Your second brain
The top step of the context ladder: context that compounds. A private set of files your AI reads at the start of every session, so it knows your work better every week.
What a second brain is
A prompt is context you type.
A project is context you store.
A second brain is context that compounds: it grows as a side effect of the work itself.
In practice it is a folder of plain files: what you are working on, what you have decided, what you have learned. The only difference from ordinary notes is that your AI reads them before it does anything else, and writes back what changed. Every session starts warm instead of cold.
How one works, in plain terms
Every second brain that keeps working has the same three parts. The folders can be anything. The shape cannot.
1. One place per fact
So nothing goes stale in copies.
- Every fact that changes lives in exactly one file.
- Everything else links to that file instead of restating it.
- Copies drift quietly. Links stay honest.
2. A log that graduates
Lessons become instructions.
- Mistakes and lessons get appended to one raw running log.
- The durable ones graduate into the always-on instructions your AI reads every session.
- The log is the receipt. The instruction is what changes behaviour.
3. A weekly review
The pass that keeps it honest.
- Once a week, the AI re-reads the log and the facts.
- Anything that looks stale gets flagged, and you confirm or correct it.
- Ten minutes, and the whole system stays worth trusting.
Two ways to run one
Same three parts, two homes. One version needs nothing new at all; the other puts the folder on your own machine. Start with the first. And this is the only section on the page where tools get named, because the shape matters more than the software.
Version 1: the Cowork business brain
A folder of markdown files inside a Cowork project. Zero new tools.
- Create a project in Cowork and fill a folder with plain markdown files: what you are working on, what you have decided, what you have learned.
- Tell Claude to read the folder before it does anything else, and to write back what changed. That is the whole setup.
- This is what I call the CEO-in-Cowork pattern: you talk to the business, it reads the files, and one project knows the whole of it, warm from the first message.
Version 2: the full local version
The same folder, living on your own machine.
- The folder moves to your computer, and Cowork on the desktop reads and writes the files exactly as before.
- Obsidian gives you a free window onto the folder: the links, the graph, the map of your thinking. A window, not an engine. The folder is the brain.
- Move here when you want to see the files laid out, when they start to multiply, or when the links between them start to matter.
One thing version 2 does not need: VS Code. The full pattern runs on a folder, Obsidian and Cowork desktop. VS Code only adds the extras from the Building-software step: memory with a full version history, the same brain synced across two machines, skills you can run as commands, and long unattended agent runs on your own files.
It catches itself
My own memory system runs exactly this shape, and it earns its keep by policing itself.
On one weekly review, the summary file I trust at the start of every session had drifted from the working notes underneath it, and the review flagged the gap before I acted on it.
That is the whole promise: files go stale quietly, and a system with a review pass catches the drift before it costs you.
Find one stale fact
You do not need a system to feel the problem. Ten minutes in your own notes will do it.
- 1
Open your own notes and find one fact you know has changed since you wrote it down. A price, a status, a plan.
- 2
Fix it in exactly one place. If the fact lives in three files, pick one as its home, correct it there, and point the other two at it.
- 3
Count how many copies you had to hunt down. That count is the argument for one place per fact.
That is the weekly review in miniature. Do it once a week and you have the habit that makes a second brain work.
The starter file
One download to begin: a one-page README plus a folder layout your AI can read as shared memory.
Second-brain starter
Drop it in a folder, edit the bits in brackets, and tell your AI to read it first.Reach for it when you want your AI to remember your work across sessions.
The ladder ends here on purpose. A second brain is shaped around your work, your files and your week, so this is the step I build with you rather than hand you as a recipe. Book a lesson → and bring the notes you already have.
The whole climb is on How to Prompt → Projects, two steps down the ladder, start at Claude 101 → More drop-in files live on Free tools → Or browse the whole resource library →