An InfoQ essay from the Certified Architect Program argues that software systems are more than code — they include the shared mental model, or “theory,” held in the minds of the people who build and maintain them. When that theory erodes, the system becomes unevolvable even if every quality gate passes.
Three forces are quietly eroding comprehension:
- Knowledge fragmentation. Decentralized decision-making optimizes flow but fragments the global picture. Teams understand their local domain but lose the “why” behind systemic boundaries.
- Team churn. Departing members take theory with them. New hires rebuild from artifacts that record the what, not the why — so they fall back on tactical patches instead of systemic improvements.
- AI-generated code. GenAI compresses the implementation layer where comprehension used to form naturally during design and coding. The result: code that passes every gate but nobody understands.
The article proposes concrete signals to monitor the decay:
- Large PR sizes and over-reliance on agentic code reviewers
- High Degree of Authorship / low truck factor — knowledge concentrated in too few people
- Rising onboarding times as a proxy for system incomprehensibility
- Changes to core modules merged without design reviews or ADRs capturing intent
The bottom line: code review needs to be reframed from a quality gate to a comprehension checkpoint — a place where the understanding built before code generation gets validated, strengthened, and spread across the team. Evolutionary architecture’s promise of safe change depends on deliberately engineering that shared understanding, because it will not survive on its own.