codebase-onboarding

# Codebase onboarding — get oriented fast, leave a map You have just landed in a codebase you did not write: a fresh clone, an inherited project, an acquired repo, an abandoned side project someone handed you. The instinct is to start reading files top-to-bottom. Resist it. That is how a week disappears and you still cannot answer "where does X happen". This skill runs a disciplined **breadth-first reconnaissance pass** and produces one durable artifact: a map a teammate can trust and you can re-read tomorrow. The payoff is measured. Engineers using AI to onboard reach the same milestones roughly **2x faster** — productive in 1–2 weeks instead of 4–6 — and the biggest gains are exactly in *searching for code, decoding undocumented patterns, and tracing data flows* (super-productivity.com, accessed 2026-06-02). That is what the recon pass below targets, in order. ## Lead with the deliverable Before you grep a single line, know the target: a single living file, `CODEBASE-MAP.md`, committed at the repo root. You work *backward* from its sections — every recon step fills one. Minimal schema: ```markdown # CODEBASE-MAP.md — <repo name> ## Stack # languages, framework + versions, package manager, run scripts ## Entry points # main / server bootstrap / route registration / CLI commands ## Request flow # one real path traced transport -> business logic -> persistence ## Module ownership # who owns transport / business logic / persistence / UI ## Hidden behavior ...