> ## 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.

# Response Block

> Transforming the upstream payload back to the client.

The `response` block defines how the data returned by the LLM Provider should be mapped and sanitized before ONR streams it back to your user. If multiple mapping directives exist in a block, the **last one wins**.

## Passthrough (No Edits)

If the upstream natively responds with the OpenAI-compatible schema (like Groq, DeepSeek, or Anyscale), simply tell ONR to let the response pass through safely.

```nginx theme={null}
response { 
  resp_passthrough; 
}
```

## Structural Schema Mapping

If the response is in a proprietary format (e.g., Anthropic or Gemini), you need to tell ONR how to map the JSON payload or Server-Sent Events (SSE) stream back into the OpenAI schema.

### JSON Responses (Non-Streaming)

```nginx theme={null}
response { 
  resp_map <mode>; 
}
```

*(Modes supported in v0.1)*:

* `anthropic_to_openai_chat`
* `openai_to_anthropic_messages`
* `gemini_to_openai_chat`
* `openai_responses_to_openai_chat`
* `openai_to_gemini_chat`

### Server-Sent Events (Streaming)

```nginx theme={null}
response { 
  sse_parse <mode>; 
}
```

*(Modes supported in v0.1)*:

* `anthropic_to_openai_chunks`
* `openai_to_anthropic_chunks`
* `gemini_to_openai_chat_chunks`
* `openai_to_gemini_chunks`
* `openai_responses_to_openai_chat_chunks`

***

## Best-Effort JSON Mutations

In addition to schema mappers, ONR can run lightweight field additions, deletions, and renamings on the final response body before yielding to the user.
These work for both static JSON responses and individual `data:` chunk payloads during SSE streaming.

```nginx theme={null}
response {
  json_del "$.usage";
  json_set "$.foo" "bar";
  
  json_set_if_absent "$.bar" "baz";
  json_rename "$.a" "$.b";
}
```

### Conditional SSE Mutations

You can conditionally delete JSON fields specifically during a running stream based on the event's internal type.

```nginx theme={null}
response {
  # If the SSE event payload has `$.type == "message_delta"`, 
  # delete the `$.usage` field from that specific event chunk.
  sse_json_del_if "$.type" "message_delta" "$.usage";
}
```

*Note: The conditional check requires an exact string match.*