ai-video-gen

Video Generation (Multi-Gateway)

Generate AI videos from text prompts. Supports multiple providers via four API paths:

| Gateway | Env Variable | Providers | Tool |

|---------|-------------|-----------|------|

| fal.ai | FAL_KEY | Seedance 2.0 (standard + fast), Kling v3/v2.1, MiniMax, VEO | seedance_video, kling_video, minimax_video, veo_video |

| HeyGen | HEYGEN_API_KEY | VEO 3.1, Kling Pro, Sora v2, Runway Gen-4, Seedance Pro / Lite (1.x) | heygen_video |

| Kling Official | KLING_API_KEY | Kling official Classic, Turbo, and basic Omni video | kling_official_video |

| Gemini API | GEMINI_API_KEY / GOOGLE_API_KEY | Gemini Omni Flash (generation + conversational editing) | gemini_omni_video |

Iterative editing — Gemini Omni. When the brief calls for *refining an existing clip* (add/remove objects, restyle, change lighting or on-screen text) rather than regenerating, Gemini Omni Flash is the only provider in the fleet with stateful multi-turn editing. See Layer 3 gemini-omni for the authoritative prompting guide (reference-image tags, timecode syntax, edit-prompt rules) before writing any prompt for it.

Preferred premium default — Seedance 2.0. When any premium gateway is configured (FAL_KEY → seedance_video, or HeyGen's Video Agent / Avatar Shots path), Seedance 2.0 is the preferred default for cinematic, trailer, and high-fidelity clip work. It is the only model in the fleet with single-pass native synchronized audio, multi-shot generation, director-level camera control, and lip-sync from quoted dialogue, and it ranks #1 on Artificial Analysis Elo as of early 2026. Switch off it only when the user has a specific reason (budget, provider preference, stylistic fit like VEO for photoreal landscape or Kling for specific anime look). See Layer 3 seedance-2-0 for the authoritative prompting and parameter guide.

IMPORTANT: Always use video_selector instead of calling provider tools directly. The selector handles availability checks, cost comparison, and automatic fallback, and its scoring engine already biases toward Seedance 2.0 for cinematic intent.

Authentication

Use whichever configured gateway best matches the user's available providers and cost/quality goals.

• HeyGen: Set HEYGEN_API_KEY to access the multi-model gateway.
• fal.ai: Set FAL_KEY to access Kling, MiniMax, and Veo through fal.ai.
• Kling Official: Set KLING_API_KEY to access Kling's official direct API via provider="kling_official".
• Gemini API: Set GEMINI_API_KEY or GOOGLE_API_KEY to access Gemini Omni video generation and conversational editing.

Do not describe any gateway as the default or top choice without checking the registry and current task fit first.

fal.ai Kling (kling_video, provider="kling") and Kling Official (kling_official_video, provider="kling_official") are different paths. Do not reuse fal.ai queue URLs, FAL_KEY, or image upload behavior when the official provider is selected.

curl -X POST "https://api.heygen.com/v1/workflows/executions" \
  -H "X-Api-Key: $HEYGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"workflow_type": "GenerateVideoNode", "input": {"prompt": "A drone shot flying over a coastal city at sunset"}}'

Default Workflow

1. Call POST /v1/workflows/executions with workflow_type: "GenerateVideoNode" and your prompt

2. Receive a execution_id in the response

3. Poll GET /v1/workflows/executions/{id} every 10 seconds until status is completed

4. Use the returned video_url from the output

Execute Video Generation

Endpoint

POST https://api.heygen.com/v1/workflows/executions

Request Fields

| Field | Type | Req | Description |

|-------|------|:---:|-------------|

| workflow_type | string | Y | Must be "GenerateVideoNode" |

| input.prompt | string | Y | Text description of the video to generate |

| input.provider | string | | Video generation provider (default: "veo_3_1"). See Providers below. |

| input.aspect_ratio | string | | Aspect ratio (default: "16:9"). Common values: "16:9", "9:16", "1:1" |

| input.reference_image_url | string | | Reference image URL for image-to-video generation |

| input.tail_image_url | string | | Tail image URL for last-frame guidance |

| input.config | object | | Provider-specific configuration overrides |

Providers

| Provider | Value | Description |

|----------|-------|-------------|

| VEO 3.1 | "veo_3_1" | Google VEO 3.1 (default, highest quality) |

| VEO 3.1 Fast | "veo_3_1_fast" | Faster VEO 3.1 variant |

| VEO 3 | "veo3" | Google VEO 3 |

| VEO 3 Fast | "veo3_fast" | Faster VEO 3 variant |

| VEO 2 | "veo2" | Google VEO 2 |

| Kling Pro | "kling_pro" | Kling Pro model |

| Kling V2 | "kling_v2" | Kling V2 model |

| Sora V2 | "sora_v2" | OpenAI Sora V2 |

| Sora V2 Pro | "sora_v2_pro" | OpenAI Sora V2 Pro |

| Runway Gen-4 | "runway_gen4" | Runway Gen-4 |

| Seedance Lite | "seedance_lite" | Seedance Lite |

| Seedance Pro | "seedance_pro" | Seedance Pro |

| LTX Distilled | "ltx_distilled" | LTX Distilled (fastest) |

curl

curl -X POST "https://api.heygen.com/v1/workflows/executions" \
  -H "X-Api-Key: $HEYGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "workflow_type": "GenerateVideoNode",
    "input": {
      "prompt": "A drone shot flying over a coastal city at golden hour, cinematic lighting",
      "provider": "veo_3_1",
      "aspect_ratio": "16:9"
    }
  }'

TypeScript

interface GenerateVideoInput {
  prompt: string;
  provider?: string;
  aspect_ratio?: string;
  reference_image_url?: string;
  tail_image_url?: string;
  config?: Record<string, any>;
}

interface ExecuteResponse {
  data: {
    execution_id: string;
    status: "submitted";
  };
}

async function generateVideo(input: GenerateVideoInput): Promise<string> {
  const response = await fetch("https://api.heygen.com/v1/workflows/executions", {
    method: "POST",
    headers: {
      "X-Api-Key": process.env.HEYGEN_API_KEY!,
      "Content-Type": "application/json",
    },
    body: JSON.stringify({
      workflow_type: "GenerateVideoNode",
      input,
    }),
  });

  const json: ExecuteResponse = await response.json();
  return json.data.execution_id;
}

Python

import requests
import os

def generate_video(
    prompt: str,
    provider: str = "veo_3_1",
    aspect_ratio: str = "16:9",
    reference_image_url: str | None = None,
    tail_image_url: str | None = None,
) -> str:
    payload = {
        "workflow_type": "GenerateVideoNode",
        "input": {
            "prompt": prompt,
            "provider": provider,
            "aspect_ratio": aspect_ratio,
        },
    }

    if reference_image_url:
        payload["input"]["reference_image_url"] = reference_image_url
    if tail_image_url:
        payload["input"]["tail_image_url"] = tail_image_url

    response = requests.post(
        "https://api.heygen.com/v1/workflows/executions",
        headers={
            "X-Api-Key": os.environ["HEYGEN_API_KEY"],
            "Content-Type": "application/json",
        },
        json=payload,
    )

    data = response.json()
    return data["data"]["execution_id"]

Response Format

{
  "data": {
    "execution_id": "node-gw-v1d2e3o4",
    "status": "submitted"
  }
}

Check Status

Endpoint

GET https://api.heygen.com/v1/workflows/executions/{execution_id}

curl

curl -X GET "https://api.heygen.com/v1/workflows/executions/node-gw-v1d2e3o4" \
  -H "X-Api-Key: $HEYGEN_API_KEY"

Response Format (Completed)

{
  "data": {
    "execution_id": "node-gw-v1d2e3o4",
    "status": "completed",
    "output": {
      "video": {
        "video_url": "https://resource.heygen.ai/generated/video.mp4",
        "video_id": "abc123"
      },
      "asset_id": "asset-xyz789"
    }
  }
}

Polling for Completion

async function generateVideoAndWait(
  input: GenerateVideoInput,
  maxWaitMs = 600000,
  pollIntervalMs = 10000
): Promise<{ video_url: string; video_id: string; asset_id: string }> {
  const executionId = await generateVideo(input);
  console.log(`Submitted video generation: ${executionId}`);

  const startTime = Date.now();
  while (Date.now() - startTime < maxWaitMs) {
    const response = await fetch(
      `https://api.heygen.com/v1/workflows/executions/${executionId}`,
      { headers: { "X-Api-Key": process.env.HEYGEN_API_KEY! } }
    );
    const { data } = await response.json();

    switch (data.status) {
      case "completed":
        return {
          video_url: data.output.video.video_url,
          video_id: data.output.video.video_id,
          asset_id: data.output.asset_id,
        };
      case "failed":
        throw new Error(data.error?.message || "Video generation failed");
      case "not_found":
        throw new Error("Workflow not found");
      default:
        await new Promise((r) => setTimeout(r, pollIntervalMs));
    }
  }

  throw new Error("Video generation timed out");
}

Usage Examples

Simple Text-to-Video

curl -X POST "https://api.heygen.com/v1/workflows/executions" \
  -H "X-Api-Key: $HEYGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "workflow_type": "GenerateVideoNode",
    "input": {
      "prompt": "A person walking through a sunlit park, shallow depth of field"
    }
  }'

Image-to-Video

{
  "workflow_type": "GenerateVideoNode",
  "input": {
    "prompt": "Animate this product photo with a slow zoom and soft particle effects",
    "reference_image_url": "https://example.com/product-photo.png",
    "provider": "kling_pro"
  }
}

Vertical Format for Social Media

{
  "workflow_type": "GenerateVideoNode",
  "input": {
    "prompt": "A trendy coffee shop interior, camera slowly panning across the counter",
    "aspect_ratio": "9:16",
    "provider": "veo_3_1"
  }
}

Fast Generation with LTX

{
  "workflow_type": "GenerateVideoNode",
  "input": {
    "prompt": "Abstract colorful shapes morphing and flowing",
    "provider": "ltx_distilled"
  }
}

Best Practices

1. Be descriptive in prompts — include camera movement, lighting, style, and mood details

2. Default to Seedance 2.0 (via seedance_video) for cinematic and motion-led work when FAL_KEY is set — single-pass synced audio, multi-shot, lip-sync, director-level camera. Use VEO 3.1 / Sora V2 Pro when the user specifically wants Google or OpenAI motion character; use ltx_distilled or veo3_fast only when speed is the hard constraint

3. Use reference images for image-to-video generation — great for animating product photos or still images

4. Video generation is the slowest workflow — allow up to 5 minutes, poll every 10 seconds

5. Aspect ratio matters — use 9:16 for social media stories/reels, 16:9 for landscape, 1:1 for square

6. Output includes asset_id — use this to reference the generated video in other HeyGen workflows

7. Output URLs are temporary — download or save generated videos promptly