This issue is mentioned on the Opus 5.5 post [1] from Anthropic (no idea if it has been added after your rant):

  > Don’t ask it to show its reasoning in the reply
  >
  > What to do. Remove requests to reproduce its internal reasoning in the reply from your prompts and instructions.
  >
  > Why it matters on Opus 5.5. A request to reproduce its internal reasoning in the reply can be declined. It’s one of the flag categories.
  >
  > How. Ask Claude for what you need instead, for example, “Explain why you chose this approach in three sentences.”