Google may already have a successor to Gemini 4 Carbon in testing. A few prominent AI watchers on X are sharing outputs from what they describe as a new internal Google checkpoint called Krypton, and the early verdict is that it’s a clear step up from Carbon. Google hasn’t announced or confirmed the model, and there are no official benchmarks, so everything below comes from user posts.
For context, Google announced Gemini 4 Carbon on October 28, barely two weeks after Gemini 4 Argon became generally available. Carbon took the top spot on version 5.0 of Artificial Analysis’s Intelligence Index with a score of 59, ahead of Claude Opus 5.5 at 58 and GPT-6 Astra at 57, but access is currently limited to vetted cyber defenders. If Krypton is real and better, Google would be iterating on its frontier model at an unusually fast clip.
“Even better than Carbon”
X user lyra (@lyraxana) wrote that Google “released a new internal checkpoint called Krypton” and that the results so far are “really impressive and even better than Carbon.” The post has racked up over 126,000 views.
lyra followed up with a side-by-side titled “Gemini 4 Krypton vs Carbon vs Argon,” posting two videos of elaborate voxel-style scenes: a castle on a hillside, a harbor village with sailing ships, a lighthouse, a windmill and a waterfall, all rendered in a Minecraft-like style. The post doesn’t label which clip came from which model, and it doesn’t say how the poster got access to Krypton.
A PS4 controller, drawn in pure code
Chetaslua (@chetaslua), who regularly posts early model tests, shared a head-to-head of Carbon and Krypton on the same prompt: draw a PS4 controller as pure SVG, in one shot. His take was that Krypton “thinks a lot in a good way,” taking roughly double the time but delivering “the best google model ever made.” He singled out the detail on the PlayStation logo as proof of what he called a real comeback for Google.
The graphic notes that both files contain no images, data URIs, external references or scripts. The biggest gap is in reasoning: Krypton used about 22,000 thinking tokens against Carbon’s roughly 4,000, which would explain both the longer wait and the extra detail. The graphic labels the model “krypton-a,” which hints that more than one Krypton variant may be in testing, though that’s speculation.
An anime built from a single prompt
Chetaslua’s second post is the more dramatic one. He claims Krypton produced an animated, anime-style clip, a vine-covered tower on a floating island above a sea of clouds at night, entirely in code with no external assets, from a single prompt. He says generation took 39 minutes and 16 seconds at 105 tokens per second, which works out to roughly 250,000 tokens of output. He called it “the RSI they were talking about,” apparently a reference to recursive self-improvement, and tagged Google’s Logan Kilpatrick and Zachary Nado. He says the code and prompt are available to verify.
That kind of run length is only practical because Google has been expanding output limits. Gemini 4 Argon supports up to 1 million output tokens in a single response, up from 64K previously, a change Google said was meant to give the model room to reason for hundreds of thousands of tokens on hard problems.
Early days
A few caveats apply. These are hand-picked demos from individual users on a model Google hasn’t acknowledged, and “internal checkpoint” could mean anything from a near-final release candidate to an experiment that never ships. Visual showcases like SVGs and voxel scenes are also a narrow slice of what a frontier model does, and Carbon’s own numbers already showed trade-offs on benchmarks like OSWorld and FrontierSWE.
Gemini 4 Krypton isn’t the only Gemini model that is rumoured. Google is also reportedly testing a Flash version of Gemini 4 Carbon called Gemini 4 Hydrogen, which also appeared to have won favourable reviews from early testers.
Still, the pattern in the posts is consistent: more thinking, longer generations and noticeably more detail. After a long stretch in which Google had fallen out of the top five AI labs on Artificial Analysis’s index, the company is now shipping at a pace that makes a Krypton follow-up to Carbon plausible. Whether it gets a formal launch, and when, is something only Google can say.