Claude Sonnet 4 is the smaller model, but it's still a major upgrade in power from the earlier Sonnet 3.7. Anthropic claims Sonnet 4 is much better at following instructions and coding.

Opus 4 is tuned for coding and long-running agent-based workflows. Sonnet 4 is similar, but tuned for reasoning and balanced for efficiency – meaning it's less expensive to run.

According to Anthropic, Claude Sonnet 4 is a significant upgrade to Claude Sonnet 3.7, offering improved coding and reasoning along with the ability to respond to instructions more precisely.

Free users of Claude can only access the new Sonnet 4 model. However, Pro, Max, Team, and Enterprise Claude plan users can access both models and extended thinking.

It balances power and efficiency, making it suitable for various uses. While not as powerful as Opus 4, Sonnet 4 offers a great mix of capability and practicality, with enhanced control over its ...

He added that once testers got their hands on Opus 4 and Sonnet 4, “no one wanted to give up access.” He called the models “much, much stronger as agents and as coders.” ...

The Sonnet 3.7 model progressed further in the game than Sonnet 3.5, and now Anthropic says the Claude 4 Models are playing the best yet, thanks to a new ability to store "memory files" of key ...