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Extension Fields

The AI Gateway supports extension fields that allow you to specify unified or backend-specific parameters directly as inline fields in your OpenAI-compatible requests. These fields are applied during the translation process to the target backend's native API format.

Overview​

Extension fields enable you to:

  • Use advanced backend-specific features not available in the OpenAI API
  • Use unified configuration fields that work across multiple providers not available in the OpenAI API

Vendor Extension Fields​

Vendor specific fields are specified as inline fields in your OpenAI request and are applied after the standard OpenAI-to-backend translation.

Unified Extension Fields​

For thinking/reasoning capabilities, you can use a unified thinking field that automatically translates to the correct backend-specific format:

  • GCP Vertex AI (Gemini): Translates to generationConfig.thinkingConfig
  • GCP Anthropic: Uses thinking field directly
  • AWS Bedrock: Uses thinking field directly

This unified approach allows you to write provider-agnostic requests while still leveraging thinking capabilities.

Supported Backends​

The following backends support extension fields:

GCP Vertex AI (Gemini)​

  • API Schema Name: GCPVertexAI
  • Supported Fields:
    • safetySettings: Configure the safety settings for gemini models that translates to SafetySetting. Gemini Docs
    • thinking: Configure thinking process for reasoning models that automatically translates to generationConfig.thinkingConfig. Gemini Docs

GCP Anthropic​

  • API Schema Name: GCPAnthropic
  • Supported Fields:
    • thinking: Configuration for enabling Claude's extended thinking. Anthropic Docs

AWS Bedrock​

  • API Schema Name: AWSBedrock
  • Supported Fields:
    • thinking: Configuration for enabling Anthropic Claude's extended thinking. AWS Docs

Usage​

Add extension fields directly as inline fields in your OpenAI request:

Using Unified Thinking Configuration​

The simplest way to enable thinking capabilities across all providers is to use the unified thinking field:

{
  "model": "gemini-2.5-pro",
  "messages": [
    {
      "role": "user",
      "content": "Explain quantum computing and show me a simple code example."
    }
  ],
  "temperature": 0.7,
  "max_tokens": 2000,
  "thinking": {
    "type": "enabled",
    "budget_tokens": 1000,
    "includeThoughts": true
  }
}

This configuration will work with any provider that supports thinking, automatically translating to the correct backend format.

Using Provider-Specific Fields​

For more fine-grained control or provider-specific features, you can use the vendor-specific fields like safetySettings for gemini models:

{
  "model": "gemini-1.5-pro",
  "messages": [
    {
      "role": "user",
      "content": "Explain quantum computing and show me a simple code example."
    }
  ],
  "temperature": 0.7,
  "max_tokens": 2000,
  "safetySettings": [
    {
      "category": "HARM_CATEGORY_HARASSMENT",
      "threshold": "BLOCK_ONLY_HIGH"
    }
  ]
}

Field Conflicts​

Vendor fields override translated fields when conflicts occur.

When using unified thinking configuration, the thinking field takes precedence over any provider-specific thinking configurations.

Unsupported Fields/Backends​

Fields and Backends other than specified in Supported Backends will be ignored.