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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 4.8 is Anthropic’s most capable generally available model, available through Anyfast via an OpenAI-compatible interface. It builds on Claude Opus 4.7 with improved long-horizon agentic coding, more reliable tool triggering, and better compaction handling.

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Key capabilities

  • OpenAI-compatible — Works as a drop-in replacement with the OpenAI SDK
  • 1M context window — 128K max output tokens
  • Adaptive thinking — Smart reasoning that triggers only when the task needs it
  • Fast mode — Up to 2.5x higher output speed at premium pricing (research preview)
  • Mid-conversation system messages — Append updated instructions without restating the full system prompt
  • Lower cache minimum — 1,024 token minimum cacheable prompt length
  • 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-4-8",
    "messages": [
      { "role": "user", "content": "Explain quantum entanglement in simple terms." }
    ]
  }'

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Parameters

ParameterTypeRequiredDescription
modelstringYesMust be claude-opus-4-8
messagesarrayYesList of { role, content } objects
max_tokensintegerNoMaximum tokens to generate
streambooleanNoEnable SSE streaming. Default: false
stopstring / arrayNoSequences that stop generation
temperature, top_p, and top_k are not supported on Claude Opus 4.8. Setting them to non-default values returns a 400 error. Use prompting to guide the model’s behavior.

API Reference

View the interactive API playground for Claude Opus 4.8.