When Anthropic launched its Claude Sonnet 4 model in May, users immediately took to the general-use large language model. “I was honestly surprised by the amount of adoption of Sonnet 4,” says Dianne Na Penn, Anthropic’s head of product management, research; she says 75% of API users switched to Sonnet 4 within a week of its release. The model quickly became a favorite with coders, capturing more than double the market share of OpenAI among enterprise developers, according to a survey by Menlo Ventures. Post-release, Anthropic significantly expanded Sonnet’s context window, allowing it to handle much longer prompts—including up to 75,000 lines of code—and more than double the size of competitors’ including OpenAI’s GPT-5. The company released Sonnet 4.5 in September, showing even quicker and more accurate calculations.
Disclosure: Investors in Anthropic include Salesforce, where TIME co-chair and owner Marc Benioff is CEO.