Suspected Gemini 4 Pro Spotted in LMArena Under '3.8 Flash' Alias

On September 17, several AI benchmarking accounts spotted an anonymous model coded "Gemini 3.8 Flash" on LMArena, speculating it is actually a checkpoint of Google's upcoming Gemini 4 Pro (or 4.0 Pro) undergoing pre-release blind testing under a disguised name. Google has not confirmed anything.

Confirmed

Anonymous test entries appeared on the Arena leaderboard, showing battle links for "Gemini 3.8 Flash (high)" against "Gemini 4".
Community users ran comparison tests against the existing Gemini 3.8 Flash.
One user tested it with the "pelican riding a bicycle SVG" prompt, and the model performed impressively.

Not yet confirmed

Whether the anonymous model is truly Gemini 4 Pro remains community speculation; Google has not verified it.
After hands-on testing, @cedricchee judged its 3D capabilities to fall well short of earlier versions of 4 Pro—close to the leap seen from the Sol-to-Astra generation—though he gave this only about 75% confidence.

Why it matters

Models appearing on LMArena under disguised codenames typically signal official blind testing ahead of a formal release, often hinting a launch is near.
@teortaxesTex quipped that if the anonymous model really is Gemini 4 Pro, Arena's current test prompts (such as SVG generation) are too easy to fully gauge a flagship model's true capabilities.
If the identity holds, this would provide the first directly comparable data point between Gemini 4 Pro and the existing 3.8 Flash.

2026-09-17 ~ 2026-09-17 · 6 related posts

Primary sources

Suspected Gemini 4 Pro spotted in Arena as gemini-3.8-flash; critics want harder tests — teortaxesTex · 2026-09-17 19:31 (UTC+08:00)
Gemini 4 Pro Checkpoint Spotted in LMArena Amid Codename Leak — cedric_chee · 2026-09-17 16:16 (UTC+08:00)
Gemini 4 Pro checkpoint spotted in Arena, 3D gains rival Sol-to-Astra jump — cedric_chee · 2026-09-17 20:08 (UTC+08:00)

[source] Gemini 4 Pro Checkpoint Spotted in LMArena Amid Codename Leak — cedric_chee · 2026-09-17
Gemini 4 Pro checkpoint spotted testing in LMArena under the name 'Gemini 3.8 flash' — airesearch12 · 2026-09-17
Rumor: Gemini 4.0 Pro spotted testing in LMArena under the name Gemini 3.8 Flash — gaganghotra_ · 2026-09-17
[source] Suspected Gemini 4 Pro spotted in Arena as gemini-3.8-flash; critics want harder tests — teortaxesTex · 2026-09-17
[source] Gemini 4 Pro checkpoint spotted in Arena, 3D gains rival Sol-to-Astra jump — cedric_chee · 2026-09-17
Gemini 4 Pro Checkpoint Spotted in LMArena — cedric_chee · 2026-09-17