Google is about to roll out a new AI model. Employees say they're testing another that's way better.

Alphabet and Google CEO Sundar Pichai Bloomberg/Getty Images Google employees are testing a newer version of the company's flagship AI model, Gemini 4. The latest internal release is codenamed Carbon. Some employees compared the latest internal update to Anthropic's Opus 5.5 model. As Google prepares to roll out its new Gemini 4 'Argon' model to the public, staff inside the company are testing better versions that may further close the gap with rivals. Most recently, employees have been trying a new version of Gemini 4 internally named Carbon, according to documents and screenshots seen by Business Insider. The model — possibly a new update to Argon, also known as a "checkpoint" — was made available inside Google's internal coding platform, Jetski, in recent days. One employee told Business Insider that Carbon "feels like Opus 5.5" for coding, referring to Anthropic's most powerful model for long-term agentic coding.