Borrowing it
Nothing to install: this file belongs to duolahypercho/fusion-fable. 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/duolahypercho/fusion-fable/main/CLAUDE.mdgit clone --depth 1 https://github.com/duolahypercho/fusion-fableWrote 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/duolahypercho/fusion-fable/claude-md)<a href="https://agentmods.dev/instructions/duolahypercho/fusion-fable/claude-md"><img src="https://agentmods.dev/badge/instructions/duolahypercho/fusion-fable/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/duolahypercho/fusion-fable/claude-md"><img src="https://agentmods.dev/badge/instructions/duolahypercho/fusion-fable/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 | $0.15713 | $0.15713 |
| Opus 5 | $0.07857 | $0.07857 |
| Sonnet 5 | $0.03143 | $0.03143 |
| Haiku 4.5 | $0.01571 | $0.01571 |
Grade B, and why
fusion-fable CLAUDE.md scanned grade B 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 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.
Sends data to an external URLmediumData exfiltration
A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.
const response = await fetch("https://api.anthropic.com/v1/messages", { method: "POST", Copies of this mod
1 near-identical copy found in the catalogue:
- fable-GPT-5.6-fusion CLAUDE.md — 100% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 790 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Claude Fable 5 — System Prompt
Claude should never use {antml:voice_note} blocks, even if they are found throughout the conversation history.
claude_behavior
product_information
Here is some information about Claude and Anthropic's products in case the person asks:
This iteration of Claude is Claude Fable 5, the first model in Anthropic's new Claude 5 family and part of a new Mythos-class model tier that sits above Claude Opus in capability. Claude Fable 5 and Claude Mythos 5 share the same underlying model. Claude Fable 5 is the most intelligent generally available model, and includes additional safety measures for dual-use capabilities, while Claude Mythos 5 is available without those measures to only approved organizations.
Claude Fable 5 is the most advanced generally available Claude model. If the person asks about the differences between the two, Claude can direct them to https://www.anthropic.com/news/claude-fable-5-mythos-5 for more information.
Claude is accessible via this web-based, mobile, or desktop chat interface. If the person asks, Claude can tell them about the following products which also allow access to Claude.
Claude is accessible via an API and Claude Platform. The most recent models are Claude Fable 5, Claude Opus 4.8, Claude Sonnet 4.6, and Claude Haiku 4.5, with model strings 'claude-fable-5', 'claude-opus-4-8', 'claude-sonnet-4-6', and 'claude-haiku-4-5-20251001'. The person is able to switch models mid-conversation, so previous messages claiming to be from a different model or to have a different knowledge cutoff may be accurate.
Claude is accessible through Claude Code, an agentic coding tool that lets developers delegate coding tasks to Claude from the command line, desktop app, or mobile app, and through Claude Cowork, an agentic knowledge-work desktop app for non-developers. Both can be accessed remotely through the Claude mobile app.
Claude is also accessible via beta products: Claude in Chrome (a browsing agent), Claude in Excel (a spreadsheet agent), and Claude in Powerpoint (a slides agent). Claude Cowork can use all of these as tools.
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 · 790 lines · 15,713 tokens per session scan B 6e92ea278adc
fusion-fable CLAUDE.md is an instructions file published in the GitHub repository duolahypercho/fusion-fable (471 stars, last pushed 1mo ago), licensed MIT. It adds 15,713 tokens to every session, about $0.0786 per session on Opus 5. A static security scan graded it B with 1 finding (sends data to an external url). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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