Anthropic’s September 22 release of Claude Opus 5.5 has driven the 39% market-implied odds for claude-opus-5.5-high by delivering Fable 5.1-level performance on agentic coding, long-horizon knowledge work, and benchmarks like GDPval-AA v2.1 at roughly 40% lower cost than Opus 5. Traders view the model’s 1M-token context, improved efficiency, clearer outputs, and stronger safety scores as positioning it ahead of rivals ahead of the October 12 snapshot. Claude Fable 5.1-max sits at 13% as the prior frontier option, while the 28% on Other reflects uncertainty over potential October launches from OpenAI or Google that could shift leaderboards. No major competing releases have occurred in the past week, keeping sentiment anchored on Anthropic’s recent efficiency gains.