Claude 4 Sonnet System Prompt
---
title: "Claude 4 System Prompt Analysis"
source: "https://simonwillison.net/2025/May/25/claude-4-system-prompt/"
category: "system-prompts"
tags: [claude, anthropic, leaked-prompt, web-search, prompt-injection]
---
# Claude 4 System Prompt Analysis
The full system prompt for Claude 4 (Sonnet 4) has been extracted and shared online, providing a detailed look at how Anthropic engineers their AI assistant's behavior.
## Key Features of the System Prompt
**1. Thinking Mode Configuration**
The system prompt includes interleaved thinking mode with a 16,000 token budget:when to use it
Community prompt sourced from the open-source GitHub repo funsaized/prompts.wine (no explicit license). A "Claude 4 Sonnet System Prompt" style prompt — adapt the placeholders and specifics to your task. Imported as-is and not independently retested here, so check the output before relying on it.
tags
codingcommunitydeveloper
source
funsaized/prompts.wine · no explicit license
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