codebase-design

codebase-design is a skill for Claude Code, Codex from OutlineDriven/odin-claude-plugin. It costs 58 tokens per session (1,710 once invoked), scanned A, original, Apache-2.0.

A design guide for building deep modules: pieces of code that hide substantial behaviour behind a small, clear interface. An interface is the information callers need to use that code correctly.

In plain words
What is it for?
Designing module interfaces, choosing clean seams between parts of a codebase, improving testability, and planning adapters.
Why use it?
It helps keep complexity inside well-placed modules, making code easier to use, maintain, and test.

Skill for Claude CodeCodex

Part of the odin plugin — 54 skills, 2 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/outlinedriven/odin-claude-plugin/codebase-design
Any agent
npx skills add OutlineDriven/odin-claude-plugin --skill codebase-design
Clone the repo
git clone --depth 1 https://github.com/OutlineDriven/odin-claude-plugin

Made for: Claude Code, Codex.

Or install odin, the plugin that ships this one along with the rest of its 54 skills, 2 agents.

Per session 58 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,710 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00058 $0.01710
Opus 5 $0.00029 $0.00855
Sonnet 5 $0.00012 $0.00342
Haiku 4.5 $0.00006 $0.00171

Measured 3d ago against content hash 63664b6a023c, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

codebase-design 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 3d 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.

skills/codebase-design/SKILL.md · 142 lines

How it starts

The opening of the file, as written. The whole thing — 142 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Codebase Design

Design deep modules: a lot of behaviour behind a small interface, placed at a clean seam, testable through that interface. Use this language and these principles wherever code is being designed or restructured. The aim is leverage for callers, locality for maintainers, and testability for everyone.

Shared vocabulary for every suggestion this skill makes. Use these terms exactly — do not substitute "component," "service," "API," or "boundary." Consistent language is the whole point.

Terms

Module Anything with an interface and an implementation. Deliberately scale-agnostic — applies equally to a function, class, package, crate, module, or tier-spanning slice. Avoid: unit, component, service.

Interface Everything a caller must know to use the module correctly. Includes the type signature, but also invariants, ordering constraints, error modes, required configuration, and performance characteristics. Avoid: API, signature (too narrow — those refer only to the type-level surface).

Implementation What sits inside a module — its body of code. Distinct from Adapter: a single thing can be a small adapter with a large implementation (e.g. a Postgres repository in Rust or a JPA repository in Java) or a large adapter with a small implementation (an in-memory fake). Reach for "adapter" when the seam is the topic; "implementation" otherwise.

Depth Leverage at the interface — the amount of behaviour a caller (or test) can exercise per unit of interface they have to learn. A module is deep when a large amount of behaviour sits behind a small interface. A module is shallow when the interface is nearly as complex as the implementation.

Seam (from Michael Feathers) A place where behaviour can be altered without editing in that place. The location at which a module's interface lives. Choosing where to put the seam is its own design decision, separate from its implementation. Avoid: boundary (overloaded with DDD's bounded context).

Read the full file on GitHub · 142 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. 3d ago First seen · 142 lines · 58 tokens per session scan A 63664b6a023c

Subscribe to this mod's changes

codebase-design is a skill published in the GitHub repository OutlineDriven/odin-claude-plugin (35 stars, last pushed 7d ago), licensed Apache-2.0. It adds 58 tokens to every session and 1,710 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.