codebase-onboarding

codebase-onboarding is a skill for Claude Code, Codex from Jamkris/everything-gemini-code. It costs 52 tokens per session (1,955 once invoked), scanned A, a copy of codebase-onboarding, MIT.

A guided analysis of an unfamiliar software repository that maps its structure, architecture, entry points, and working conventions.

In plain words
What is it for?
Use it when joining a repository, opening a project for the first time, or creating a GEMINI.md guide for Gemini CLI.
Why use it?
It reduces the time needed to understand a new project and gives new contributors a clear starting point.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: mentions Gemini CLI.

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/jamkris/everything-gemini-code/codebase-onboarding
Any agent
npx skills add Jamkris/everything-gemini-code --skill codebase-onboarding
Clone the repo
git clone --depth 1 https://github.com/Jamkris/everything-gemini-code

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 codebase-onboarding

README.md
[![agentmods](https://agentmods.dev/badge/skills/jamkris/everything-gemini-code/codebase-onboarding.svg)](https://agentmods.dev/skills/jamkris/everything-gemini-code/codebase-onboarding)
Your own site
<a href="https://agentmods.dev/skills/jamkris/everything-gemini-code/codebase-onboarding"><img src="https://agentmods.dev/badge/skills/jamkris/everything-gemini-code/codebase-onboarding.svg" alt="Measured on agentmods" height="20"></a>
Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,955 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin 81% 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 5.1 $0.00052 $0.01955
Opus 5 $0.00026 $0.00978
Sonnet 5 $0.00010 $0.00391
Haiku 4.5 $0.00005 $0.00196

Measured 2d ago against content hash e2c1c0f5c63c, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

codebase-onboarding 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

81% identical to codebase-onboarding — 59 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/codebase-onboarding/SKILL.md · 234 lines

How it starts

The opening of the file, as written. The whole thing — 234 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Codebase Onboarding

Systematically analyze an unfamiliar codebase and produce a structured onboarding guide. Designed for developers joining a new project or setting up Gemini CLI in an existing repo for the first time.

When to Use

  • First time opening a project with Gemini CLI
  • Joining a new team or repository
  • User asks "help me understand this codebase"
  • User asks to generate a GEMINI.md for a project
  • User says "onboard me" or "walk me through this repo"

How It Works

Phase 1: Reconnaissance

Gather raw signals about the project without reading every file. Run these checks in parallel:

1. Package manifest detection
   → package.json, go.mod, Cargo.toml, pyproject.toml, pom.xml, build.gradle,
     Gemfile, composer.json, mix.exs, pubspec.yaml

2. Framework fingerprinting
   → next.config.*, nuxt.config.*, angular.json, vite.config.*,
     django settings, flask app factory, fastapi main, rails config

3. Entry point identification
   → main.*, index.*, app.*, server.*, cmd/, src/main/

4. Directory structure snapshot
   → Top 2 levels of the directory tree, ignoring node_modules, vendor,
     .git, dist, build, __pycache__, .next

5. Config and tooling detection
   → .eslintrc*, .prettierrc*, tsconfig.json, Makefile, Dockerfile,
     docker-compose*, .github/workflows/, .env.example, CI configs

6. Test structure detection
   → tests/, test/, __tests__/, *_test.go, *.spec.ts, *.test.js,
     pytest.ini, jest.config.*, vitest.config.*

Phase 2: Architecture Mapping

From the reconnaissance data, identify:

Tech Stack

  • Language(s) and version constraints
  • Framework(s) and major libraries
  • Database(s) and ORMs
  • Build tools and bundlers
  • CI/CD platform

Architecture Pattern

  • Monolith, monorepo, microservices, or serverless
  • Frontend/backend split or full-stack
  • API style: REST, GraphQL, gRPC, tRPC

Key Directories Map the top-level directories to their purpose:

src/components/  → React UI components
src/api/         → API route handlers
src/lib/         → Shared utilities
src/db/          → Database models and migrations
tests/           → Test suites
scripts/         → Build and deployment scripts

Read the full file on GitHub · 234 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. 2d ago First seen · 234 lines · 52 tokens per session scan A e2c1c0f5c63c

Subscribe to this mod's changes

codebase-onboarding is a skill published in the GitHub repository Jamkris/everything-gemini-code (87 stars, last pushed 3mo ago), licensed MIT. It adds 52 tokens to every session and 1,955 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 81% identical to codebase-onboarding, differing in 59 lines, and is treated as a copy.