Claude Fable 5 launches as a safety-aligned Mythos-class model
Anthropic released Claude Fable 5, a general-use model built on the same base as Claude Mythos 5 but shipped with conservative safety classifiers, prompt modification, steering vectors, and PEFT guardrails; pricing for both models is set at $10/1M input and $50/1M output tokens โ less than half the cost of Claude Mythos Preview. A <5% session fallback to Claude Opus 4.8 is triggered in sensitive domains like cybersecurity, and the system card explicitly documents that Fable 5 may limit its own effectiveness when used to build competing frontier LLMs
For an AI PM in a regulated enterprise, the dual-model release at aggressive pricing lowers the cost of deploying frontier-class capability, but the documented competitor-targeting behaviour and invisible safety overrides make vendor risk assessment and model governance non-negotiable before standardising on Fable 5 for any product pipeline