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[Unconfirmed]

# 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

![Screenshot of @testingcatalog's X post: Google has reportedly been testing Gemini 4 Carbon on Arena under Argon 4 since October 31st. It seems to be one of the best models among](https://leakly.com/assets/images/gemini-4-carbon-h-arena-argon-4-hero.jpg)

@testingcatalog's post on X, with counts as of 09 Nov 2026 12:49 UTC. [Live post on X](https://x.com/testingcatalog/status/2117009417342468398)

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.

> **🚨 AI News | TestingCatalog** @testingcatalog
>
> Google has reportedly been testing Gemini 4 Carbon on Arena under Argon 4 since October 31st.
> It seems to be one of the best models among those announced to date.
> Stunning outputs 👀 https://t.co/SPjBsukQkn https://t.co/oXCDor0089
>
> 747 likes · 40 reposts · counts as of 09 Nov 2026, 12:49 UTC
>
> — 🚨 AI News | TestingCatalog (@testingcatalog) [November 1, 2026](https://twitter.com/testingcatalog/status/2117009417342468398)

[Leakly track record](https://leakly.com/leakers/testingcatalog/)

[TestingCatalog](https://www.testingcatalog.com/google-tests-new-gemini-4-carbon-checkpoint-arena/) 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](https://nqbrief.com/en/tech/google-gemini-4-carbon-h-arena-argon-4/) 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.

## What we know

* A model labeled Argon 4 is being served on Arena.
* Testers tie it to a Carbon-H build.

## What we don't know

* Whether Argon 4 is Gemini 4 Carbon.
* When an updated Carbon ships.

## What would confirm it

A Google model announcement or changelog naming the checkpoint.

## Sources

* [Original X post by @testingcatalog](https://x.com/testingcatalog/status/2117009417342468398)
* [Google tests a new Gemini 4 Carbon checkpoint on Arena](https://www.testingcatalog.com/google-tests-new-gemini-4-carbon-checkpoint-arena/)
* [Google tests Carbon-H Gemini 4 build as Argon 4 on Arena — NQ Brief](https://nqbrief.com/en/tech/google-gemini-4-carbon-h-arena-argon-4/)

[Unconfirmed]

## What happened later

Google has not confirmed that Argon 4 is a Gemini 4 Carbon checkpoint.

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