Claude Fable 5.1 now available on AI Gateway
Claude Fable 5.1 from Anthropic is now available on Vercel's AI Gateway, featuring improvements in agentic coding, knowledge work, and multi-stage research. The model includes safety classifiers for cybersecurity and biology, with support for fallback models to ensure requests succeed when safety checks are triggered.
is now available on AI Gateway.Claude Fable 5.1 from Anthropic
Fable 5.1 improvements compared to previous Claude models are concentrated in long, multi-stage work like agentic coding, knowledge work, and research that takes several rounds of searching and following up.
Anthropic ships Fable 5.1 with cybersecurity and biology safety classifiers enabled. Finding vulnerabilities in source code is allowed, but some routine coding and debugging may still be refused. To ensure requests are still serviced when the safety classifiers are triggered, use .model fallbacks
Add a array to listing the models to try. AI Gateway sends the request to Fable 5.1 first, and if Anthropic refuses it, works down the array in order and returns the response from the first model that succeeds:modelsproviderOptions.gateway
This request falls back to Opus 5, then Sonnet 5, if a safety classifier is triggered. The same option works on every AI Gateway API format, including Chat Completions, Messages, and OpenAI Responses.models
Try Fable 5.1 in the .model playground
To use it in a coding agent, see the , then run to connect agents like Claude Code, Codex, OpenCode, Cursor, Pi, and more and select inside the agent.coding agents guidevercel ai-gateway coding-agents setupanthropic/claude-fable-5.1
Anthropic does not support Zero Data Retention for Fable 5.1. Prompts and completions are retained for 30 days and are not used to train Claude.
You can view available on AI Gateway.all language models
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