How to Build an AI Second Brain With Obsidian and Claude Code

The phrase “second brain” has been floating around productivity circles for a good couple of years, I’d reckon — mostly meaning “a place where I keep my notes.” Yes, it was probably always a bit generous. A folder of markdown files isn’t exactly a brain, is it? It doesn’t think, nor does it connect ideas. It doesn’t notice that you’ve been circling the same problem for six months without realising it.

However, that changed when people started pointing AI agents at those folders.

In early 2026, a specific combination took off: Obsidian (a note-taking app built on local markdown files) plus Claude Code (Anthropic’s terminal-based AI agent that can read, write, and navigate a file system). The result is a setup where an AI agent can read everything you’ve ever written, walk the connections between your notes, surface patterns across months of thinking, and actually do work inside your vault — filing notes, running weekly reviews, generating ideas grounded in your context rather than generic training data.

Vin Vashishta held a demo on the Startup Ideas Podcast in February 2026, which really popularised the workflow. He typed /ideas into a…