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Fable, and to a certain extent Opus, work best when allowed to use their own judgement about how to do a task rather than being given dictated, rigid instructions.

A tip from the Claude Code team: let Fable and Opus decide how to approach a task themselves instead of prescribing exact rules. ✦ AI generated

Cat Wu and Thariq Shihipar · Simon Willison's Weblog · 2026-07-03 · original ↗

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One of the most interesting tips I got from the Fireside Chat I hosted with Cat Wu and Thariq Shihipar from the Claude Code team at AIE on Wednesday was to let Fable (and to a certain extent Opus) use their own judgement rather than dictating how they should work.

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✳ Fable ✳ Opus ◉ Cat Wu ◉ Thariq Shihipar

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In practice · 3

Rather than giving Fable an explicit rule like 'only use automated testing for larger features, don't update and run tests for small copy or design changes,' it's better to tell Fable to use its own judgement about when to write tests.Cat Wu and Thariq Shihipar · Simon Willison's Weblog · conf 85%To avoid burning through valuable Fable tokens before the price increase, tell Fable to hand off smaller tasks to other models, letting it use its own judgement about which model to use.Jesse Vincent · Simon Willison's Weblog · conf 70%For all coding tasks use your judgement to decide an appropriate lower power model and run that in a subagent.Simon Willison · Simon Willison's Weblog · conf 60%

Counterpoint · 2

Giving an AI coding agent strict, explicit rules about how to write components (e.g., banning side-effect-heavy patterns) makes the code it produces easier to read afterward, because it ends up matching the style you'd have written yourself.Scott Tolinski · Syntax · conf 80%Giving an AI coding agent strict, explicit rules about how it's allowed to write code (like banning side effects/useEffect) makes the output read like code you'd actually want to read.Scott Tolinski · Syntax · conf 60%

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rebuts → Giving an AI coding agent strict, explicit rules about how to write components (e.g., banning side-effect-heavy patterns) makes the code it produces easier to read afterward, because it ends up matching the style you'd have written yourself.Scott Tolinski · Syntax explains mechanism → Fable is, on a vibes level, the best AI model Scott has used, standing out for reliably executing large, complex tasks with less handholding than other models.Scott Tolinski · Syntax