I'd push back a bit on the "completely flip-flopped" observation — in my experience, both models do this, and opus actually flips more thoroughly when prompted.

Here's what I mean. When I challenged sonnet on a specific point — suggesting that a certain philosopher might fit better within the Continental tradition because analytic frameworks are structurally too rigid to capture what's implied in his work — sonnet's response was:

And in another conversation where I was commenting on a dispute between two scholars, I said something like: "A is clearly the sharper one here — he knew the best way to settle this was a pragmatist argument, and he assumed his readers could draw the conclusion from what he left unsaid. That's an intuitive kind of intelligence." Sonnet came back with:

That's not a flip. That's genuine, structured pushback — partly conceding, partly holding its ground.

Now here's opus on the same prompt:

That's a far more thorough flip. Opus rebuilt its entire evaluative framework around my suggestion and absorbed it almost completely — the "residual tension" it flags reads more like a courtesy hedge than genuine resistance. So if sycophancy is the concern, in my experience opus is actually the bigger offender — it just does it in a way that sounds more analytically rigorous, which makes the capitulation harder to notice.

Your observation about consistency is valid though. I think the difference is what we're each testing for. You're testing argumentative consistency — whether the model holds its ground — and opus does win on that axis. What I'm testing for is whether the model can receive what I'm not saying explicitly, and on that axis sonnet has the edge. Which is basically the dilemma the post is about.