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Claude 4 Sonnet vs Opus for Claude Code

Claude 4 Sonnet and Claude 4 Opus serve different roles in Claude Code development workflows. Understanding their strengths helps you optimize both performance and costs by choosing the right model for each task type.

How to Choose Between Them​

Set Claude 4 Sonnet as your default for most development work, then tactically switch to Opus for complex architectural decisions:

# Set Sonnet as default
export ANTHROPIC_MODEL="claude-sonnet-4-20250514"

# Switch to Opus for specific complex tasks
claude --model claude-opus-4-20250514 "Review codebase"

I use Opus for 90% of my development work and only switch to Sonnet for simple, routine tasks.

Why Choose Strategically​

Cost Optimization - Claude 4 Opus costs approximately 5x more than Claude 4 Sonnet, making tactical selection crucial for budget management.

Performance Balance - Sonnet provides excellent performance for standard development tasks while Opus excels at complex reasoning and architectural decisions. Opus can be overkill for simple tasks, making responses slower than necessary.

Workflow Efficiency - Using the right model for each task type optimizes both speed and quality without overspending on unnecessary capability.

Claude 4 Sonnet Best For:

  • Large Codebases - 1M token context window via API (5x larger than Opus)
  • Standard Development - Feature implementation and routine coding tasks
  • Debugging & Troubleshooting - Most debugging scenarios and error resolution
  • Code Generation - Moderate complexity code creation and editing
  • Documentation - Writing and editing technical documentation
  • Task Coordination - Workflow management and sub-agent orchestration
  • Extended Sessions - Long development conversations without context resets
  • Daily Development - 80% of typical Claude Code usage

Claude 4 Opus Best For:

  • Complex Architecture - System design requiring deep reasoning and planning (200K context)
  • Strategic Planning - Multi-phase project planning and implementation strategies
  • Algorithm Optimization - Time complexity analysis and performance optimization
  • Multi-Step Logic - Intricate problems with complex dependencies
  • Creative Solutions - Novel approaches requiring nuanced understanding
  • Code Reviews - Architectural judgment and design pattern evaluation
  • Complex Refactoring - Large-scale changes (though Sonnet's 1M context may handle many cases)
  • Critical Decisions - When maximum reasoning capability is essential

Cost-Performance Benefits:

  • 5x Cost Difference - Tactical selection can reduce costs by 60-80%
  • Context Window Advantage - Sonnet's 1M tokens via API often eliminates need for Opus on large projects
  • Quality Maintenance - Right-sized intelligence for each task type
  • Budget Flexibility - Savings allow for more complex task experimentation
  • Orchestration Opportunities - Cost savings enable sub-agent delegation strategies

I observe that most developers default to Opus for everything, missing significant cost optimization opportunities while not necessarily improving output quality for routine tasks.

Opus Plan Mode - Best of Both Worlds​

The newest option bridges the Sonnet vs Opus dilemma: Opus Plan Mode automatically uses Opus 4.1 for planning and analysis, then switches to Sonnet 4 for execution and implementation.

How It Works:

  • Planning Phase - Leverages Opus 4.1's advanced reasoning for strategic analysis
  • Execution Phase - Uses efficient Sonnet 4 for implementation and code changes
  • Automatic Switching - Seamless transition without user intervention

Key Advantages:

  • Intelligent Planning - Get Opus-quality strategic thinking where it matters most
  • Cost Efficiency - Avoid expensive Opus execution costs through smart model switching
  • Professional Workflow - Ideal for Max subscribers doing complex development work

Perfect For:

  • Complex projects requiring both intelligent planning AND cost efficiency
  • Long development sessions where token optimization matters
  • Professional developers who need Opus intelligence without full Opus expense
  • Teams balancing quality and budget constraints

Activation: Select option 4 in /model command: "Use Opus 4.1 in plan mode, Sonnet 4 otherwise"

This hybrid approach eliminates the need to choose between Sonnet and Opus by strategically using each model's strengths at the optimal time.

Tactical Strategy

Start with Sonnet as your default model. When you encounter complex architectural decisions or intricate reasoning challenges, explicitly switch to Opus for those specific tasks.

Cost Awareness

Since Opus costs 5x more than Sonnet, using Sonnet for routine tasks allows you to affordably use Opus when you truly need its advanced reasoning capabilities.

See Also: Tactical Model Selection|Change Model|Token Optimization|Pricing

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