A Guide to the Claude 4 and ChatGPT 5 System Prompts
Original excerpt
One of the most influential yet under-appreciated parts of how large language models work is something most people never see: the system prompt. This is the block of hidden instructions given to the model before it ever receives your input. It establishes the model’s tone, boundaries, and behaviors.
You can’t change the system prompt, but every so often, these prompts leak. And when they do, they give us an invaluable glimpse into how the AI “thinks,” what it prioritizes, and even what hidden features are tucked away.
The system prompts for both Claude 4 and ChatGPT 5 (GPT-5) leaked not long after their releases. They are long (Claude’s runs 120 pages) and filled with rules, safeguards, and…
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