Gemini 4 Carbon early test results are in ahead of release

Barely a week after Gemini 4 Argon went public, Google's next checkpoint, Carbon, is showing up on LMArena and with partners. Early testers say it's a clear step up in 3D work, with a few familiar weak spots.

Gemini 4 Argon has only been public for about a week, and Google already seems to be lining up its successor. Gemini 4 Carbon, the checkpoint Business Insider first reported on inside Google's Jetski coding tool earlier this month, now appears to be reaching people outside the company.

According to X user Lentils, a Carbon early access program has started, with partners getting access and the model being tested on LM Arena. They expect a release "very close" and describe Carbon as noticeably better than Argon at 3D work, while frontend and UI output is still weak. It's also slower, though, in their words, "less lazy."

Gemini 4 Carbon EAP has officially started. Early access has been given to partners and it's being tested in LMArena. The release is very close.

It's noticeably better than Gemini 4 Argon at 3D, though frontend/UI is still bad. It's also slower but less lazy.

An output from the updated Carbon checkpoint 😼

Like I said in my previous post, Carbon is noticeably better than Gemini 4 Argon at 3D (tho still not perfect). It seems like Google is currently focusing on improving that domain before moving on to frontend/UI https://t.co/2SSFlH0JRo pic.twitter.com/RMIcBU8XHf

Meanwhile, reliable leaker Lyra also quoted that post with a screenshot of Google's Gemini API Early Access Program docs, which describe an invite-only group of developers, researchers and partners getting upcoming Gemini API and AI Studio models before launch.

Gemini 4 Cabrón https://t.co/Z7EdDF1hg2 pic.twitter.com/OLBxTYEngk

The Trusted Tester Agreement is quite clear: unreleased models, codenames, benchmarks, and outputs should remain private until launch, and the models shouldn’t be used in production. Google asks testers to send evaluations and comparisons privately, making the steady stream of Carbon outputs on X awkward.

Gemini 4 Carbon (updated checkpoint) pic.twitter.com/htcGYGWG8Q

Now, on the early outputs, Lumina shared most of them in multiple posts. They say Carbon has been on Arena since yesterday and that it's a clear improvement over Argon. However, they noted it's "incredibly slow," roughly two to four times slower depending on the task. Their voxel pagoda comparison sets Carbon next to other frontier models, and they say it has "noticeably higher quality than Argon does."

Gemini 4 Carbon (Voxel Pagoda) vs Frontier Models

These are some frontier models against it for reference, it has noticeably higher quality than Argon does, as i said it's a lot slower though https://t.co/jQ9O0FR3rr pic.twitter.com/AvRLvAbTTM

They also ran the classic SVG pelican on a bicycle test. Again, they call out weak UI and slow speed, but say Carbon otherwise "feels good" across the wide range of tasks they've tried.

Gemini 4 Carbon (SVG Pelican on Bicycle)

Few things to point out, the UI isn't very good, and it's also incredibly slow

Otherwise it feels good an a vast array of tasks I have tried it on https://t.co/jQ9O0FQvBT pic.twitter.com/JC4D0CzQaN

It's worth noting, however, that these are arena matchups and hand-picked prompts, not benchmarks, and nobody can be sure which checkpoint they're served.

While we wait for the new Carbon model to arrive, Logan Kilpatrick also just posted that Google processed around 25 trillion tokens in the first 72 hours after Argon launched. So Google might want to keep up its pace before the hype dies down.

A faster cadence of Gemini 4 checkpoints would also matter beyond the chatbot. We recently spotted broader Computer Use permissions in the Gemini desktop app, and Google appears to be building Nano Banana 3 Pro on top of Gemini 4, with a November to December window in view.

Meanwhile, Google isn't the only company pushing new models left and right. OpenAI is preparing GPT-6.1 Terra, which has surfaced in Microsoft code, and Anthropic's Fable 5.5 is already reaching partners, with several more models apparently on the way. If Carbon fixes Argon's 3D weaknesses without making users wait too long, Google could have a strong answer ready.

We'll have to wait and test it ourselves once it arrives before jumping to conclusions.

A mystery model called Kibitz has turned up on Arena, and testers believe it's Moonshot AI's Kimi K3.1. Early outputs look strong, especially for 3D work, and a launch may be days away.

A new Managed Agents section is in the works for AI Studio, bringing agent setup, environments, credentials, triggers and run history into one place.