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xAI (Grok)

The xai provider supports xAI's Grok models through an API interface compatible with OpenAI's format. The provider supports both text and vision capabilities depending on the model used.

Setup​

To use xAI's API, set the XAI_API_KEY environment variable or specify via apiKey in the configuration file.

export XAI_API_KEY=your_api_key_here

Supported Models​

The xAI provider includes support for the following model formats:

Grok-4 Models​

  • xai:grok-4-0709 - Latest flagship reasoning model (256K context)
  • xai:grok-4 - Alias for latest Grok-4 model
  • xai:grok-4-latest - Alias for latest Grok-4 model

Grok-3 Models​

  • xai:grok-3-beta - Latest flagship model for enterprise tasks (131K context)
  • xai:grok-3-fast-beta - Fastest flagship model (131K context)
  • xai:grok-3-mini-beta - Smaller model for basic tasks, supports reasoning effort (32K context)
  • xai:grok-3-mini-fast-beta - Faster mini model, supports reasoning effort (32K context)
  • xai:grok-3 - Alias for grok-3-beta
  • xai:grok-3-latest - Alias for grok-3-beta
  • xai:grok-3-fast - Alias for grok-3-fast-beta
  • xai:grok-3-fast-latest - Alias for grok-3-fast-beta
  • xai:grok-3-mini - Alias for grok-3-mini-beta
  • xai:grok-3-mini-latest - Alias for grok-3-mini-beta
  • xai:grok-3-mini-fast - Alias for grok-3-mini-fast-beta
  • xai:grok-3-mini-fast-latest - Alias for grok-3-mini-fast-beta

Grok-2 and previous Models​

  • xai:grok-2-latest - Latest Grok-2 model (131K context)
  • xai:grok-2-vision-latest - Latest Grok-2 vision model (32K context)
  • xai:grok-2-vision-1212
  • xai:grok-2-1212
  • xai:grok-beta - Beta version (131K context)
  • xai:grok-vision-beta - Vision beta version (8K context)

You can also use specific versioned models:

  • xai:grok-2-1212
  • xai:grok-2-vision-1212

Configuration​

The provider supports all OpenAI provider configuration options plus Grok-specific options. Example usage:

promptfooconfig.yaml
# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-3-mini-beta
    config:
      temperature: 0.7
      reasoning_effort: 'high' # Only for grok-3-mini models
      apiKey: your_api_key_here # Alternative to XAI_API_KEY

Reasoning Support​

Grok-3 introduces reasoning capabilities for specific models. The grok-3-mini-beta and grok-3-mini-fast-beta models support reasoning through the reasoning_effort parameter:

  • reasoning_effort: "low" - Minimal thinking time, using fewer tokens for quick responses
  • reasoning_effort: "high" - Maximum thinking time, leveraging more tokens for complex problems
info

Reasoning is only available for the mini variants. The standard grok-3-beta and grok-3-fast-beta models do not support reasoning.

Grok-4 Specific Behavior​

Grok-4 introduces significant changes compared to previous Grok models:

  • Always uses reasoning: Grok-4 is a reasoning model that always operates at maximum reasoning capacity
  • No reasoning_effort parameter: Unlike Grok-3 mini models, Grok-4 does not support the reasoning_effort parameter
  • Unsupported parameters: The following parameters are not supported and will be automatically filtered out:
    • presencePenalty / presence_penalty
    • frequencyPenalty / frequency_penalty
    • stop
  • Larger context window: 256,000 tokens compared to 131,072 for Grok-3 models
  • Uses max_completion_tokens: As a reasoning model, Grok-4 uses max_completion_tokens instead of max_tokens
promptfooconfig.yaml
# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4
    config:
      temperature: 0.7
      max_completion_tokens: 4096

Region Support​

You can specify a region to use a region-specific API endpoint:

providers:
  - id: xai:grok-2-latest
    config:
      region: us-west-1 # Will use https://us-west-1.api.x.ai/v1

This is equivalent to setting base_url="https://us-west-1.api.x.ai/v1" in the Python client.

Live Search (Beta)​

You can optionally enable Grok's Live Search feature to let the model pull in real-time information from the web or X. Pass a search_parameters object in your provider config. The mode field controls how search is used:

  • off – Disable search
  • auto – Model decides when to search (default)
  • on – Always perform live search

Additional fields like sources, from_date, to_date, and return_citations may also be provided.

promptfooconfig.yaml
providers:
  - id: xai:grok-3-beta
    config:
      search_parameters:
        mode: auto
        return_citations: true
        sources:
          - type: web

For a full list of options see the xAI documentation.

Vision Support​

For models with vision capabilities, you can include images in your prompts using the same format as OpenAI. Create a prompt.yaml file:

prompt.yaml
- role: user
  content:
    - type: image_url
      image_url:
        url: '{{image_url}}'
        detail: 'high'
    - type: text
      text: '{{question}}'

Then reference it in your promptfoo config:

promptfooconfig.yaml
# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
prompts:
  - file://prompt.yaml

providers:
  - id: xai:grok-2-vision-latest

tests:
  - vars:
      image_url: 'https://example.com/image.jpg'
      question: "What's in this image?"

Image Generation​

xAI also supports image generation through the Grok image model:

providers:
  - xai:image:grok-2-image

Example configuration for image generation:

promptfooconfig.yaml
# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
prompts:
  - 'A {{style}} painting of {{subject}}'

providers:
  - id: xai:image:grok-2-image
    config:
      n: 1 # Number of images to generate (1-10)
      response_format: 'url' # 'url' or 'b64_json'

tests:
  - vars:
      style: 'impressionist'
      subject: 'sunset over mountains'

For more information on the available models and API usage, refer to the xAI documentation.

Examples​

For examples demonstrating text generation, image creation, and web search, see the xai example.

You can run this example with:

npx promptfoo@latest init --example xai

See Also​