Architecture Audit

A deep module has a simple interface hiding a large implementation. Deep modules are more testable, more AI-navigable, and let you test at the seam instead of inside. See references/deep-modules.md for examples and anti-patterns.

Glossary

Use these terms exactly in every suggestion — don't drift into "component," "service," "API," or "boundary." Consistent language is the point. Full definitions in references/language.md.

• Module — anything with an interface and an implementation (function, class, package, slice).
• Interface — everything a caller must know to use the module: types, invariants, error modes, ordering, config. Not just the type signature.
• Implementation — the code inside.
• Depth — leverage at the interface: a lot of behaviour behind a small interface. Deep = high leverage. Shallow = interface nearly as complex as the implementation.
• Seam — where an interface lives; a place behaviour can be altered without editing in place. (Use this, not "boundary.")
• Adapter — a concrete thing satisfying an interface at a seam.
• Leverage — what callers get from depth.
• Locality — what maintainers get from depth: change, bugs, knowledge concentrated in one place.

Key principles: