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

# models.yaml

> Model routing, aliasing, and load balancing across upstream providers.

The `models.yaml` file acts as the internal DNS for your gateway. It maps the model names requested by your clients to the specific upstream providers capable of fulfilling them.

## File Structure

```yaml theme={null}
models:
  # The model string your client sends in their JSON request
  gpt-4o-mini:
    providers:
      - openai
      - azure-openai
    strategy: round_robin
    owned_by: open-next-router

  claude-haiku-4-5:
    providers:
      - anthropic
    strategy: round_robin
```

### Directives

* `providers`: An array of provider names (these exact names must match your `.conf` files in the `providers` directory).
* `strategy`: The load balancing strategy relative to the configured providers. Currently, `round_robin` is supported by default.
* `owned_by`: (Optional) Overrides the internal owner metadata reported when querying `/v1/models`.

## Routing Flow and Priority

When a request arrives at ONR, the gateway must determine which provider's DSL to execute. It selects the upstream based on this strict priority:

1. **Forced Override** (Highest): If the client explicitly maps a provider via the `x-onr-provider` HTTP header.
2. **Model Registry Matching**: Iterating through your `models.yaml` dictionary to find a matching model string.
3. **Round Robin Execution**: If the chosen model lists multiple providers, ONR will load-balance the requests across the array uniformly per request.