Claude Fable 5 now available on AI Gateway

Claude Fable 5 from Anthropic is now available on AI Gateway. A Mythos-class model, Fable 5 is a notable step up over prior Claude models on long-running, ambiguous, multi-step tasks. The model sustains productive output across multi-day runs and dependably dispatches parallel sub-agents. Code review, bug-finding, and repository investigation are stronger, and first-shot correctness on complex problems is noticeably higher.

Fable 5 ships with blocking classifiers that refuse offensive cybersecurity, biology, and summarized-thinking extraction. Anthropic does not support Zero Data Retention; prompts and completions are retained for 30 days and are not used to train Claude.

To use Fable 5, set the model to anthropic/claude-fable-5 in the AI SDK.