| name | improve-codebase-architecture |
| description | Identify architectural friction and propose deepening opportunities for testability using deletion-test, seam, locality vocabulary |
| allowed-tools | Read Grep Glob Bash Write Edit |
| compatibility | Works best in codebases with CONTEXT.md domain documentation. Creates CONTEXT.md lazily when absent. Pairs with grill-with-docs for terminology refinement and code-refactoring for implementation.
|
| metadata | {"tags":"architecture, refactoring, deep-modules, testability, locality, leverage","platforms":"Claude, ChatGPT, Gemini, Codex","version":"1.0","source":"mattpocock/skills"} |
Improve Codebase Architecture
Surface architectural friction and propose deepening opportunities — refactors that turn shallow modules into deep ones. Goal: testability and AI-navigability.
Vocabulary (use these terms exactly)
- Module — anything with an interface and implementation (function, class, package, slice)
- Interface — everything a caller must know: types, invariants, error modes, ordering, config
- Depth — leverage at the interface: much behavior behind a small interface. Deep = high leverage. Shallow = interface nearly as complex as the implementation
- Seam — where an interface lives; a place behavior can be altered without editing in place
- 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:
- Deletion test: imagine deleting the module. If complexity vanishes, it was a pass-through. If complexity reappears across N callers, it was earning its keep.
- The interface is the test surface.
- One adapter = hypothetical seam. Two adapters = real seam.
When to use this skill
- User wants architectural improvement opportunities
- Codebase is hard to navigate or test
- Modules feel tightly coupled or shallow
- Refactoring would improve testability
When not to use this skill
- Quick targeted refactors → use
code-refactoring
- Design review of a plan → use
grill-with-docs
- Implementation tickets → use
to-issues
Process
1. Explore
Read domain glossary (CONTEXT.md) and ADRs first. Then walk the codebase organically, noting friction:
- Where does understanding one concept require bouncing between many small modules?
- Where are modules shallow — interface nearly as complex as the implementation?
- Where have pure functions been extracted for testability, but real bugs hide in how they're called?
- Where do tightly-coupled modules leak across seams?
- Which parts are untested or hard to test through their current interface?
Apply the deletion test to suspected shallow modules.
2. Present candidates
Numbered list of deepening opportunities. For each:
- Files — which files/modules are involved
- Problem — why the current architecture causes friction
- Solution — plain English description of what would change
- Benefits — in terms of locality, leverage, and test improvement
Use CONTEXT.md vocabulary for domain terms. Use the vocabulary above for architecture terms.
ADR conflicts: if a candidate contradicts an ADR, only surface it when friction is real enough to warrant revisiting. Mark clearly: "contradicts ADR-0007 — but worth reopening because…"
Ask: "Which of these would you like to explore?" — do NOT propose interfaces yet.
3. Grilling loop
Once user picks a candidate, drop into a grilling conversation. Walk the design tree: constraints, dependencies, module shape, what sits behind the seam, what tests survive.
Side effects as decisions crystallize:
- New concept not in CONTEXT.md? Add the term immediately
- Fuzzy term sharpened? Update CONTEXT.md right there
- User rejects with a load-bearing reason? Offer an ADR (only when a future explorer would need it to avoid re-suggesting the same thing)
Instructions
- Identify the task trigger and expected output.
- Follow the workflow steps in this skill from top to bottom.
- Validate outputs before moving to the next step.
- Capture blockers and fallback path if any step fails.
Examples
- Example: Apply this skill to a small scope first, then scale to full scope after validation passes.
Best practices
- Keep outputs deterministic and auditable.
- Prefer small reversible changes over broad risky edits.
- Record assumptions explicitly.
References
- Project standards:
.agent-skills/skill-standardization/SKILL.md
- Validator script:
.agent-skills/skill-standardization/scripts/validate_skill.sh
