# Gen-4.5 - Core.Today AI API

> Runway's Gen-4.5 model, offering state-of-the-art video motion quality, prompt adherence, and visual fidelity for text-to-video and image-to-video generation.

- **Provider**: Runway
- **Model ID**: runwayml/gen-4.5
- **Category**: Video Generation
- **Credits**: 1400 per 5s video (default) — billed per second (279/s, 5-10s)
- **Speed**: Medium
- **Quality**: Ultra

## Features
- State-of-the-art motion quality and prompt adherence
- Flat per-second pricing regardless of aspect ratio
- Text-to-video or image-to-video from an optional first frame
- 5 or 10 second duration options
- Wide range of aspect ratios including 21:9 cinematic

## Use Cases
- High-fidelity brand and marketing videos
- Complex prompt-driven scenes requiring precise motion control
- Animating a first-frame image into a fluid 5-10 second clip
- Cinematic 21:9 shots for trailers or hero content
- Reproducible generations using a fixed seed

## API Endpoint

Base URL: https://api.core.today/v1
Create Prediction: POST /predictions
Get Status: GET /predictions/{job_id}

## Authentication
Header: X-API-Key: YOUR_API_KEY

## Input Parameters

### Required
- **prompt**: string - Text prompt for video generation

### Optional
- **image**: string - Optional initial image (first frame). If omitted, video is generated from text only
- **duration**: integer (default: 5) - Duration of the output video in seconds
  Options: 5, 10
- **aspect_ratio**: string (default: 16:9) - Video aspect ratio
  Options: 16:9, 9:16, 4:3, 3:4, 1:1, 21:9
- **seed**: integer - Random seed for reproducible generation

## Examples

### Text-to-Video (10s)
A fully text-driven scene at the maximum 10-second duration
```json
{
  "model": "runwayml/gen-4.5",
  "input": {
    "prompt": "A dense, verdant jungle world made up of small lego-like pieces. We see a rainbow chameleon running through the 3D world, the camera in and out of focus.",
    "duration": 10,
    "aspect_ratio": "16:9"
  }
}
```

### Cinematic 21:9 Clip (5s)
A shorter, cheaper clip in a wide cinematic aspect ratio
```json
{
  "model": "runwayml/gen-4.5",
  "input": {
    "prompt": "A vintage train winding through snow-capped mountains at golden hour",
    "duration": 5,
    "aspect_ratio": "21:9"
  }
}
```

## Response Format
```json
{
  "job_id": "abc123",
  "status": "pending | processing | completed | failed",
  "result": "URL or data (when completed)"
}
```

## Usage Flow
1. POST /predictions with model and input -> receive job_id
2. GET /predictions/{job_id} -> poll until status is completed or failed
3. Result contains output URL(s)

## Tips
- Pricing is a flat $0.12/sec regardless of resolution or aspect ratio
- duration only accepts 5 or 10 seconds — a 10s clip costs exactly 2x a 5s clip
- Providing an initial image anchors the first frame and often improves motion coherence
- Use a fixed seed to reproduce or slightly vary a specific result

## Documentation
https://replicate.com/runwayml/gen-4.5