Initial impressions of Claude Fable 5

Claude Fable 5 is a new AI model released by Anthropic that matches the capabilities of Claude Mythos 5 but includes stricter guardrails (safety restrictions to prevent harmful use) that trigger frequently enough to require new API mechanisms for handling rejections. The model has a 1 million token context window (the amount of text it can process at once), costs twice as much as previous models, and demonstrates notably stronger knowledge retention compared to earlier versions like Claude Opus 4.8.