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Overview

Nebius is an OpenAI-compatible provider offering comprehensive API support. Bifrost delegates to the OpenAI implementation with standard parameter filtering. Key features:
  • Full OpenAI compatibility - Chat, text completion, embeddings, and responses
  • Streaming support - Server-Sent Events with delta-based updates
  • AI Project ID - Nebius-specific project identifier support
  • Tool calling - Complete function definition and execution
  • Parameter filtering - Removes unsupported OpenAI-specific fields

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Supported Operations

OperationNon-StreamingStreamingEndpoint
Chat Completions✅✅/v1/chat/completions
Responses API✅✅/v1/chat/completions
Text Completions✅✅/v1/completions
Embeddings✅-/v1/embeddings
Image Generation✅-/v1/images/generations
List Models✅-/v1/models
Speech (TTS)❌❌-
Transcriptions (STT)❌❌-
Files❌❌-
Batch❌❌-
Unsupported Operations (❌): Speech, Transcriptions, Files, and Batch are not supported by the upstream Nebius API. These return UnsupportedOperationError.

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1. Chat Completions

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Request Parameters

Nebius supports all standard OpenAI chat completion parameters. For full parameter reference and behavior, see OpenAI Chat Completions.

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Nebius-Specific Parameters

ai_project_id (Optional): Nebius allows specifying a project ID for resource organization: 
curl -X POST http://localhost:8080/v1/chat/completions \
  -H "Content-Type: application/json" \
  -d '{
    "model": "nebius/model-name",
    "messages": [...],
    "ai_project_id": "project-123"
  }'
The ai_project_id is appended as a query parameter to the request URL.

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Filtered Parameters

Removed for Nebius compatibility:
  • prompt_cache_key - Not supported
  • verbosity - Anthropic-specific
  • store - Not supported
  • service_tier - Not supported
Nebius supports all standard OpenAI message types, tools, responses, and streaming formats. For details on message handling, tool conversion, responses, and streaming, refer to OpenAI Chat Completions.

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2. Responses API

Converted internally to Chat Completions: 
ResponsesRequest → ChatRequest → ChatCompletion → ResponsesResponse
Same parameter support and message handling as Chat Completions. Supports ai_project_id via extra_params.

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3. Text Completions

Nebius supports legacy text completion format:
ParameterMapping
promptDirect pass-through
max_tokensmax_tokens
temperature, top_pDirect pass-through
stopStop sequences
frequency_penalty, presence_penaltyPenalty parameters

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4. Embeddings

Nebius supports text embeddings:
ParameterNotes
inputText or array of texts
modelEmbedding model name
encoding_format”float” or “base64”
dimensionsCustom output dimensions (optional)
Response returns embedding vectors with usage information.

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5. Image Generation

Request Parameters
ParameterTypeRequiredNotes
modelstring✅Model identifier
promptstring✅Text description of the image to generate
sizestring❌Image size in WxH format (e.g., "1024x1024"). Converted to separate width and height integers
output_formatstring❌Output format: "png", "jpeg", "webp". Note: "jpeg" is converted to "jpg"
response_formatstring❌Response format: "url" or "b64_json"
seedint❌Seed for reproducible generation
negative_promptstring❌Negative prompt
num_inference_stepsint❌Number of inference steps
extra_paramsobject❌Nebius-specific parameters (see below)
Extra Parameters (via extra_params)
ParameterTypeNotes
guidance_scaleintGuidance scale (0-100)
ai_project_idstringNebius project ID (added as query parameter)
Request Conversion
  • Model & Prompt: bifrostReq.Model → req.Model (pointer), bifrostReq.Input.Prompt → req.Prompt (pointer)
  • Size Conversion: params.size (WxH format like "1024x1024") is split into:
    • width: Integer extracted from first part (e.g., 1024)
    • height: Integer extracted from second part (e.g., 1024)
  • Output Format:
    • params.output_format → req.ResponseExtension
    • Special conversion: "jpeg" → "jpg" (Nebius uses "jpg" not "jpeg")
  • Response Format: params.response_format → req.ResponseFormat (passed directly: "url" or "b64_json")
  • Seed & Negative Prompt: params.seed → req.Seed, params.negative_prompt → req.NegativePrompt (passed directly)
  • Num Inference Steps: params.num_inference_steps → req.NumInferenceSteps (passed directly)
  • Extra Parameters:
    • guidance_scale → req.GuidanceScale (int pointer)
    • ai_project_id → Added as query parameter ?ai_project_id={value} to the request URL
Response Conversion
  • Image Data: Each item in response.data[] → ImageData with:
    • url: From data[].url
    • b64_json: From data[].b64_json
    • revised_prompt: From data[].revised_prompt
    • index: Sequential index (0, 1, 2, …)
  • ID: response.id → response.ID
  • Provider: Set to nebius in ExtraFields
Endpoint: /v1/images/generations Streaming: Image generation streaming is not supported by Nebius.

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6. List Models

Lists available Nebius models with capabilities and context lengths.

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Unsupported Features

FeatureReason
Speech/TTSNot offered by Nebius API
Transcription/STTNot offered by Nebius API
Batch OperationsNot offered by Nebius API
File ManagementNot offered by Nebius API

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Caveats

Severity: Medium Behavior: Cache control directives are removed from messages Impact: Prompt caching features don’t work Code: Stripped during JSON marshaling
Severity: Low Behavior: OpenAI-specific fields filtered out Impact: prompt_cache_key, verbosity, store removed Code: filterOpenAISpecificParameters
Severity: Low Behavior: User field > 64 characters silently dropped Impact: Longer user identifiers are lost Code: SanitizeUserField enforces 64-char max