> something started changing around March.

The economics catching up with the providers in regards to how much compute they can burn per request and have it make sense for them financially?

A sort of model collapse where Opus 5 seems to love throwing out long paragraphs of text and it needs to be "fixed" by changing the output style and other patches.

I'm not sure, it might also catch up to Kimi K3 and GLM 5.3 and the models that I'm moving to from Anthropic.