Model Selection

Kiro provides three powerful AI agent options to handle your development tasks: Auto, Claude Sonnet 4.0, and Claude Sonnet 4.5. Each offers distinct advantages depending on your needs and usage patterns.

Available models

Auto (Recommended)

Auto is Kiro's default intelligent model router that combines multiple frontier models with advanced optimization techniques.

Key benefits:

• Cost-effective – Approximately 23% less expensive than direct Sonnet 4 usage
• Smart routing – Automatically chooses the optimal model for each task
• Consistent quality – Delivers Sonnet 4-level results across different task types
• Plan efficiency – Makes your usage limits go further

What model does Auto use?

Auto uses best in class LLM models (Claude Sonnet 4 and alike) to provide you the best quality for the type of tasks assigned to the agent. We maintain a very high bar to ensure that the quality of what is offered under Auto compares to or exceeds the quality of separate models made available to our users.

Claude Sonnet 4.0

Direct access to Anthropic's Claude Sonnet 4.0 model for users who prefer consistent model selection or have specific requirements for using this particular model.

Key benefits:

• Predictable behavior – Same model for all interactions
• Direct access – No routing or optimization layers
• Full control – Complete transparency in model selection

Claude Sonnet 4.5

An experimental preview of Anthropic's Claude Sonnet 4.5 model for users who want to test the latest Anthropic model.

Key benefits:

• Task optimization – Better performance on specialized tasks
• Advanced logic – Enhanced reasoning capabilities
• Extended memory – Improved context handling for longer conversations

Cost comparison

Understanding the credit consumption differences:

Model	Credit Usage	Example Task Cost
Auto	1.0x	10 credits
Sonnet 4.0	1.3x	13 credits
Sonnet 4.5	1.3x	13 credits

Choosing the right model

Auto

Consider using Auto when:

• Cost efficiency matters – You want to maximize your plan's value
• General development work – Most coding, debugging, and planning tasks
• Variable task types – Working on diverse projects with different requirements
• Plan optimization – You want your limits to stretch further

Sonnet 4.0 & Sonnet 4.5

Consider using Sonnet 4.0 or Sonnet 4.5 when:

• Consistency is critical – You need predictable model behavior
• Specific requirements – Your workflow depends on Sonnet 4's particular capabilities
• Model transparency – You prefer knowing exactly which model handles each request
• Budget flexibility – Higher costs aren't a primary concern

How to switch models

In the chat interface

1. Access model selector

   • Look for the model dropdown in the chat interface
   • Default selection is Auto

2. Choose your model

   • Select Auto for intelligent routing
   • Select Claude Sonnet 4.0 for direct access
   • Select Claude Sonnet 4.5 for the latest Anthropic model

3. Confirmation

   • Your selection applies to subsequent messages
   • Current conversation context is maintained

Best practices

Maximizing efficiency

• Start with Auto – Use it as your default for most tasks
• Monitor usage – Track how different models affect your plan consumption
• Switch strategically – Use Sonnet 4 or Sonnet 4.5 for specific high-stakes tasks
• Experiment – Try both models for similar tasks to compare results

Cost management

• Plan accordingly – Factor model choice into your tier selection
• Track patterns – Understand which tasks benefit most from each model
• Optimize workflows – Adjust development practices based on model strengths
• Consider overages – Enable if you need flexibility beyond plan limits