sections, preserve everyone else's. Files are UPPERCASE in docs/. Every recommendation lands as a checkbox or a table row with owner and priority. See references/artifact-templates.md when creating a docs/ file for the first time — create it from the full skeleton (all section headings), then fill the sections your phase names.
8. Every expensive-to-reverse decision gets a Decision Log row (decision, why, alternatives rejected) before any code assumes it. Default to a modular monolith: services split only along proven bounded contexts.

Intake

Ask these before creating the tracker:

1. What will the app do, and what is the one feature that is genuinely your competitive advantage? (frames the core subdomain in Phase 2 — where to invest deep modeling versus buy off-the-shelf)
2. What stack are you leaning toward — language, web framework, ORM, database? (gates the Phase 1 boundary and Phase 4 data decisions; treated as a detail, never the skeleton)
3. What load is realistic in year one — rough daily active users and the main actions each takes? (gates Phase 3 sizing: requirements before solutions)
4. What outbound dependencies will it call — payments, email, LLM APIs, shipping, queues? (gates the Phase 6 integration-point audit)
5. Which data is the system of record, and are there second read patterns like search, analytics, or feeds? (gates Phase 4 consistency and derived-data decisions)
6. Has anyone validated that people actually want this app? (if not, route to create-business / create-app first — do not architect an unvalidated idea)
7. How many teams will own this system, and how much of the journey do you want now? (gates the team-topologies optional phase and the Phase 8 appetite)

Phase-skip heuristics: skip Phase 3's scaling machinery and most of Phase 4's replication when year-one load is far below any threshold (a single indexed DB is the answer — record it and move on); skip the team-topologies optional phase for a single-team app. Never skip Phase 1 or Phase 2 — boundaries and the domain model are the additive work that makes every later decision cheap; Phase 6 resilience is not optional once real users and outbound calls exist. Then create the tracker from the template and confirm the plan.

Done when docs/DESIGN-CODE-ARCHITECTURE-PLAN.md exists with every phase statused and the user has confirmed the plan.

Phases

Phases run in the listed order, from hardest-to-reverse to tunable to cross-cutting — each assumes the previous phase's artifact exists. Any phase can be entered, skipped, or deferred per the Operating Rules; Phases 1-2 are the additive work that makes everything after them cheap to change.

The phases form a dependency chain that mirrors the system: Domain-Driven Design says where the boundaries belong (contexts and aggregate seams); Clean Architecture says which way dependencies cross them; Data-Intensive Apps decides what lives inside them at the persistence layer; System Design says how much infrastructure that actually requires — usually far less than feared. Software Design keeps the modules deep instead of multiplying into shallow ceremony, Release It! hardens the integration points, Pragmatic Programmer supplies the cross-cutting habits that hold the structure over time, and the 37signals Way governs the whole thing by fixing time and cutting scope.

Phase 1 — Draw the boundaries (clean-architecture)

Purpose: Keep business rules independent of the framework, database, and vendors so every later decision stays swappable — the move that buys back all the others.