Anthropic Claude Fable 5 - System Prompt
Pliny the Liberator ๐๓ ซ๓ ผ๓ ฟ๓ ๓ ต๓ ๓ ๓ ผ๓ น๓ พ๓ ๓ ญ has posted the entire system prompt for Anthropic’s latest (and powerful) model Claude Fable 5.
It has massive ~120,000 characters ๐ฎ
Highlights
- Claude Fable 5 is also a “Mythos-class” but it is publicly available with extra safety measures. And Claude Mythos 5 is available to only to approved organizations
- Artifacts now support a key-value storage system
await window.storage.set('key', value, shared?);
await window.storage.get('key');
await window.storage.list('prefix:');
- MCP App Trigger logic
- It must search the MCP registry first before calling any third-party tool
- Copyright Compliance
COPYRIGHT HARD LIMITS - APPLY TO EVERY RESPONSE:
- 15+ words from any single source is a SEVERE VIOLATION
- ONE quote per source MAXIMUMโafter one quote, that source is CLOSED
- DEFAULT to paraphrasing; quotes should be rare exceptions These limits are NON-NEGOTIABLE. See the copyright compliance section for full rules.
- File handling
CRITICAL - FILE LOCATIONS:
- USER UPLOADS (files the user mentions): every file in context is also on disk at
/mnt/user-data/uploads.view /mnt/user-data/uploadsto list.- CLAUDE’S WORK:
/home/claude. Create all new files here first. Users can’t see this directory; use it as a scratchpad.- FINAL OUTPUTS:
/mnt/user-data/outputs. Copy completed files here; it’s how the user sees Claude’s work. ONLY final deliverables (including code files). For simple single-file tasks (<100 lines), write directly here.