Good-faith answer: I can't be certain. But I've been using CC since its release, and Cursor before that (and actually going all the way back to GPT3 to do codegen in the Playground). After getting used to the CC workflow, the way that I use it has been pretty consistent. To be specific, I use basically the same AGENTS.md with small modifications for each project, and I live almost exclusively in Plan mode and the best model (currently Opus 4.5).

My initial prompting is boilerplate at this point, and looks like this:

(Explain overall objective / problem without jumping to a solution)

(Provide all the detail / file references / past work I can think of)

(Ask it "what questions do you have for me before we build a plan?")

And then go back and forth until we have a plan.

Compared to my work with CC six months ago, it's just much more capable, able to solve more nuanced bugs, and less likely to generate spaghetti code.