Second brain.

A second brain is all of your AI agent's context kept as local Markdown files in one central place. Every agent reads from the same source of truth, and because it's just files on your machine, that reading is fast and cheap.

For personal use it's hard to beat. I keep mine in Obsidian and Claude pulls from it for everything.

Where it falls down is scale. Once you're trying to build a proper company second brain with a team, a folder of markdown files stops being enough. As I've said, "I don't think it's the best setup once you're trying to build a proper company second brain with a team." At that point you want something more structured that the whole team and their agents can read and write to at once. For one person though, the local files are plenty.