The system prompt for Claude 3.7, an advanced large language model (LLM), has been leaked and revealed to be approximately 24,000 tokens long, or about 110 kilobytes in size. This length is substantially greater than that of other LLMs, such as OpenAI's o4-mini used in ChatGPT, whose system prompt is around 2,218 words or 15.1 kilobytes—approximately 13% of Claude 3.7's prompt size. The extensive system prompt defines the model's behavior, tool usage, and citation format, and is designed to enhance logical reasoning and reduce hallucinations. Comparisons between Claude 3.7 and its predecessor, Claude 3.5, indicate notable differences, though these may not be apparent without adapting prompting techniques. All system prompts from OpenAI's o4 to Claude 3.7 have been leaked on GitHub, providing insights into the underlying mechanisms of these models. Some users have expressed dissatisfaction with Claude 3.7's performance compared to earlier versions.