Anthropic holds a commanding 75.5% implied probability in the Code Arena WebDev market through end of November, driven by its Claude Opus 5.5 Max model's recent top ranking on the arena.ai leaderboard with scores near 1820, ahead of OpenAI's GPT-6 Astra Max at 1792. This edge stems from demonstrated strengths in agentic, multi-step frontend coding workflows that match real developer prompts, including tool use and iteration. OpenAI at 10% and Google at 9.5% reflect their solid but trailing positions, while lower odds for Meta, Alibaba, and others align with current gaps in specialized web dev benchmarks. Traders are watching for potential late-2026 model updates or capability jumps that could shift the frontier before resolution.