Two Minute Papers · 2026-09-24 · notable
Two Minute Papers — 'Claude Opus 5.5 AI: A Massive Leap Forward'
Two Minute Papers covers Claude Opus 5.5, the Anthropic model released on 22 September 2026 at $4 / $20 per million tokens, 40% less than Opus 5, which Anthropic says performs at the level of Claude Fable 5.1 on most work.
Károly Zsolnai-Fehér looks at Anthropic's new Claude Opus 5.5.
What is it?
'Claude Opus 5.5 AI: A Massive Leap Forward' went up on Two Minute Papers on 24 September 2026, two days after Anthropic released the model. The video links Anthropic's Claude Opus 5.5 page as its main source.
How does it work?
Anthropic's own numbers for Claude Opus 5.5 include 66.4% on Terminal-Bench 4.0 against 52.3% for Opus 5, and 54.4% on FrontierCode v1.1 against 48.0%. Anthropic also says the model writes output 30% faster than Opus 5 and resists prompt injection better.
Why does it matter?
A cheaper Opus changes which model developers pick by default. Anthropic prices Opus 5.5 at $4 per million input tokens and $20 per million output tokens, 40% below Opus 5, and ships it on AWS, Google Cloud and Microsoft Azure.
Who is it for?
developers choosing a frontier model