---
type: source
title: "Full Guide - Build Your Own AI Second Brain with Claude Code"
description: "Rather than running an out-of-the-box agent like OpenClaw, you should build your own AI second brain on top of Claude Code and Obsidian so you control the permissions, understand the codebase, and minimize exposure to the lethal trifecta."
youtube_id: 1FiER-40zng
url: https://www.youtube.com/watch?v=1FiER-40zng
slug: full-guide-build-your-own-ai-second-brain-with-claude-code
published: 2026-04-01
duration: "0:25:05"
recency_rank: 22
raw: "../raw/full-guide-build-your-own-ai-second-brain-with-claude-code.md"
tags: [second-brain, claude-code, agent-security, memory-systems]
created: 2026-07-21
updated: 2026-07-21
---

# Full Guide - Build Your Own AI Second Brain with Claude Code

Cole walks through the architecture of the AI second brain he's built on Claude Code and Obsidian over three months, which he says saves him at least a dozen hours a week by taking low-leverage work off his plate. He opens by answering why you'd build your own instead of running OpenClaw: a second brain inherently satisfies all three legs of the lethal trifecta (private data access, untrusted content, and an exfiltration vector), so it is inherently risky, which means you want maximum control over the implementation. Building your own lets you define permissions up front, start from a zero-trust read-only posture, and layer capabilities in over time, while still taking inspiration from OpenClaw's open-source memory-layer and heartbeat patterns.

## Concepts covered

- [Second Brain](../concepts/second-brain.md)
- [The Lethal Trifecta](../concepts/lethal-trifecta.md)
- [Memory Systems](../concepts/memory-systems.md)
- [Self-Evolving Memory](../concepts/self-evolving-memory.md)
- [Claude Code Hooks](../concepts/claude-code-hooks.md)
- [Retrieval-Augmented Generation (RAG)](../concepts/rag.md)
- [Skills](../concepts/skills.md)
- [Agent Security](../concepts/agent-security.md)
- [Heartbeat](../concepts/heartbeat.md)
- [PRD-First Development](../concepts/prd-first-development.md)
- [Phases of Work](../concepts/phases-of-work.md)

## Entities

- [Claude Code](../entities/tools/claude-code.md)
- [Obsidian](../entities/tools/obsidian.md)
- [OpenClaw](../entities/tools/openclaw.md)
- [Claude Agent SDK](../entities/tools/claude-agent-sdk.md)
- [Dynamous](../entities/organizations/dynamous.md)
- [Cole Medin](../entities/people/cole-medin.md)

## Key moments

- **[0:03:26]** Explains the lethal trifecta and why a second brain always satisfies all three legs
- **[0:07:00]** Argument for building your own vs running OpenClaw: control, understanding, custom permissions
- **[0:09:31]** Memory layer walkthrough: soul.md, user.md, memory.md, daily logs
- **[0:11:01]** Hooks (session-start, pre-compact, session-end) and the daily reflection promotion process
- **[0:12:54]** RAG over indexed daily logs in SQLite/Postgres
- **[0:13:42]** Skills as the capability layer, powered by the memory layer
- **[0:15:31]** Direct integrations with a zero-trust Python API permission layer
- **[0:17:21]** The heartbeat: proactive, deterministic API gathering then Claude Code reasoning
- **[0:19:00]** The create-second-brain-PRD skill and building in phases

## Transcript

[Raw transcript](../raw/full-guide-build-your-own-ai-second-brain-with-claude-code.md)
