I'm not so sure. Opus 4.1 was more capable than 4.5, but it was too damn expensive and slow.
Opus 4.5 is like a cheaper, faster Opus 4.1. It's so much cheaper, in fact, that the weekly limits on Claude Code now apply to Sonnet, not to Opus, as they phased out 4.1 in favor of 4.5.
Capable how?
Able to independently find bugs, think through a complex codebase, better at "big picture" thinking and planning bigger edits, in my experience.