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Claude Sonnet 4.5 Thinking is the Extended Thinking version of Claude Sonnet 4.5, available through Starrise AI via OpenAI-compatible interface. Combining Sonnet 4.5’s excellent balance of speed and capability with step-by-step internal reasoning enabled by default, it significantly improves accuracy on complex tasks while maintaining fast response times.

Key Capabilities

  • OpenAI-compatible — Drop-in replacement for the OpenAI SDK, no other code changes needed
  • Extended Thinking — Step-by-step internal reasoning enabled by default
  • Best coding model — Top-performing for code generation, refactoring, and debugging
  • Enhanced reasoning — Significantly improved accuracy on complex multi-step tasks
  • Long context — Supports large document processing and multi-turn conversations
  • Streaming — Real-time token streaming via SSE

Quick Example

Parameters

API Reference

View the interactive API Playground for Claude Sonnet 4.5 Thinking.