xAI Grok on Bifrost: Models, Endpoints, Setup, and Mappings

xAI Grok provider summary

xAI powers the Grok family of models. Bifrost delegates to the OpenAI implementation with standard parameter filtering, vision support, and reasoning on select models.

Key features:

Full OpenAI compatibility — chat, text completion, and responses
Vision support — image URLs and base64 for multimodal models
Streaming — Server-Sent Events with delta-based updates
Reasoning — extended thinking on grok-3-mini via reasoning_effort
Tool calling — function definitions and execution

Common xAI Grok model IDs used in Bifrost routes:

grok-3-20250415 (Latest)
grok-3-mini-20250415 (Efficient, reasoning enabled)
grok-2-vision-1212 (Vision)

Property	Details
Description	xAI's Grok models for chat, reasoning, vision, and image generation.
Provider route on Bifrost	xai/<model>
Provider doc	xAI
API endpoint for provider	https://api.x.ai
Supported endpoints	/v1/chat/completions, /v1/responses, /v1/completions, /v1/images/generations, /v1/models

Supported operations

Embeddings, Speech, Transcriptions, Files, and Batch return UnsupportedOperationError. See Supported operations in Bifrost docs.

Operation	Non-streaming	Streaming	Upstream endpoint
Chat Completions	Yes	Yes	/v1/chat/completions
Responses API	Yes	Yes	/v1/responses
Text Completions	Yes	Yes	/v1/completions
Image Generation	Yes	—	/v1/images/generations
List Models	Yes	—	/v1/models
Embeddings	No	No	-
Speech (TTS)	No	No	-
Transcriptions (STT)	No	No	-
Files	No	No	-
Batch	No	No	-

Supported OpenAI parameters

Quick reference of OpenAI parameters accepted when routing through xAI Grok via Bifrost.

[
  "stream",
  "temperature",
  "top_p",
  "max_tokens",
  "max_completion_tokens",
  "stop",
  "tools",
  "tool_choice",
  "user",
  "reasoning",
  "response_format"
]

Supported xAI Grok models

Use the provider prefix xai/ in Bifrost model routes for deterministic provider targeting.

Family	Model ID	Bifrost route	Typical usage
Grok 3	grok-3-20250415	xai/grok-3-20250415	Latest model
Grok 3 Mini	grok-3-mini-20250415	xai/grok-3-mini-20250415	Efficient variant
Grok 2 Vision	grok-2-vision-1212	xai/grok-2-vision-1212	Vision capabilities

API reference

OpenAI-compatible endpoints routed to xAI via Bifrost.

1) Chat Completions

Primary path at /v1/chat/completions. xAI supports standard OpenAI chat parameters. See Chat Completions in Bifrost docs and OpenAI Chat Completions.

Filtered parameters

Parameter	Reason	Notes
prompt_cache_key	Not supported	Removed for xAI compatibility
verbosity	Anthropic-specific	Removed for xAI compatibility
store	Not supported	Removed for xAI compatibility
service_tier	Not supported	Removed for xAI compatibility

Reasoning support

grok-3-mini supports extended reasoning via reasoning_effort (e.g. high). Other Grok-3 and Grok-4 models error if this parameter is set. Bifrost converts the internal Reasoning structure to xAI's string format.

Vision support

Vision models accept image URLs, base64-encoded images, and multiple images per message.

curl -X POST http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "xai/grok-2-vision-1212",
    "messages": [{
      "role": "user",
      "content": [
        {"type": "text", "text": "What is in this image?"},
        {"type": "image_url", "image_url": {"url": "https://example.com/image.jpg"}}
      ]
    }]
  }'

{
  "model": "xai/grok-3-mini",
  "messages": [{"role": "user", "content": "Solve this step by step"}],
  "reasoning_effort": "high"
}

2) Responses API

Forwarded directly to /v1/responses (not chat fallback). Same parameters and message handling as Chat Completions. Full streaming support. See Responses API in Bifrost docs.

ResponsesRequest → /v1/responses → ResponsesResponse

curl -X POST http://localhost:8080/v1/responses \
  -H "Content-Type: application/json" \
  -d '{
    "model": "xai/grok-3-20250415",
    "input": "Hello",
    "max_output_tokens": 1024
  }'

3) Text Completions

Legacy format at /v1/completions. Supports streaming via stream: true. See Text Completions in Bifrost docs.

Parameter	Mapping	Notes
prompt	Direct pass-through
max_tokens	max_tokens
temperature	Direct pass-through
top_p	Direct pass-through
stop	Stop sequences
frequency_penalty	Penalty parameters
presence_penalty	Penalty parameters

curl -X POST http://localhost:8080/v1/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "xai/grok-3-20250415",
    "prompt": "Hello, my name is",
    "max_tokens": 50
  }'

4) Image Generation

OpenAI-compatible format at /v1/images/generations. Conversion matches OpenAI Image Generation. Responses unmarshal into BifrostImageGenerationResponse. Streaming not supported. See Image Generation in Bifrost docs.

quality, size, and style are not supported by xAI at this time.

curl -X POST http://localhost:8080/v1/images/generations \
  -H "Content-Type: application/json" \
  -d '{
    "model": "xai/grok-2-image",
    "prompt": "A serene mountain landscape at sunset",
    "n": 1
  }'

5) List Models

GET /v1/models — lists available xAI models with capabilities and context lengths. No request parameters required. See List Models in Bifrost docs.

curl http://localhost:8080/v1/models

Unsupported features

These operations are not offered by the upstream xAI API. Bifrost returns UnsupportedOperationError.

Feature	Reason
Embeddings	Not offered by xAI API
Speech/TTS	Not offered by xAI API
Transcription/STT	Not offered by xAI API
Batch operations	Not offered by xAI API
File management	Not offered by xAI API

Implementation caveats

Caveat	Impact	Severity
Reasoning model-specific	Only grok-3-mini supports reasoning_effort; other Grok models error	High
Image generation parameters	quality, size, style parameters not supported	Low
Vision limited to specific models	Only vision-capable models accept image content	Medium
Embeddings unsupported	Embeddings operation returns UnsupportedOperationError	Low