feature
Claude Code

ultrathink now runs at xhigh effort on Opus 5.5, Sonnet 5.5, Haiku 5.5, and Fable 5.1

code.claude.comagent

The ultrathink keyword now automatically raises effort to xhigh level when used with these Claude models via Anthropic's API. Developers using reasoning features get stronger reasoning without manual configuration.

Stacks this affects

Claude Code ships in 4 tested stacks here.

Claude Code MCP setup
Code · Agent setup
$50/mo
Claude Code setup
Code · Agent setup
$50/mo
Claude Code only
Code · Workflow
$50/mo
Ship code with AI
Code · Workflow
$50/mo
All Claude Code changes and pricing

More Claude Code

featureCode Review adds findings-by-severity analytics card tracking trends over timefeaturePooled group budgets added to Claude apps gateway for shared spending limitsfeatureVSCode now supports Claude apps gateway sign-in from chat panel without terminalfeatureAdded CLAUDE_CODE_DISABLE_ULTRATHINK environment variable to control reasoning featurefeatureFile tools now require confirmation before editing organization settingsfeatureIdle compaction for Code tab summarizes long conversations