FULL STORY

Gemini 4 Pro: Secret Arena Testing and Race to Launch

An unreleased model suspected to be Gemini 4 Pro appeared anonymously on LMArena, followed by reports that Google has entered the final training sprint and aims to launch Gemini 4 by year's end to catch up with Anthropic and OpenAI.

2026-09-26 ~ 2026-09-27 · 2 episodes · 10 posts

Episode 1 · Suspected Gemini 4 Pro Spotted in Anonymous Arena Testing (2026-09-26, 8 posts)

Between 09-26 and 09-27, multiple users reported spotting an unreleased checkpoint suspected to be Google Gemini 4 Pro on LMArena, possibly tested anonymously under the placeholder name "gemini-3.8-flash." Leaks claim it outperforms Claude Opus 5.5 and GPT-6 Astra at roughly 1/5 the cost with 2M context. None of this is officially confirmed, but it has triggered intensive community blind testing.

Confirmed

  • On 09-26, @cedricchee found Google had deployed a new Gemini 4 Pro checkpoint on Arena competing against GPT-6 Astra and Fable, with Gemini 4 Pro currently leading; @markk posted "don't underestimate Google DeepMind," previewing a strong comeback (unverified).
  • The same day, WorldofAI summarized the week's leaks: the Barium-B checkpoint reportedly beat Claude Opus 5.5 and GPT-6 Astra on new benchmarks, with release timing predictions; the roundup also mentioned Kimi K4 and a mystery model.
  • On 09-27, @CodeByPoonam relayed @TimJayas's testing: a model routed under "gemini-3.8-flash" on LMArena performed like the rumored Gemini 4 Pro — a mechanical hummingbird prompt produced high-quality output close to Fable, clearly better than current flagships.
  • @CodeByPoonam also compiled 10 community generation examples; @Wanderspor relayed a Reddit roundup claiming leaked specs of 1/5 competitor cost and 2M context, which would upend frontier-model economics if released in October.

Unconfirmed

  • Whether the anonymous model is truly Gemini 4 Pro: @aiforsuccess's comparison screenshots (relayed by @CodeByPoonam) showed it "completely crushing" Opus 5.5, but the poster cautioned it cannot be 100% confirmed; @markk's claims are also unverified.
  • A same-prompt comparison against Claude Opus 5.5 High concluded Gemini 4 "has not yet reached" that level, contradicting the "crushing" narrative.
  • No official data exists on rankings, pricing, or release timing.

Why it matters

  • If true, Google would field a highly competitive next-gen flagship against OpenAI (GPT-6 Astra) and Anthropic (Opus 5.5), potentially reshaping frontier-model economics with drastically lower costs — driving intense community attention, with some calling it potentially the biggest comeback in AI history.

Episode 2 · Google's Gemini 4 Enters Final Training Push, May Launch by Year-End (2026-09-26, 2 posts)

Google is preparing to launch Gemini 4 to close the gap with Anthropic and OpenAI. DeepMind chief Koray Kavukcuoglu confirmed the model has entered early post-training, with a possible launch before year-end.