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How to Switch Claude Models

I regularly switch between Claude models depending on the complexity of my tasks. Sonnet 4 for most daily work, Opus 4 when I need deep reasoning for complex refactoring or architectural decisions. I use Opus for debugging and solving algorithmic time-complexity issues.

Available Models​

  • Claude 4 Sonnet (claude-sonnet-4-20250514): Latest balanced performance and speed, excellent for most coding tasks, default choice for daily development
  • Claude 4 Opus (claude-opus-4-20250514): Maximum capability for complex tasks, best for complex architectural decisions, slower but more thorough responses, higher token usage
  • Opus Plan Mode: Hybrid approach using Opus 4.1 for planning and Sonnet 4 for execution, ideal for cost-effective intelligent development
  • Claude 3.5 Haiku (claude-3-5-haiku-20241022): Fastest and most cost-effective, good for simple repetitive tasks, limited reasoning capabilities

Switching Methods​

1. Command Line Flag (Start Session)

Switch models when starting Claude Code:

# Start with Sonnet 4 (default)
claude --model claude-sonnet-4-20250514

# Start with Opus 4
claude --model claude-opus-4-20250514

# Start with Haiku 3.5
claude --model claude-3-5-haiku-20241022

2. Session Command (Mid-Session)

Switch models during an active Claude Code session using the interactive /model command:

# Open interactive model selection menu
/model

# Available options:
# 1. Default (recommended) - Opus 4.1 for up to 20% of usage limits, then use Sonnet 4
# 2. Opus - Opus 4.1 for complex tasks (reaches usage limits faster)
# 3. Sonnet - Sonnet 4 for daily use
# 4. Opus Plan Mode - Use Opus 4.1 in plan mode, Sonnet 4 otherwise ✔

# Direct model specification (alternative method):
/model claude-opus-4-20250514
/model claude-sonnet-4-20250514
/model claude-3-5-haiku-20241022

Model Selection Strategy​

I observe distinct patterns in when each model excels:

  • Use Sonnet 4 for: Daily coding tasks, bug fixes and debugging, writing tests and documentation, code reviews and explanations, most refactoring work
  • Use Opus 4 for: Complex architectural decisions, large-scale refactoring across multiple files, performance optimization analysis, debugging complex interaction patterns, design pattern implementation, UI/UX design and frontend work
  • Use Opus Plan Mode for: Complex planning with cost efficiency, long development sessions, professional work needing Opus intelligence without full cost, avoiding 200K token pricing ($6/$22.50 per M tokens)
  • Use Haiku 3.5 for: Repetitive tasks, simple file operations, basic documentation updates
My Strategy

I start with Sonnet 4 for most tasks. Only switch to Opus 4 when encountering problems that require deeper reasoning. Use Haiku 3.5 when running low on usage limits but need quick assistance.

Token Awareness

Switching models mid-session increases token consumption because the new model must process the entire conversation history. Consider starting fresh sessions when changing models for long conversations.

See Also: Claude Code Usage Limits|Plan Mode|Tactical Model Selection|Pricing Plans

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