create-architecture

# Create Architecture

This skill produces `docs/architecture/architecture.md` — the master architecture
document that translates all approved GDDs into a concrete technical blueprint.
It sits between design and implementation, and must exist before sprint planning begins.

**Distinct from `/architecture-decision`**: ADRs record individual point decisions.
This skill creates the whole-system blueprint that gives ADRs their context.

Resolve the review mode (once, store for all gate spawns this run):
1. If `--review [full|lean|solo]` was passed → use that
2. Else read `production/review-mode.txt` → use that value
3. Else → default to `lean`

See `.claude/docs/director-gates.md` for the full check pattern.

**Argument modes:**
- **No argument / `full`**: Full guided walkthrough — all sections, start to finish
- **`layers`**: Focus on the system layer diagram only
- **`data-flow`**: Focus on data flow between modules only
- **`api-boundaries`**: Focus on API boundary definitions only
- **`adr-audit`**: Audit existing ADRs for engine compatibility gaps only

---

## Phase 0: Load All Context

Before anything else, load the full project context in this order:

### 0a. Engine Context (Critical)

Read the engine reference library completely:

1. `docs/engine-reference/[engine]/VERSION.md`
   → Extract: engine name, version, LLM cutoff, post-cutoff risk levels
2. `docs/engine-reference/[engine]/breaking-changes.md`
   → Extract: all HIGH and MEDIUM risk changes
3. `docs/engine-reference/[engine]/deprecated-apis.md`
   → Extract: APIs to avoid
4. `docs/engine-reference/[engine]/current-best-practices.md`
   → Extract: post-cutoff best practices that differ from training data
5. All files in `docs/engine-reference/[engine]/modules/`
   → Extract: current API patterns per domain

If no engine is configured, stop and prompt:
> "No engine is configured. Run `/setup-engine` first. Architecture cannot be
> written without knowing which engine and version you are targeting."

### 0b. Design Context + Technical Requirements Extraction

Read all approved design documents and extract technical requirements from each:

1. `design/gdd/game-concept.md` — game pillars, genre, core loop
2. `design/gdd/systems-index.md` — all systems, dependencies, priority tiers
3. `.claude/docs/technical-preferences.md` — naming conventions, performance budgets,
   allowed libraries, forbidden patterns
4. **Every GDD in `design/gdd/`** — for each, extract technical requirements:
   - Data structures implied by the game rules
   - Performance constraints stated or implied
   - Engine capabilities the system requires
   - Cross-system communication patterns (what talks to what, how)
   - State that must persist (save/load implications)
   - Threading or timing requirements

Build a **Technical Requirements Baseline** — a flat list of all extracted
requirements across all GDDs, numbered `TR-[gdd-slug]-[NNN]`. This is the
complete set of what the architecture must cover. Present it as:

```
## Technical Requirements Baseline
Extracted from [N] GDDs | [X] total requirements

| Req ID | GDD | System | Requirement | Domain |
|--------|-----|--------|-------------|--------|
| TR-combat-001 | combat.md | Combat | Hitbox detection per-frame | Physics |
| TR-combat-002 | combat.md | Combat | Combo state machine | Core |
| TR-inventory-001 | inventory.md | Inventory | Item persistence | Save/Load |
```

This baseline feeds into every subsequent phase. No GDD requirement should be
left without an architectural decision to support it by the end of this session.

### 0c. Existing Architecture Decisions

Read all files in `docs/architecture/` to understand what has already been decided.
List any ADRs found and their domains.

### 0d. Generate Knowledge Gap Inventory

Before proceeding, display a structured summary:

```
## Engine Knowledge Gap Inventory
Engine: [name + version]
LLM Training Covers: up to approximately [version]
Post-Cutoff Versions: [list]

### HIGH RISK Domains (must verify against engine reference before deciding)
- [Domain]: [Key changes]

### MEDIUM RISK Domains (verify key APIs)
- [Domain]: [Key changes]

### LOW RISK Domains (in training data, likely reliable)
- [Domain]: [no significant post-cutoff changes]

### Systems from GDD that touch HIGH/MEDIUM risk domains:
- [GDD system name] → [domain] → [risk level]
```

Use `AskUserQuestion`:
- Prompt: "One or more engine domains are HIGH RISK — the LLM's knowledge may be unreliable for these areas. Architectural recommendations in these domains should be cross-referenced with the engine docs before being acted on. How would you like to proceed?"
- Options:
  - `[A] Proceed — flag HIGH RISK domains throughout the output`
  - `[B] Let me check the engine reference first — pause here`
  - `[C] Show me which domains are HIGH RISK and why`

---

## Phase 1: System Layer Mapping

Map every system from `systems-index.md` into an architecture layer. The standard
game architecture layers are:

```
┌─────────────────────────────────────────────┐
│  PRESENTATION LAYER                         │  ← UI, HUD, menus, VFX, audio
├─────────────────────────────────────────────┤
│  FEATURE LAYER                              │  ← gameplay systems, AI, quests
├─────────────────────────────────────────────┤
│  CORE LAYER                                 │  ← physics, input, combat, movement
├─────────────────────────────────────────────┤
│  FOUNDATION LAYER                           │  ← engine integration, save/load,
│                                             │    scene management, event bus
├─────────────────────────────────────────────┤
│  PLATFORM LAYER                             │  ← OS, hardware, engine API surface
└─────────────────────────────────────────────┘
```

For each GDD system, ask:
- Which layer does it belong to?
- What are its module boundaries?
- What does it own exclusively? (data, state, behaviour)

Present the proposed layer assignment and ask for approval before proce