A practical how-to guide

Building a Second Brain for Strategists

How I combined Claude and Obsidian to build a personal knowledge system from scratch, in a single afternoon, with no coding background.

Phillip Lee 12th Street Strategy Written May 2026
What's in this guide
1
The problem

Why strategists need a second brain

Strategy work is cognitively demanding in specific ways. On any given day I'm switching between client demands, projects at different points of development, internal responsibilities, and my own professional development. At its very essence it's about intake + synthesis + output.

Much of what I read, write, and think across those contexts gets used in the moment but isn't necessarily documented in a way that easily compounds.

The concept of the second brain has been around for a while in more tech-centered circles. Andrej Karpathy wrote a great piece about it. The key insight being that the second brain isn't just a filing system or a note taking app, it's a persistent, compounding platform that lives locally. When connected to a chat interface the platform turns into a thinking partner that makes the stuff you capture and create exponentially more useful. Over time it gets richer with every source you add and every working session you run.

This guide is written for strategists who recognize the situation above. It will get you to a working base layer. How you build on top of it will be specific to you, your clients, your domains, your working style.

Worth reading before you start: Andrej Karpathy's LLM Wiki and Noah Brier's Claudsidian on GitHub. Both shaped how this was built.

2
Prerequisites

What you'll need to build the vault

This guide is written for Mac. If you're on a PC, the same approach applies. Work through the Mac-specific steps with your LLM and it'll translate them for your setup.

Required
A Mac
Terminal comes pre-installed. That's all you need on the hardware side.
$20/mo
Claude Pro
For vault working sessions and Claude Code. claude.ai
Free
Obsidian
The vault app. Local, private, yours forever. obsidian.md
Pre-installed
Terminal
On every Mac. You've probably never opened it. That changes today.

The morning digest (Section 4) requires a separate Anthropic API account with a small amount of credit. You don't need it to build the vault.

3
The foundation

Building the second brain vault

Credit where it's due: this build was inspired by Claudsidian by Noah Brier and the LLM Wiki concept from Andrej Karpathy. What's here is notionally similar but built for one person's specific domains and working style. That specificity is the point.

Obsidian is a free note-taking application that stores everything as plain markdown files on your Mac. Markdown is a simple text format, think of it as a plain text document with very light formatting built in. There's no proprietary format, no app lock-in. Your notes are plain text files that any app can read.

1
Install Obsidian and create your vault on iCloud

Download Obsidian at obsidian.md. When it asks where to create your vault, navigate to your iCloud Drive folder and name it "Second Brain." Storing it in iCloud gives you automatic sync to your phone for free, no Obsidian subscription needed.

When Obsidian opens you'll see an empty sidebar on the left and a blank note in the middle. That's your vault. Everything you build lives here.

2
Open Terminal: it's not what you think

Press Cmd + Space, type "Terminal," hit Enter. You'll see a window with a blinking cursor. This is your direct line to your computer's operating system.

The thing most non-technical people don't realize: you don't need to download anything from a browser. You just tell your computer what you want, and it goes and gets it. Every installation in this guide is a single line you paste and hit Enter. No fuss.

Install Homebrew, the tool that manages everything else:

Terminal: paste and hit Enter
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

It'll ask for your Mac password. Type it (you won't see anything appear, that's normal) and hit Enter. Takes a few minutes. Follow any instructions at the end about adding Homebrew to your PATH.

3
Create your folder structure

Run this single command to create all your folders at once:

Terminal
cd ~/Library/Mobile\ Documents/iCloud~md~obsidian/Documents/Second\ Brain && mkdir -p "00 - Inbox" "01 - Projects" "02 - Areas" "03 - Resources" "04 - Archive" "05 - Daily Notes" "06 - Daily Digest"

Switch to Obsidian and the folders appear in the sidebar automatically.

What each folder is for: Inbox: everything lands here first, unsorted. Projects: active work with a deadline. Areas: ongoing domains of your work and thinking with no end date. Resources: reference material worth keeping. Archive: completed work. Daily Notes: your day-by-day capture log. Daily Digest: where the morning digest lands (covered in Section 4).

This structure is a starting point, not a prescription. Rename folders, add new ones, reorganize as you learn how you actually use it. The structure should serve how you think, not the other way around.
4
Build your Area notes: the interview

Area notes are the anchors of your knowledge graph, the domains that everything else connects to. Don't create these from a template. Have Claude interview you.

Open a new Claude conversation and paste the following. The Karpathy reference is intentional; it primes Claude with the right conceptual framework for what you're building before it starts asking questions:

Paste this into Claude to start the interview
I'm building a personal knowledge base in Obsidian using the LLM Wiki approach described by Andrej Karpathy (https://gist.github.com/karpathy/442a6bf555914893e9891c11519de94f), the idea that the wiki is a persistent, compounding artifact that the LLM writes and maintains while I source and ask questions. I need your help designing my Area notes, the core domains that anchor my knowledge graph. Please interview me to understand what those should be. Ask me one question at a time. I'm a [your role] and I want to use this for [your goals].
What domains do you work in and think about most?
What clients or types of clients do you serve?
What are you actively building or working toward?
What do you find yourself thinking about outside of work?
What knowledge areas feel underdeveloped or scattered?
What would you want to be able to pull up instantly?

Once through the interview, ask Claude to write the Area note files and give you the Terminal commands to create them.

5
Migrate your existing notes and files

This step is bigger than it might sound. You can migrate not just notes but project files, strategy decks, research documents, meeting notes, and anything else that represents how you think and work. The vault can house all of it.

The key word is intention. Don't data dump. Bring things in because they matter, not because they exist. The goal isn't a complete archive — it's a curated knowledge base that actually reflects how you think.

Copy the contents of a note or document, paste it into Claude, and say:

Prompt for migrating existing notes
Here are notes I've been keeping: [paste your notes]. Help me identify the distinct ideas in here, suggest where each piece should live in my Obsidian vault, and write properly formatted markdown notes with dates, tags, and links to my Area notes. Give me the Terminal commands to create the files.

Claude reads what you have, identifies the threads, proposes a structure, and gives you the commands to create properly formatted notes. What feels like a pile of scattered thinking can become a connected knowledge base in an afternoon. This took the longest time for me. I had a lot of notes that I revisited, read through, and intentionally pasted into Claude to have a conversation about. I didn't put them all in at once. I tried to be somewhat organized by topic area in the way I fed the notes into the machine.

If you've got a lot to get through, do it in batches. Group by topic or project. Let Claude help you figure out the structure as you go rather than trying to plan the whole taxonomy upfront.

For strategy decks and research documents, the same principle applies. Drop the key thinking into Claude, ask it to extract the ideas that belong in your vault, and have it write notes that capture the substance rather than just recreating the format.

6
Install Claude Code and create the brain alias

Claude Code turns Obsidian from a static note app into a live thinking partner. It runs in Terminal, sits inside your vault directory, and can read, write, and connect notes directly based on what you ask it to do.

Terminal: install Node.js then Claude Code
brew install node npm install -g @anthropic-ai/claude-code

Navigate to your vault and launch:

Terminal
cd ~/Library/Mobile\ Documents/iCloud~md~obsidian/Documents/Second\ Brain && claude

Authenticate via the browser with your Claude Pro account, not an API key. Then create the alias so opening your vault is a single word:

Terminal
echo "alias brain='cd ~/Library/Mobile\ Documents/iCloud~md~obsidian/Documents/Second\ Brain && claude'" >> ~/.zprofile && source ~/.zprofile

From now on, type brain in any Terminal window to open Claude Code in your vault.

7
Your first working session

Type brain, wait for Claude Code to load, and try one of these:

First prompts to try in Claude Code
Read all the files in my 00 - Inbox folder and help me process them; suggest where each one should live permanently.
I have a client meeting tomorrow about [topic]. Read my relevant notes and help me build talking points.
Read everything in my Areas folder and identify the themes that keep appearing across multiple notes.

Claude Code has access to everything in your vault. The more you put in, the richer these sessions become.

4
A universal use case

Building the morning digest

With your vault built, the most immediately useful thing you can add is an automated morning digest. It is a system that goes out into the world every day, synthesizes what happened over the past 24 hours across the topics you care about, and delivers a clean briefing directly into your vault's Daily Digest folder.

This is the workflow I think every strategist could use regardless of specialty. Your topics will be different from mine, your prompts will be tailored to your context, but the system is universal.

How the digest feeds the brain: Every morning the digest lands in your 06 - Daily Digest folder as a dated note. You read it, clip what's interesting into today's daily note, and those daily notes become the raw material for your weekly processing sessions, where you move things into permanent homes in Projects, Areas, and Resources. The digest feeds the brain. The brain feeds the work.

What you'll need for the digest

In addition to what you built in Section 3, the digest as I've built it requires an Anthropic API account that is separate from your Claude Pro subscription. This is what runs the digest automatically without touching your daily Claude usage. Go to console.anthropic.com, create an account, add a small amount of credit (I put in $5 and it's plenty of credit for this task for months on end), and set a hard monthly spend limit so it never auto-reloads beyond what you load manually. Then install Python and feedparser from Terminal:

Terminal
brew install python pip3 install feedparser requests
1
The interview: decide what you want before you build anything

Same principle as the vault: have Claude interview you before writing a single line of code. Open a new Claude conversation and paste this:

Paste this into Claude to start your digest interview
I want to build a daily news digest that synthesizes the past 24 hours across topics I care about and delivers it as a markdown note into my Obsidian vault every morning. The topics that I'm most interested in include [insert areas that matter most to you]. However, before we build anything, please interview me about what I want. Ask me one question at a time.

It's worth going back and forth here to really sharpen what you actually care about so you don't just get a generic skim-level newsletter. This is a prompt I revisit most often as I sharpen my focus or notice certain voices and publications dominating my feed.

One thing to make sure gets built into the script: each section should include both a synthesis paragraph that gives you a view of that topic over the past 24 hours and a set of links at the bottom. The synthesis is the thing you actually read. The links are there when something in the synthesis catches your attention and you want to go deeper.

2
Get your API key

In your Anthropic console: Settings → API Keys → Create Key. Name it "Morning Digest." Copy it. You'll only see it once. You'll paste it into the script Claude writes for you.

3
Get Claude to write the script

Back in your Claude conversation from Step 1, ask Claude to build the complete script:

Prompt for generating the script
Based on our interview, please write the complete Python script for my morning digest. Use the model claude-sonnet-4-6. For each section write a detailed prompt that reflects my professional context and ends with a strategic "so what" tailored to where I am in my career. Include delivery to my Obsidian vault at: ~/Library/Mobile Documents/iCloud~md~obsidian/Documents/Second Brain/06 - Daily Digest and a once-per-day check so it doesn't run twice. My Anthropic API key is [paste your key].

Claude will write the complete script. Copy it, then in Terminal:

Terminal: paste the script after running this, then press Ctrl+D
cat > ~/morning_digest.py
4
Run it manually first

Test before scheduling:

Terminal
python3 ~/morning_digest.py

A dated note should appear in your Daily Digest folder within a minute or two. If something looks wrong, paste the error into Claude and it'll fix it.

5
Set up the alias and schedule

Create a shortcut so typing digest runs it on demand:

Terminal
echo "alias digest='rm -f ~/.morning_digest_lastrun && python3 ~/morning_digest.py'" >> ~/.zprofile && source ~/.zprofile

Then schedule it to run automatically at 7:30am daily. Replace [yourusername] with your Mac username:

Terminal
(crontab -l 2>/dev/null; echo "30 7 * * * /usr/bin/python3 /Users/[yourusername]/morning_digest.py >> /Users/[yourusername]/digest.log 2>&1") | crontab -

Your Mac needs to be open and awake at 7:30am. If it's asleep, just type digest when you're ready.

6
Tune the feeds over time

The first version will be imperfect. Some feeds will be too noisy, others exactly right. After a week or two, go back to Claude and say: "The [section] keeps pulling from [source] and it's not useful." Ask it to help you find better sources and update the script. This tuning is part of the process. The digest gets significantly better over the first month.

5
Putting it together

The daily workflow in practice

Once both systems are running, the daily workflow is lighter than it sounds. The goal is to keep capture friction as low as possible and do the thinking and organizing in concentrated sessions.

Morning

The digest arrives in your vault at 7:30am as a dated note in the Daily Digest folder. Open Obsidian with your coffee. Read through the sections. When something grabs you, a story, a pattern, a connection to something you're working on, copy it into today's daily note in the Daily Notes folder. One paste, move on. You're capturing, not organizing.

During the day

Anything worth keeping, a new way to articulate an idea or insight, a pattern you're seeing that impacts a project, an article, a half-formed idea, all of that goes into today's daily note. Keep it open in the background. The only rule is a date at the top. No formatting, no decisions about where it belongs. Just get it in and allow the LLM to organize it later.

Weekly

Type brain in Terminal. Ask Claude Code to read your daily notes from the past week and help you process them, move clippings into permanent Area and Resource notes, identify patterns, surface connections. This is where the compounding happens. Budget 20–30 minutes.

On demand

Building a pitch deck, walking into a review, getting ready for an all hands, type brain, tell Claude Code what you're preparing for, ask it to read your relevant notes. Because it has access to everything you've built, the context it brings draws on your actual thinking and research, not generic information.

This works with research documents, meeting notes, and strategy decks too. Drop files into your Projects or Resources folders, then ask Claude Code to synthesize them. You can say 'read the files in this project folder and help me pull out the key points of view' and it will work through them and give you something you can actually use.

The compounding effect is real but takes time. The system gets noticeably more useful around weeks four to six. Before that it can feel like overhead. After that it starts to feel like thinking with something that actually knows your work. Keep going through the early friction.
6
The bigger picture

What this is actually for

The morning digest is one use case. The vault is built to house everything you think about and work on as a strategist.

I'm still discovering what that means for my own work. Meeting notes, deck outlines, half-formed ideas that become a proactive brief, primary research readouts, KPI trackers and more. All of it belongs in here. Not on a file server or scattered across note apps and email threads. In one place, connected, searchable, and available to an intelligence that can help you do something with it.

That's what this is really for. Not productivity but skill amplification. The more you put in, the more you're able to see. The more you're able to see, the more value you can bring.

One last thing: you don't have to use Claude. You don't have to use Obsidian. This is how I did it. The tools I chose made it fast to build and easy to iterate on, but they're not the point. The point is having a place where your thinking accumulates, connects, and compounds over time, and an intelligence that can help you work with it. That capability is available through multiple tools and combinations. The takeaway isn't the stack, it's what the stack makes possible.

Further reading: Claudsidian by Noah Brier. Karpathy's LLM Wiki. Both worth reading before you start. If you build one, I'd like to know what you made differently.

Built in an afternoon. Better every week since.

No coding background required. Just a willingness to have the conversation and iterate on what you actually need.

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