Anthropic leads market-implied odds at 78% for the top Code Arena WebDev AI model by end of November, driven by Claude Opus 5.5's dominant leaderboard position with an 1810 Elo-style score on LMArena WebDev, well ahead of OpenAI's GPT-6 Astra at 1773. Traders appear to weigh Anthropic's September 2026 release of Opus 5.5 and subsequent Sonnet 5.5, which deliver superior performance on agentic web development tasks involving multi-step reasoning, UI generation, and tool use. OpenAI trails at 16.5% despite GPT-6 family updates, while Google, Meta, and others sit lower amid weaker benchmark results. The 50% levels for many entrants reflect uncertainty in a fast-moving field where new model releases or capability shifts could alter standings before resolution. These odds aggregate trader assessments of demonstrated AI capabilities on public leaderboards rather than guarantees.