Anthropic Releases Claude Opus 5.5, Matching Fable 5.1 Performance at 40% Lower Cost

Anthropic unveiled Claude Opus 5.5 on September 22, delivering performance parity with its more expensive Fable 5.1 flagship while slashing costs by 40 percent and accelerating output speeds by over 30 percent. The new model represents a significant competitive shift in the market for frontier-tier language models, arriving just as OpenAI released two lower-cost variants—GPT-6 Sol and Luna—minutes later in a rapid industry response.