> ## Documentation Index
> Fetch the complete documentation index at: https://docs.getbifrost.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# vLLM

> vLLM API guide - OpenAI-compatible self-hosted inference, chat, text, embeddings, rerank, and streaming

## Overview

vLLM is an **OpenAI-compatible provider** for self-hosted inference. Bifrost delegates to the shared OpenAI provider implementation. Key characteristics:

* **OpenAI compatibility** - Chat, text completions, embeddings, rerank, and streaming
* **Self-hosted** - Typically runs at `http://localhost:8000` or your own server
* **Optional authentication** - API key often omitted for local instances
* **Responses API** - Supported via chat completion fallback

### Supported Operations

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

<Note>
  **Unsupported Operations** (❌): Image Generation, Speech, Files, and Batch are not supported and return `UnsupportedOperationError`.
</Note>

***

## Authentication

* **API key**: Optional. For local vLLM instances, the key is often left empty.
* When set, the key is sent as `Authorization: Bearer <key>`.

***

## Configuration

* **Base URL**: Default is `http://localhost:8000`. Override via provider `network_config.base_url`.
* **Model names**: Depend on the models loaded in your vLLM instance (e.g. `meta-llama/Llama-3.2-1B-Instruct`, `BAAI/bge-m3` for embeddings).

<Tabs>
  <Tab title="Gateway">
    ```bash theme={null}
    # Point to local or remote vLLM instance (default: http://localhost:8000)
    curl -X POST http://localhost:8080/v1/chat/completions \
      -H "Content-Type: application/json" \
      -d '{
        "model": "vllm/meta-llama/Llama-3.2-1B-Instruct",
        "messages": [{"role": "user", "content": "Hello"}]
      }'

    # Gateway provider config: set base_url for remote vLLM
    # "network_config": { "base_url": "http://vllm-endpoint:8000" }
    ```
  </Tab>

  <Tab title="Go SDK">
    ```go theme={null}
    config := &schemas.ProviderConfig{
        NetworkConfig: schemas.NetworkConfig{
            BaseURL: "http://localhost:8000",  // optional; default is http://localhost:8000
            DefaultRequestTimeoutInSeconds: 30,
        },
    }
    provider, _ := vllm.NewVLLMProvider(config, logger)

    response, _ := provider.ChatCompletion(ctx, key, request)
    ```
  </Tab>
</Tabs>

***

## Getting started

1. Run a vLLM server (Docker or pip). Example with Docker:
   ```bash theme={null}
   docker run --gpus all -p 8000:8000 vllm/vllm-openai:latest --model meta-llama/Llama-3.2-1B-Instruct
   ```
2. Verify the server:
   ```bash theme={null}
   curl http://localhost:8000/v1/models
   ```
3. Use Bifrost with model prefix `vllm/<model_id>` (e.g. `vllm/meta-llama/Llama-3.2-1B-Instruct`).

***

# 1. Chat Completions

vLLM supports standard OpenAI chat completion parameters. For full parameter reference, see [OpenAI Chat Completions](/providers/supported-providers/openai#1-chat-completions). Message types, tools, and streaming follow the same behavior.

***

# 2. Responses API

Bifrost converts Responses API requests to Chat Completions and back:

```
BifrostResponsesRequest
  → ToChatRequest()
  → ChatCompletion
  → ToBifrostResponsesResponse()
```

***

# 3. Text Completions

| Parameter     | Mapping        |
| ------------- | -------------- |
| `prompt`      | Sent as-is     |
| `max_tokens`  | max\_tokens    |
| `temperature` | temperature    |
| `top_p`       | top\_p         |
| `stop`        | stop sequences |

***

# 4. Embeddings

vLLM supports `/v1/embeddings`. Use model IDs exposed by your vLLM server (e.g. `BAAI/bge-m3`).

***

# 5. List Models

Lists models from your vLLM instance via `/v1/models`. Available models depend on what is loaded on the server.

***

# 6. Rerank

vLLM supports reranking for pooling/cross-encoder reranker models. Bifrost sends requests to `/v1/rerank` and automatically falls back to `/rerank` when required by your vLLM deployment.

```bash theme={null}
curl -X POST http://localhost:8080/v1/rerank \
  -H "Content-Type: application/json" \
  -d '{
    "model": "vllm/BAAI/bge-reranker-v2-m3",
    "query": "What is machine learning?",
    "documents": [
      {"text": "Machine learning is a subset of AI."},
      {"text": "Python is a programming language."},
      {"text": "Deep learning uses neural networks."}
    ],
    "params": {
      "return_documents": true
    }
  }'
```

<Note>
  Your upstream vLLM server must be started with a rerank-capable model (pooling/cross-encoder task support).
</Note>

***

## Caveats

<Accordion title="Default base URL is localhost">
  **Severity**: Low\
  **Behavior**: Default base URL is `http://localhost:8000`.\
  **Impact**: For remote or custom ports, set `network_config.base_url` in the provider config.
</Accordion>

<Accordion title="Error responses with HTTP 200">
  **Severity**: Low\
  **Behavior**: vLLM may return HTTP 200 with an error payload (e.g. `{"error": {"code": 404, "message": "..."}}`) instead of 4xx/5xx.\
  **Impact**: Bifrost normalizes these into standard error responses so clients see consistent error handling.
</Accordion>