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Alphabet and Google CEO Sundar Pichai Bloomberg/Getty Images Google employees are testing a newer version of the company's flagship AI model, Gemini 4.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.

However, they caveated that they would need to test it more.

Google's internal testing shows how the company is moving fast with its new generation of Gemini 4 models, which it announced in late September .

It also underscores how Google is competing in the fast-moving race for AI coding agents.

Anthropic and OpenAI have pulled ahead among developers with models built for complex engineering work.

Early versions of Argon tested internally were generally well received by staff, according to conversations with employees and internal message threads seen by Business Insider.

However, one employee said early versions of Argon felt behind on some coding tasks, comparing the model to Claude Opus 5, an older Anthropic release.

The latest updates might close that gap, but Google is not guaranteed to release them.