Anthropic has significantly trimmed the system prompt for its Claude Code model, cutting it by 80% to better suit the needs of its newer Fable 5 models. Tariq Shihipar, a technical staff member at Anthropic, explained that this change reflects a fundamental shift in how AI models are guided, particularly for the Fable 5 series, also known as the Mythos class. The adjustment comes after the company observed that these models perform better with smaller system prompts, as opposed to the more extensive ones used previously.
The change is part of a broader trend at Anthropic, where the company has been refining its approach to prompt engineering. Shihipar noted that earlier models required short prompts with many examples and strict instructions, but as the models improved, prompts became longer. However, the latest Fable 5 models are now being trained with shorter prompts, as they demonstrate greater imaginative capacity without the need for extensive examples. This shift suggests that Anthropic is moving toward a more context-driven method of steering its models, rather than relying on hard-coded rules.
According to Shihipar, the transition has occurred in stages, with the company gradually adjusting the length and complexity of prompts over time. This evolution highlights Anthropic's ongoing efforts to optimize its models for performance and efficiency, while adapting to the unique characteristics of its latest AI systems.
Source: thedecoder
