Obsidian + Claude Code is how Andrej Karpathy turns 15 years of notes into a brain that works while he sleeps.
The method behind it costs $0 and takes 5 minutes a day and it outlived every productivity app since 2011.
Every idea, link, and half-thought gets appended to the top of a single note, with no sorting, no folders, no tags. Once a week he scrolls through, and anything that still matters gets copied back to the top.
Weak ideas sink. Strong ideas resurface 5, 10, 20 times and by the 20th pass your brain has already wired them into everything else you know.
Repetition as a filter. That's the whole system.
Now the 2026 upgrade almost nobody is running:
Drop that note into an Obsidian vault and open the folder with Claude Code not the chat app, the terminal agent that reads files.
3 commands change everything:
read my last 30 days of notes and find the 3 ideas I keep circling without acting on link every note mentioning this project into a CLAUDE.md of what I actually believe about it draft this week's post from the idea that resurfaced most
Claude Code doesn't search your vault it walks it, follows the wikilinks, and hands you the patterns you were too close to see.
Karpathy method filters the signal, Obsidian stores it, Claude Code compounds it.
One is a habit, one is a folder, one is $20 a month together they're the closest thing to a second brain that thinks back.
Most people collect notes for 10 years and never read them once.
His notes read him.