Architecture Design Skill

Trigger

• Keywords: architecture, architecture design, architecture doc, component diagram, 3-architecture, system design, document architecture

When NOT to Use

• Tech spec writing (use /tech-spec)
• Code implementation (use /feature-dev)
• Architecture consulting only (use /codex-architect)
• Implementation roadmap (use /deep-analyze)

Usage

/architecture                          # Auto-detect feature, create/update
/architecture <feature-keyword>        # Specify feature
/architecture --skip-debate            # Skip Phase 3 adversarial debate

Workflow

sequenceDiagram
    participant U as User
    participant C as Claude
    participant E as Explore Agent
    participant X as Codex
    participant D as Architecture Designer
    participant B as /codex-brainstorm

    C->>C: Phase 0: Context Resolution
    par Phase 1: Research
        C->>E: Track A: Code pattern analysis (background)
        C->>C: Track B: Read tech-spec (inline)
    end
    E-->>C: Component list + dependencies
    C->>X: Track C: Architecture advice
    X-->>C: Independent recommendations
    C->>D: Phase 2: Architecture Design
    D-->>C: Component + flow + decisions
    C->>B: Phase 3: Verification (debate)
    B-->>C: Equilibrium conclusion
    C->>C: Phase 4: Write 3-architecture.md
    C->>U: Auto-trigger /codex-review-doc

Phase 0: Context Resolution

Detect the target feature using the 5-level cascade.

See @skills/tech-spec/references/feature-context-resolution.md for the full algorithm.

node scripts/resolve-feature-cli.js 2>/dev/null || echo '{}'

State	Mode
3-architecture.md exists	Update (incremental)
3-architecture.md absent + 2-tech-spec.md exists	Create (tech-spec-informed)
3-architecture.md absent + no tech-spec	Create (code-only research)
Feature not resolved	Gate: Need Human

Scope Gate

For small features (tech-spec WBS has only 1 task, or no tech-spec and < 3 related files), suggest keeping architecture in tech-spec Section 3 instead of creating a separate document. Use AskUserQuestion to confirm.

Phase 1: Architecture Research (parallel)

Launch research tracks. Tracks A and B run in parallel; Track C runs after both complete.

Track A: Code Pattern Analysis (background)

Agent({
  description: "Analyze architecture patterns for <feature>",
  subagent_type: "Explore",
  run_in_background: true,
  prompt: "Analyze the codebase architecture for feature <key>:
    1. Trace execution paths of related modules
    2. Map component dependencies (imports, calls)
    3. Identify integration points with other features
    4. Read docs/architecture.md for global context
    Output: component list + dependency graph + integration points"
})

Fallback: subagent_type: "general-purpose" if Explore unavailable.

Track B: Tech-spec Extraction (inline)

If 2-tech-spec.md exists:

• Read Section 3 (Technical Solution) — architecture diagram, data model, API design
• Read Section 4 (Risks) — constraints, dependencies
• Read Section 7 (Open Questions) — unresolved design decisions

If no tech-spec: skip (code-only mode).

Track C: Codex Architecture Advice (after A+B)

mcp__codex__codex({
  prompt: <from references/codex-prompt.md>,
  sandbox: 'read-only',
  'approval-policy': 'never',
})

Provide feature context metadata only — never feed Claude's conclusions (per @rules/codex-invocation.md).

Save threadId for potential follow-up.

Graceful degradation: Codex unavailable → proceed without (warn in output).

Phase 2: Architecture Design

Dispatch architecture-designer agent with merged research results:

Agent({
  description: "Design architecture for <feature>",
  subagent_type: "architecture-designer",
  prompt: `Design the architecture for <feature>.

  ## Input Context
  ${TECH_SPEC_SUMMARY}
  ${CODE_ANALYSIS}
  ${CODEX_ADVICE}

  ## Required Output
  Follow the output template at @skills/architecture/references/template.md:
  1. Component diagram (Mermaid flowchart)
  2. Component responsibility table
  3. Data flow (Mermaid sequence diagram)
  4. Integration points with existing systems
  5. Architecture decisions (AD-N: context → options → decision → rationale)
  6. Deployment considerations (if applicable)

  ## Constraints
  - Follow @rules/docs-writing.md conventions
  - Reference actual code (file:line, not invented)
  - Mark assumptions explicitly
  - Redact credentials/secrets per @rules/security.md`
})

Fallback: if architecture-designer agent unavailable, use solution-architect agent.

Phase 3: Verification (conditional)

Invoke /codex-brainstorm via Skill tool:

Skill("codex-brainstorm", `Evaluate the proposed architecture for <feature>.

Focus: scalability, maintainability, integration complexity, testability.

Constraints:
- Component diagram from Phase 2
- Tech-spec constraints from Phase 1
- Known risks`)

Must produce: threadId + equilibrium conclusion.

Skip Conditions

Condition	Action
--skip-debate flag	Skip Phase 3
Scope gate triggered (small feature)	Skip Phase 3
Update mode (incremental change)	Skip Phase 3

Graceful degradation: /codex-brainstorm timeout → record timeout in Verification section, still output document.

Phase 4: Output

Write docs/features/<key>/3-architecture.md using the output template.

See references/template.md for the full template.

Cross-References

Auto-insert links:

• > **Source**: [Tech Spec](./2-tech-spec.md) (if exists)
• > **Request**: [Request](./requests/YYYY-MM-DD-*.md) (if active request found)

Auto-Trigger

After Write completes, auto-trigger /codex-review-doc per @rules/auto-loop.md.

Arguments

Argument	Default	Description
<feature-keyword>	auto-detect	Target feature
--skip-debate	false	Skip Phase 3 adversarial debate

Verification

• Feature context resolved (create/update mode determined)
• Research completed (code + tech-spec + Codex)
• Architecture design includes all required sections
• Mermaid diagrams are valid
• Architecture decisions use AD-N format with rationale
• Cross-references to tech-spec and request docs included
• /codex-review-doc passed (auto-triggered)
• No git add/commit/push executed

References

• references/template.md — Output template for 3-architecture.md
• references/codex-prompt.md — Codex independent architecture research prompt
• @skills/tech-spec/references/feature-context-resolution.md — 5-level feature detection

Examples

Input: /architecture
Action: Auto-detect feature → research (code + spec + Codex) → design → debate → write 3-architecture.md → /codex-review-doc

Input: /architecture statusline-config
Action: Resolve "statusline-config" → read tech-spec → research code → design → write → review

Input: /architecture --skip-debate
Action: Auto-detect → research → design → skip debate → write → review