Checked fact 8278 Oct 2026Agents and apps

Anthropic lists a minimum cacheable prompt length of 512 tokens for Claude Fable 5.1, Mythos 5.1, Opus 5.5, Opus 5, Sonnet 5.5, Fable 5, Mythos 5 and Haiku 5.5. Quote: "512 tokens for Claude Fable 5.1"

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The exact words it rests on

512 tokens for Claude Fable 5.1, Claude Mythos 5.1 , Claude Opus 5.5, Claude Opus 5, Claude Sonnet 5.5, Claude Fable 5, Claude Mythos 5 , and Claude Haiku 5.5

What the source said when we opened it, on 8 Oct 2026.

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Prompt caching
Anthropic

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Checked by the notis newsroom on 8 Oct 2026, against the source above.

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How prompt caching bills a repeated prompt start 8 Oct 2026

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“Anthropic lists a minimum cacheable prompt length of 512 tokens for Claude Fable 5.1, Mythos 5.1, Opus 5.5, Opus 5, Sonnet 5.5, Fable 5, Mythos 5 and Haiku 5.5. Quote: "512 tokens for Claude Fable 5.1".” ai notis, checked 8 Oct 2026. Source: Prompt caching (Anthropic). https://ainotis.com/c/827

As a reference (APA style)

ai notis. (2026, October 8). Anthropic lists a minimum cacheable prompt length of 512 tokens for Claude Fable 5.1, Mythos 5.1, Opus 5.5, Opus 5, Sonnet 5.5, Fable 5, Mythos 5 and Haiku 5.5. Quote: "512 tokens for Claude Fable 5.1" [Checked claim 827]. ai notis. https://ainotis.com/c/827

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