**Recent stealth testing of an advanced model on LMSYS Chatbot Arena has driven strong trader consensus around an imminent high-scoring Gemini Pro debut.** In mid-September 2026, multiple developers reported a model labeled “gemini-3.8-flash” on Arena exhibiting capabilities far beyond the official Gemini 3.8 Flash (released September 2 with ~1494 Text Arena Elo). Users highlighted exceptional performance in complex SVG generation, spatial reasoning, long-horizon coding, and agentic tasks, with leaked benchmarks reportedly exceeding GPT-6 Astra and leading Claude variants. The model, internally codenamed Argon, reportedly featured a 10-million-token context window and persistent memory—specs consistent with a frontier Pro release. This follows Google’s May 2026 I/O announcement of Gemini 3.5 series (Flash launched; Pro repeatedly delayed) and the decision to accelerate development toward Gemini 4 Pro. Current Arena leaders remain Anthropic’s Claude variants (1531 Elo peak), with Gemini 3.1 Pro at 1505. Traders view the disguised testing as preparation for an official Pro-labeled debut, likely in October, that would resolve the market’s 1480+ and 1490+ outcomes at high implied probabilities. Key upcoming catalysts include any Google confirmation, fall hardware event, or direct leaderboard addition of a qualifying Pro model before year-end. Uncertainties around exact timing, naming, and final benchmark scores persist given Google’s history of timeline slippage.