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/CLAUDE.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/claude-md)<a href="https://agentmods.dev/instructions/huytieu/cog-second-brain/claude-md"><img src="https://agentmods.dev/badge/instructions/huytieu/cog-second-brain/claude-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/claude-md"><img src="https://agentmods.dev/badge/instructions/huytieu/cog-second-brain/claude-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 | $0.04178 | $0.04178 |
| Opus 5.5 | $0.01671 | $0.01671 |
| Sonnet 5.5 | $0.00836 | $0.00836 |
| Haiku 4.5 | $0.00418 | $0.00418 |
Grade A, and why
COG-second-brain CLAUDE.md scanned grade A with 1 finding 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 3d 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.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
- **Verification means observing the artifact**: curl the URL, screenshot the page, re-fetch the issue, diff the file. Never re-read a worker's own summary of it. Mandatory for external mutations; see § Skill Post-Condit How it starts
The opening of the file, as written. The whole thing — 252 lines — stays where its author put it; the contents beside it link to each section on GitHub.
COG Second Brain — Framework Instructions
Opt-in verification harness:
WORKFLOW.md· Universal surface:AGENTS.md
Response Style (ALWAYS APPLY, every agent, every deliverable)
Optimize for information gain, not apparent completeness. The failure mode is framework slop: ordinary reasoning dressed as a consulting memo. Full pattern list: .claude/skills/no-ai-slop/SKILL.md § Structural slop.
- Start with the answer or strongest finding; no introduction announcing how you will answer.
- Write at 80% ASD-STE100: instructions 20 words max with one instruction each, descriptive sentences 25 words max, paragraphs 6 sentences max, active voice, one term per meaning, noun clusters three words max, keep articles. Technical terms and the writer's own voice in edits stay as they are. Rules:
.claude/skills/no-ai-slop/SKILL.md§ Controlled-language target. An explanation for someone who did not build the thing opens with an ELI5 paragraph: three sentences, everyday words, one analogy. - When the goal is understanding, climb the format ladder: STE prose, then a diagram, then an HTML page, then an explainer video. Use the highest rung the content and medium support, and offer the next rung in one line when it would help. § Output format ladder in the same skill.
- Never invent named frameworks, gates, layers, pillars, lenses, or numbered taxonomies unless they exist in the source material or the categorization materially simplifies a complex subject.
- No sections for 1-2 paragraphs; default to continuous prose with occasional descriptive headings.
- Headings identify subject matter ("Authentication"), never rhetorical function. Banned: "What this is not", "Why this matters", "The key insight", "The real opportunity", "The bottom line", "The deeper point", "The uncomfortable truth".
- No straw-man contrasts ("It's not X, it's Y", "This isn't about X", "While it may seem...", "Unlike...") unless X is a position someone relevant actually holds.
- Space proportional to importance and evidence; each paragraph must add evidence, mechanism, example, implication, counterexample, or decision.
- Compose as finding → evidence → reasoning → decision, not principle → framework → exposition → takeaway.
- Prefer concrete nouns over abstract labels. Stop when the useful information is exhausted.
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.
- 3d ago Changed b76fc75e0018
- 24d ago Changed · +2 lines · +176 tokens per session 74ac36cd5503
- 1mo ago First seen · 250 lines · 4,002 tokens per session scan A 9ff2da4c033f
COG-second-brain CLAUDE.md is an instructions file published in the GitHub repository huytieu/COG-second-brain (1,322 stars, last pushed 4d ago), licensed MIT. It adds 4,178 tokens to every session, about $0.0167 per session on Opus 5.5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
Other instructions, from other repositories
multiagent-template copilot-instructions.md
Instructions for Neftedollar/multiagent-template, covering workspace structure, how to work in this repo, multi-agent pipeline, orchestrator role and escalate to human only for.
runtm copilot-instructions.md
Copilot instructions for runtm-ai/runtm, covering runtm tool instructions, critical rules, structure, adding endpoints and app/api/v1/myendpoint.py.
vscode buildNext.instructions.md
Working notes and architecture documentation for the new esbuild-based build system in build/next. Use when making changes to the new build pipeline (transpile/bundle commands, NLS plugin, source-map handling, resource copying, or self-hosting watch tasks).
next.js AGENTS.md
AGENTS.md instructions for vercel/next.js, covering next.js development guide, codebase structure, monorepo overview, core package: packages/next and other important packages.
vscode oss-third-party-notices.instructions.md
Instructions for microsoft/vscode, covering vs code oss third-party-notices pipeline, architecture, pipeline flow in ci, cache eligibility and rollout and applying the notice (cutover).
langchain AGENTS.md
AGENTS.md instructions for langchain-ai/langchain, covering global development guidelines for the langchain monorepo, corridor security analysis, project architecture and context, monorepo structure and development tools & commands.