2026-09-18 06:57:16
Opus 5.5 efficiency jump — but only at lower effort levels. At low, medium and high effort it is 1.9–3.3× faster and 1.6–2.4× cheaper than Opus 5. Python at low effort now costs $0.38 and 35 seconds, against Opus 5's $0.75 and 117 s. At xhigh the two models are indistinguishable; at max 5.5 is 1.3× slower in Python and 1.9× slower in Go with high variability. Three Python runs at max took 1030, 1688 and 3333 seconds. Opus 5's defaults to high; 5.5's defaults to medium. https://github.com/adrianco/retort/blob/main/model-blog.md