✳︎ MY AI GUIDE
Build a Claude second brain
Connect Claude to an Obsidian vault and it keeps a living wiki of everything you know: it reads your notes, links them together, and answers questions with citations from your own knowledge.
The workflow is Andrej Karpathy’s "LLM Wiki". His original write-up (and his exact prompt) is here on GitHub. This page is the plain-English setup.
📥You add raw material once: articles, book highlights, meeting notes, voice-memo transcripts, anything.
🔗Claude does the filing: it reads each new note, writes it into a wiki of linked markdown pages, and updates the cross-references automatically.
💬You ask questions and get answers built from YOUR notes, with links back to the exact pages, then the new insight is saved straight back in.
📈It compounds: the more you feed it, the smarter your own knowledge base gets. No more starting every chat from zero.
Before you start
What you need
✓Obsidian is 100% free on Mac, Windows, Linux, iOS and Android.
✓A little comfort with the terminal. You will paste about three commands. No coding, promise. Full copy buttons below.
!Claude Code runs on a paid Claude plan (Pro or Max), or on pay-as-you-go API credits. This is the one part that is not free. The vault, the notes and Obsidian all are.
!You will install Node.js (a free one-time download) so Claude Code can run. Step 2 covers it.
The Setup
Five steps, about fifteen minutes
Tap each step as you finish it. Do them in order, top to bottom.
0/5
1. Download Obsidian and make a vault
Your notes live here
Get Obsidian free at obsidian.md and install it. Open it and choose Create new vault, give it a name like brain, and pick a folder for it. A vault is nothing scary, it is just a normal folder of plain-text notes on your computer.
2. Install Node.js, then Claude Code
A one-time setup
First install Node.js (free) from nodejs.org (grab the LTS version). Then open your terminal (Terminal on Mac, PowerShell on Windows) and install Claude Code with one command:
npm install -g @anthropic-ai/claude-code
3. Open your vault inside Claude Code
Point Claude at your notes
In the same terminal, move into your vault folder and start Claude. Swap in your real vault path (on Mac you can drag the folder onto the terminal to paste its path):
cd path/to/your/brain-vault
claude
4. Paste the wiki prompt
This builds the whole system
Once Claude is running inside the vault, paste in Karpathy’s wiki instructions. Grab his exact prompt from his gist (it tells Claude to keep three folders: your raw sources, the wiki it writes, and an index). Claude sets up the structure and is ready to start filing.
5. Feed it a note and ask a question
Watch it compound
Drop any article, note or transcript into your vault folder, then tell Claude to process it. It reads it, writes wiki pages, and links it to what you already have. Then ask a real question, you will get an answer with links to your own pages. Do this a few times a week and in a month it genuinely feels like a second brain.
That is the whole system running. Now go feed it your first real note 👇
Day One
3 things to try first
Once the wiki is built, copy any of these into Claude Code to feel the magic.
1 · Process a new note
The everyday move
Read the new file I just dropped in, add it to the wiki, create or update any relevant pages, and link it to everything related. Tell me the 3 most interesting connections you found.
2 · Ask your own brain
Answers with citations
Using only my notes, what have I learned about [topic]? Give me a short summary and link the exact pages it came from. If my notes disagree with each other, point that out.
3 · Find the gaps
Turns reading into a plan
Look across my whole wiki on [topic] and tell me what is thin or missing. What 3 things should I go read or capture next to round it out?
💡The real unlock: keep Obsidian open on one side and Claude on the other. Watch the graph view light up with new links every time Claude files a note. That is the moment it clicks.
Stuck?
Quick fixes
For this exact setup, yes, Claude Code runs on a Pro or Max plan (or API credits). Everything else is free. If you only want to dabble first, you can build a simpler version by chatting in the Claude app and pasting notes in by hand, but the auto-filing magic needs Claude Code.
Close the terminal and open a fresh one after installing, that reloads the path. Still nothing? Make sure Node.js installed correctly by running node -v, it should print a version number. On Windows, use PowerShell rather than the old Command Prompt.
Your vault stays on your own computer, it is just local files. Claude reads them to do the filing, the same as any AI you paste text into. Nothing gets published anywhere. It is a git-friendly folder of markdown, so you can even back it up privately.
Anything you would want to remember: article highlights, book notes, podcast or YouTube transcripts, meeting notes, your own thoughts. Tip: install the free Obsidian Web Clipper browser extension so saving an article into your vault is one click.
Totally normal, week one is just setup. The payoff is week three, when you ask it something and it pulls a thread across ten notes you had forgotten you took. Stick with it past the first few captures.
Don’t have Claude yet?
You will want a Pro or Max plan to run Claude Code. Start there, then come back and build your brain.
Get Claude →