# S1 (Free)

Fish Audio S1 is trained on over 2 million hours of audio with online RLHF (GRPO). It achieves 0.8% WER and 0.4% CER on Seed TTS Eval. S1 supports open-domain emotion, tone, and special effect markers.

- **Model ID:** `fish-audio/s1-free`
- **Type:** speech
- **Providers:** fish-audio
- **Context window:** Not applicable
- **Maximum output tokens:** 0
- **Pricing:** See the provider details below
- **Canonical page:** https://vercel.com/ai-gateway/models/s1-free

## Supported parameters

Detailed capability metadata has not been reported for this model.

## Example

```ts
import { experimental_generateSpeech as generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';

const result = await generateSpeech({
  model: gateway.speechModel('fish-audio/s1-free'),
  text: 'Hello from the Vercel AI Gateway!',
  // Browse voices at https://fish.audio/app/discovery
  // Open a voice, then use "Copy Model Id" in its "..." menu.
  voice: '933563129e564b19a115bedd57b7406a',
});

await writeFile('speech.mp3', result.audio.uint8Array);
```

## Links

- [Model page](https://vercel.com/ai-gateway/models/s1-free)
- [AI Gateway documentation](https://vercel.com/docs/ai-gateway)
- [Provider model documentation](https://docs.fish.audio/developer-guide/models-pricing/models-overview)
- [Provider pricing](https://docs.fish.audio/developer-guide/models-pricing/models-overview)