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Claude Opus 5.5 Explained: The New #1, in Plain English

Anthropic's Claude Opus 5.5 launched September 22, 2026 and went straight to the top of our standings. What changed, what it costs, and who should switch.

By Alex · · 2 min read

In this guide
  1. What is it?
  2. Why it's #1 this week
  3. What does it cost?
  4. Should you switch?
  5. Head-to-head

Anthropic released Claude Opus 5.5 on September 22, 2026, and it debuted at #1 in our Power Rankings and in our coding category. Here's why, without the jargon.

What is it?

Opus 5.5 is the first model in Anthropic's new Claude 5.5 family. It replaces Opus 5 as Anthropic's default flagship. Anthropic has said Sonnet 5.5 and Haiku 5.5, the smaller and cheaper siblings, will follow "in the weeks ahead."

It sits below Anthropic's two largest models, Claude Fable 5.1 and the access-restricted Claude Mythos 5.1, in price. But in several tests, it beats them.

Why it's #1 this week

  • Independent verdict: it took the top spot on the Artificial Analysis Intelligence Index with a score of 58 at max effort, several points ahead of the previous leader. GPT-6 Astra scores 53.
  • Coding: on Terminal-Bench 4.0 it scored 66.4% at extra-high effort, against 57.9% for GPT-6 Astra, 55.8% for Fable 5.1, 52.3% for Opus 5 and 37.3% for GPT-5.6 Sol.
  • Launch benchmarks: it led six of the nine benchmarks Anthropic published.

Where it doesn't win: GPT-6 Astra still leads on AutomationBench and Terminal-Bench-Science. If your work is mostly automating computer tasks, Astra is worth testing too.

What does it cost?

$4 per million input tokens and $20 per million output tokens. That's 20% cheaper than Opus 5, and well under the $10/$50 charged for Fable 5.1 and GPT-6 Astra.

AnthropicClaude Opus 5.5Language model · $4 in / $20 out

Should you switch?

  • If you code with AI: yes, try it. It's our #1 coding model this week.
  • If you're on Opus 5: it's better and cheaper. It's an easy upgrade.
  • If you pay for Fable 5.1: test your hardest tasks on Opus 5.5. You may be able to save 60%.
  • If you're a casual ChatGPT user: there's no need to switch just for this, but see ChatGPT vs Claude vs Gemini for which subscription fits you best.

Head-to-head

The crown rarely lasts long in 2026. Follow the weekly standings to see whether Opus 5.5 keeps it.

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