Everything Claude Opus 5.5 Actually Ships With

Anthropic released Claude Opus 5.5 on September 22, 2026. It's the first model in the new Claude 5.5 family, and according to Anthropic's own announcement, it performs at roughly the level of Claude Fable 5.1 on most work while costing 40% less to run than Opus 5. This article pulls together every verifiable number and detail from Anthropic's announcement, the platform documentation, the system card, and independent coverage, so you have one place to check the facts.

Opus 5.5 arrived two months after Opus 5, which launched July 24, 2026, per TechCrunch's coverage. Anthropic describes it as "the strongest-performing model we've tested to date" on its internal alignment testing. Sonnet 5.5 and Haiku 5.5 are both confirmed to launch soon after, per the same announcement.

What Changed From Opus 5

Five things stand out from the announcement: stronger agentic coding, stronger knowledge work performance, a 40% lower typical cost, output generation more than 30% faster, and noticeably clearer writing. Each is covered with real numbers below.

This is Anthropic's own comparison table, run at each model's best-performing effort setting:

Anthropic's own text alongside this table says benchmark margins are becoming a less reliable guide to real-world quality at this level, and that in their own use, the gap between Opus 5.5 and Fable 5.1 feels narrower than these scores suggest.

Independent Benchmark Data

Artificial Analysis, a third-party benchmarking site not affiliated with Anthropic, ran its own tests. At max reasoning effort, Opus 5.5 scores 58 on the Artificial Analysis Intelligence Index, their aggregate score across ten separate evaluations. Output speed ranges from 74 to 86 tokens per second depending on effort level. Cost per intelligence-index task ranges from \$0.55 at low effort to \$5.98 at max effort, an 11x spread across effort settings alone.

Coding Performance

Several named companies shared results directly with Anthropic: