A third-party research institute Anthropic partnered with to test Claude Opus 4 recommended against deploying an early version because it tends to "scheme."

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.