Something unusual is happening on the LMSYS Chatbot Arena. AI researchers and developers testing blind prompts noticed that a model disguised under the alias gemini-3.8-flash was turning in performances far beyond what any lightweight tier could produce. It wasn’t long before tech trackers realized they were looking at an early preview checkpoint of Gemini 4 Pro.
The discovery quickly set social media ablaze. AI developer Hakm (@Hakm_x) was among the first to flag the suspicious performance boost to the broader community:
Gemini 4.0 pro new checkpoint on arena
codenamed : Gemini 3.8 flash pic.twitter.com/NfB4kGvEfb— Hakm (@hakmgpt) September 25, 2026
Shortly after, creator Bee (@thtbee_) posted a viral breakdown showcasing the model’s spatial visual capabilities and raw output density:
Gemini 4 Pro guys!!
I’m blown away by the quality and details here..
A new checkpoint of it is being tested in Arena under the name “gemini-3.8-flash”
Gemini is back in the game nd i can now see why google is so confident as to release an early preview version of it! pic.twitter.com/WhHU9zFJxN
— Bee (@thtbee_) September 25, 2026
As reported in recent updates tracking NokiaPowerUser’s coverage on Gemini 4 Pro leaks, this isn’t the first time Google has used anonymous Arena deployments to stress-test next-generation architectures before an official key note. However, the sheer leap in code synthesis speed and 3D visual math has caught even seasoned engineers by surprise.
From 3D Airships to F1 Cars: Pushing Three.js to Its Limits
The most striking evidence of Gemini 4 Pro’s presence comes from complex spatial rendering tests using Three.js. Rather than outputting simplified code snippets or static 2D mockups, the model generated complete, production-ready WebGL scenes in a single pass.
Tech creator Harshith (@Harshith_x) shared a remarkable result where the model built a fully interactive atmospheric vehicle in record time:
Gemini 4 Pro in Arena under the name “gemini-3.8-flash”
> photorealistic exploration airship using three js
it did in under 10 mins https://t.co/vi3i3oy81K pic.twitter.com/aIuXSJEKJs
— Harshith (@HarshithLucky3) September 25, 2026
AI researcher Lumina (@Lumina_x) ran a direct side-by-side comparison between the standard release model and the mysterious checkpoint, noting how rapidly the new candidate operates:
🚨A new Gemini 4 Pro checkpoint might be in arena
“Gemini 3.8 flash” is acting suspiciously good again
I’ll show a comparison against the real Gemini 3.8 Flash shortly, but this took under 5 minutes to make pic.twitter.com/32h24jH9bU
— Lumina (@LuminaBench) September 25, 2026
In even more demanding stress tests, developers asked the checkpoint to construct a modern Formula 1 race car from scratch. The prompt required a bespoke monocoque design, double-wishbone suspension with separate upper and lower A-arms at all four corners, PBR satin carbon fiber materials, realistic slick tires, and studio HDR lighting—all controllable via smooth camera orbiting.
Where previous generative models struggle with floating parts or broken geometry, this candidate authored clean, bug-free WebGL code that rendered accurately on the first attempt.
| Feature Category | Standard Production Flash Tier | Stealth Arena Candidate (gemini-3.8-flash) |
| 3D & WebGL Capabilities | Basic box/cylinder meshes & partial scripts | Bespoke geometry, working suspension A-arms & complex 3D scenes |
| Material Rendering | Simple Phong / Lambert shaders | Custom PBR materials (satin carbon fiber, clearcoat, rubber) |
| Generation Speed | Fast for basic text tasks | Renders full interactive 3D apps (F1 cars, airships) in 5–10 mins |
| Code Completion | Requires iterative bug fixes | Single-pass runnable projects with built-in orbit controls |
What This Stealth Test Means for Google’s Next Big Rollout
Google’s decision to deploy flagship preview candidates under lightweight aliases allows their team to gather real-world telemetry without the immediate pressure of an official product announcement. The benchmarks coming out of these tests suggest that Gemini 4 Pro focuses heavily on long-horizon task execution, native multi-turn coding, and deep spatial reasoning.
For web developers, 3D artists, and software engineers, these early leaks offer a clear glimpse of where generative AI is heading. When a model can architect a complex, physically styled 3D application from a single text prompt in under ten minutes, the boundary between conceptual design and production deployment becomes almost seamless.


















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