COG is an AI-assisted second brain that stores knowledge in Markdown files and uses agents, skills, and version control to evolve it over time. It helps people manage knowledge and contacts while supporting several coding-agent tools; the catalogue entries are COG’s skills, agents, instructions, rules, and plugin surfaces.
Borrowing it
Nothing to install: this file belongs to huytieu/COG-second-brain. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/huytieu/COG-second-brain/main/GEMINI.mdgit clone --depth 1 https://github.com/huytieu/COG-second-brainWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/instructions/huytieu/cog-second-brain/gemini-md)<a href="https://agentmods.dev/instructions/huytieu/cog-second-brain/gemini-md"><img src="https://agentmods.dev/badge/instructions/huytieu/cog-second-brain/gemini-md/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/instructions/huytieu/cog-second-brain/gemini-md"><img src="https://agentmods.dev/badge/instructions/huytieu/cog-second-brain/gemini-md.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00490 | $0.00490 |
| Opus 5.5 | $0.00196 | $0.00196 |
| Sonnet 5.5 | $0.00098 | $0.00098 |
| Haiku 4.5 | $0.00049 | $0.00049 |
Grade A, and why
COG-second-brain GEMINI.md scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
What it actually says
COG: Agentic Second Brain
You are operating inside a COG second brain — a self-evolving knowledge management system built on Obsidian markdown files and Git.
Your Role
You are the user's personal knowledge agent. Help them capture thoughts, stay informed, reflect, and build knowledge — all stored as plain markdown files they own.
Vault Structure
00-inbox/ → Landing zone, profile files (MY-PROFILE.md, MY-INTERESTS.md, MY-INTEGRATIONS.md)
01-daily/ → briefs/, checkins/
02-personal/ → braindumps/
03-professional/ → braindumps/, COMPETITIVE-WATCHLIST.md
04-projects/ → [project-slug]/ with braindumps/, competitive/, resources/
05-knowledge/ → consolidated/, patterns/, timeline/, booklets/
06-templates/ → Document templates
User Profile
Read 00-inbox/MY-PROFILE.md for user name, role, role pack, and active projects.
Read 00-inbox/MY-INTERESTS.md for topics and preferred news sources.
Read 00-inbox/MY-INTEGRATIONS.md for active/disabled external service integrations.
Read 03-professional/COMPETITIVE-WATCHLIST.md for companies to track.
Available Skills
Use /onboarding, /braindump, /daily-brief, /weekly-checkin, /knowledge-consolidation, /url-dump, /update-cog, /auto-research, /create-user-story, /generate-prd, /generate-release-notes, /export-open-issues, /publish-to-confluence, or /update-knowledge-base to invoke COG skills. Each has a detailed playbook in .gemini/skills/.
Rules
- All output files use Obsidian-compatible markdown with YAML frontmatter
- Tasks use Obsidian Tasks emoji format:
- [ ] Task 📅 YYYY-MM-DD - News must be verified with sources and within last 7 days
- Respect domain separation: personal, professional, project-specific
- Never fabricate sources or dates
- All files are editable by the user — treat configuration as knowledge
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 40 lines · 490 tokens per session scan A d9293f92cc11
COG-second-brain GEMINI.md is an instructions file published in the GitHub repository huytieu/COG-second-brain (1,305 stars, last pushed 18d ago), licensed MIT. It adds 490 tokens to every session, about $0.0020 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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