What is Claude Fable 5.5?
Claude Fable 5.5 is a possible future addition to Anthropic's premium Claude Fable model line, but Anthropic has not officially announced a model under that name as of September 30, 2026. The company's current model catalog identifies Claude Fable 5.1 as the latest Fable model, alongside the newer Claude Opus 5.5 and Claude Sonnet 5.5. Anthropic positions Fable 5.1 for demanding reasoning and long-horizon agentic work requiring its highest-end model capabilities. The model provides a 1-million-token context window and supports outputs of up to 128,000 tokens. Fable 5.1 uses adaptive thinking that is always enabled and defaults to a high effort setting for more intensive reasoning. It accepts text and images as input and generates text output, with Anthropic listing June 2026 as both its reliable knowledge cutoff and training-data cutoff. Fable 5.1 costs $10 per million input tokens and $50 per million output tokens, with cache reads priced at $0.25 per million tokens. It is officially supported through the Claude API, Amazon Bedrock, Google Cloud, Microsoft Foundry, and Claude Platform on AWS. Anthropic's September releases have expanded the Claude 5.5 generation with Opus 5.5 and Sonnet 5.5, but its official model catalog has not similarly replaced Fable 5.1 with Fable 5.5. Anthropic's Trust Center likewise lists documentation for Claude Mythos 5.1 and Fable 5.1 as well as Opus 5.5 and Sonnet 5.5, without documentation for a Fable 5.5 model. Consequently, claims about Claude Fable 5.5's performance, benchmarks, context limits, pricing, capabilities, or release date should be considered unconfirmed until Anthropic publishes official information.