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

# Use Gen 4 Image with Comfy Router

> Call runway/gen4_image through Comfy Router: endpoint, request shape and the response Router returns.

API Reference for `runway/gen4_image`, served by Comfy Router from Runway.

## Quick start

Create a key in [your Comfy workspace](https://platform.comfy.org/profile/api-keys) and export it as `COMFY_API_KEY`. The Python and TypeScript snippets use the Comfy SDKs (`pip install comfy-sdk`, `npm install @comfyorg/sdk`); the cURL snippet is the same call over raw HTTP.

**Model ID:** `runway/gen4_image`

**Endpoint:** `POST https://api.comfy.org/v2/models/runway/gen4_image`

<CodeGroup>
  ```python Python theme={null}
  from comfy_sdk import Comfy

  # Reads COMFY_API_KEY from the environment.
  # The SDK automatically creates an idempotency key and reuses it for automatic retries.
  with Comfy() as client:
      result = client.models.run(
          "runway/gen4_image",
          {
              "promptText": "a red circle",
              "ratio": "1024:1024",
          },
      )

  print(result)
  ```

  ```typescript TypeScript theme={null}
  import { comfy } from "@comfyorg/sdk";

  // Reads COMFY_API_KEY from the environment.
  // The SDK automatically creates an idempotency key and reuses it for automatic retries.
  const { data } = await comfy.models.run("runway/gen4_image", {
    promptText: "a red circle",
    ratio: "1024:1024",
  });

  console.log(data);
  ```

  ```bash cURL theme={null}
  curl https://api.comfy.org/v2/models/runway/gen4_image \
    -H "X-API-Key: $COMFY_API_KEY" \
    -H "Idempotency-Key: $(uuidgen)" \
    -H "Content-Type: application/json" \
    -d "{\"promptText\": \"a red circle\", \"ratio\": \"1024:1024\"}"
  ```
</CodeGroup>

## Schema

### Input

<ParamField body="model" type="string">
  Model to use for generation. On the Comfy Router route `POST /v2/models/runway/{model}` this field is supplied from the path and MUST NOT be sent; on the v1 `POST /proxy/runway/text_to_image` route it is required and constrained to `gen4_image`.
</ParamField>

<ParamField body="promptText" type="string" required>
  Text prompt for the image generation
</ParamField>

<ParamField body="ratio" type="string" required>
  Possible values: `1920:1080`, `1080:1920`, `1024:1024`, `1360:768`, `1080:1080`, `1168:880`, `1440:1080`, `1080:1440`, `1808:768`, `2112:912`
</ParamField>

<ParamField body="referenceImages" type="object[]">
  Array of reference images to guide the generation
</ParamField>

<ParamField body="referenceImages[].uri" type="string" required>
  A HTTPS URL or data URI containing an encoded image
</ParamField>

Generated from the schema Router serves at `GET /v2/models/runway/gen4_image/openapi.json`, the same document it validates a call against before the request reaches the provider.

### Output

<ResponseField name="createdAt" type="string (date-time)" required>
  Task creation timestamp

  Format: `date-time`
</ResponseField>

<ResponseField name="id" type="string" required>
  Task ID
</ResponseField>

<ResponseField name="output" type="string[]">
  The finished generation's asset URLs — for `runway/gen4_image` each element is an IMAGE URL. Present once the task terminates successfully; this list IS the result.
</ResponseField>

<ResponseField name="progress" type="number">
  Float value between 0 and 1 representing the progress of the task. Only available if status is RUNNING.

  Range: `0` to `1`

  Format: `float`
</ResponseField>

<ResponseField name="status" type="string" required>
  Possible statuses for a Runway task.

  Possible values: `SUCCEEDED`, `RUNNING`, `FAILED`, `PENDING`, `CANCELLED`, `THROTTLED`
</ResponseField>

## Examples

### Input

```json theme={null}
{
  "promptText": "a red circle",
  "ratio": "1024:1024"
}
```

### Output

```json theme={null}
{
  "createdAt": "2027-01-01T00:00:00Z",
  "id": "5f7c1b28-9a03-4e61-8d2f-1b2c3d4e5f60",
  "output": [
    "https://example.invalid/runway/gen4_image/generated.png"
  ],
  "status": "SUCCEEDED"
}
```

## Before you ship

The SDKs create an `Idempotency-Key` and reuse it for automatic retries. For manual retries, reuse the original key. Router can hold the connection for up to 10 minutes.

When a request fails, Router sends an `X-Comfy-Error-Type` response header explaining why. A `422` means Router rejected the input before calling the provider. Download generated assets promptly because [result URLs can expire](/development/comfy-router/reference#result-assets).

<CardGroup cols={3}>
  <Card title="Headers" icon="list" href="/development/comfy-router/headers">
    Authentication, idempotency, request IDs, error buckets, retry pacing, spend limits.
  </Card>

  <Card title="Using the Router API" icon="code" href="/development/comfy-router/api">
    Model discovery, validation errors, retries, and billing.
  </Card>

  <Card title="Limitations" icon="triangle-exclamation" href="/development/comfy-router/limitations">
    What Router does not do today, and what to use instead.
  </Card>
</CardGroup>