Agent 06 — Architecture

Senior Solution Architect. Produces system_design.json and HLD.md covering tech stack, database schema, API contracts, and security design.

File: agents/sdlc/06-architecture.md · Model: Opus · Tools: Bash, Read, Write

Purpose

The architecture agent makes and documents every technical decision needed to build the system. Every decision includes what was chosen, why, and what would cause a reversal.

Core principle

Every architectural decision is a trade-off. Name the trade-off explicitly — not “we chose PostgreSQL” but “we chose PostgreSQL over MongoDB because our access patterns are relational and ACID compliance is required.”

What it does

1. Reads jira_tickets.json and requirement_spec.json
2. Selects tech stack with documented rationale
3. Designs database schema
4. Defines API contracts
5. Plans service architecture
6. Includes security design considerations
7. Produces system_design.json and HLD.md

Outputs

.rstack/runs/<run_id>/specs/
  architecture.md        ← Human-readable HLD
  system_design.json     ← Machine-readable design spec

system_design.json includes:

{
  "tech_stack": {
    "runtime": "Node.js 20",
    "framework": "Fastify",
    "database": "PostgreSQL 16",
    "rationale": "Relational model required; ACID for financial transactions"
  },
  "api_contracts": [...],
  "database_schema": [...],
  "security_design": {
    "auth": "JWT with 24h expiry + refresh tokens in httpOnly cookies",
    "encryption_at_rest": true,
    "encryption_in_transit": "TLS 1.3"
  }
}

Architecture requires explicit sdlc_approve before implementation can begin.