EFFORT

Since Claude Code 2.1.311, typing ultrathink runs that turn at xhigh effort on Opus 5.5, Sonnet 5.5, Haiku 5.5 and Fable 5.1. When it works, when it does not, and caps.

Low, medium, high, xhigh, and max for adaptive reasoning control.

Interactive UI to switch models and effort sliders mid-session.

Configure model, effort, tools, MCP servers, and invocation scope.