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Prompting Claude Fable 5.2 to Restructure Code

Simon Willison·· 3 days agoQuoting Prompting Claude Fable 5.2
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Simon Willison
What
shares a prompting technique that encourages Claude Fable 5.2 to improve code structure
Quote
If you want the model to improve the structure as it works, say that the code is its own: This codebase is yours: what it's for and how it's built are your call, and you'll keep building on it.

What happened

Anthropic says Claude Fable 5.2 responds closely to prompts about who owns the code it works on. In tests on small coding tasks, it merged repeated code in about half of the tries when told the codebase was its own, compared with under a tenth of tries without that instruction.

Read next

See the full storyAnthropic Releases Claude Fable 5.2 and Mythos 5.2 with Lower API Prices

The story so far

Anthropic released Claude Fable 5.2 and Claude Mythos 5.2, lowering API prices to $8 per million input tokens and $40 per million output tokens, from $10 and $50. Anthropic says both models improve coding, reasoning, and vision, and that Fable produces responses faster than version 5.1. Fable is available to paid users with safeguards for risky cybersecurity and biology tasks; Mythos is limited to organizations approved through Anthropic’s verification programs. The launch reports cite strong benchmark results, including Fable’s first-place score on Artificial Analysis’ Intelligence Index v5 at its highest compute tier. Those figures come from the named benchmark evaluations; Anthropic’s prerelease examples also include software migrations, electronic devices, and physics problems. TechCrunch reports that an optional faster serving mode costs twice as much, while the lower API prices apply to standard use.

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