On September 22, 2026, Anthropic, a US-based AI company, launched Claude Opus 5.5, a new AI model that delivers performance comparable to its top-tier Fable 5.1 while costing 40% less to run than its predecessor. The model is priced at $4 per million input tokens and $20 per million output tokens, 20% below Opus 5. It is available on AWS, Google Cloud, and Azure. Opus 5.5 underwent external safety testing and includes enhanced safeguards. It outperformed OpenAI's GPT-5.6 Sol on a software development benchmark. Claude Sonnet 5.5 and Haiku 5.5 are expected in coming weeks.
We’ll perform a deep-dive analysis of all sources and publicly available external materials, then prepare a structured timeline of events, an in-depth report explaining the background and context, and multiple perspectives.