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Documentation Index

Fetch the complete documentation index at: https://docs.anyfast.ai/llms.txt

Use this file to discover all available pages before exploring further.

Claude Opus 4.1 Thinking is the extended thinking variant of Claude Opus 4.1, available through Anyfast via an OpenAI-compatible interface. It combines Opus’s unmatched intelligence with step-by-step internal reasoning enabled by default, delivering the highest accuracy available on the most demanding tasks including advanced mathematics, scientific research, and complex architectural decisions.

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Key capabilities

  • OpenAI-compatible — Works as a drop-in replacement with the OpenAI SDK
  • Extended thinking — Step-by-step internal reasoning enabled by default
  • Maximum intelligence — The most capable reasoning model available
  • Deep analysis — Excels at advanced math, science, and complex problem solving
  • Long context — Handles large documents and multi-turn conversations
  • Streaming — Supports real-time token streaming via SSE

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Quick example

curl https://www.anyfast.ai/v1/messages \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-opus-4-1-20250805-thinking",
    "messages": [
      { "role": "user", "content": "Solve step by step: If 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 trip?" }
    ]
  }'

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Parameters

ParameterTypeRequiredDescription
modelstringYesMust be claude-opus-4-1-20250805-thinking
messagesarrayYesList of { role, content } objects
max_tokensintegerNoMaximum tokens to generate
temperaturefloatNo0–2. Controls randomness. Default: 1
streambooleanNoEnable SSE streaming. Default: false
top_pfloatNoNucleus sampling threshold. Default: 1
stopstring / arrayNoSequences that stop generation

API Reference

View the interactive API playground for Claude Opus 4.1 Thinking.