Install Claude Code & Second Brain OS on a Mac (Step-by-Step for One Person Businesses)

Hey there,

You’ve got a Second Brain OS account. Now you and I are going to put it inside Claude Code on your Mac, so every agent, skill and tool you own is one slash command away in your terminal.

No packages to hunt down, no developer setup. One command installs Claude Code, one command connects Second Brain OS, and a folder of its own keeps Claude Code out of the rest of your Mac. Give it 15 minutes.

If the terminal is new to you, that’s fine. You’ll type four or five things into it, and each one is below exactly as you type it.

You’ll need:

A Mac and a Claude subscription (the $20 Pro plan is enough).
Your Second Brain OS login at secondbrainos.com/dashboard.

Step 1: Open the Terminal

The terminal is where Claude Code lives. Open Finder, search for Terminal and open it. (Spotlight works too: press Cmd + Space, type Terminal, press Enter.)

You’ll know this worked when a small window opens with a blinking cursor next to your username.

Step 2: Install Claude Code

Paste this into the terminal and press Enter:

curl -fsSL https://claude.ai/install.sh | bash

Within a few seconds Claude Code is installed. If it’s already on your Mac, the same command updates it to the latest version.

You’ll know this worked when the terminal reports that Claude Code installed successfully.

Step 3: Connect Second Brain OS

Go to secondbrainos.com/dashboard and open My Agents.
Copy the npx command shown there. It already carries your user ID and secret, so don’t share it.
Paste it into the terminal and press Enter. If it asks to install packages, type y and press Enter.

It looks like this, with your own values:

npx secondbrainos-mcp-server@latest <your-user-id> <your-secret>

When it finishes, type clear, then fully quit the terminal (Cmd + Q, not just closing the window) and open it again. Claude Code only picks up the new connection on a fresh start.

Step 4: Give Claude Code a folder of its own

If you type claude straight away, Claude Code opens in your home folder, which is every file on your Mac. Two reasons not to:

Memory. Everything Claude Code learns and writes builds up in one place, and it has complete access to that knowledge.
Safety. You decide what it can touch. One folder, not your whole machine.

Later you may want it working across folders. That’s for the future. Today, one folder.

In Finder press Cmd + Shift + G, type ~ and press Enter. This is your user folder, the one you log in with.
Create a new folder and name it something like Knowledge-Base.

Now open it from the terminal:

Type clear and press Enter.
Type cd (with the space), then press Tab repeatedly until Knowledge-Base/ appears, then press Enter.
Type claude and press Enter.
Choose Yes, trust this folder.

You’ll know this worked when Claude Code opens and the path shown at the top ends in Knowledge-Base.

Step 5: Check Second Brain OS is loaded

Inside Claude Code, type:

/mcp

You should see secondbrainos listed as connected. Then run:

/secondbrainos:start_secondbrainos

This loads your Second Brain OS context and lists every agent and skill you own. It’s free to run.

You’ll know this worked when you see your agents and skills listed. The list depends on what you’ve bought, so yours may be shorter or longer than mine.

Step 6: Two settings that save you tokens

Not mandatory, but they make a $20 plan go a lot further.

Type /config.
Set Thinking mode to false. Otherwise Claude Code can spend minutes thinking after every prompt.
Go down to Model. Up and down arrows choose the model; left and right arrows change the effort level. Set it to low effort and confirm.
Press Esc to go back.

Step 7: Try it

Ask Claude Code for something your purchases cover. For example:

Create a system prompt for my AI receptionist

Claude Code picks the right Second Brain OS skill and interviews you for what it needs.

When it asks permission for each action, that’s Claude Code being careful. Manual approval is a good way to start. Once you trust it, switch to auto mode with Shift + Tab.

Troubleshooting

Problem	Fix
`/mcp` doesn’t list secondbrainos	Fully quit the terminal and any open Claude desktop app (`Cmd + Q`), reopen, run `claude` again.
`command not found: claude`	Quit and reopen the terminal so it picks up the new install.
`npx: command not found`	Node.js is missing. Install it from nodejs.org, reopen the terminal, rerun Step 3.
Fewer tools than you expected	Your tools match your purchases. Check them under My Agents in the dashboard.
Claude Code opened in the wrong folder	Type `/exit`, `cd` into `Knowledge-Base`, run `claude` again.

What you’ve done

Claude Code runs on your Mac, in its own folder, connected to Second Brain OS, with settings that don’t waste your tokens.

Your next action: open Claude Code in Knowledge-Base, run /secondbrainos:start_secondbrainos, and pick one agent from the list to try today.

On Windows? The Windows version of this guide covers PowerShell.