> The same modularity that keeps a system inside a human’s head keeps each change inside a well-defined boundary the agent can reason about reliably.

Not only that. Good modularity also:

- improves code reusability, reduces unnecessary code duplication

- helps agents and engineers make better data model, data structure, design pattern, naming, and algorithm choices

- surfaces incorrect irregularities or outdated exceptions to a rule

- enables clean, independent upgrades of parts of a system to improve performance

- reduces stale references in code and comments (and the confusion that results, both from agents and humans)

Bad modularity is basically a summary of what constitutes pathological LLM code. How often have you tried to grok an AI-built project and found trivially unreusable code, unnecessary duplication (everywhere!), bad data structure and algorithm choices, and stale references?