Anthropic launches Claude Fable 5.1 for coding and science

Anthropic has launched Claude Fable 5.1, its new frontier model for coding, knowledge work and scientific tasks. The company says the model is generally available, while Claude Mythos 5.1 uses the same base model with different safeguards and is limited to trusted access programs for cybersecurity and life-science work.

The practical hook is cost and usability, not just benchmark movement. Anthropic says Fable 5.1 should cost about 25% less than Fable 5 for typical token-billed workloads because cache reads are cheaper. For highly agentic work, the company says savings can reach roughly 45%.

Anthropic is also trying to make the model easier for enterprise customers to deploy. Its new Enterprise Frontier Safeguards are meant to keep customer data inside customer-controlled cloud infrastructure while still blocking adversarial use. The rollout starts with enterprise customers in phases.

On capability, Anthropic claims large gains in science and long-running tasks: higher scores on Terminal-Bench-Science, stronger computer-use results, and examples such as protein binder design, Venus elevation mapping and GPU-kernel optimization for biology models. For readers, the larger signal is that frontier model launches are becoming less about chat quality alone and more about controlled access to powerful research and security workflows.