Anthropic launches Claude Fable 5.1 after inking $35B cloud deal with Lambda

Anthropic launched Claude Fable 5.1 and Claude Mythos 5.1, their most advanced large language models yet, just a day after signing a $35 billion infrastructure deal with cloud startup Lambda Inc. Both models are nearly identical, with the main difference being that Fable 5.1 is restricted from being used for cybersecurity and biology-related tasks.

Mythos 5.1, which can only be accessed by a limited number of trusted organizations, will not have this restriction. Fable 5.1 has achieved impressive results on various AI benchmarks, scoring 52.6% on Terminal-Bench-Science 0.1 and 13% higher on Terminal-Bench 4.0 coding tests. It also has more relaxed guardrails, allowing researchers to use it for software vulnerability discovery.

However, it lacks the strongest cyber capabilities compared to Mythos 5.1. Fable 5.1 will be available to the general public, while Mythos 5.1 is accessible through specialized programs for cybersecurity researchers and biologists. Anthropic claims that the prompt caching mechanism for Fable 5.1 allows it to run workloads 25% more cost-efficiently than its predecessor.

The company expects its infrastructure requirements to increase over time, having leased $35 billion worth of infrastructure from Lambda, which could translate to between 350 and 437 megawatts of capacity. The infrastructure will be housed in a data center being built in Nueces County, Texas, with Nvidia leasing the campus.