improve-codebase-architecture

A code-review guide for finding architectural weaknesses and refactoring opportunities in an existing codebase. It uses the project’s documented terminology and decisions.

In plain words
What is it for?
Use it to plan refactors, consolidate related modules, improve testability, and make a codebase easier for AI tools to understand and navigate.
Why use it?
It helps reveal tightly connected code, hard-to-test areas, and modules whose interfaces are nearly as complicated as their implementations. This gives developers a consistent way to discuss and improve structure.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/sammcj/agentic-coding/improve-codebase-architecture
Any agent
npx skills add sammcj/agentic-coding --skill improve-codebase-architecture
Clone the repo
git clone --depth 1 https://github.com/sammcj/agentic-coding

Made for: Claude Code, Codex.

Per session 66 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,636 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 86% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00066 $0.01636
Opus 5 $0.00033 $0.00818
Sonnet 5 $0.00013 $0.00327
Haiku 4.5 $0.00007 $0.00164

Measured 2d ago against content hash 7a9cb134503d, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

improve-codebase-architecture scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

86% identical to improve-codebase-architecture — 73 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

Skills/improve-codebase-architecture/SKILL.md · 89 lines

How it starts

The opening of the file, as written. The whole thing — 89 lines — stays where its author put it; the contents beside it link to each section on GitHub.

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):

  • 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.

This skill is informed by the project's domain model. The domain language gives names to good seams; ADRs record decisions the skill should not re-litigate.

Process

1. Explore

Scope before you scan - YAGNI. Deepening a module pays off by making future changes to it easier, so a deepening opportunity in code nobody touches is a refactor you never cash in. Decide where to look before you look:

  • If the user named a direction - a module, a subsystem, a pain point - take it and skip the inference below.
  • Otherwise, read back over the last ~20 commits (git log --oneline -20 --name-only) to find the hot spots - the files and areas that keep coming up - and let those paths pull your attention first. If the changes are scattered with no clear hot spot, widen the net.

Read the full file on GitHub · 89 lines

Files

What ships with it

4 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 89 lines · 66 tokens per session scan A 7a9cb134503d

Subscribe to this mod's changes

improve-codebase-architecture is a skill published in the GitHub repository sammcj/agentic-coding (158 stars, last pushed 8d ago), licensed Apache-2.0. It adds 66 tokens to every session and 1,636 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 86% identical to improve-codebase-architecture, differing in 73 lines, and is treated as a copy.

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