> ## 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 LTX 2.5 Fast with Comfy Router

> Call ltx/ltx-2-5-fast through Comfy Router: endpoint, request shape and the response Router returns.

API Reference for `ltx/ltx-2-5-fast`, served by Comfy Router from LTX.

## 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:** `ltx/ltx-2-5-fast`

**Endpoint:** `POST https://api.comfy.org/v2/models/ltx/ltx-2-5-fast`

<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(
          "ltx/ltx-2-5-fast",
          {
              "duration": 2,
              "fps": 24,
              "generate_audio": False,
              "prompt": "A single red maple leaf resting on a plain white background.",
              "resolution": "1280x720",
          },
      )

  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("ltx/ltx-2-5-fast", {
    duration: 2,
    fps: 24,
    generate_audio: false,
    prompt: "A single red maple leaf resting on a plain white background.",
    resolution: "1280x720",
  });

  console.log(data);
  ```

  ```bash cURL theme={null}
  curl https://api.comfy.org/v2/models/ltx/ltx-2-5-fast \
    -H "X-API-Key: $COMFY_API_KEY" \
    -H "Idempotency-Key: $(uuidgen)" \
    -H "Content-Type: application/json" \
    -d "{\"duration\": 2, \"fps\": 24, \"generate_audio\": false, \"prompt\": \"A single red maple leaf resting on a plain white background.\", \"resolution\": \"1280x720\"}"
  ```
</CodeGroup>

## Schema

### Input

<ParamField body="duration" type="integer" required>
  Video duration in seconds (maximum depends on resolution and frame rate)

  Possible values: `2`, `3`, `4`, `5`, `6`, `8`, `10`, `12`, `14`, `16`, `18`, `20`
</ParamField>

<ParamField body="fps" type="integer" default="25">
  Frame rate in frames per second

  Possible values: `24`, `25`, `48`, `50`
</ParamField>

<ParamField body="generate_audio" type="boolean" default="true">
  Generate audio for the video
</ParamField>

<ParamField body="model" type="string">
  Model to use for generation. On the Comfy Router route `POST /v2/models/ltx/{model}` this field is supplied from the path and may be omitted. The spellings LTX serves on this operation -- the set Comfy Router addresses as `ltx/<model>` -- are ltx-2-5-fast and ltx-2-5-pro; they are written out here rather than constrained to an enum for the reason the comment above gives. Which resolutions each one admits is the `x-comfy-model-resolutions` matrix on the `resolution` property below.
</ParamField>

<ParamField body="prompt" type="string" required>
  Text prompt describing the desired video content
</ParamField>

<ParamField body="resolution" type="string" required>
  Output video resolution. The enum is the union over all models; the supported set is per model. Supported pairs: ltx-2-5-fast: 1280x720, 720x1280, 1920x1080, 1080x1920, 2560x1440, 1440x2560, 3840x2160, 2160x3840; ltx-2-5-pro: 1280x720, 720x1280, 1920x1080, 1080x1920. Other (model, resolution) pairs are not supported; the v2 routes reject them with 400. The same matrix is published machine-readably in this property's x-comfy-model-resolutions extension.

  Possible values: `1280x720`, `720x1280`, `1920x1080`, `1080x1920`, `2560x1440`, `1440x2560`, `3840x2160`, `2160x3840`
</ParamField>

Generated from the schema Router serves at `GET /v2/models/ltx/ltx-2-5-fast/openapi.json`, the same document it validates a call against before the request reaches the provider.

### Output

<ResponseField name="completed_at" type="string">
  Job completion timestamp (ISO 8601)
</ResponseField>

<ResponseField name="created_at" type="string">
  Job creation timestamp (ISO 8601)
</ResponseField>

<ResponseField name="error" type="object">
  Present when status is failed
</ResponseField>

<ResponseField name="error.message" type="string" />

<ResponseField name="error.type" type="string" />

<ResponseField name="id" type="string">
  Unique job identifier
</ResponseField>

<ResponseField name="result" type="object">
  Present when status is completed; output URLs expire 24 hours after completion
</ResponseField>

<ResponseField name="result.video_url" type="string">
  URL of the generated video
</ResponseField>

<ResponseField name="status" type="string">
  Job status (pending, processing, completed, failed)
</ResponseField>

## Examples

### Input

```json theme={null}
{
  "duration": 2,
  "fps": 24,
  "generate_audio": false,
  "prompt": "A single red maple leaf resting on a plain white background.",
  "resolution": "1280x720"
}
```

### Output

```json theme={null}
{
  "completed_at": "2026-01-01T00:02:10Z",
  "created_at": "2026-01-01T00:00:00Z",
  "id": "3f7a1b28-5c0d-4e91-8a6f-1b2c3d4e5f60",
  "result": {
    "video_url": "https://example.invalid/ltx/generated.mp4"
  },
  "status": "completed"
}
```

## 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>