If Opus 4.6 was the turning point model for handling routine tasks and substantial tasks, then Opus 5.5 (actually Fable5 already had this capability when it first launched, it just cost too much) is definitely the turning point model for open-ended problems, ambitious goals, and large-scale tasks. I used two 20x usages, and after experiencing it, the agent is definitely ready to move on to the next stage. I was so excited I couldn't sleep - this is definitely a moment worth commemorating.
Introducing Claude Opus 5.5, the first model in our new Claude 5.5 family.
It performs at the level of Claude Fable 5.1 for most tasks, and costs 40% less to run than Opus 5.