promptfoo--promptfoo/site/docs/providers/xai.md

title, description, keywords

title	description	keywords
xAI (Grok) Provider	Use xAI Grok models for text, image, video, and voice workflows, including Grok 4.3, Grok Imagine, regional endpoints, and Responses API tools.	xai grok grok-4.3 grok-imagine-image grok-4 grok-3 reasoning vision llm agentic

xAI (Grok)

The xai provider supports xAI's Grok models through an API interface compatible with OpenAI's format, including text, vision, image generation, video generation, and voice workflows.

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

When xAI is the selected fallback provider family, Promptfoo can use xAI defaults for grading, suggestions, synthesis, and web search. xAI does not currently expose a public embeddings or moderation API, so those defaults fall back to OpenAI when xAI is selected. Explicit provider IDs in your config still take precedence.

Supported Models

The xAI provider includes support for the following model formats. xAI's public model catalog currently recommends grok-4.3 for general chat and coding workloads; consult the catalog when choosing a new default for a long-lived integration.

:::caution Legacy xAI model aliases

xAI periodically retires older model slugs and keeps them working by redirecting them to newer replacements. As of the May 15, 2026 (12:00 PM PT) retirement, requests to grok-4-1-fast-reasoning, grok-4-1-fast-non-reasoning, grok-4-fast-reasoning, grok-4-fast-non-reasoning, grok-4-0709, grok-code-fast-1, and grok-3 (including the *-beta, *-fast, and *-latest aliases on each of those families) are redirected to grok-4.3 — reasoning variants run with low reasoning effort, non-reasoning variants run with none — and billed at standard Grok 4.3 pricing. The grok-imagine-image-pro slug is similarly redirected to xAI's quality image model. For new configs, prefer current catalog models such as grok-4.3 or grok-imagine-image-quality directly.

:::

Grok 4.3 Models

• xai:grok-4.3 - General-purpose reasoning model
• xai:grok-4.3-latest - Alias for the Grok 4.3 family

Grok 4.20 Models

• xai:grok-4.20-0309-reasoning - Reasoning model
• xai:grok-4.20 - Alias for the Grok 4.20 reasoning family
• xai:grok-4.20-reasoning - Alias for the Grok 4.20 reasoning family
• xai:grok-4.20-reasoning-latest - Alias for the Grok 4.20 reasoning family
• xai:grok-4.20-0309-non-reasoning - Non-reasoning variant
• xai:grok-4.20-non-reasoning - Alias for the Grok 4.20 non-reasoning family
• xai:grok-4.20-non-reasoning-latest - Alias for the Grok 4.20 non-reasoning family
• xai:grok-4.20-multi-agent-0309 - Multi-agent variant
• xai:grok-4.20-multi-agent - Alias for the Grok 4.20 multi-agent family
• xai:grok-4.20-multi-agent-latest - Alias for the Grok 4.20 multi-agent family

Grok 4.1 Fast Models

• xai:grok-4-1-fast-reasoning - Frontier model optimized for agentic tool calling with reasoning (2M context)
• xai:grok-4-1-fast-non-reasoning - Fast variant for instant responses without reasoning (2M context)
• xai:grok-4-1-fast - Alias for grok-4-1-fast-reasoning
• xai:grok-4-1-fast-reasoning-latest - Alias for grok-4-1-fast-reasoning
• xai:grok-4-1-fast-non-reasoning-latest - Alias for grok-4-1-fast-non-reasoning

Grok Code Fast Models

• xai:grok-code-fast-1 - Speedy and economical reasoning model optimized for agentic coding (256K context)
• xai:grok-code-fast - Alias for grok-code-fast-1
• xai:grok-code-fast-1-0825 - Specific version of the code-fast model (256K context)

Grok-4 Fast Models

• xai:grok-4-fast-reasoning - Fast reasoning model with 2M context window
• xai:grok-4-fast-non-reasoning - Fast non-reasoning model for instant responses (2M context)
• xai:grok-4-fast - Alias for grok-4-fast-reasoning
• xai:grok-4-fast-reasoning-latest - Alias for grok-4-fast-reasoning
• xai:grok-4-fast-non-reasoning-latest - Alias for grok-4-fast-non-reasoning

Grok-4 Models

• xai:grok-4-0709 - 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:

Promptfoo uses xAI's model-specific cache-read rate by default. Custom pricing can be set with cost, inputCost, outputCost, and cacheReadCost (all per-token rates).

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4.3
    config:
      temperature: 0.7
      reasoning_effort: 'high' # none, low, medium, or high
      apiKey: your_api_key_here # Alternative to XAI_API_KEY

Reasoning Support

Multiple Grok models support reasoning capabilities:

Grok 4.3: General-purpose reasoning model recommended by xAI's public model catalog. Chat requests can set reasoning_effort to none, low, medium, or high; Responses API requests use reasoning.effort.

Grok Code Fast Models: The grok-code-fast-1 family are reasoning models optimized for agentic coding workflows. They support:

• Function calling and tool usage
• Web search via search_parameters
• Fast inference with built-in reasoning

Grok 4.3 Specific Behavior

Grok 4.3 is the best starting point for general text workflows:

• Responses API recommended: Use xai:responses:grok-4.3 for server-side tools, multi-turn state, and newer xAI capabilities
• Configurable reasoning: reasoning_effort defaults to xAI's low mode; set none, medium, or high when the workload calls for it
• Unsupported parameters: Same restrictions as other Grok 4-family reasoning models (presence_penalty, frequency_penalty, and stop)

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4.3
    config:
      temperature: 0.7
      max_completion_tokens: 4096

Grok-3 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

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

:::

Grok 4.1 Fast Specific Behavior

Grok 4.1 Fast is xAI's frontier model specifically optimized for agentic tool calling:

• Two variants: grok-4-1-fast-reasoning for maximum intelligence, grok-4-1-fast-non-reasoning for instant responses
• Massive context window: 2,000,000 tokens for handling complex multi-turn agent interactions
• Optimized for tool calling: Trained specifically for high-performance agentic tool calling via RL in simulated environments
• Low latency and cost: $0.20/1M input tokens, $0.50/1M output tokens with fast inference
• Unsupported parameters: Same restrictions as Grok-4 (no presence_penalty, frequency_penalty, stop, reasoning_effort)

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4-1-fast-reasoning
    config:
      temperature: 0.7
      max_completion_tokens: 4096

Grok-4 Fast Specific Behavior

Grok-4 Fast models offer the same capabilities as Grok-4 but with faster inference and lower cost:

• Two variants: grok-4-fast-reasoning for reasoning tasks, grok-4-fast-non-reasoning for instant responses
• 2M context window: Same large context as Grok 4.1 Fast
• Same parameter restrictions as Grok-4: No presence_penalty, frequency_penalty, stop, or reasoning_effort

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4-fast-reasoning
    config:
      temperature: 0.7
      max_completion_tokens: 4096

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

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-4
    config:
      temperature: 0.7
      max_completion_tokens: 4096

Grok Code Fast Specific Behavior

The Grok Code Fast models are optimized for agentic coding workflows and offer several key features:

• Built for Speed: Designed to be highly responsive for agentic coding tools where multiple tool calls are common
• Economical Pricing: At $0.20/1M input tokens and $1.50/1M output tokens, significantly more affordable than flagship models
• Reasoning Capabilities: Built-in reasoning for code analysis, debugging, and problem-solving
• Tool Integration: Excellent support for function calling, tool usage, and web search
• Coding Expertise: Particularly adept at TypeScript, Python, Java, Rust, C++, and Go

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:grok-code-fast-1
    # or use the alias:
    # - id: xai:grok-code-fast
    config:
      temperature: 0.1 # Lower temperature often preferred for coding tasks
      max_completion_tokens: 4096
      search_parameters:
        mode: auto # Enable web search for coding assistance

Region Support

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

providers:
  - id: xai:grok-4.3
    config:
      region: eu-west-1 # Will use https://eu-west-1.api.x.ai/v1

This is equivalent to setting base_url="https://eu-west-1.api.x.ai/v1" in the Python client. The same region option is also accepted by the xAI image, video, Responses, and realtime voice providers.

xAI's public regional docs say the global endpoint automatically routes requests and gives access to every model available to your team. The current public model catalog shows xAI's language, Grok Imagine image, and Grok Imagine video models in both us-east-1 and eu-west-1. Regional endpoints are useful for data-residency requirements, but xAI warns that not every model is guaranteed in every region over time; for the latest region-by-region availability, use the xAI Console or the model pages on xAI's site.

Live Search (Beta)

:::warning

xAI's current documentation recommends the Responses API for server-side tools. Promptfoo still passes legacy search_parameters through for older configs, but new search configs should use the Agent Tools API.

:::

Legacy configs can still pass a search_parameters object. 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.

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.

Agent Tools API (Responses API)

Use the xai:responses:<model> provider to access xAI's Agent Tools API, which enables autonomous server-side tool execution for web search, X search, code execution, collections search, and remote MCP tools.

providers:
  - id: xai:responses:grok-4.3
    config:
      temperature: 0.7
      max_output_tokens: 4096
      tools:
        - type: web_search
        - type: x_search

Available Agent Tools

Tool	Description
web_search	Search the web and browse pages
x_search	Search X posts, users, and threads
code_execution / code_interpreter	Execute Python code in a sandbox
collections_search / file_search	Search uploaded knowledge bases
mcp	Connect to remote MCP servers

Web Search Tool

tools:
  - type: web_search
    filters:
      allowed_domains:
        - example.com
        - news.com
      # OR excluded_domains (cannot use both)
    enable_image_understanding: true

X Search Tool

tools:
  - type: x_search
    from_date: '2025-01-01' # ISO8601 format
    to_date: '2025-11-27'
    allowed_x_handles:
      - elonmusk
    enable_image_understanding: true
    enable_video_understanding: true

Code Interpreter Tool

tools:
  - type: code_interpreter
    container:
      pip_packages:
        - numpy
        - pandas

Complete Example

providers:
  - id: xai:responses:grok-4.3
    config:
      temperature: 0.7
      tools:
        - type: web_search
          enable_image_understanding: true
        - type: x_search
          from_date: '2025-01-01'
        - type: code_interpreter
          container:
            pip_packages:
              - numpy
      tool_choice: auto # auto, required, or none
      parallel_tool_calls: true

tests:
  - vars:
      question: What's the latest AI news? Search the web and X.
    assert:
      - type: contains
        value: AI

Responses API Configuration

Parameter	Type	Description
temperature	number	Sampling temperature (0-2)
max_output_tokens	number	Maximum tokens to generate
max_tool_calls	number	Maximum tool calls for one request
top_p	number	Nucleus sampling parameter
tools	array	Agent tools to enable
tool_choice	string	Tool selection mode: auto, required, none
parallel_tool_calls	boolean	Allow parallel tool execution
stream	boolean	Request streamed response deltas
instructions	string	System-level instructions
previous_response_id	string	For multi-turn conversations
store	boolean	Store response for later retrieval
include	array	Additional response data to return
reasoning	object	Reasoning configuration for Grok 4.3 or multi-agent models
response_format	object	JSON schema for structured output
cost	number	Per-token input and output cost override
inputCost	number	Per-token input cost override
outputCost	number	Per-token output cost override
cacheReadCost	number	Per-token cached-input cost override

Supported Models

The Responses API works with current Grok models, including:

• grok-4.3
• grok-4.20-reasoning
• grok-4.20-non-reasoning
• grok-4.20-multi-agent
• grok-4-1-fast-reasoning (recommended for agentic workflows)
• grok-4-1-fast-non-reasoning
• grok-4-fast-reasoning
• grok-4-fast-non-reasoning
• grok-4

Migration from Live Search

If you're using Live Search via search_parameters, migrate to the Responses API:

Before (Live Search - deprecated):

providers:
  - id: xai:grok-4-1-fast-reasoning
    config:
      search_parameters:
        mode: auto
        sources:
          - type: web
          - type: x

After (Responses API):

providers:
  - id: xai:responses:grok-4.3
    config:
      tools:
        - type: web_search
        - type: x_search

Deferred Chat Completions

:::info Not Yet Supported

xAI offers Deferred Chat Completions for long-running requests that can be retrieved asynchronously via a request_id. This feature is not yet supported in promptfoo. For async workflows, use the xAI Python SDK directly.

:::

Function Calling

xAI supports standard OpenAI-compatible function calling for client-side tool execution:

providers:
  - id: xai:grok-4-1-fast-reasoning
    config:
      tools:
        - type: function
          function:
            name: get_weather
            description: Get the current weather for a location
            parameters:
              type: object
              properties:
                location:
                  type: string
                  description: City and state
              required:
                - location

Structured Outputs

xAI supports structured outputs via JSON schema:

providers:
  - id: xai:grok-4
    config:
      response_format:
        type: json_schema
        json_schema:
          name: analysis_result
          strict: true
          schema:
            type: object
            properties:
              summary:
                type: string
              confidence:
                type: number
            required:
              - summary
              - confidence
            additionalProperties: false

You can also load schemas from external files:

config:
  response_format: file://./schemas/analysis-schema.json

Nested file references and variable rendering are supported (see OpenAI documentation for details).

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:

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

Then reference it in your promptfoo config:

# 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?"

Embeddings

xAI does not currently expose a public embeddings API. Use the OpenAI provider (or another embedding provider) for similarity assertions.

Image Generation

xAI also supports image generation through Grok Imagine:

providers:
  - xai:image:grok-imagine-image

Current Grok Imagine image model IDs include:

• xai:image:grok-imagine-image
• xai:image:grok-imagine-image-quality
• xai:image:grok-imagine-image-pro

grok-imagine-image-quality is xAI's newer quality-oriented image model and the better default for new higher-quality image workflows. Older image-model aliases may continue to resolve through xAI-managed redirects.

Example configuration for image generation:

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

providers:
  - id: xai:image:grok-imagine-image
    config:
      n: 1 # Number of images to generate (1-10)
      response_format: 'url' # 'url' or 'b64_json'
      aspect_ratio: '16:9'
      resolution: '2k'

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

Image Editing

Use the same provider with image, images, or mask inputs to call xAI's image-editing endpoint:

providers:
  - id: xai:image:grok-imagine-image
    config:
      image:
        url: 'https://example.com/source.png'
      mask:
        url: 'https://example.com/mask.png'
      quality: 'high'

prompts:
  - 'Render this as a pencil sketch with detailed shading'

Pricing

Promptfoo uses the exact usage.cost_in_usd_ticks value returned by xAI when available. When the API omits usage, Promptfoo falls back to its local Imagine image estimate, including documented output rates and source-image media-input charges on edit requests.

Video Generation

xAI supports video generation through the Grok Imagine API using the xai:video:grok-imagine-video provider:

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
prompts:
  - 'Generate a video of: {{scene}}'

providers:
  - id: xai:video:grok-imagine-video
    config:
      duration: 5 # 1-15 seconds
      aspect_ratio: '16:9'
      resolution: '720p'

tests:
  - vars:
      scene: a cat playing with yarn
    assert:
      - type: cost
        threshold: 1.0

Configuration Options

Option	Type	Default	Description
duration	number	8	Video length in seconds (1-15)
aspect_ratio	string	16:9	Aspect ratio: 16:9, 4:3, 1:1, 9:16, 3:4, 3:2, 2:3
resolution	string	720p	Output resolution: 720p, 480p
reference_images	array	-	Reference images for reference-to-video mode
poll_interval_ms	number	10000	Polling interval in milliseconds
max_poll_time_ms	number	600000	Maximum wait time (10 minutes)

Image-to-Video

Animate a static image by providing an image URL:

providers:
  - id: xai:video:grok-imagine-video
    config:
      image:
        url: 'https://example.com/image.jpg'
      duration: 5

Video Editing

Edit an existing video with text instructions:

providers:
  - id: xai:video:grok-imagine-video
    config:
      video:
        url: 'https://example.com/source-video.mp4'

prompts:
  - 'Make the colors more vibrant and add slow motion'

:::note Video editing skips duration, aspect ratio, and resolution validation since these are determined by the source video. :::

Reference-to-Video

Guide generation with up to seven reference images:

providers:
  - id: xai:video:grok-imagine-video
    config:
      reference_images:
        - url: 'https://example.com/person.jpg'
        - url: 'https://example.com/shirt.jpg'
      duration: 10

Reference-to-video requires a non-empty prompt, cannot be combined with image or video, and is limited to 10 seconds.

Pricing

Promptfoo uses the exact usage.cost_in_usd_ticks value returned by xAI when available. When the API omits usage, Promptfoo falls back to the video provider's local duration-based estimate.

Voice Agent API

The xAI Voice Agent API enables real-time voice conversations with Grok models via WebSocket. Use the xai:voice:<model> provider format.

providers:
  - xai:voice:grok-voice-think-fast-1.0

Configuration

# yaml-language-server: $schema=https://promptfoo.dev/config-schema.json
providers:
  - id: xai:voice:grok-voice-think-fast-1.0
    config:
      voice: 'Ara' # Ara, Rex, Sal, Eve, or Leo
      instructions: 'You are a helpful voice assistant.'
      modalities: ['text', 'audio']
      turn_detection:
        type: server_vad
        threshold: 0.85
        silence_duration_ms: 500
        prefix_padding_ms: 333
      websocketTimeout: 60000 # Connection timeout in ms
      tools:
        - type: web_search
        - type: x_search

Available Voices

Voice	Description
Ara	Female voice
Rex	Male voice
Sal	Male voice
Eve	Female voice
Leo	Male voice

Turn Detection

Use turn_detection to tune server-side voice activity detection:

Option	Type	Description
type	string	server_vad for automatic detection
threshold	number	Activation threshold from 0.1 to 0.9
silence_duration_ms	number	Silence required before ending the turn
prefix_padding_ms	number	Audio kept before detected speech to avoid clipping

Built-in Tools

The Voice API includes server-side tools that execute automatically:

Tool	Description
web_search	Search the web for information
x_search	Search posts on X (Twitter)
file_search	Search uploaded files in vector stores

tools:
  - type: web_search
  - type: x_search
    allowed_x_handles:
      - elonmusk
      - xai
  - type: file_search
    vector_store_ids:
      - vs-123
    max_num_results: 10

Custom Function Tools and Assertions

You can define custom function tools inline or load them from external files:

providers:
  - id: xai:voice:grok-voice-think-fast-1.0
    config:
      # Inline tool definition
      tools:
        - type: function
          name: set_volume
          description: Set the device volume level
          parameters:
            type: object
            properties:
              level:
                type: number
                description: Volume level from 0 to 100
            required:
              - level

      # Or load from external file (YAML or JSON)
      # tools: file://tools.yaml

tests:
  - vars:
      question: 'Set the volume to 50 percent'
    assert:
      # Check that the correct function was called with correct arguments
      - type: javascript
        value: |
          const calls = output.functionCalls || [];
          return calls.some(c => c.name === 'set_volume' && c.arguments?.level === 50);

      # Or use tool-call-f1 for function name matching
      - type: tool-call-f1
        value: ['set_volume']
        threshold: 1.0

External tools file example:

- type: function
  name: get_weather
  description: Get the current weather for a location
  parameters:
    type: object
    properties:
      location:
        type: string
    required:
      - location

- type: function
  name: set_reminder
  description: Set a reminder for the user
  parameters:
    type: object
    properties:
      message:
        type: string
      time:
        type: string
    required:
      - message
      - time

When function tools are used, the provider output includes a functionCalls array with:

• name: The function name that was called
• arguments: The parsed arguments object
• result: The result returned by your function handler (if provided)

Custom Endpoint Configuration

You can configure a custom WebSocket endpoint for the Voice API, useful for proxies or regional endpoints:

providers:
  - id: xai:voice:grok-voice-think-fast-1.0
    config:
      # Option 1: Full base URL (transforms https:// to wss://)
      apiBaseUrl: 'https://my-proxy.example.com/v1'

      # Option 2: Host only (builds https://{host}/v1)
      # apiHost: 'my-proxy.example.com'

You can also use the XAI_API_BASE_URL environment variable:

export XAI_API_BASE_URL=https://my-proxy.example.com/v1

URL transformation: The provider automatically converts HTTP URLs to WebSocket URLs (https:// → wss://, http:// → ws://) and appends /realtime to reach the Voice API endpoint.

Complete WebSocket URL Override

For advanced use cases like local testing, custom proxies, or endpoints requiring query parameters, you can provide a complete WebSocket URL that will be used exactly as specified without any transformation:

providers:
  - id: xai:voice:grok-voice-think-fast-1.0
    config:
      # Use this URL exactly as-is (no transformation applied)
      websocketUrl: 'wss://custom-endpoint.example.com/path?token=xyz&session=abc'

This is useful for:

• Local development and testing with mock servers
• Custom proxy configurations
• Adding authentication tokens or session IDs as URL parameters
• Using alternative WebSocket gateways or regional endpoints

Audio Configuration

Configure input/output audio formats:

config:
  audio:
    input:
      format:
        type: audio/pcm
        rate: 24000
    output:
      format:
        type: audio/pcm
        rate: 24000

Supported formats: audio/pcm, audio/pcmu, audio/pcma Supported sample rates: 8000, 16000, 22050, 24000, 32000, 44100, 48000 Hz

Complete Example

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

providers:
  - id: xai:voice:grok-voice-think-fast-1.0
    config:
      voice: 'Ara'
      instructions: 'You are a helpful voice assistant.'
      modalities: ['text', 'audio']
      tools:
        - type: web_search

tests:
  - vars:
      question: 'What are the latest AI developments?'
    assert:
      - type: llm-rubric
        value: Provides information about recent AI news

Pricing

The Voice Agent API is billed at $0.05 per minute of connection time.

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.

npx promptfoo@latest init --example xai/chat

For real-time voice conversations with Grok, see the xai-voice example.

npx promptfoo@latest init --example xai/voice

See Also

• OpenAI Provider

Troubleshooting

502 Bad Gateway Errors

If you encounter 502 Bad Gateway errors when using the xAI provider, this typically indicates:

• An invalid or missing API key
• Server issues on x.ai's side

The xAI provider will provide helpful error messages to guide you in resolving these issues.

Solution: Verify your XAI_API_KEY environment variable is set correctly. You can obtain an API key from https://x.ai/.

Controlling Retries

If you're experiencing timeouts or want to control retry behavior:

• To disable retries for 5XX errors: PROMPTFOO_RETRY_5XX=false
• To reduce retry delays: PROMPTFOO_REQUEST_BACKOFF_MS=1000 (in milliseconds)

Reference

• x.ai documentation