Miguel Afonso Caetano<p>"Anthropic publish most of the system prompts for their chat models as part of their release notes. They recently shared the new prompts for both Claude Opus 4 and Claude Sonnet 4. I enjoyed digging through the prompts, since they act as a sort of unofficial manual for how best to use these tools. Here are my highlights, including a dive into the leaked tool prompts that Anthropic didn’t publish themselves.</p><p>Reading these system prompts reminds me of the thing where any warning sign in the real world hints at somebody having done something extremely stupid in the past. A system prompt can often be interpreted as a detailed list of all of the things the model used to do before it was told not to do them.</p><p>I’ve written a bunch about Claude 4 already. Previously: Live blogging the release, details you may have missed and extensive notes on the Claude 4 system card.</p><p>Throughout this piece any sections in bold represent my own editorial emphasis."</p><p><a href="https://simonwillison.net/2025/May/25/claude-4-system-prompt/" rel="nofollow noopener" translate="no" target="_blank"><span class="invisible">https://</span><span class="ellipsis">simonwillison.net/2025/May/25/</span><span class="invisible">claude-4-system-prompt/</span></a></p><p><a href="https://tldr.nettime.org/tags/AI" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>AI</span></a> <a href="https://tldr.nettime.org/tags/GenerativeAI" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>GenerativeAI</span></a> <a href="https://tldr.nettime.org/tags/Claude" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Claude</span></a> <a href="https://tldr.nettime.org/tags/Claude4" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Claude4</span></a> <a href="https://tldr.nettime.org/tags/Anthropic" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Anthropic</span></a> <a href="https://tldr.nettime.org/tags/SystemPrompts" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>SystemPrompts</span></a> <a href="https://tldr.nettime.org/tags/PromptEngineering" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>PromptEngineering</span></a> <a href="https://tldr.nettime.org/tags/LLMs" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>LLMs</span></a> <a href="https://tldr.nettime.org/tags/Chatbots" class="mention hashtag" rel="nofollow noopener" target="_blank">#<span>Chatbots</span></a></p>