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ultrathink

Invoke deep sequential thinking for complex problem-solving. Use when the user says 'use ultrathink', 'ultrathink', or when tackling problems that require careful step-by-step reasoning, planning, hypothesis generation, or multi-step analysis.

$ Installer

git clone https://github.com/dashed/claude-marketplace /tmp/claude-marketplace && cp -r /tmp/claude-marketplace/plugins/ultrathink ~/.claude/skills/claude-marketplace

// tip: Run this command in your terminal to install the skill

SKILL.md

View on GitHub →

name: ultrathink description: "Invoke deep sequential thinking for complex problem-solving. Use when the user says 'use ultrathink', 'ultrathink', or when tackling problems that require careful step-by-step reasoning, planning, hypothesis generation, or multi-step analysis." license: MIT

Ultrathink

Ultrathink activates the Sequential Thinking MCP tool (mcp__sequential_thinking__sequentialthinking) to enable deep, structured reasoning through complex problems.

When to Use

Invoke ultrathink when:

User explicitly requests it ("use ultrathink", "ultrathink this")
Complex problems requiring step-by-step decomposition
Planning and design with room for revision
Analysis that might need course correction
Problems where full scope isn't initially clear
Multi-step solutions requiring maintained context
Situations requiring hypothesis generation and verification

How to Use

Call the sequential thinking tool with structured thoughts:

mcp__sequential_thinking__sequentialthinking:
  thought: "Your current thinking step"
  nextThoughtNeeded: true/false
  thoughtNumber: 1
  totalThoughts: 5 (estimate, can adjust)

Parameters

Parameter	Type	Required	Description
`thought`	string	Yes	Current thinking step - analysis, revision, question, or realization
`nextThoughtNeeded`	boolean	Yes	True if more thinking needed, false when done
`thoughtNumber`	integer	Yes	Current thought number in sequence
`totalThoughts`	integer	Yes	Estimated total thoughts (can adjust up/down)
`isRevision`	boolean	No	Whether this revises previous thinking
`revisesThought`	integer	No	Which thought number is being reconsidered
`branchFromThought`	integer	No	Branching point thought number
`branchId`	string	No	Branch identifier
`needsMoreThoughts`	boolean	No	Signal that more thoughts needed at "end"

Key Capabilities

Dynamic adjustment: Revise total thought count as understanding evolves
Revision support: Question or revise previous thoughts
Branching: Explore alternative approaches from any point
Hypothesis cycle: Generate hypothesis, verify, repeat until satisfied
Non-linear thinking: Don't need to build linearly - can backtrack

Process Pattern

Start with initial estimate of needed thoughts
Break down the problem systematically
Question or revise previous thoughts as needed
Generate solution hypotheses when appropriate
Verify hypotheses against the chain of thought
Add more thoughts if needed, even at the "end"
Express uncertainty when present
Set nextThoughtNeeded: false only when truly done

Example

Thought 1: "Let me analyze this authentication bug. The user reports login failures after password reset..."
Thought 2: "Looking at the code flow: reset generates token -> user clicks link -> new password set. The issue might be..."
Thought 3: "Hypothesis: The session isn't being invalidated after password change. Let me verify..."
Thought 4 (revision): "Actually, reconsidering thought 2 - the token expiry might be the issue, not session..."
Thought 5: "Verified: Token expiry is set to 1 hour but email delivery can take longer. Solution: extend to 24 hours."

Best Practices

Start with reasonable thought estimate (3-7 for most problems)
Don't hesitate to revise or add thoughts
Mark revisions with isRevision: true and revisesThought: N
Express uncertainty rather than guessing
Use branching for exploring alternatives
Only set nextThoughtNeeded: false when confident in solution