Learn Unfamiliar Codebase

Learn Unfamiliar Codebase is a skill for Claude Code, Codex from GktuOktay/ai-skills. It costs 47 tokens per session (1,124 once invoked), scanned A, original, MIT.

A method for quickly understanding an unfamiliar software project by starting with its documentation, package files, and folder structure.

In plain words
What is it for?
Use it when joining a new project, tracing its architecture, locating tests and configuration, or preparing to make a focused change.
Why use it?
It helps you find the most informative files first instead of reading a large codebase randomly.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

Good fit Use it when joining a new project, tracing its architecture, locating tests…

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Install with agentmods
npx agentmods add skills/gktuoktay/ai-skills/learn-codebase
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.

Any agent
npx skills add GktuOktay/ai-skills --skill learn-codebase
Clone the repo
git clone --depth 1 https://github.com/GktuOktay/ai-skills

Made for: Claude Code, Codex.

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 Learn Unfamiliar Codebase

README.md
[![agentmods](https://agentmods.dev/badge/skills/gktuoktay/ai-skills/learn-codebase.svg)](https://agentmods.dev/skills/gktuoktay/ai-skills/learn-codebase)
Your own site
<a href="https://agentmods.dev/skills/gktuoktay/ai-skills/learn-codebase"><img src="https://agentmods.dev/badge/skills/gktuoktay/ai-skills/learn-codebase.svg" alt="Measured on agentmods" height="20"></a>
Per session 47 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,124 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
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 5.1 $0.00047 $0.01124
Opus 5 $0.00023 $0.00562
Sonnet 5 $0.00009 $0.00225
Haiku 4.5 $0.00005 $0.00112

Measured 6d ago against content hash 9bd7eefc310c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

Learn Unfamiliar Codebase 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 6d 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.

.agents/skills/learn-codebase/SKILL.md · 87 lines

How it starts

The opening of the file, as written. The whole thing — 87 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Learn Unfamiliar Codebase Skill

Overview

This skill provides a systematic approach to rapidly onboarding onto, understanding, and navigating large, unfamiliar codebases. It is designed to move an agent from zero knowledge to productive contribution in the shortest time possible by prioritizing high-signal files and architectural patterns.

Phase 1: The First-Pass Strategy (High-Level Context)

Do not dive into source code immediately. Understand the box before looking inside.

1. Documentation & Manifests

Read these files first to understand what the project is, what it depends on, and how it is built.

  • README.md, CONTRIBUTING.md, ARCHITECTURE.md
  • Package manifests: package.json (Node), pom.xml (Java), Cargo.toml (Rust), go.mod (Go), Podfile / Package.swift (iOS), requirements.txt / pyproject.toml (Python).

Goal: Answer "What are the core dependencies?" (e.g., React, Express, CoreData, Django).

2. Directory Structure Analysis

Use directory listing tools to get a bird's-eye view. Look for standard conventions.

  • src/, lib/, app/ -> Source code.
  • tests/, spec/, __tests__/ -> Testing structure.
  • config/, scripts/, docker/ -> Infrastructure.

Goal: Answer "How is the code organized?" (e.g., by feature, by layer/type, monolith vs. microservices).

Phase 2: Finding Entry Points

To trace execution, you must know where it begins.

  • Web Apps: Look for index.js, main.ts, App.tsx, pages/_app.tsx (Next.js).
  • Backend APIs: Look for server.js, main.go, manage.py, Program.cs, routes configurations.
  • Mobile Apps: Look for AppDelegate.swift, @main struct App, MainActivity.java.
  • CLIs: Look for bin/, cli.js, main.rs.

Phase 3: Identifying Architectural Patterns

Analyze the code organization to determine the architectural style. Look for:

  1. MVC (Model-View-Controller): Are there directories explicitly named models, views, controllers?
  2. Clean Architecture / Hexagonal: Are there layers for domain, usecases, infrastructure, adapters?
  3. Feature-Based Modular: Is code grouped by domain concept? (e.g., src/features/authentication/, src/features/users/).
  4. State Management: Look for Redux (store/, reducers/), Vuex, Context APIs, or core database abstraction layers (ORMs, DAOs).

Read the full file on GitHub · 87 lines

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. 6d ago First seen · 87 lines · 47 tokens per session scan A 9bd7eefc310c

Subscribe to this mod's changes

Learn Unfamiliar Codebase is a skill published in the GitHub repository GktuOktay/ai-skills (2 stars, last pushed 3d ago), licensed MIT. It adds 47 tokens to every session and 1,124 once invoked, about $0.0002 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 2026-08-31.

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