{"repo":"KalarisLabs/claude-fable-5-system-prompt","free":true,"listed":false,"github":"https://github.com/KalarisLabs/claude-fable-5-system-prompt","clone":"git clone https://github.com/KalarisLabs/claude-fable-5-system-prompt.git","description":"system prompt of claude fable 5","language":"Python","stars":180,"topics":["ai-agents","claude","claude-5","prompt-engineering","system-prompts","system-prompts-leak"],"license":null,"category":"ai-agents","readme_excerpt":"Claude Fable 5 System Prompt The Complete Leaked System Prompt from Anthropic's Most Intelligent Model Curated & Extracted by Sayan Chowdhury .%20Full%20analysis%3A&url=https://github.com/saynchowdhury/claude-fable-5-system-prompt) The complete Claude Fable 5 (Mythos-class) system prompt archive. Discover Anthropic's agentic AI rules, tools, and secrets. Key Revelations Full Prompt Analysis Fable 5 vs Opus 4.8 Highlights --- What Is This? This repository contains the complete system prompt ( 1,580 lines, 120KB) for Claude Fable 5 , Anthropic's most capable generally-available AI model as of June 2026. The prompt was extracted from a live claude.ai session and reveals the inner architecture, behavioral guidelines, tool definitions, and safety frameworks that govern how Claude Fable 5 thinks, responds, and interacts. This is the most detailed look yet into how Anthropic engineers its flagship model's behavior. --- Key Revelations Mythos-Class: A New Model Tier Above Opus Claude Fable 5 belongs to an entirely new \"Mythos-class\" model tier that sits above Claude Opus in capability. The prompt confirms: \"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 Mythos 5 is available without safety measures to approved organizations only - Model strings: claude-fable-5 , claude-opus-4","default_branch":null,"files":null,"tree":[],"storefront":"/r/KalarisLabs","claimed":false,"request_supported":{"post":"https://gitbuyer.com/r/KalarisLabs/claude-fable-5-system-prompt/request-supported","requests":0},"note":"indexed from public GitHub; nothing is for sale on this page. Clone it from GitHub. Paid listings live at /search."}