There's no shot they're doing that. Would be suicide as soon as anyone notices, and by the looks of it, they didn't even clean up the URL here to "hide" the fact that this is Kimi K2.5 so i doubt there's any grand conspiracy here.

What's way more likely is that Opus has been quantized by anthropic or something similar. Or that Opus was updated and didn't work well with Cursor's harness after. Or a token caching issue. Etc.