---
library_name: transformers.js
tags:
  - time-series
  - forecasting
  - chronos
  - onnx
pipeline_tag: time-series-forecasting
---

# Chronos-2 ONNX

This is an ONNX export of the [Chronos-2](amazon/chronos-2) time series forecasting model, optimized for use with [transformers.js](https://huggingface.co/docs/transformers.js).

## Model Details

- **Model Type:** Time Series Forecasting
- **Architecture:** T5-based encoder-decoder with patching
- **Context Length:** 8192 timesteps
- **Output Patch Size:** 16 timesteps
- **Quantile Levels:** 21 levels (0.01, 0.05, ..., 0.95, 0.99)
- **Model Dimension:** 768
- **Layers:** 12
- **Attention Heads:** 12

## Files

- `model.onnx` - FP32 ONNX model (456.3 MB)
- `model_quantized.onnx` - INT8 quantized model (124.7 MB, ~70% size reduction). transformers.js symlinks point to this file by default.
- `config.json` - Model configuration
- `generation_config.json` - Generation parameters
- `onnx/` - transformers.js-compatible directory structure

## Usage

### JavaScript (transformers.js)

```javascript
import { pipeline } from '@huggingface/transformers';

// Load the forecasting pipeline
const forecaster = await pipeline('time-series-forecasting', 'kashif/chronos-2-onnx');

// Your historical time series data
const timeSeries = [605, 586, 586, 559, 511, 487, 484, 458, ...];  // 100+ timesteps

// Generate 16-step forecast with quantiles
const output = await forecaster(timeSeries, {
    prediction_length: 16,
    quantile_levels: [0.1, 0.5, 0.9],  // 10th, 50th (median), 90th percentiles
});

// Output format: { forecast: [[t1_q1, t1_q2, t1_q3], ...], quantile_levels: [...] }
console.log('Median forecast:', output.forecast.map(row => row[1]));  // Extract median

// Clean up
await forecaster.dispose();
```

### Batch Forecasting

```javascript
const batch = [
    [100, 110, 105, 115, 120, ...],  // Series 1
    [50, 55, 52, 58, 60, ...],       // Series 2
];

const outputs = await forecaster(batch);
// Returns array of forecasts, one per input series
```

### Forecast with Covariates

```javascript
const result = await forecaster(
    {
        target: salesSeries,
        past_covariates: {
            temperature: pastTemps,
            promo: pastPromoFlags,
        },
        future_covariates: {
            temperature: futureTemps,
            promo: futurePromoFlags,
        },
    },
    {
        prediction_length: 24,
        quantile_levels: [0.1, 0.5, 0.9],
    },
);

console.log(result.forecast[0]);  // Quantile matrix for the target series
```

## Performance

- **Inference Time:** ~35-80ms per series (CPU, Node.js)
- **Speedup vs PyTorch:** 3-8x faster
- **Accuracy:** <1% error vs PyTorch reference

## Technical Details

### Preprocessing

Chronos-2 uses automatic preprocessing:
1. **Repeat-padding:** Input is padded to be divisible by patch_size (16)
2. **Instance normalization:** Per-series z-score normalization
3. **arcsinh transformation:** Nonlinear transformation for better modeling

All preprocessing is handled automatically by the pipeline.

### Output Format

The model outputs quantile forecasts:

```typescript
interface Chronos2Output {
    forecast: number[][];        // [prediction_length, num_quantiles]
    quantile_levels: number[];   // The quantile levels for each column
}
```

Extract specific quantiles:
```javascript
const median = output.forecast.map(row => row[1]);    // 50th percentile
const lower = output.forecast.map(row => row[0]);     // 10th percentile (lower bound)
const upper = output.forecast.map(row => row[2]);     // 90th percentile (upper bound)
```

## Limitations

- **Maximum context:** 8192 timesteps
- **Fixed prediction length:** 16 timesteps (for now; autoregressive unrolling coming soon)
- **Univariate only:** Single time series per input (multivariate support coming)

## Citation

```bibtex
@article{ansari2024chronos,
  title={Chronos: Learning the Language of Time Series},
  author={Ansari, Abdul Fatir and others},
  journal={arXiv preprint arXiv:2403.07815},
  year={2024}
}
```

## License

Apache 2.0

## Links

- [Chronos-2 Paper](https://arxiv.org/abs/2403.07815)
- [Chronos GitHub](https://github.com/amazon-science/chronos-forecasting)
- [transformers.js Documentation](https://huggingface.co/docs/transformers.js)