Anthropic’s September 22 release of Claude Opus 5.5 has driven the 66% market-implied odds for claude-opus-5.5-high, as the model delivers Fable 5.1-level results on coding, agentic workflows, and knowledge tasks while cutting runtime costs by roughly 40% and improving speed and safety scores. Official benchmarks show gains on Terminal-Bench, FrontierCode, and CursorBench, with external evaluations from METR and Frontier Design confirming stronger alignment performance than prior Opus versions. Fable 5.1-max sits at 12% because its earlier September 1 launch established the prior frontier for long-horizon work, yet traders see limited near-term upside before the October 12 snapshot. With no major competitor releases reported in the final days of September, the recent Opus update and its practical advantages anchor current trader consensus.