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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

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Claude Code v2.1.170

Fable 5 Noted in System Prompt Model Guidance

The system prompt context now mentions Fable 5 when describing available models: "The most recent Claude models are Fable 5 and the Claude 4.X family. Model IDs — Fable 5: '[id]', Opus 4.8: '[id]', Sonnet 4.6: '[id]', Haiku 4.5: '[id]'."

Evidence

Updated system prompt string (search for "The most recent Claude models are Fable 5")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.170 →