Skip to main content
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

curl https://ai.alad.com/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-5-20250929-thinking",
    "messages": [
      { "role": "user", "content": "Solve step by step: A train travels 120 km in 2 hours, then slows down and travels 80 km in 3 hours. What is the average speed for the entire journey?" }
    ]
  }'

​
Parameters

ParameterTypeRequiredDescription
modelstringYesFixed value: claude-sonnet-4-5-20250929-thinking
messagesarrayYesArray of { role, content } objects
max_tokensintegerNoMaximum number of tokens to generate
temperaturefloatNo0–2, controls randomness, default 1
streambooleanNoEnable SSE streaming, default false
top_pfloatNoNucleus sampling threshold, default 1
stopstring / arrayNoSequences where generation stops

API Reference

View the interactive API Playground for Claude Sonnet 4.5 Thinking.