Anthropic released Claude Opus 5.5 on September 22, saying it performs at the level of Claude Fable 5.1 on most work. At list price, it costs well under half as much per token. It leads Fable 5.1 on Terminal-Bench 4.0, FrontierCode, and CursorBench. Anthropic says the gap between the two models “is narrower than these scores suggest.” Opus 5.5 costs $4 per million input tokens and $20 per million output tokens. Fable 5.1 costs $10 and $50. Anthropic’s own model docs still point developers to Fable 5.1 for “demanding reasoning and long-horizon agentic work” and list it as the slower of the...

Source: The New Stack