COG: The Easiest Second Brain That Actually Self-Evolves

COG = Claude + Obsidian + Git

A self-evolving second brain system using Claude Code, Obsidian markdown files, and Git version control. No database, no vendor lock-in—just .md files that think.

What is COG?

COG is a personal productivity and knowledge management system that:

• 🧠 Self-evolves: Learns your patterns and auto-organizes content
• 🔄 Self-heals: Updates cross-references when you reorganize
• 📝 Plain text: Just markdown files (no database, no vendor lock-in)
• 📱 Multi-device: Syncs via iCloud to iPhone, iPad, Mac
• 🔒 Privacy-first: Your data, your files, your control
• 🎯 Specialized agents: Custom AI assistants for specific workflows
• ✅ Verification-first: No AI hallucinations, sources required

Quick Start

Prerequisites

• Claude Code - Required
• Obsidian - Recommended for viewing/editing your notes
• Git - Already on your system if you can run the clone command below

Installation (2 Steps)

1. Clone this repo to where you want your second brain:

   git clone https://github.com/huytieu/COG-second-brain.git
   cd COG-second-brain

2. Open Claude Code and run onboarding:

   code .
   # In Claude Code, ask: "Run onboarding" or "Set up my COG profile"

That's it! The onboarding will personalize COG for your needs in 2-3 minutes.

What just happened?

• The cloned repo IS your second brain - all files are ready to use
• .claude/skills/ contains 5 AI skills ready to invoke
• Onboarding will create your personalized directory structure
• Just run onboarding to set up and personalize COG

Want Obsidian integration?

• Open Obsidian → "Open folder as vault" → Select the COG-second-brain folder
• Now you can view/edit notes in Obsidian while using Claude Code for AI features

Detailed Setup Guide

See SETUP.md for optional configurations (Git sync, iCloud, etc.).

What You Get

5 Powerful Skills

COG uses Claude's Agent Skills architecture - specialized capabilities that Claude automatically invokes when relevant to your request.

Setup & Personalization:

• onboarding - Personalize COG for your workflow (run this first!)

Daily Operations:

• braindump - Quick capture of raw thoughts with intelligent domain classification and competitive intelligence extraction
• daily-brief - Personalized news intelligence with verified sources (7-day freshness requirement)

Weekly & Strategic:

• weekly-checkin - Cross-domain pattern analysis and strategic reflection
• knowledge-consolidation - Build frameworks from scattered insights across all your notes

How Skills Work:

Skills are self-contained AI capabilities that combine orchestration and specialized processing. Unlike the old command/subagent split, each skill now:

• Automatically activates when Claude detects relevant user intent
• Handles the complete workflow from user interaction to file creation
• Contains all necessary instructions, analysis frameworks, and verification protocols
• Uses progressive disclosure to load information only as needed

For example:

• Ask "What's on my mind?" → Claude invokes the braindump skill
• Say "Give me my daily brief" → Claude invokes the daily-brief skill
• Request "Weekly review" → Claude invokes the weekly-checkin skill

This architecture leverages Claude Code's native skill system for better performance and simpler maintenance.

Key Features

1. Self-Evolving Intelligence

COG doesn't just store notes—it actively learns:

• Pattern recognition: Identifies recurring themes across your notes
• Auto-classification: Categorizes content by domain (personal/professional/projects)
• Knowledge consolidation: Synthesizes scattered insights into frameworks
• Adaptive learning: Gets better at understanding your thinking patterns

Weekly Evolution Cycle:

Monday-Friday: Capture thoughts via braindump skill
Friday: Run knowledge-consolidation skill
→ COG analyzes ALL your notes
→ Builds frameworks you didn't explicitly create
→ Updates "single source of truth" files
→ Next week, it knows more about how you think

2. Self-Healing System

• Rename a file? COG updates all cross-references
• Change project structure? Auto-reclassifies content
• New project emerges? Auto-creates tracking folders
• Competitive intel mentioned? Auto-updates competitor files

3. Verification-First (No AI Hallucinations)

• All news must be verified with sources and dates
• 7-day freshness requirement for current events
• Explicit confidence levels for all analysis
• Multi-source cross-referencing required

4. Privacy-First Architecture

• Strict domain separation: Personal, professional, project-specific
• Local-first: Works offline, syncs when online
• No servers: Your data never leaves your devices
• Version controlled: Full history with Git

Directory Structure

This structure is created automatically when you run onboarding.

your-obsidian-vault/
├── .claude/
│   └── skills/                # 5 specialized skills
│       ├── onboarding/
│       │   └── SKILL.md
│       ├── braindump/
│       │   └── SKILL.md
│       ├── daily-brief/
│       │   └── SKILL.md
│       ├── weekly-checkin/
│       │   └── SKILL.md
│       └── knowledge-consolidation/
│           └── SKILL.md
├── 00-inbox/                  # Temporary processing area
│   ├── MY-PROFILE.md          # Your profile (created by onboarding)
│   ├── MY-INTERESTS.md        # Your topics & news sources
│   └── WELCOME-TO-COG.md      # Getting started guide
├── 01-daily/                  # Daily briefs and check-ins
│   ├── briefs/
│   └── checkins/
├── 02-personal/               # Personal domain (strict privacy)
│   ├── braindumps/
│   ├── development/
│   └── wellness/
├── 03-professional/           # Professional domain
│   ├── braindumps/
│   ├── leadership/
│   ├── strategy/
│   ├── skills/
│   └── COMPETITIVE-WATCHLIST.md  # Companies/people to track
├── 04-projects/               # Project-specific tracking
│   └── [your-project]/
│       ├── braindumps/
│       ├── competitive/       # Auto-updated intel
│       └── content/
└── 05-knowledge/              # Consolidated insights
    ├── consolidated/
    ├── patterns/
    └── timeline/

Example Workflows

First Time Setup (After Cloning)

In Claude Code, ask: "Run onboarding" or "Set up my COG profile"

The onboarding skill will ask:

• Your name
• What you do (your job/role)
• Topics you're interested in (3-5 main areas)
• Where you get your news (preferred sources)
• Active projects you're working on (optional)
• Companies/people you want to track (optional)

Takes 2 minutes. Everything is stored as readable markdown files.

Onboarding creates:

• 00-inbox/MY-PROFILE.md - Your basic info and projects
• 00-inbox/MY-INTERESTS.md - Your topics and news sources
• 03-professional/COMPETITIVE-WATCHLIST.md - Companies/people you're tracking (if any)
• 04-projects/[project-name]/ folders for each active project

After onboarding, COG will:

• Personalize daily briefs to your topics
• Offer your projects when you braindump
• Auto-extract competitive intel you care about

Daily Intelligence Briefing

Ask Claude: "Give me my daily brief" or "What's the news today?"

Generates a personalized briefing with:

• Verified news from the last 7 days
• Strategic analysis relevant to your interests
• Competitive intelligence auto-extracted
• Actionable next steps

Brain Dump → Strategic Insights

Ask Claude: "I need to braindump" or "What's on my mind?"

Single integrated workflow:

1. Quick capture: Preserves spontaneity, no filtering
2. Intelligent processing: Automatically extracts themes, actions, connections

The system automatically:

• Classifies by domain
• Detects competitive intelligence
• Cross-references related content
• Identifies action items

Knowledge Consolidation

Ask Claude: "Consolidate my knowledge" or "Build frameworks from my notes"

Weekly or monthly:

• Analyzes patterns across all braindumps
• Builds frameworks from scattered insights
• Updates "single source of truth" knowledge base
• Tracks evolution of thinking over time

Why COG Works

What Works

• ✅ Setup is trivial: Clone repo, run onboarding. Done in 2 minutes.
• ✅ Maintenance-free: Self-heals and auto-organizes
• ✅ Actually portable: Works on iPhone, iPad, Mac via iCloud
• ✅ Custom skills >> generic AI: Specialized beats ChatGPT for repeated tasks
• ✅ Git for thoughts: Version control shows thinking evolution

What Doesn't Work

• ⚠️ Requires discipline—system only works if used consistently
• ⚠️ Not for everyone—if you don't think in text files, this won't click
• ⚠️ Requires Claude Code (though adaptable to other AI environments)

Unexpected Benefits

• 💡 Thinking partner, not just storage: Writing brain dumps knowing they'll be analyzed improves clarity
• 📊 Pattern recognition: Discover insights you'd miss manually
• 🔗 Cross-domain insights: Personal wellness affects professional productivity (tracked quantitatively)
• 📅 Time patterns: Git history reveals when you think best

Advanced Configuration

Customizing Skills

Edit .claude/skills/[skill-name]/SKILL.md to customize workflows:

---
name: my-custom-skill
description: What this skill does
---

# My Custom Skill

## When to Invoke
[When Claude should use this skill]

## Process Flow
[How it works]

Adding New Skills

Create .claude/skills/my-skill/SKILL.md:

---
name: my-skill
description: Brief description for Claude to know when to invoke this
---

# My Custom Skill

## Purpose
[What this skill does]

## When to Invoke
[User intent patterns that should trigger this]

## Process Flow
[Detailed instructions]

Template Customization

Modify 06-templates/*.md to match your workflow:

---
type: "custom-type"
domain: "personal|professional|project"
# Add your metadata fields
---

Syncing Across Devices

iCloud Sync (Recommended)

• Store vault in iCloud Drive/Obsidian/
• Automatically syncs to all Apple devices
• Obsidian mobile works perfectly

Git Sync

# Daily workflow
git add .
git commit -m "Update knowledge base"
git push

Combine both: iCloud for instant sync, Git for version history.

Contributing

Contributions welcome! Please read CONTRIBUTING.md first.

Ideas for contributions:

• New specialized agents
• Additional slash commands
• Template improvements
• Documentation enhancements
• Example workflows

Roadmap

• Gemini support (in addition to Claude)
• Web interface for knowledge graph visualization
• Mobile-first commands (optimized for Obsidian mobile)
• Team collaboration features (with privacy preservation)
• Integration with calendar/task management tools

Real-World Results

After 3 months of use:

• 120+ structured braindumps processed
• Daily briefs with 95%+ source accuracy
• 5 major strategic insights discovered
• 0 maintenance required
• 0 vendor lock-in anxiety

FAQ

Q: Why not just use Notion/Roam/Obsidian alone? A: COG adds self-evolving intelligence. It doesn't just store—it learns, analyzes, and synthesizes insights automatically.

Q: Do I need Claude Code specifically? A: Claude Code is recommended, but you can adapt the commands for any AI environment (VSCode + Claude extension, custom API integration, etc.)

Q: How much does it cost? A: COG is free (MIT license). You only pay for Claude Code usage (Anthropic's pricing).

Q: Is my data private? A: Yes. Everything is local markdown files. COG uses Claude's API only when you invoke commands. No data stored on external servers.

Q: Can I use this for team collaboration? A: Currently designed for personal use. Team features planned for future releases.

Q: What if I don't use Git? A: Git is optional but recommended for version history. COG works fine without it using just iCloud sync.

License

MIT License - see LICENSE for details.

Feel free to use COG for personal or commercial projects. If you build something cool with it, I'd love to hear about it!

Support COG's Development

If COG has helped you build a better second brain, consider supporting its continued development:

• ⭐ Star this repo to increase visibility
• 💝 Sponsor on GitHub - Monthly support with perks
• ☕ Buy me a coffee - One-time appreciation
• 🐛 Report bugs
• 💬 Share ideas
• 📖 Contribute

COG is free and open-source (MIT license). Your support helps keep it that way while enabling new features and better documentation.

Acknowledgments

Built with:

• Claude Code by Anthropic
• Obsidian for markdown management
• Inspiration from Zettelkasten, Building a Second Brain, and GTD methodologies

Star History

---

TL;DR: COG is a self-evolving second brain using Claude Code + Obsidian + Git. Just .md files that sync via iCloud and learn your patterns. Setup in 3 steps, zero maintenance required.

⭐ Star this repo if you find it useful!