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Grok 4.1 Fast Reasoning

xaixai/grok-4-1-fast-reasoning

xAI's latest fast reasoning model with 2M token context window. Combines speed with strong reasoning capabilities, supporting text and image inputs with function calling and structured outputs.

Context Length
2M
Max Output
66K
Input Priceper 1M tokens
$0.360/ 1M tokens
Output Priceper 1M tokens
$0.900/ 1M tokens

Modalities

textimage→text

Pricing Breakdown

TypeRate
Input$0.360 / 1M tokens
Output$0.900 / 1M tokens

Supported Parameters

temperaturemax_tokenstop_ptoolstool_choiceresponse_formatreasoningstop

API Usage Examples

Use the global api.therouter.ai endpoint shown below for new integrations; the legacy China accelerated endpoint is retired.

cURL
curl https://api.therouter.ai/v1/chat/completions   -H "Content-Type: application/json"   -H "Authorization: Bearer $THE_ROUTER_API_KEY"   -d '{
    "model": "xai/grok-4-1-fast-reasoning",
    "messages": [
      {"role": "user", "content": "Summarize the key points from this input."}
    ]
  }'
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