Google's unreleased Gemini 4 Argon model spotted in Antigravity

Hidden references to a Gemini 4 Argon model with low, medium, and high reasoning effort settings have appeared in Antigravity, according to Testing Catalog, which reported the finding on X on October 9, 2026.

Business Insider reports that Google employees are testing an internal Gemini 4 checkpoint called "Carbon," which performs at the Opus 5.5 level on coding tasks.

The references show a model name and reasoning settings, but the reports do not establish a release date or confirm that Argon and Carbon are the same model. Google has not commented in the reports provided.