Borrowing it
Nothing to install: this file belongs to oborchers/fractional-cto. 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/oborchers/fractional-cto/main/CLAUDE.mdgit clone --depth 1 https://github.com/oborchers/fractional-ctoWrote 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/oborchers/fractional-cto/claude-md)<a href="https://agentmods.dev/instructions/oborchers/fractional-cto/claude-md"><img src="https://agentmods.dev/badge/instructions/oborchers/fractional-cto/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/oborchers/fractional-cto/claude-md"><img src="https://agentmods.dev/badge/instructions/oborchers/fractional-cto/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 | $0.01504 | $0.01504 |
| Opus 5 | $0.00752 | $0.00752 |
| Sonnet 5 | $0.00301 | $0.00301 |
| Haiku 4.5 | $0.00150 | $0.00150 |
Grade A, and why
fractional-cto CLAUDE.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 10d 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.
How it starts
The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.
CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
Project Overview
fractional-cto is a Claude Code plugin marketplace containing opinionated, research-backed plugins for software engineering. It is purely markdown/JSON/bash — no build system, no runtime dependencies, no tests to run.
Local Development
# Test a plugin locally
claude --plugin-dir /path/to/fractional-cto/<plugin-name>
There is no build step, linter, or test suite. Validation is manual: start a Claude session with the plugin and verify hooks fire, skills invoke, and commands work.
Architecture
Marketplace Registry
.claude-plugin/marketplace.json is the central registry listing all available plugins. Each plugin lives in its own top-level directory.
Plugin Structure
<plugin-name>/
├── .claude-plugin/plugin.json # Plugin manifest (name, version, keywords)
├── README.md # Plugin docs and principle overview
├── hooks/
│ ├── hooks.json # Registers SessionStart hook
│ └── session-start.sh # Injects meta-skill index into session context
├── commands/
│ └── <name>-review.md # Manual review command
├── agents/
│ └── <name>-reviewer.md # Comprehensive audit agent (model: sonnet)
└── skills/
├── using-<name>-principles/ # Meta-skill: index of all principle skills
└── <principle-name>/ # Individual principle skills, each with:
├── SKILL.md # Principles, checklists, good/bad patterns
└── examples/ # Code examples relevant to the domain
Activation Flow
- SessionStart hook (
hooks/hooks.json→hooks/session-start.sh) fires on startup/resume/clear/compact session-start.shreads the meta-skill (using-*-principles/SKILL.md), escapes it, and outputs JSON withadditional_context- Claude now knows the available principle skills and when to invoke each
- Skills are invoked automatically when Claude detects relevant work, or manually via the plugin's review command
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.
- 10d ago First seen · 116 lines · 1,504 tokens per session scan A 579f71ccc282
fractional-cto CLAUDE.md is an instructions file published in the GitHub repository oborchers/fractional-cto (29 stars, last pushed 1mo ago), licensed MIT. It adds 1,504 tokens to every session, about $0.0075 per session on Opus 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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