Guided journey from an app idea to a deliberate architecture: boundaries, domain model, data decisions, and resilience, making only the expensive-to-reverse decisions and deferring the rest. Orchestrates eight skills phase by phase - clean-architecture, domain-driven-design, system-design, ddia-syst

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 Phase Skill Question it answers Artifact 1 clean architecture Do source code dependencies point inward — is the core testable with no DB, web, or framework? Creates docs/ARCHITECTURE.md 2 domain driven design Where does the business actually split, and what does each term mean? Extends docs/ARCHITECTURE.md 3 system design How little system does our real load actually need? Extends docs/ARCHITECTURE.md 4 ddia systems Which data model, storage engine, and consistency does each workload need? Extends docs/ARCHITECTURE.md 5 software design philosophy Is complexity hidden behind deep modules, or is this classitis? Extends docs/TECH DEBT.md 6 release it Will it degrade gracefully when a dependency is slow or down? Creates docs/RELIABILITY.md 7 pragmatic programmer What thin slice proves the boundaries, and what habits keep them reversible? Extends docs/TESTING.md + docs/TECH DEBT.md 8 37signals way What is essential for v1, and what speculative abstraction do we cut? Extends docs/ARCHITECTURE.md + docs/TECH DEBT.md 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](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. Brief (fallback): The Dependency Rule — source code dependencies point inward: Frameworks → Interface Adapters → Use Cases → Entities; nothing inner names anything outer. Database, web, and vendors are details, plugins to your rules. Enforce with Dependency Inversion: a use case owns a repository interface; the Postgres/Stripe implementation lives in an outer adapter. Draw full boundaries only at real volatility (DB, external services, delivery); collapse layers elsewhere — direction matters, not folder count. Invoke: Use the clean architecture skill with a concrete first feature and the stack from intake. Ask it to layer that feature (entities, a use case with request/response models, repository + gateway interfaces, the HTTP controller and DB adapter in the outer ring), and to flag which boundaries are ceremony versus earning their cost at real volatility. Decide with the user: (1) Modular monolith versus services — default to a modular monolith with clean internal boundaries; a microservice with a shared data model is a distributed monolith, strictly worse. (2) Which volatility points get full boundaries with interfaces now versus collapsed layers. Artifact: Create docs/ARCHITECTURE.md with System Context (what it does, integrations), Layer Map & Dependency Rule (layers, what depends on what; violation location fix status), and the monolith versus services choice in Decision Log (date decision why alternatives rejected). Update the tracker. Done when: the layer map exists, the first feature is layered with framework/ORM types confined to the outer ring, the core is designed to test with no DB/web/framework, the monolith versus services decision is a Decision Log row, and Phase 1 shows done . Phase 2 — Model the domain (domain driven design) Purpose: Put boundaries where the business actually splits and make the code speak the domain — cheapest now, inventing the vocabulary from a blank page. Brief (fallback): The model is the code — build a Ubiquitous Language so team words are code words. Name after domain concepts ( Order.place() , not OrderManager.process() ); a name that resists is a design signal, not an annoyance. Bounded contexts: a region where a word means exactly one thing ("Customer" differs in billing versus support) — these are your future service seams. Aggregates: a small root cluster enforcing invariants, immediately consistent inside and eventually consistent outside; reference other aggregates by ID. Push behavior into entities — no anemic data bags. Invoke: Use the domain driven design skill with the domain vocabulary and the Phase 1 layer map. Ask for the bounded context map built from the words the team actually uses, the core aggregates with their invariants, and a subdomain classification (core / supporting / generic). Decide with the user: (1) Where the same word legitimately means different things across contexts — do NOT unify into one omniscient model. (2) Which subdomain is core (invest deep modeling) versus generic (buy or use OSS — auth, email, payments). Artifact: Extend docs/ARCHITECTURE.md: Bounded Contexts & Context Map (contexts, relationships, anti corruption layers) and Domain Glossary (Ubiquitous Language) (term meaning code name); record aggregate and core domain choices in Decision Log . Update the tracker. Done when: contexts are mapped with their relationships, the glossary names the core terms, each aggregate states its invariants and by ID references, the core subdomain is chosen, and the context boundaries line up with the Phase 1 layer map. Phase 3 — Size the system honestly (system design) Purpose: Prove with numbers how small the system can be, so you skip the machinery you cannot justify. Brief (fallback): Start with requirements, not solutions. Back of envelope: QPS = daily active users × actions/day ÷ 86,400, peak 2 5× average; storage = records/day × size × retention. For hundreds to thousands of users, a single indexed DB plus a read path cache carries you a long time. Scale in order: vertical first, then cache aside (TTL + explicit invalidation), then read replicas, and shard last, only

design-code-architecture