Crosscutting Concepts
Baseline arc42 Chapter 8 concepts every system documents: threat model, security, test, observability, error handling
A semantic contract: vocabulary your project supplies itself — ready to drop into your CLAUDE.md / AGENTS.md.
- 8.1 Threat Model — STRIDE; threats get IDs (T-001…).
- 8.2 Security — every mitigation references the T-IDs it closes.
- 8.3 Test — testing pyramid; tests trace to Use Cases and Business Rules.
- 8.4 Observability — logs, metrics, traces, audit trails.
- 8.5 Error Handling — retry, circuit breaker, fallback, recovery.
arc42 leaves Chapter 8 open. We require five baseline crosscutting concepts, in this order:
Add further Chapter 8.x concepts (persistence, i18n, accessibility, configuration, performance) only when the system actually has that concern.