Polymarket traders have put the probability of Anthropic releasing its next Mythos-class AI model at 74% by Sept. 9, 2026, and 81% by Sept. 15, with the odds rising to 87% by the end of the month. The related contract family has recorded more than $233,000 in trading volume, while broader Polymarket markets covering the AI model race have generated more than $6 million. Traders also assign 96% odds to a new Opus model and 85% odds to a new Sonnet model by Dec. 31, 2026. Anthropic launched Claude Fable 5 and Claude Mythos 5 on June 9, 2026, after a limited preview began in April. Mythos is Anthropic's highest-capability model tier, with advanced code reasoning and vulnerability-detection capabilities, and Project Glasswing partners have used the models to identify more than 23,000 vulnerabilities. Anthropic has not formally announced a September release, leaving the contracts to reflect trader expectations based largely on the company's release pattern rather than disclosed plans.