improve-codebase-architecture

improve-codebase-architecture is a skill for Claude Code, Codex from mick-gsk/drift. It costs 64 tokens per session (865 once invoked), scanned A, a copy of deep-module-refactor, MIT.

A code-review guide for finding design changes that can make a codebase easier to test and understand. It focuses on deep modules: parts of the program with a small interface that hide more of the implementation.

In plain words
What is it for?
It is for exploring a codebase, finding refactoring opportunities, improving testability, reducing tight coupling, and making the code easier for AI tools to navigate.
Why use it?
It helps identify code where understanding or testing requires following too many small, tightly connected pieces. It turns selected improvement ideas into GitHub issue proposals for discussion.

Skill for Claude CodeCodex

Part of the drift plugin — 31 skills, 17 agents shipped together

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/mick-gsk/drift/improve-codebase-architecture
Any agent
npx skills add mick-gsk/drift --skill improve-codebase-architecture
Clone the repo
git clone --depth 1 https://github.com/mick-gsk/drift

Made for: Claude Code, Codex.

Or install drift, the plugin that ships this one along with the rest of its 31 skills, 17 agents.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for improve-codebase-architecture

README.md
[![agentmods](https://agentmods.dev/badge/skills/mick-gsk/drift/improve-codebase-architecture.svg)](https://agentmods.dev/skills/mick-gsk/drift/improve-codebase-architecture)
Your own site
<a href="https://agentmods.dev/skills/mick-gsk/drift/improve-codebase-architecture"><img src="https://agentmods.dev/badge/skills/mick-gsk/drift/improve-codebase-architecture.svg" alt="Measured on agentmods" height="20"></a>
Per session 64 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 865 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 95% 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 $0.00064 $0.00865
Opus 5 $0.00032 $0.00432
Sonnet 5 $0.00013 $0.00173
Haiku 4.5 $0.00006 $0.00086

Measured 4d ago against content hash c6dd6ad7daad, 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 4d 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

95% identical to deep-module-refactor — 6 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.

.github/skills/improve-codebase-architecture/SKILL.md · 77 lines

How it starts

The opening of the file, as written. The whole thing — 77 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Improve Codebase Architecture

Explore a codebase like an AI would, surface architectural friction, discover opportunities for improving testability, and propose module-deepening refactors as GitHub issue RFCs.

A deep module (John Ousterhout, "A Philosophy of Software Design") has a small interface hiding a large implementation. Deep modules are more testable, more AI-navigable, and let you test at the boundary instead of inside.

Process

1. Explore the codebase

Use the Agent tool with subagent_type=Explore to navigate the codebase naturally. Do NOT follow rigid heuristics — explore organically and note where you experience friction:

  • Where does understanding one concept require bouncing between many small files?
  • Where are modules so shallow that the interface is nearly as complex as the implementation?
  • Where have pure functions been extracted just for testability, but the real bugs hide in how they're called?
  • Where do tightly-coupled modules create integration risk in the seams between them?
  • Which parts of the codebase are untested, or hard to test?

The friction you encounter IS the signal.

2. Present candidates

Present a numbered list of deepening opportunities. For each candidate, show:

  • Cluster: Which modules/concepts are involved
  • Why they're coupled: Shared types, call patterns, co-ownership of a concept
  • Dependency category: See REFERENCE.md for the four categories
  • Test impact: What existing tests would be replaced by boundary tests

Do NOT propose interfaces yet. Ask the user: "Which of these would you like to explore?"

3. User picks a candidate

4. Frame the problem space

Before spawning sub-agents, write a user-facing explanation of the problem space for the chosen candidate:

  • The constraints any new interface would need to satisfy
  • The dependencies it would need to rely on
  • A rough illustrative code sketch to make the constraints concrete — this is not a proposal, just a way to ground the constraints

Read the full file on GitHub · 77 lines

Files

What ships with it

1 file 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. 4d ago First seen · 77 lines · 64 tokens per session scan A c6dd6ad7daad

Subscribe to this mod's changes

improve-codebase-architecture is a skill published in the GitHub repository mick-gsk/drift (14 stars, last pushed 1mo ago), licensed MIT. It adds 64 tokens to every session and 865 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to deep-module-refactor, differing in 6 lines, and is treated as a copy.

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