(2026-04-13) The Complete Guide To Karpathys Second Brain

Aakash: The Complete Guide to Andrej Karpathy's Second Brain. in today’s deep dive, I cover the knowledge system Karpathy posted that’s permanently replacing RAGs (LLM-Wiki). It’s the first thing I’ve tried that makes your AI knowledge compound instead of reset.

today’s deep dive:

• Why every second brain you’ve built eventually died
• What Karpathy actually figured out (and why it spread so fast)
• Four use cases for engineers and builders
• How to set it up in 30 minutes
• What it looks like after 30 days

1. Why Your Second Brain Keeps Dying

*You hit a hard problem. You solved it. Three months later the same problem shows up in a different form and you can’t remember what you figured out the first time.

The folder exists. The notes exist. The solution is gone. It lived in your head and left when you moved on.*

Every AI tool has the same flaw underneath. NotebookLM, ChatGPT uploads, Notion AI: they all retrieve at query time instead of building anything persistent. Ask a question, get an answer, session ends. Tomorrow: scratch. Your knowledge never compounds. The AI never gets smarter about your domain.

2. What Andrej Karpathy Actually Figured Out

what if instead of waiting until query time to process your sources, the AI compiled them once at ingest and maintained that compilation as new sources arrived?

Three pieces make it work.*

• Raw is your junk drawer. Articles, transcripts, docs, notes. Dump it in without organizing.*
• Wiki is what the AI builds from raw*
• Schema is a single CLAUDE.md file that tells the AI what your knowledge base is about and how to organize it. You write this once. The AI follows it every session.

The tedious part of maintaining a knowledge base is the bookkeeping. Humans abandon wikis because the maintenance burden grows faster than the value.

3. Four Use Cases

Use Case 1 - Stakeholder Memory

The wiki ends up knowing your CTO better than most new employees do after their first month.
Every meeting note, Slack thread, and email thread goes into raw/. The wiki builds a page per stakeholder: what they care about, what they’ve pushed back on, what language has landed, what they’ve approved and why.

Before your next meeting with the CTO, run this:

• Pull the stakeholder page for [Name].
• What have they pushed back on before?
• What framing has landed with them?
• What should I lead with tomorrow?
• You walk in knowing exactly what objections are coming, what framing will land, and what to address defensively

Use Case 2 - Side project context that doesn’t evaporate

Your side project gets weekends. By the time you open it Saturday morning you can’t remember what you were building toward. You spend the first hour just getting back up to speed.

Drop your planning notes, decisions, and TODOs into raw/ after every session. Write a brief note before you close the laptop about where you left off. The wiki maintains your running context.
Saturday morning prompt:

• Where did I leave off on [project]?
• What was I trying to solve and what's the next step?

Use Case 3 - Team Onboarding That Doesn’t Lose Knowledge When People Leave

A senior employees leaves your team. Years of context walk out with them

If the wiki exists, the transition is painful but survivable. If it doesn’t, the next employees starts over.

Use Case 4 - Solutions you solved once and forgot

You spent four hours debugging a gnarly issue last month. You found the fix. You moved on. Now it’s back, in a slightly different form, and you’re starting from zero.
Drop your debugging notes into raw/ when you solve something non-obvious. The answer is usually there. The problem is you never had anywhere to put it. (I rarely find a dev who keeps progress notes or a Programmer's Notebook.)

4. How to Set It Up

Path A: Use My Skill
Use this skill I’ve created for you...

Path B: Do it Manually
Create the folder structure:...

Four folders. Raw is source material the AI reads but never modifies. Wiki is what the AI builds. Outputs is where answers to queries live. Git gives you version history for free.

Write a CLAUDE.md that tells Claude what this knowledge base is for, how to categorize sources, and what to do when new sources contradict old ones.

Read the wiki summary after each ingest. Ask one question. Do that five times and you already have 15-30 interconnected pages.

One thing to resist: the instinct to dump everything at once.

5. What 30 Days Looks Like

You ask a question and the wiki answers with something you forgot you knew. A note from two months ago surfaces in response to a problem you’re facing today. A contradiction between two things you read six weeks apart gets flagged automatically.

The wiki made me a better researcher because knowing it would compound made me more deliberate about what I put in.