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.

This command is informed by the project's domain model and built on a shared design vocabulary:

• Run the /codebase-design skill for the architecture vocabulary (module, interface, depth, seam, adapter, leverage, locality) and its principles (the deletion test, "the interface is the test surface", "one adapter = hypothetical seam, two = real"). Use these terms exactly in every suggestion — don't drift into "component," "service," "API," or "boundary."
• The domain language in CONTEXT.md gives names to good seams; accepted ADRs in docs/adr/ record decisions this command should not re-litigate.

Process

1. Explore

Read the project's domain glossary (CONTEXT.md) first, and respect accepted ADRs in the area you're touching; treat proposed ADRs as planning context only when they belong to the current work.

Then use the Agent tool with subagent_type=Explore to walk the codebase. Don't follow rigid heuristics — explore organically and note where you experience friction: