Claude 4 Sonnet is a leaner model, with improvements built on Anthropic's Claude 3.7 Sonnet model. The 3.7 model often had problems with overeagerness and sometimes did more than the person asked it to do, Amodei said. While it's a less resource-intensive model, it still performs well, he said.

Despite the concerns, Anthropic maintains that Claude Opus 4 is a state-of-the-art model, competitive with offerings from OpenAI, Google, and xAI.

Anthropic released its latest Claude 4 models — Claude Opus 4 and Claude Sonnet 4 — but Windsurf users were not given immediate access. Varun Mohan, co-founder of Windsurf, said in a post on X, “Unfortunately, Anthropic did not provide our users direct access to Claude Sonnet 4 and Opus 4 on day one.”