Developing Codebase Onboarding

Codebase Onboarding

Explore a codebase and produce .tmp/llm*.md docs so future Claude sessions (and humans) can ramp up instantly.

Process

1. Register Project in LatticeCast PM

Use Skill(developing-project-management) — "Setup Project" section.

This creates the PM board with tickets, views (Table/Kanban/Timeline), and shared workspace.

2. Scan Project Root

Read overview first (if they exist). ex:

• README.md, CLAUDE.md, *.md — project overview
• package.json / pyproject.toml / Cargo.toml — stack + deps
• docker-compose.yml — services architecture
• .env.example — config shape

3. Map Directory Structure

find . -type f -not -path './.git/*' -not -path './node_modules/*' -not -path './.tmp/*' | head -200

Identify layers: frontend, backend, API, DB, auth, infra, tests.

4. Trace Key Flows

For each major module, trace:

• Entry point — where does it start?
• Data flow — input → processing → output
• Dependencies — what does it import/call?
• Config — env vars, constants, feature flags

5. Write .tmp/llm*.md Docs

Create .tmp/ if not exists. examples: (just possible, not must)

| File | Content | |------|---------| | llm.arch.md | Overall architecture, tech stack, directory map | | llm.arch.auth.md | Auth flow, session handling, permissions | | llm.arch.db.md | DB schema, ORM, migrations, key queries | | llm.arch.api.md | API routes, request/response shapes, middleware | | llm.frontend.md | UI structure, components, state management | | llm.backend.md | Server logic, services, business rules | | llm.infra.md | Deploy, CI/CD, Docker, env config | | llm.gotchas.md | Non-obvious quirks, footguns, tech debt |

Only create files for domains that exist in the project. Skip what's not there.

6. Doc Format

Each llm*.md follows:

# [Domain] — [Project Name]

## Overview
One paragraph: what this layer does and why.

## Key Files
- `path/to/file.ts` — what it does
- `path/to/other.ts` — what it does

## Architecture
How components connect. Use ascii diagram if complex:

A → B → C ↓ D

## Patterns
- Pattern name — brief explanation
- Another pattern — brief explanation

## Gotchas
- Non-obvious thing 1
- Non-obvious thing 2

Rules

• All output goes to ./.tmp/ — never /tmp/
• Keep each doc under 100 lines — dense, scannable
• File paths must be current — verify they exist before writing
• No opinions — document what IS, not what should be
• Skip boilerplate/obvious stuff — only document what's non-trivial
• If project is large, prioritize: auth > API > DB > frontend > infra

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: LatticeCast
• Source: LatticeCast/claude-skills
• License: MIT

Install and usage instructions live in the source repository linked above.