---
title: "Local vLLM Proxy"
description: "Expose one Local vLLM deployment as multiple model servers"
position: 7
---

LocalVLLMModelProxy (in `responses_api_models/local_vllm_model_proxy`) is a lightweight model server that forwards requests to an existing [LocalVLLMModel](/model-server/local-vllm) instead of launching its own vLLM engine.
It is a subclass of VLLMModel, so it accepts the same configuration fields, but it owns no GPUs.

## When to use it

Use a proxy when you need several model servers that share **one** vLLM deployment but differ in their request-time configuration.
For example, one server with reasoning enabled and one with reasoning disabled through the request params, or servers with different sampling parameters.
Without the proxy you would have to launch a separate vLLM engine (and duplicate GPUs) for each variation.

At startup the proxy waits for its referenced LocalVLLMModel to come up, reads that server's inner vLLM endpoint (`base_url`, `api_key`, `model`), and routes all of its own requests there.

If you are working with an existing vLLM endpoint that you manage outside of Gym, use [VLLMModel](/model-server/vllm) instead.

## Configuration

A proxy is a normal model server config that adds a `model_server` reference pointing at the LocalVLLMModel it should forward to:

```yaml
policy_model_reasoning_off:
  responses_api_models:
    local_vllm_model_proxy:
      entrypoint: app.py

      # Request-time settings that differ from the backing server
      chat_template_kwargs:
        enable_thinking: false

      # Standard VLLMModel fields
      return_token_id_information: false
      uses_reasoning_parser: true

      model_server:
        type: responses_api_models
        name: policy_model   # name of the LocalVLLMModel server to proxy to
```

Run it alongside the backing LocalVLLMModel by chaining both configs in `config_paths`:

```bash
gym env start \
    --config responses_api_models/local_vllm_model/configs/openai/gpt-oss-20b-reasoning-high.yaml \
    --config responses_api_models/local_vllm_model_proxy/configs/local_vllm_model_proxy.yaml \
    ++policy_model_proxy.responses_api_models.local_vllm_model_proxy.model_server.name=gpt-oss-20b-reasoning-high
```

| Parameter | Type | Default | Description |
|-----------|------|---------|-------------|
| `model_server` | `ModelServerRef` | — | **Required.** The LocalVLLMModel server to forward requests to, by `type` and `name`. |

`base_url`, `api_key`, and `model` are populated automatically from the backing server and should **not** be set in your config.
All other VLLMModel fields (`chat_template_kwargs`, `extra_body`, `return_token_id_information`, and so on) behave as documented in the [VLLMModel configuration reference](/model-server/vllm#vllmmodel-configuration-reference).
