improve-codebase-architecture

Analyze codebases for architectural friction and propose module-deepening refactors as testability improvements.

- Explores codebases organically to surface shallow modules, tightly-coupled components, and untested seams rather than following rigid heuristics

- Applies John Ousterhout's "deep module" principle: small interfaces hiding large implementations for better testability and AI navigability

- Generates multiple radically different interface designs (minimalist, flexible, caller-optimized, ports & adapters) via parallel sub-agents, then recommends the strongest approach

- Creates GitHub issue RFCs documenting the problem space, design trade-offs, and refactoring rationale

Improve Codebase Architecture

Surface architectural friction and propose deepening opportunities - refactors that turn shallow modules into deep ones. The aim is testability and AI-navigability.

Glossary

Use these terms exactly in every suggestion. Consistent language is the point - don't drift into "component," "service," "API," or "boundary." Full definitions in 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 (see LANGUAGE.md for the full list):