ultrathink

name	ultrathink
description	Use when the user asks about "thinking modes", "effort levels", "how hard should Claude think", or wants to pick between low/medium/high/xhigh/max for a task — explains the cost/quality tradeoff per level and recommends one based on the work shape.
when_to_use	Reach for this when picking an `effort:` value for a new skill or `/effort` for the current turn, or when teaching the reasoning modes. Do NOT use for changing the effort level — use the `/effort` command instead; ultrathink is the explanation, not the switch.
disable-model-invocation	true
model	haiku
allowed-tools	[]
logical	explanation of effort levels emitted with cost/quality tradeoff per level

Ultrathink: Master Claude's Reasoning Modes

Effort Levels

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
xhigh	Hardest tasks needing deeper reasoning; persists in settings	High
max	Deepest reasoning, session-only (set per-turn or via env)	Highest

Ultrathink Keyword

Include "ultrathink" anywhere in your prompt to request deeper reasoning on that turn. Claude Code recognizes the keyword and adds an in-context instruction to think harder — your session effort level is unchanged. No need to change global settings.

Example: "ultrathink: design the auth system for this app considering OAuth, JWT, and session-based approaches"

Ultracode Keyword (a different mechanism)

ultracode is a separate keyword. ultrathink adds an in-context "think harder" instruction for one turn; ultracode (or /effort ultracode) tells Claude Code to plan a native dynamic workflow — a background script that orchestrates many subagents with verification built in — for the task. It pairs xhigh effort with automatic workflow orchestration, lasts the session, and uses more tokens per task. Reach for ultrathink to reason harder in place; reach for ultracode to fan a large task out to a verified multi-agent workflow. It appears in the /effort menu only on Claude Code builds that support dynamic workflows — if you don't see it there, the feature isn't available.

When Deep Thinking Helps

• Complex architectural decisions
• Multi-step debugging with non-obvious root causes
• Code that has security implications
• Algorithm design and optimization
• Evaluating trade-offs between approaches

When Deep Thinking Wastes Tokens

• Simple file reads or searches
• Straightforward bug fixes with clear cause
• Formatting or renaming
• Standard CRUD operations

Adaptive Thinking (current Opus and Sonnet)

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.

Monitor Tool

Use the Monitor tool to stream events from background scripts in real time. Useful for watching long-running subagent output without polling.

Toggle

• Shortcut: Alt+T (toggle thinking visibility)
• Command: /effort to change level
• Focus View: Ctrl+O (condensed view — shows prompts, tool summaries, responses only)