Google appears to be testing a new Gemini 4 Carbon build on Arena as "Argon 4"
Testers say the Carbon-H checkpoint is better at coding, design and 3D. Google has not commented.
Leaked on 01 November 2026
Google has reportedly been testing Gemini 4 Carbon on Arena under the name Argon 4 since October 31, @testingcatalog reported on November 1, quoting a tester who says the build is called Carbon-H.
TestingCatalog says testers find Carbon-H much better than earlier Carbon builds at coding, design and 3D, with some outputs "strangely similar to Opus 5.5." NQ Brief also reports that web development and front-end UI work remain weak points, according to testers.
Google has not confirmed that Argon 4 is a Gemini 4 Carbon checkpoint.