Google is testing a newer Gemini 4 called Carbon inside its coding tool, Business Insider reports

Google employees are testing a newer Gemini 4 model internally named Carbon, Business Insider reported at 19:37 UTC today, citing internal documents and screenshots. It was made available in Jetski, Google's internal coding platform, in recent days. Gemini 4 Argon, the model Google announced on September 30, is still not public.

WHAT IS REPORTED

From Hugh Langley's story in Business Insider: Carbon may be a new checkpoint of Argon, but BI could not determine whether it will ship under the Argon name or as a different Gemini 4 model, and Google is not guaranteed to release it. An internal document shows Google tested a series of Gemini 4 models named Argon, Barium and Carbon, and notes that a model called "Barium-B" was the one chosen to become the public Argon. One employee told BI that Carbon "feels like Opus 5.5" for coding, adding that it needs more testing. Another said early versions of Argon felt behind on some coding tasks, closer to Claude Opus 5. Google declined to comment.

WHERE ARGON STANDS

Google said Argon goes to trusted testers in its Fairwind Program first, then to paid API customers and Google AI Ultra subscribers, with no date. Gemini 4 is not on the Gemini API model list our watcher reads, on OpenRouter or on models.dev (rechecked 20:30 UTC). The public traces so far are a GitHub commit on October 7 and a merged pull request by an Alphabet engineer on October 9, both crediting Gemini 4 Argon.

WHAT WE DO NOT KNOW

Whether Carbon ships, under what name, and when. The Opus 5.5 comparison is one employee's impression, not a benchmark. @LuminaBench first pointed to the report on X.