Build a Second Brain in Claude and Obsidian That Actually Gets Smarter Every Day
Your best ideas are scattered across a dozen places right now.
Notes apps. Browser tabs. Old Claude chats you closed and will never find again. Every time you sit down to work, you rebuild context from memory and forget most of it within a week.
A second brain fixes that. One place that holds everything you know, with Claude sitting on top of it — reading it, connecting it, growing it. You stop re-explaining yourself every session because the system already remembers. Ask it anything you’ve ever written down and it answers from the whole thing.
This is the idea Andrej Karpathy popularized in April 2026 with his LLM Wiki pattern. The setup takes one evening. Unlike a chat history that rots, this one gets sharper every single day you use it.
Below is the full walkthrough — written so you can follow it even if you’ve never opened Claude Code or Obsidian before. Every step spells out exactly what to click and what to type.
What you’re actually building
Two tools. Two jobs.
Obsidian is the storage. A free notes app that keeps everything as plain text files on your own computer. Notes link to each other, and over time those links form a graph — a visible map of how your ideas connect. It lives on your machine, not in a company’s cloud, and the files are yours forever.
Claude is the brain on top. It reads the entire vault, files new information where it belongs, links it to what’s already there, and answers questions across all of it.
The whole thing is just text files. That means it’s not locked to any one AI. Point a different model at it next year and it still works, because you own the brain, not the tool.
Step 1: Install Claude Desktop
Go to claude.com/download in your browser and download the desktop app for your system (Windows or Mac). Run the installer and open the app.
Sign in with your Claude account. You need a paid plan (Pro is $20/month). The free tier won’t work for this.
At the top of the app you’ll see tabs: Chat, Cowork, and Code. Click the Code tab. This is Claude Code — the version that can actually read and write files on your computer. If it asks you to upgrade, your plan needs to be paid first.