Anthropic cuts Claude Code system prompts by 80%
Decision Brief
What changedAnthropic reduced Claude Code's system prompt length by 80% because the Fable 5 model prefers smaller prompts.
Why it mattersFable 5 excels at inferring intent from few instructions; lengthy prompts constrain its creativity, so trimming lowers latency and improves output quality.
Who should careTeams building on model APIs, AI coding tool users
Affected stackClaude Code
Builder actionEvaluate
Source confidenceMedium · Reliable media or first-hand reporting
Anthropic announced an 80% reduction in Claude Code's system prompt size. Employee Tariq Shihipar explained that the new Fable 5 model requires fewer instructions and examples—excessive rules actually hinder performance because the model is more imaginative than the prompts provided. Instead of strict rules, Anthropic now guides the model through context.
Summary basis: official / RSS sourceUnless it says 'full article read', this summary is based only on publicly available content — it never pretends to have read restricted originals.
Sources
- The Decoder：AI News
- The Decoder：AI News