Claude Fable 5 in Python: Build a Self-Checking Agent

Claude Fable 5 in Python: Build a Self-Checking Agent

On June 9, 2026 Anthropic did something it had spent the prior week warning against: it shipped its most powerful model to the public. Claude Fable 5 is the generally available, safety-hardened sibling of the internal Mythos 5 system. Same raw capability, but wrapped in a guardrail layer that quietly hands risky requests off to Opus 4.8 instead of answering them. Within hours it was live on the Anthropic API, AWS Bedrock, GitHub Copilot, Databricks, and Microsoft Foundry, and the demo making the rounds was a one-click "type a sentence, get a playable video game" toy.