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Claude Fable

by Anthropic

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Overview

Claude Fable 5 is an Anthropic Claude model described as a Mythos-level model for ambitious long-running work.

Details

Claude Fable 5 is identified in Anthropic-provided source excerpts as a Claude model with API model ID `claude-fable-5`. Anthropic’s product-page excerpt describes it as a Mythos-level model for ambitious long-running work and says the page states pricing, while Anthropic’s announcement excerpt says Claude Fable 5 was announced on June 9, 2026 as a Mythos-class model made safe for general use. Claude API documentation excerpts describe Claude Fable 5 as Anthropic’s most capable widely released model, with a 1M context window and up to 128k output tokens. Availability should be verified before production use because the supplied excerpts conflict: one product-page excerpt says the model is currently unavailable, while API documentation excerpts say general availability began June 9, 2026.

When to Use

Evaluate Anthropic’s Claude Fable 5 for ambitious long-running work where the supplied Anthropic excerpts indicate a large context window is relevant. Plan Claude API integrations that need the official model identifier `claude-fable-5`. Estimate costs using Anthropic’s published Claude Fable 5 per-token pricing before sending production traffic.

Getting Started

  1. Review the Claude Fable product page: https://www.anthropic.com/claude/fable
  2. Check the Claude API models overview for the current status of `claude-fable-5`
  3. context window
  4. and output limits: https://platform.claude.com/docs/en/about-claude/models/overview
  5. Review Anthropic’s Claude API pricing page before production use: https://platform.claude.com/docs/en/about-claude/pricing
  6. Consult Anthropic’s system-card index and launch announcement for safety and release context.

Key Features

  • •API model ID: `claude-fable-5`.
  • •Described by Anthropic as a Mythos-level model for ambitious long-running work.
  • •Claude API documentation excerpt lists a 1M context window.
  • •Claude API documentation excerpt lists up to 128k output tokens.
  • •Anthropic’s Help Center excerpt says Claude Fable 5 uses safeguards for areas including cybersecurity and biology
  • •with some blocked requests rerun on Claude Opus 4.8 with a visible model-switch notice.

Capabilities

  • •long-running work
  • •large-context reasoning
  • •Claude API integration
  • •commercial token-priced model

Last updated Jul 31, 2026