❯ Google is reportedly testing a new Gemini 4 version called Carbon internally, and employees say it feels close to Claude Opus 5.5 for coding

The next version before Argon shipsAccording to Business Insider, as Google prepares to roll out its Gemini 4 Argon model to the public, staff are already testing a newer version internally named Carbon. The report is based on documents and screenshots it reviewed; Carbon appeared in recent days on Jetski, Google’s internal coding platform.

"Feels like Opus 5.5"One employee told Business Insider that Carbon “feels like Opus 5.5” for coding, adding that more testing was needed. Another said early versions of Argon felt behind on some coding tasks, comparable to Anthropic’s older Claude Opus 5. An internal document shows Google has tested a series of Gemini 4 models codenamed Argon, Barium and Carbon, with Barium-B chosen as the one to be known publicly as Argon.

Where the public rollout standsGoogle announced Gemini 4 in late September, saying Argon delivers frontier performance on some coding and knowledge-work benchmarks and has a strong focus on defensive cybersecurity, with partners in a vulnerability-testing program getting access first. According to TestingCatalog, paid API customers and Google AI Ultra subscribers follow, and Google has not confirmed a date for wider availability. Whether Carbon will be released, and under what name, is also undetermined.

Developers are waiting for a reasonBusiness Insider writes that Anthropic and OpenAI have pulled ahead among developers with models built for complex engineering work, and Google is under pressure to show it can still compete at the frontier. Google launched its enterprise Gemini agent this week, and for an agent to work well, the underlying model’s coding ability comes first.

▮ SIGNALInternal codenames are piling up while public access remains limited to a few partners; model iteration is now moving faster than release and safety evaluation can keep pace with.