OpenAI’s GPT-6 Astra series has anchored trader consensus at 79% implied probability for second place on the Code Arena WebDev leaderboard through early October 2026. The model’s strong category performance in data analytics, consumer product builds, and content tools, combined with its September launch momentum, has kept it within striking distance of Anthropic’s leading Claude Opus 5.5 and Fable 5.1 variants. Anthropic’s consistent top rankings explain its 15% odds, while lower probabilities for Google, Alibaba, Moonshot, and others reflect narrower leads in agentic frontend workflows and fewer recent high-impact releases. With the October resolution approaching, any new model drops or sustained leaderboard shifts in the next few weeks could alter the second-place ordering.