Gemini 4: Google is internally testing ‘Carbon’, a version that employees compare to Opus 5.5 in terms of programming

Ahead of Argon’s public roll-out, Google’s teams are testing a new version of Gemini 4 on their internal code platform. Its release is not guaranteed.

According to internal documents seen by Business Insider, Google employees have been testing a new version of Gemini 4 internally called "Carbon" for a few days, made available on Jetski, the in-house development platform. One employee believes that the model is similar to Claude Opus 5.5 in terms of code, but said that it should be tested more.

Argon, Barium, Carbon

Google has been testing a series of Gemini 4 models under the codenames Argon, Barium and Carbon, which do not correspond to the public names: the "Barium-B" variant has thus become the model marketed under the Argon name. It is unclear whether Carbon will be an update to Argon or another member of the Gemini 4 family, and Google has not committed to releasing it.

Argon, announced at the end of September and presented as focused on cyber defense, must first be open to partners in the Fairwind program before a wider deployment. The first versions had been considered to be behind on certain programming tasks, while Anthropic and OpenAI took the lead with developers.