Claude Code ultrathink now runs at xhigh effort on the 5.5 models and Fable 5.1

In the interactive terminal, the ultrathink keyword now runs its turn at xhigh effort on Opus 5.5, Sonnet 5.5, Haiku 5.5 and Fable 5.1 through Anthropic's API. Typed while Claude is working, it raises the rest of that turn.

Who is affected:

Claude Code users who type ultrathink in the terminal will get higher effort, which may use more of their usage limits.

Suggested next step:

Avoid typing ultrathink when you do not need xhigh effort.