AWS is rolling out access to Anthropic’s Claude Fable 5 model via Amazon Bedrock, with account availability based on Bedrock usage or AWS Support requests. The service routes harmful prompts to the Opus 4.8 model to reduce costs and applies 30-day data retention for all Mythos-class model traffic.

Hex built a suite of analytical evals to test data-analysis models and found Claude Fable 5 outperforms its Opus 4.x predecessors by 10–15%, nailing both semantically modeled and raw-data tasks with fewer mistakes. They’ve also designed a tougher “Frontier” benchmark for long-horizon, open-ended scenarios, where Fable 5’s careful assumptions and cross-checks boost its pass rate to around 58%.

Anthropic disabled Mythos 5 and Fable 5 after a US Commerce Department export-control order barred their use abroad. The administration asked for a pause amid reports of a narrow jailbreak letting Fable 5 analyze code for vulnerabilities. Anthropic says the issue produced only minor findings and that other models, like GPT-5.5, have similar capabilities.