Anthropic launches Claude Opus 5.5, a cheaper rival to its top-tier fable

Anthropic released Claude Opus 5.5 on Tuesday, September 22, a new AI model that delivers performance comparable to its top-tier Fable 5.1 while costing around 40% less to run than its predecessor, as the company positions itself for what could be the largest IPO in history.

The San Francisco-based lab, valued at $965 billion, said Opus 5.5 is valued at $4 per million input tokens and $20 per million output tokens. This marks 20% below Opus 5 and well under Fable 5.1’s $10/$50 pricing.

The model is available on Amazon Web Services, Google Cloud, and Microsoft Azure. As per Anthropic, Opus 5.5 outscored OpenAI’s GPT 5.6 Sol on a software development benchmark while costing roughly one-third as much to run.

The company also reported the model was about 85% less likely than Opus 5 or Mythos 5.1 to attempt bypassing containment boundaries in safety evaluations. External testing was conducted by independent groups Frontier Designer and METR.

This launch coincides with Anthropic's plans for an upcoming fall IPO that is expected to be the biggest in history. The investor community has been expecting that an upgrade would lead to the publication of the much-awaited prospectus of the firm, to see whether Anthropic can continue growing amidst stiff competition and rising consumer price sensitivity.