I honestly am very disappointed with this. I've only learned about CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING and showThinkingSummaries: true from this post. I've been wondering for a while where the summaries went and am always hoping like roulette that it thinks a lot. No wonder if there suddently is an "adaptive thinking" mode. I would have opted out 2 months ago if it was documented or communicated in any way publicly. Why change behavior without notice or any new user facing settings.
I just googled "CLAUDE_CODE_DISABLE_ADAPTIVE_THINKING" and it seems like many people don't know about it.
And ULTRATHINK sets the effort to high, but then there is also /effort max?