What is the --model Flag in Claude Code

The --model flag selects which Claude AI model to use for your session, enabling you to choose between Claude Sonnet 4.5, Claude Haiku 4.5 (near-frontier), Opus, and Claude 3.5 Haiku (legacy) based on task complexity, speed requirements, and cost considerations.

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How to Use It

Use --model when launching Claude Code with simple aliases like sonnet, opus, or haiku, or specify the full model name for precise version control.

claude --model claude-sonnet-4-5-20250929
claude --model claude-haiku-4-5
claude --model claude-opus-4-20250514
claude --model claude-3-5-haiku-20241022

Why Use Different Models

Different models offer distinct advantages for specific development scenarios. Sonnet 4.5 provides balanced performance for most coding tasks, Haiku 4.5 achieves 90% of Sonnet's capability at 3x cost savings, Opus delivers maximum reasoning for complex problems, and Haiku 3.5 (legacy) offers basic fast responses.

Strategic Usage:

• Sonnet 4.5: Regular development, file operations, routine coding (most tasks)
• Haiku 4.5: Lightweight agents, high-frequency tasks, 90% capability at 3x savings (near-frontier)
• Opus: Complex debugging, architecture decisions, security analysis (premium tasks)
• Haiku 3.5: Legacy simple edits, basic formatting (consider upgrading to Haiku 4.5)

I use Sonnet 4.5 for daily development work, Haiku 4.5 for lightweight agents and high-frequency tasks (90% capability at 3x cost savings), escalate to Opus for complex architectural decisions, and use Haiku 4.5 when approaching usage limits.

Model Access by Plan

Claude Pro ($17/month annually, $20/month monthly) - Access to Sonnet model with 5x usage limits compared to free tier.

Claude Max 5x ($100/month) - Access to Sonnet with 5x higher usage limits than Pro, plus limited Opus access.

Claude Max 20x ($200/month) - Full access to all models including unrestricted Opus with 20x higher usage limits than Pro.

API Usage - Pay-per-token pricing with access to all models based on API tier.

Smart Model Selection

Strategic model selection balances performance, cost, and development speed in Claude Code workflows. Plan with Opus, implement with Sonnet, use Haiku 4.5 for lightweight agents (90% capability, 3x savings) for optimal efficiency.

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See Also: Model Comparison|Pricing|Configuration