Opus 5.5 vs Opus 5 vs Fable 5.1: Coding Benchmark Results

We’ve now run three generations of frontier models through the same expert-created terminal-bench style task set: Fable 5.1 in September, Opus 5 in July, and, now Opus 5.5. For this analysis, the task set contained 200 trajectories, of 24 tasks, with every failure traced to a judge-confirmed root cause. A generational climb On the task set, pass@1 is 61.5% for…