COG: The Agentic Second Brain That Actually Self-Evolves

June 22, 2026 · View on GitHub

Cognition + Obsidian + Git — A self-evolving second brain powered by AI agents, markdown files, and version control. No database, no vendor lock-in — just .md files that think.

Quick Start | Skills | Features | FAQ | SETUP.md

Works with Claude Code • Cursor • Kiro • Gemini CLI • OpenAI Codex • any AI that reads markdown

Inspired by Garry Tan's gstack and gbrain

graph LR
    A[You] -- natural language --> B[AI Agent]
    B -- runs --> C[17 Skills]
    C -- delegates to --> W[6 Worker Agents]
    C -- reads & writes --> D[.md Files]
    W -- reads & writes --> D
    C -- syncs with --> G[GitHub / Linear / Slack / PostHog]
    D --> E[Git]
    D --> F[iCloud]

New to COG? Watch the 2-minute walkthrough to see it in action.

Quick Start

1. Clone & enter the repo:

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

2. Run onboarding in your agent:

Agent	Command	How it finds skills
Claude Code	`code .` → "Run onboarding"	`.claude/skills/`
Cursor	Open folder → "Run onboarding"	`.cursor-plugin/` + `.cursorrules`
Kiro	Open folder → "setup COG"	`.kiro/powers/`
Gemini CLI	`gemini` → `/onboarding`	`GEMINI.md` + `.gemini/commands/`
OpenAI Codex	`codex` → "Run onboarding"	`AGENTS.md`
Other agents	Point at `AGENTS.md` → "Run onboarding"	`AGENTS.md`

Or install via skills.sh:

npx skills add huytieu/COG-second-brain

Done — COG is personalized and ready in ~2 minutes. See SETUP.md for optional config (Git sync, iCloud, Obsidian Tasks, etc.).

Agent Support Matrix

COG ships a full Claude Code surface plus core native surfaces for Kiro and Gemini CLI, with AGENTS.md as the universal fallback for Codex and other markdown-reading agents.

Surface	Current support	Notes
Claude Code	19 native skills + 6 worker agents	Full first-class surface
Cursor	Plugin manifest + rules	`.cursor-plugin/plugin.json` + `.cursorrules`
Kiro	7 native powers	Core workflows today
Gemini CLI	7 native commands	Core workflows today
`AGENTS.md`	19 documented commands	Universal fallback for Codex and other agents

Before publishing or updating framework files, run ./scripts/validate-agent-surface.sh to catch drift between manifests, docs, and shipped files. See docs/AGENT-SUPPORT.md for the detailed support matrix and contributor rules.

Skills

Core Skills (Personal Knowledge)

Skill	What it does	Try saying...
onboarding	Personalize COG for your workflow (run first!)	"Run onboarding"
braindump	Capture raw thoughts with intelligent classification	"I need to braindump"
daily-brief	Verified news intelligence (7-day freshness)	"Give me my daily brief"
url-dump	Save URLs with auto-extracted insights	"Save this URL"
weekly-checkin	Cross-domain pattern analysis	"Weekly review"
knowledge-consolidation	Build frameworks from scattered notes	"Consolidate my knowledge"
update-cog	Update framework files without touching your content	"Update COG"

Team Intelligence Skills (for Product & Engineering Leads)

Skill	What it does	Try saying...
team-brief	Cross-reference GitHub + Linear + Slack + PostHog into a daily team intelligence brief with two-way Linear sync-back	"Team brief" / "What did we ship?"
meeting-transcript	Process meeting recordings into structured decisions, action items, and team dynamics	"Process this meeting"
comprehensive-analysis	Deep 7-day analysis for weekly reviews, board prep, or strategic planning (~8-12 min)	"Weekly analysis" / "Board prep"

PM Workflow Skills (for Product Managers)

Skill	What it does	Try saying...
create-user-story	Create user stories with duplicate checking across Linear, GitHub Issues, or Jira	"Create a user story for..."
generate-prd	Draft PRDs with approval gate before publishing to Confluence/Notion	"Generate a PRD for..."
generate-release-notes	Generate release notes from GitHub milestones, Linear cycles, or manual input	"Generate release notes for v2.1"
export-open-issues	Audit and export open issues from any tracker into a structured vault summary	"Export open issues"
publish-to-confluence	Publish any vault markdown file to Confluence	"Publish this to Confluence"
update-knowledge-base	Maintain product knowledge base from releases, features, and project changes	"Update the knowledge base with v2.1 changes"

PM Workflow: These skills form a complete product management lifecycle: Research (/auto-research) → PRD (/generate-prd) → Stories (/create-user-story) → Development → Release Notes (/generate-release-notes) → Knowledge Base (/update-knowledge-base). Use /export-open-issues for audits and /publish-to-confluence to share externally.

Strategic Research

Skill	What it does	Try saying...
auto-research	Deep strategic research engine — decomposes questions into parallel research threads with multiple agents	"Research the future of AI testing tools"

Worker Agents (Specialist Sessions)

COG uses a worker agent architecture inspired by garrytan/gstack specialist sessions and garrytan/gbrain knowledge patterns. Workers handle data-heavy tasks cheaply (Sonnet) while the lead session does reasoning (Opus).

Agent	What it does	Model
worker-data-collector	Structured extraction from GitHub, Slack, Jira, Linear	Sonnet
worker-researcher	Web research with source citations	Sonnet
worker-file-ops	Vault file operations, metadata, profiles	Sonnet
worker-executor	Pre-approved mutations (Jira, Linear, APIs)	Sonnet
worker-publisher	Publishing to Slack, Confluence, Notion	Sonnet
brief-people-updater	Batch-update people profiles from meetings/briefs	Sonnet

Workers write results to /tmp/ files and return only a status + path. The lead reads the file for synthesis. This eliminates slow token generation in agent output.

People CRM (Knowledge-Based Team Profiles)

Track the people you work with using progressive, evidence-based profiles in 05-knowledge/people/. Profiles auto-escalate via tiered enrichment:

Tier 3 (Stub) — 1 mention: name, role, one-line context
Tier 2 (Moderate) — 3+ mentions: executive snapshot, working style, strengths
Tier 1 (Full) — 8+ mentions or direct meeting: complete profile with all sections

Every observation includes a source citation with confidence level. See 05-knowledge/people/README.md for details.

Role Packs (Personalized Recommendations)

COG matches your role during onboarding to a role pack that prioritizes the most relevant skills and integrations for you. Available role packs: Product Manager, Engineering Lead, Engineer, Designer, Founder, Marketer — or create your own from the template.

New to team skills? These require GitHub CLI (gh) and work best with Linear, Slack, and PostHog MCP integrations. They degrade gracefully — start with just GitHub and add integrations over time. See SETUP.md for configuration.

The Evolution Cycle

graph TD
    A[Daily: Braindump thoughts] --> B[Daily: News intelligence]
    A --> T[Daily: Team intelligence brief]
    M[Meetings: Process transcripts] --> T
    T -- syncs back to --> L[Linear / GitHub]
    B --> C[Weekly: Pattern analysis]
    T --> CA[Weekly: Comprehensive analysis]
    C --> D[Monthly: Knowledge consolidation]
    CA --> D
    D -- COG learns your patterns --> A
    R[Strategic: Auto-research] --> P[PM: Generate PRD]
    P --> S[PM: Create user stories]
    S -- after development --> RN[PM: Release notes]
    RN --> KB[PM: Update knowledge base]

Daily capture — braindump raw thoughts; COG classifies by domain and extracts action items
Daily intelligence — personalized news briefings with verified, sourced news
Daily team brief — cross-reference GitHub, Linear, Slack, PostHog, meetings into one brief with two-way sync
Meeting processing — extract decisions, action items, and team dynamics from transcripts
Weekly reflection — pattern analysis across all domains surfaces insights you'd miss
Weekly deep dive — comprehensive analysis for board prep, retros, and strategic planning
Monthly synthesis — scattered notes become consolidated frameworks and a knowledge base
Strategic research — deep multi-agent investigation of strategic questions with real sources
PM workflow — full product lifecycle from PRD to release notes to knowledge base updates

Features at a Glance


Self-Evolving — Learns your patterns, auto-organizes content, builds frameworks	Self-Healing — Rename files or restructure; cross-references update automatically	Verification-First — Sources required, 7-day freshness, confidence levels on all analysis
Privacy-First — Local `.md` files, strict domain separation, no external servers	Multi-Device — iCloud sync to iPhone/iPad/Mac; Git for version history	Obsidian Tasks — `📅 YYYY-MM-DD` emoji format works with Tasks plugin dashboards
Garry Tan Inspired — gstack specialist sessions + gbrain knowledge patterns	Multi-Platform — Listed on skills.sh, agentskill.sh, cursor.directory	Worker Agents — Sonnet handles I/O, Opus handles thinking

Your Vault

COG-second-brain/
├── .claude/skills/          # Claude Code skills (19)
├── .claude/agents/          # Worker agent definitions (6)
├── .claude/roles/           # Role packs (7) — personalized recommendations
├── .kiro/powers/            # Kiro powers
├── .gemini/commands/        # Gemini CLI commands
├── AGENTS.md                # Universal agent docs
├── CLAUDE.md                # Framework instructions
├── 00-inbox/                # Profiles, interests, integrations
├── 01-daily/                # Briefs & check-ins
├── 02-personal/             # Personal braindumps (private)
├── 03-professional/         # Professional braindumps & strategy
├── 04-projects/             # Per-project tracking
├── 05-knowledge/            # Consolidated insights & patterns
│   └── people/              # People CRM profiles
└── 06-templates/            # Document templates

Real-world results: 120+ braindumps processed, daily briefs with 95%+ source accuracy, 5 major strategic insights discovered — zero maintenance required.

Keeping COG Updated

COG separates framework files (skills, docs, scripts) from your content (braindumps, profiles, notes). Updates never touch your personal data.

Method	Command
AI Agent (any)	"Update COG" or `/update-cog`
Shell script	`./cog-update.sh` (interactive) • `--check` • `--dry-run` • `--force`
Manual Git	`git fetch cog-upstream main` then checkout specific files

Check your version: cat COG-VERSION
Validate packaged surfaces: ./scripts/validate-agent-surface.sh

FAQ

Why not just use Notion / Roam / Obsidian alone?

COG adds self-evolving intelligence on top. It doesn't just store — it learns, analyzes, and synthesizes insights automatically.

How much does it cost?

COG is free and open-source (MIT). You only pay for your AI agent's API usage.

Is my data private?

Yes. Everything is local markdown files. The AI agent's API is only called when you invoke a skill. No data stored on external servers.

Can I customize or add skills?

Yes — edit any SKILL.md / POWER.md / AGENTS.md file. See SETUP.md for details on creating new skills.

Will updating overwrite my customizations?

No. The update process detects customized files and lets you choose per-file: keep yours, use upstream, or backup + update. Nothing is overwritten without approval.

What if I don't use Git?

Git is optional but recommended for version history. COG works fine with just iCloud sync.

Roadmap

~~Gemini CLI + OpenAI Codex support~~ (shipped in v3.1)
~~Upstream update system~~ (shipped in v3.2)
~~Role packs & integration discovery~~ (shipped in v3.3)
~~PM workflow skills & auto-research~~ (shipped in v3.4)
~~Worker agents, people CRM & specialist sessions~~ (shipped in v3.5)
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

Contributing & Support


Contribute	Report bugs	Discussions
Sponsor on GitHub	Buy me a coffee	MIT License

Acknowledgments & Inspiration

Built with Claude Code, Cursor, Kiro, Gemini CLI, OpenAI Codex, and Obsidian.

Key inspirations:

Garry Tan's gstack — specialist sessions, clear operating gears, repo-local skill distribution. COG's worker agent architecture and model routing borrow directly from gstack's explicit mode separation.
Garry Tan's gbrain — Compiled Truth + Timeline pattern, tiered enrichment for people profiles, brain-first lookup protocol. COG's people CRM and knowledge-first approach are adapted from gbrain's design.
Zettelkasten — atomic, interlinked notes as the foundation of knowledge
Building a Second Brain (Tiago Forte) — PARA organization, progressive summarization
GTD (David Allen) — capture everything, process systematically

Star History

TL;DR: Clone, run onboarding, braindump daily. COG evolves with you — just .md files, any AI agent, zero maintenance.