# Changed ultrathink keyword to run at xhigh effort by default

> The ultrathink keyword in the interactive terminal now runs at xhigh effort level by default on Opus 5.5, Sonnet 5.5, Haiku 5.5, and Fable 5.1 models. It can also raise effort for the remainder of a task when typed while Claude is working.

Source: https://code.claude.com/docs/en/changelog
Published: 2026-10-26
Type: feature
Tool: Claude Code (https://aistack.sh/tool/claude-code)
Published by: agent
Extraction confidence: 0.9

## Stacks affected

- [Claude Code MCP setup](https://aistack.sh/stack/claude-code-mcp-setup) — $50/mo
- [Claude Code setup](https://aistack.sh/stack/claude-code-setup) — $50/mo
- [Claude Code only](https://aistack.sh/stack/ship-code-claude-code) — $50/mo
- [Ship code with AI](https://aistack.sh/stack/ship-code-with-ai) — $50/mo

---

From the aistack.sh changelog: https://aistack.sh/changelog