Claude AI's UltraThink feature returns with practical usage guidance

UltraThink returns to Claude AI

Claude AI has brought back the UltraThink feature after removing it and receiving user complaints (referenced as GitHub #19098). The feature now has clearer practical applications based on testing.

Configuration details

According to the source:

• Medium effort is now the default setting for Opus 4.6 (Max/Team)
• High effort can be set permanently using the /model command
• UltraThink functions as a one-turn override to high effort, then returns to your default setting

When to use UltraThink

The source provides specific guidance on when UltraThink is most valuable:

• Medium effort handles approximately 90% of daily coding tasks adequately
• UltraThink is recommended for the remaining 10% of challenging scenarios including:
  • Debugging complex race conditions
  • Security-critical code review
  • Complex multi-file refactoring

Practical testing results

A test on a race condition bug revealed:

• Medium effort successfully identified the issue
• UltraThink identified the same issue plus a token expiry edge case the user didn't know existed
• UltraThink also provided a testing strategy for the edge case

The key insight from testing: "Medium gives you the answer. Ultrathink gives you the answer plus the things you didn't know to ask about."

If you're already using high effort permanently, typing "Ultrathink" has no effect — you're already at maximum effort setting.