Claude Opus 4 has been updated to Claude Opus 4.1.

This is a correctly named incremental update, with the bigger news being ‘we plan to release substantially larger improvements to our models in the coming weeks.’

It is still worth noting if you code, as there are many indications this is a larger practical jump in performance than one might think.

We also got a change to the Claude.ai system prompt that helps with sycophancy and a few other issues, such as coming out and Saying The Thing more readily. It's going to be tricky to disentangle these changes, but that means Claude effectively got better for everyone, not only those doing agentic coding.

Tomorrow we get an OpenAI livestream that is presumably GPT-5, so I’m getting this out of the way now. Current plan is to cover GPT-OSS on Friday, and GPT-5 on Monday.