26, 2026. (AP Photo/Patrick Sison) Pages from the Anthropic website and the company’s logo are displayed on a computer screen in New York on Thursday, Feb.
Claude produced more than 90% of the contributions to Anthropic’s codebase in September, according to the company’s S-1 filing with the US Securities and Exchange Commission. The numbers back it up: average daily code contributions per engineer in the July to September quarter were more than 45 times their average daily level in 2024. Anthropic’s workforce grew from about 940 employees at the end of 2024 to roughly 5,300 by late September, and the company says its strategy is to keep growing the business without adding staff at the same pace. Regrettable attrition, meanwhile, stood at about 1% for the 12 months ending September 30. In March 2025, he said AI would be writing 90% of code within three to six months, and could be writing essentially all of it within a year.
The 335-page document, filed on October 26, sets Anthropic up for a Nasdaq listing under the ticker “ANT”, possibly as early as next month. Anthropic says it now relies on its models to research, design and develop the models that come after them, a process the company calls closing the loop. “Claude itself has become one of the most powerful drivers of our progress,” the company wrote in the filing. By October that year, he told an audience at Salesforce’s Dreamforce conference that the number already held true within Anthropic. Boris Cherny, who heads Claude Code, said in June that he had not written a line of code by hand in about eight months.
Anthropic’s own AI now writes most of the software inside the company. The filing also shows how the job of an Anthropic engineer has changed. Its software engineers now mostly direct and review Claude’s output instead of writing code line by line. Coding is only one part of a wider shift. Claude runs experiments, generates training data, and automates evaluations and safety audits. It has also helped with algorithmic improvements that let Anthropic get more out of its computing resources. That reliance shapes hiring too. A recent internal report noted that it has been filling a smaller share of junior technical positions as AI agents take on coding, bug fixes and similar tasks. The figure will not surprise anyone who has followed CEO Dario Amodei. He also argued that companies might end up needing more engineers, since each one becomes far more productive with AI doing the bulk of the typing. Some teams inside the company have gone even further. The filing pairs all this with a note of caution. Among its long list of risk factors, Anthropic warns that its AI systems may behave in unintended, misaligned or autonomous ways that could damage the business. That is the same system now responsible for nine in every ten contributions to the company’s codebase, and increasingly, for helping build the next Claude. You use AI every day. Now get your AI Quotient. Take the AIQ test.