Claude Sonnet 4

Claude Sonnet 4 is a hybrid reasoning model that offers both near-instant responses and extended thinking capabilities. It significantly improves upon Claude Sonnet 3.7’s performance while maintaining efficiency for everyday use cases.

Key Capabilities

Dual Operating Modes

• Standard mode: Fast responses for typical tasks
• Extended thinking: Deep reasoning for complex problems (up to 64K tokens)

Core Features

• Advanced coding capabilities with 72.7% performance on SWE-bench
• Enhanced instruction following and steerability
• Parallel tool execution
• Memory improvements when given access to local files
• Web search integration during extended thinking (beta)
• 65% reduction in shortcut/loophole behavior compared to Sonnet 3.7

Performance Benchmarks

Coding

• SWE-bench Verified: 72.7%
• Described as “state-of-the-art” for coding tasks

Reasoning (with extended thinking)

• GPQA Diamond: 75.5% (70.0% without extended thinking)
• MMMLU: 88.2% (85.4% without extended thinking)
• MMMU: 77.6% (72.6% without extended thinking)
• AIME: 40.0% (33.1% without extended thinking)

Pricing

• Input: $3 per million tokens
• Output: $15 per million tokens

Safety and Reliability

• Implements AI Safety Level 3 (ASL-3) protections
• Extensive testing and evaluation
• Reduced tendency to use shortcuts or exploit loopholes
• Thinking summaries available (condensed from full reasoning when needed)

Use Cases

Sonnet 4 is optimized for:

• Daily coding tasks and development workflows
• Complex instruction following
• Multi-file codebase operations
• Autonomous application development
• Long-form reasoning and analysis
• Agent-based workflows

Limitations

• Does not match Claude Opus 4 performance in most domains
• Extended thinking features require paid plans
• Memory capabilities depend on developer-provided file access