Anthropic's new Opus 5.5 and Sonnet 5.5, explained for business owners and creators. What changed, which model to use, how to set the new effort dial, and five jobs to hand them this week.
● Beginner
- Updated Oct 3, 2026
- SECTION 01
- Meet Your Two New Teammates
You open Claude on a Monday to draft the week's newsletter, and the model menu says something new: Opus 5.5. You paste in the same rough notes as always. The draft comes back faster, cleaner, and with the main point in the first sentence instead of buried in paragraph four. Your prompt didn't change. The model did.
Anthropic released two new Claude models in the last week of September 2026. Claude Opus 5.5 arrived on Tuesday, September 22. Claude Sonnet 5.5 followed six days later, on Monday, September 28. They're the first members of what Anthropic calls the Claude 5.5 family, and a third model, Haiku 5.5, is promised "in the coming weeks."