Just one more anecdote:
I'm on the enterprise team plan so a decent amount of usage.
In March I could use Opus all day and it was getting great results.
Since the last week of March and into April, I've had sessions where I maxed out session usage under 2 hours and it got stuck in overthinking loops, multiple turns of realising the same thing, dozens of paragraphs of "But wait, actually I need to do x" with slight variations of the same realisation.
This is not the 'thinking effort' setting in claude code, I noticed this happening across multiple sessions with the same thinking effort settings, there was clearly some underlying change that was not published that made the model get stuck in thinking loops more for longer and more often without any escape hatch to stop and prompt the user for additional steering if it gets stuck.
I’ve seen the point raised elsewhere that this could be the double usage promo that was available from the 13th of March to the 28th. ie. people getting used to the promo then feeling impacted when it finished.
Although it seems that enterprise wasn’t included, so maybe not in your case.
https://support.claude.com/en/articles/14063676-claude-march...
this timing matches my experience, enterprise plan, but using opus from vscode - finished a heavy refactor of a large C# codebase mid march, tried to do basically the same thing early april and couldn't
It's probably because you didn't specify "make no mistakes" /s
In all seriousness though, I've observed the same thing with my own usage.
Whenever I see Opus say “but wait, …”—which is all the time—I get a little bit closer toward throwing my computer out the window. Sometimes I just collapse the thinking section, cross my fingers, and wait for the answer. It’s too frustrating watching the thinking process.