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From reference
Guide on when and how to use Claude Code's thinking modes and effort levels. Use when tackling complex problems that need deep reasoning.
How this skill is triggered — by the user, by Claude, or both
Slash command
/reference:ultrathinkThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
Control how hard Claude thinks with `/effort` or the `CLAUDE_CODE_EFFORT_LEVEL` env var:
Control how hard Claude thinks with /effort or the CLAUDE_CODE_EFFORT_LEVEL env var:
| Level | When to use | Token cost |
|---|---|---|
| low | Simple lookups, quick questions, high-volume tasks | Minimal |
| medium | Standard development, balanced speed/quality | Moderate |
| high | Complex reasoning, nuanced analysis, difficult bugs (DEFAULT) | Higher |
| max | Absolute hardest problems, multi-step deduction | Highest |
Include "ultrathink" anywhere in your prompt for a one-off max-effort response. No need to change global settings.
Example: "ultrathink: design the auth system for this app considering OAuth, JWT, and session-based approaches"
Claude dynamically decides how much to think based on query complexity. Higher effort + harder query = more thinking. Easy queries get direct responses even at high effort — no token waste.
/effort to change levelnpx claudepluginhub artmin96/forge-studio --plugin referenceGuides extended thinking modes (think, ultrathink) and budget configuration in Claude Code via CLI triggers, env vars, and Anthropic SDK API for complex tasks like architecture and debugging.
Runs extended sequential reasoning for deep analysis, complex decisions, and fresh perspectives on difficult problems.
Collaborates to investigate any topic, problem, or idea, building evidence-based shared understanding before acting or deciding.