Recent releases of OpenAI's GPT-6 series and Anthropic's Claude Opus 5 models have driven top MathArena scores into the low-to-mid 80s as of late October 2026, with GPT-6.1 Sol leading at roughly 84% expected performance across recent competitions. These gains stem from improved chain-of-thought reasoning and tool use on uncontaminated problems from sources like AIME, HMMT, and FrontierMath. Trader sentiment reflects the tight race between OpenAI and Anthropic labs, limited remaining calendar time before December 31, and the difficulty of rapid further gains on saturated or harder tiers. New model updates or scaling announcements in November could still shift implied probabilities for ambitious score thresholds.