Google launched Gemini 3 Pro, the first model to break 1500 Elo on LMArena, with a 'Deep Think' reasoning mode for the hardest problems. It took the outright frontier lead across benchmarks and public preference rankings.

The release reportedly triggered a 'code red' inside OpenAI, which scrambled its roadmap and rushed GPT-5.2 out within weeks to answer it. The November–December 2025 stretch became one of the most intense head-to-head periods in AI history.

Gemini 3 Pro cemented Google's return to the frontier after years of playing catch-up, and its Deep Think mode became the template for maximum-effort reasoning tiers.