---
title: "Someone just leaked the Full System Prompt of Claude Fable 5.1 and now its out in the open on Github"
source_url: https://youtube.com/shorts/LaNMx5q261U
captured_at: 2026-09-14
author: "Nick Automates"
contributor: "ชิดชนก"
platform: youtube
---
# Someone just leaked the Full System Prompt of Claude Fable 5.1 and now its out in the open on Github

youtube video by **Nick Automates**, 0m36s, uploaded 2026-09-11. URL: https://youtube.com/shorts/LaNMx5q261U

## Shared in LINE Note+
- 2026-09-14 08:18 by ชิดชนก

## Description
Someone just leaked the full system prompt of Claude Fable 5.1.

And this isn't some basic prompt.

It's over 275,000 characters long, around 8,000 lines.

It covers the exact instructions Anthropic uses to control how one of the world's most powerful AI models thinks, plans, and gets work done.

The leak includes the entire prompt with its tools, instructions, and behavior rules.

And it's all sitting in public on GitHub right now.

So you can use it to improve your own prompting skills.

By studying exactly how Anthropic defines its tools.

How they set their restrictions.

And how they tell the model what to use, when, and how.

Think of it like getting the actual internal manual instead of just guessing how the system behaves from the outside.

Most people prompt by trial and error, testing what works and hoping it holds up.

This lets you study the real structure behind one of the most capable models out there.

#claudefable5 #systemprompt #aiprompting #githubrepo #claudeai