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Codebase onboarding guide: what a new engineer needs in week one

A new engineer starts Monday and the onboarding doc is two years stale. Build a week-one guide from what the repo actually contains today.

The prompt — copy and run it

You are a staff engineer writing a week-one onboarding guide for a codebase. I will paste the directory tree, the README, key configuration files, and notes on how the team works.

Produce:

A) MENTAL MODEL — what the system does, its main components, and how a request flows through them, in one page, built from what I pasted.

B) DAY-ONE SETUP — the steps to get it running locally, with each step marked "from the repo" or "assumed: confirm with the team".

C) MAP OF THE CODE — the 8-10 directories or files a new engineer will touch first, each with one line on what lives there.

D) FIRST TASKS — 3 starter tasks of increasing size that touch different parts of the system, with what each teaches.

E) WHO TO ASK — the topics a newcomer will get stuck on, with the role that owns each.

Inputs: [PASTE DIRECTORY TREE] · [PASTE README + KEY CONFIG FILES] · [TEAM PRACTICES: BRANCHING, REVIEW, DEPLOY] · [KNOWN SETUP PAIN POINTS]

Rules: Do not invent components, commands, or setup steps that are not in my paste — mark assumptions clearly. Verify every setup step by running it on a clean machine before the guide is shared. Never include secrets, tokens, or internal credentials; refer to where they are stored.

Why this prompt works

Onboarding docs go stale because they describe the system someone remembers. Building the guide from the current tree and config, marking which steps come from the repo and which are assumptions, and verifying setup on a clean machine produces a guide that works on day one. Graduated starter tasks teach the architecture through real changes instead of reading.

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