extended-thinking
Extended thinking (ultrathink) configuration for Claude API. Activate for complex reasoning tasks, deep analysis, multi-step problem solving, and tasks requiring careful deliberation. Enables Claude's internal reasoning with configurable thinking budgets.
npx skills add majiayu000/claude-skill-registry --skill extended-thinking --agent claude-code
Same command for any agent — swap --agent for codex, cursor, copilot.
Weekly change comes from our own snapshots, not the repository page — it measures attention, not adoption.
# Extended Thinking (Ultrathink) Skill Enable Claude's extended thinking capabilities for complex reasoning tasks that benefit from internal deliberation before responding. ## When to Use - **Complex problem solving** requiring multi-step reasoning - **Code architecture decisions** with multiple trade-offs - **Debugging complex issues** needing systematic analysis - **Strategic planning** with many variables - **Mathematical or logical proofs** - **Security analysis** requiring threat modeling - **Performance optimization** with multiple factors ## Supported Models | Model | Extended Thinking | Summarized Thinking | |-------|------------------|---------------------| | Claude Opus 4.5 | ✓ Full | - | | Claude Opus 4.1 | ✓ Full | - | | Claude Opus 4 | ✓ | ✓ Summarized | | Claude Sonnet 4.5 | ✓ Full | - | | Claude Sonnet 4 | ✓ | ✓ Summarized | | Claude Haiku 4.5 | ✓ Full | - | ## API Configuration ### Basic Extended Thinking (Python) ```python import anthropic client = anthropic.Anthropic() response = client.messages.create( model="claude-sonnet-4-20250514", max_tokens=16000, thinking={ "type": "enabled", "budget_tokens": 10000 # Minimum 1,024 }, messages=[{ "role": "user", "content":
- When to Use
- Supported Models
- API Configuration
- Basic Extended Thinking (Python)
- TypeScript Configuration
- Streaming (Required for maxtokens > 21,333)
- Budget Recommendations
- Tool Use with Extended Thinking
- Interleaved Thinking (Claude 4 Models)
- Constraints
- Best Practices
- Integration with Claude Code
- See Also
The CLI automatically handles extended thinking for supported models Use opus or sonnet models for complex tasks claude --model claude-opus-4-5-20250514 "Analyze this codebase architecture"
What does the extended-thinking skill do?
Extended thinking (ultrathink) configuration for Claude API. Activate for complex reasoning tasks, deep analysis, multi-step problem solving, and tasks requiring careful deliberation. Enables Claude's internal reasoning with configurable thinking budgets.
How do I install it?
Run `npx skills add majiayu000/claude-skill-registry --skill extended-thinking --agent claude-code` — it drops the skill into your project so the agent can pick it up. Swap the --agent value for codex, cursor or copilot if you use one of those.
Where does this skill come from?
From majiayu000/claude-skill-registry, a repository with 534 stars. We read it straight from the repository tree rather than a submitted listing, so what you see here is what is actually published.
Is a popular skill a good skill?
Not necessarily. Stars measure attention, not adoption — a repository can trend for a week and be abandoned. That is why we show the weekly change from our own snapshots next to the total, instead of a single flattering number.