---
title: "OpenRouter"
description: "OpenRouter API conversion guide - routing to multiple providers, reasoning support, parameter handling, and streaming"
icon: "split"
---

## Overview

OpenRouter is an **OpenAI-compatible provider routing service** that accesses models from multiple providers (OpenAI, Anthropic, Google, Meta, etc.) through a unified interface. Bifrost delegates to the OpenAI implementation with special handling for reasoning models. Key features:
- **Provider aggregation** - Access 100+ models from multiple vendors
- **Reasoning support** - Extended thinking for supported models
- **Parameter compatibility** - Intelligent reasoning effort conversion
- **Streaming support** - Full SSE support with usage tracking
- **Tool calling** - Complete function definition and execution

### Supported Operations

| Operation | Non-Streaming | Streaming | Endpoint |
|-----------|---------------|-----------|----------|
| Chat Completions | ✅ | ✅ | `/v1/chat/completions` |
| Responses API | ✅ | ✅ | `/v1/responses` |
| Text Completions | ✅ | ✅ | `/v1/completions` |
| List Models | ✅ | - | `/v1/models` |
| Embeddings | ✅ | - | `/v1/embeddings` |
| Image Generation | ❌ | ❌ | - |
| Speech (TTS) | ❌ | ❌ | - |
| Transcriptions (STT) | ❌ | ❌ | - |
| Files | ❌ | ❌ | - |
| Batch | ❌ | ❌ | - |

<Note>
**Unsupported Operations** (❌): Image Generation, Speech, Transcriptions, Files, and Batch are not supported by the upstream OpenRouter API. These return a `BifrostError` with an error code of `"unsupported_operation"`.

**Note**: OpenRouter's Responses API is currently in **beta**.
</Note>

---

# 1. Chat Completions

## Request Parameters

OpenRouter supports all standard OpenAI chat completion parameters. For full parameter reference and behavior, see [OpenAI Chat Completions](/providers/supported-providers/openai#1-chat-completions).

### Reasoning Parameter Handling

OpenRouter supports extended thinking on compatible models:

```json
// Bifrost request
{
  "reasoning": {
    "effort": "high",
    "max_tokens": 10000
  }
}

// OpenRouter conversion
{
  "reasoning_effort": "high"
}
```

**Reasoning Models:** gpt-oss-120b and compatible models with special handling for reasoning content.

### Cache Control Stripping

Anthropic-specific cache control directives are automatically removed:

```go
// Bifrost supports cache control from Anthropic
{
  "messages": [{
    "role": "user",
    "content": [{
      "type": "text",
      "text": "...",
      "cache_control": {"type": "ephemeral"}  // ← Stripped
    }]
  }]
}

// Sent to OpenRouter without cache directives
```

### Filtered Parameters

Removed for OpenRouter compatibility:
- `prompt_cache_key` - Not supported
- `verbosity` - Anthropic-specific
- `store` - Not supported
- `service_tier` - OpenAI-specific

OpenRouter 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](/providers/supported-providers/openai#1-chat-completions).

---

# 2. Responses API

OpenRouter's Responses API is handled as a distinct endpoint at `/v1/responses`. This API is currently in **beta** on OpenRouter.

Same parameter support as Chat Completions, with requests forwarded directly to the Responses API endpoint without conversion to Chat Completions.

**Special Message Handling (gpt-oss vs other models):**
For details on how reasoning is handled differently between gpt-oss and other models, see [OpenAI Responses API documentation](/providers/supported-providers/openai) for the comprehensive explanation of reasoning conversion (summaries vs. content blocks).

---

# 3. Text Completions

OpenRouter supports legacy text completion format:

| Parameter | Mapping |
|-----------|---------|
| `prompt` | Direct pass-through |
| `max_tokens` | max_tokens |
| `temperature`, `top_p` | Direct pass-through |
| `stop` | Stop sequences |

---

# 4. List Models

Lists 100+ models available through OpenRouter, including:
- OpenAI (GPT-4, GPT-4 Turbo, etc.)
- Anthropic (Claude 3 family)
- Google (Gemini)
- Meta (Llama)
- Mistral
- And many more

---

# 5. Embeddings

OpenRouter supports embeddings through their OpenAI-compatible API. This allows you to generate vector embeddings for text using models from various providers.

| Parameter | Mapping |
|-----------|---------|
| `input` | Direct pass-through (string or array of strings) |
| `model` | Model ID (e.g., `cohere/embed-multilingual-v3.0`, `amazon/amazon-embeddings-v2`) |
| `dimensions` | Number of dimensions for the output embedding |
| `encoding_format` | Output format (`float` or `base64`) |

**Supported Models:** OpenRouter supports various embedding models including:
- Cohere (embed-multilingual-v3.0, embed-english-v3.0, etc.)
- Amazon (amazon-embeddings-v2)
- And other providers

The embedding request/response follows the standard OpenAI format.

---

## Unsupported Features

| Feature | Reason |
|---------|--------|
| Image Generation | Not offered by OpenRouter API |
| Speech/TTS | Not offered by OpenRouter API |
| Transcription/STT | Not offered by OpenRouter API |
| Batch Operations | Not offered by OpenRouter API |
| File Management | Not offered by OpenRouter API |

---

## Caveats

<Accordion title="Cache Control Stripped">
**Severity**: Medium
**Behavior**: Anthropic cache control directives are removed
**Impact**: Prompt caching features unavailable
**Code**: Stripped during JSON marshaling
</Accordion>

<Accordion title="Parameter Filtering">
**Severity**: Low
**Behavior**: OpenAI-specific parameters filtered
**Impact**: prompt_cache_key, verbosity, store removed
**Code**: filterOpenAISpecificParameters
</Accordion>

<Accordion title="User Field Size Limit">
**Severity**: Low
**Behavior**: User field > 64 characters silently dropped
**Impact**: Longer user identifiers are lost
**Code**: SanitizeUserField enforces 64-char max
</Accordion>