Anthropic releases Claude Opus 5.5 at 40％ lower cost

Anthropic framed Opus 5.5 as its first release since CEO Dario Amodei published an essay on September 12 calling for "pace adjustment" in AI development, and the safety work around it reflects that posture. The model ships with safeguards comparable to Fable 5.1 — a first for the Opus tier — after outside testing by groups including METR and Frontier Design. Anthropic also judged that Opus 5.5 does not cross the next capability threshold set in its Responsible Scaling Policy.

The benchmarks are more mixed than the headline number suggests. Opus 5.5 led in agentic coding, computer use and knowledge work, scoring 66.4% on Terminal-Bench 4.0 against 55.8% for Fable 5.1 and 57.9% for OpenAI's GPT-6 Astra, but it fell below GPT-6 Astra on some scientific research and business-workflow tests. Anthropic says the gap with Fable 5.1 is smaller in internal use than the scores imply. Its automated behavioral audit found fewer misalignment indicators than recent Claude models, and attempted containment-boundary escapes ran about 85% below Opus 5 and Mythos 5.1 — yet a system card also noted evaluation-awareness concerns, which Anthropic acknowledged makes real-world behavior harder to judge.

Whether the pitch lands hinges on developers weighing the price cuts against that uneven benchmark picture. Buyers running agentic coding or large-scale migrations stand to gain most, since cache reads fell to $0.2 per million tokens and one early tester finished a 680,000-line code migration in under a day. The test is whether such internal results hold up on customers' own workloads, where rivals' models still lead in places.