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cto.new works with the best frontier LLMs for chat and code generation. Chat supports:
  • Anthropic Sonnet 4.5 (default)
  • OpenAI GPT-5
Planning and coding agents support:
  • GPT-5-Codex (default)
  • GPT-5
  • Anthropic Claude 4.5 Sonnet
  • Google Gemini 2.5 Pro
  • Sonnet 4.5 - GPT-5-Codex Alloy
Model alloys combine two LLM models in the same agent thread. Our research shows it improves performance by several percentage points.
You can set the model for planning and coding on a per repo basis from the repository settings menu.
Performance may vary. Be prepared to experiment with settings when changing models