Text to Speech

AI Gateway Text to Speech

Generate spoken audio from text with Google, Microsoft, and OpenAI speech models. Use this for voiceovers, audio versions of written content, or spoken responses in your app.

Use this to turn text into spoken audio. For live, two-way voice, see Realtime; to transcribe recorded audio, see Speech to Text.

Text to speech is in beta and access is rolling out gradually. Speech models may not appear in the model catalog yet for your team.

Supported models

Provider	Model ID
Google	`google/gemini-3.8-flash-lite-tts`
Google	`google/gemini-3.8-flash-tts`
Microsoft	`microsoft/mai-voice-2`
Microsoft	`microsoft/mai-voice-2-flash`
Microsoft	`microsoft/mai-voice-2.1`
Microsoft	`microsoft/mai-voice-2.1-flash`
OpenAI	`openai/tts-1`
OpenAI	`openai/tts-1-hd`

Generate speech with the AI SDK

For SDK options and result types, see AI SDK speech and Python speech.

Use generateSpeech with a speech model from the AI Gateway provider:

generate-speech.ts

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('openai/tts-1'),
  text: 'Hello! Thanks for trying out AI Gateway.',
  voice: 'alloy',
  outputFormat: 'mp3',
});
 
await writeFile('greeting.mp3', result.audio.uint8Array);
 
console.log("Saved greeting.mp3");

generate-speech.py

import asyncio
import ai
import base64
from pathlib import Path
 
async def main():
    result = await ai.ops.generate_audio(
        ai.get_model('openai/tts-1'),
        'Hello! Thanks for trying out AI Gateway.',
        params=ai.ops.AudioParams(voice="alloy", output_format="mp3"),
    )
    audio = result.value[0]
    data = audio.data if isinstance(audio.data, bytes) else base64.b64decode(audio.data)
    Path("greeting.mp3").write_bytes(data)
    print("Saved greeting.mp3")
 
asyncio.run(main())

Speech support ships in the stable AI SDK releases. Install it with pnpm add ai @ai-sdk/gateway.

The Python examples use the AI SDK for Python beta. These audio operations use dedicated AI Gateway endpoints. They are separate from Chat Completions, Messages, and Responses. See the Python SDK setup for installation requirements.

Generate speech with Google

Use either google/gemini-3.8-flash-lite-tts or google/gemini-3.8-flash-tts with gateway.speechModel(). Both support single-voice narration and two-speaker dialogue.

Choose a prebuilt voice such as Kore, Puck, Zephyr, or Charon. Voice names are case-sensitive, and the default is Kore. Set instructions to control delivery without changing the spoken text:

generate-google-speech.ts

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('google/gemini-3.8-flash-lite-tts'),
  text: 'Welcome to the audio edition.',
  voice: 'Kore',
  instructions: 'Warm, relaxed, and speaking slowly',
  outputFormat: 'wav',
});
 
await writeFile('greeting.wav', result.audio.uint8Array);
 
console.log('Saved greeting.wav');

generate-google-speech.js

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('google/gemini-3.8-flash-lite-tts'),
  text: 'Welcome to the audio edition.',
  voice: 'Kore',
  instructions: 'Warm, relaxed, and speaking slowly',
  outputFormat: 'wav',
});
 
await writeFile('greeting.wav', result.audio.uint8Array);
 
console.log('Saved greeting.wav');

Google returns WAV audio by default. Save result.audio.uint8Array directly as it already includes the WAV header. Gemini 3.8 also supports pcm, mulaw, and alaw through outputFormat.

Generate dialogue with Google

For two-speaker dialogue, configure voices and structured turns under providerOptions.google. Set text to an empty string because turns supplies the transcript. Each turn's speechMetadata.speaker must match a configured speaker:

generate-google-dialogue.ts

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('google/gemini-3.8-flash-tts'),
  text: '',
  outputFormat: 'wav',
  providerOptions: {
    google: {
      multiSpeakerVoiceConfig: {
        speakerVoiceConfigs: [
          {
            speaker: 'Host',
            voiceConfig: { prebuiltVoiceConfig: { voiceName: 'Kore' } },
          },
          {
            speaker: 'Guest',
            voiceConfig: { prebuiltVoiceConfig: { voiceName: 'Puck' } },
          },
        ],
      },
      turns: [
        {
          text: 'What are we exploring today?',
          speechMetadata: { speaker: 'Host', style: 'curious' },
        },
        {
          text: 'How to turn text into spoken audio.',
          speechMetadata: { speaker: 'Guest', style: 'cheerful' },
        },
      ],
    },
  },
});
 
await writeFile('dialogue.wav', result.audio.uint8Array);
 
console.log('Saved dialogue.wav');

generate-google-dialogue.js

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('google/gemini-3.8-flash-tts'),
  text: '',
  outputFormat: 'wav',
  providerOptions: {
    google: {
      multiSpeakerVoiceConfig: {
        speakerVoiceConfigs: [
          {
            speaker: 'Host',
            voiceConfig: { prebuiltVoiceConfig: { voiceName: 'Kore' } },
          },
          {
            speaker: 'Guest',
            voiceConfig: { prebuiltVoiceConfig: { voiceName: 'Puck' } },
          },
        ],
      },
      turns: [
        {
          text: 'What are we exploring today?',
          speechMetadata: { speaker: 'Host', style: 'curious' },
        },
        {
          text: 'How to turn text into spoken audio.',
          speechMetadata: { speaker: 'Guest', style: 'cheerful' },
        },
      ],
    },
  },
});
 
await writeFile('dialogue.wav', result.audio.uint8Array);
 
console.log('Saved dialogue.wav');

A turn's speechMetadata.style overrides instructions. Turns without a style inherit instructions. For more options, see the AI SDK Google speech documentation.

Generate speech with Microsoft

Use microsoft/mai-voice-2.1 or microsoft/mai-voice-2 for high-fidelity, long-form narration, and microsoft/mai-voice-2.1-flash or microsoft/mai-voice-2-flash for low-latency voice agents. All four models use gateway.speechModel() and share the same voices and options.

Choose a prebuilt voice such as en-US-Harper, de-DE-Mia, or es-MX-Valeria. Each voice name includes its locale, which sets the spoken language, and the default is en-US-Harper. Set providerOptions.azure.style to control delivery, and styleDegree to set its intensity:

generate-microsoft-speech.ts

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('microsoft/mai-voice-2-flash'),
  text: 'Thanks for calling! Your order shipped this morning.',
  voice: 'en-US-Ethan',
  outputFormat: 'mp3',
  providerOptions: {
    azure: { style: 'excited', styleDegree: 1.5 },
  },
});
 
await writeFile('order-update.mp3', result.audio.uint8Array);
 
console.log('Saved order-update.mp3');

generate-microsoft-speech.js

import { generateSpeech } from 'ai';
import { gateway } from '@ai-sdk/gateway';
import { writeFile } from 'node:fs/promises';
 
const result = await generateSpeech({
  model: gateway.speechModel('microsoft/mai-voice-2-flash'),
  text: 'Thanks for calling! Your order shipped this morning.',
  voice: 'en-US-Ethan',
  outputFormat: 'mp3',
  providerOptions: {
    azure: { style: 'excited', styleDegree: 1.5 },
  },
});
 
await writeFile('order-update.mp3', result.audio.uint8Array);
 
console.log('Saved order-update.mp3');

Microsoft returns MP3 audio by default. MAI-Voice also supports wav, pcm, and opus through outputFormat. When you omit voice, language picks a default voice for that language, such as de-DE-Mia for de. For more options, see the AI SDK Azure speech documentation.

Request options

Option	Description
`text`	The text to convert to speech. Required.
`voice`	The voice to use, such as `alloy`. Available voices depend on the model.
`outputFormat`	The audio format, such as `mp3` or `wav`.
`instructions`	Directions for how the model should speak, such as tone or pacing.
`speed`	Playback speed. Defaults to 1.
`language`	The language of the input text.

Support for each option varies by model. Unsupported options are reported in warnings on the result instead of failing the request.

Generate speech with the REST API

You can also call the speech endpoint directly. Send a POST request with the model in the ai-model-id header. The response contains the audio as a base64-encoded string:

generate-speech-rest.ts

import { writeFile } from 'node:fs/promises';
 
const response = await fetch(
  'https://ai-gateway.vercel.sh/v4/ai/speech-model',
  {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${process.env.AI_GATEWAY_API_KEY}`,
      'ai-gateway-protocol-version': '0.0.1',
      'ai-speech-model-specification-version': '4',
      'ai-model-id': 'openai/tts-1',
      'Content-Type': 'application/json',
    },
    body: JSON.stringify({
      text: 'Hello! Thanks for trying out AI Gateway.',
      voice: 'alloy',
      outputFormat: 'mp3',
    }),
  },
);
 
const result = await response.json();
await writeFile('greeting.mp3', Buffer.from(result.audio, 'base64'));
 
console.log("Saved greeting.mp3");

request.py

import json
import os
import urllib.request
 
request = urllib.request.Request(
    'https://ai-gateway.vercel.sh/v4/ai/speech-model',
    data=json.dumps({'text': 'Hello! Thanks for trying out AI Gateway.', 'voice': 'alloy', 'outputFormat': 'mp3'}).encode(),
    headers={'Authorization': "Bearer " + os.environ["AI_GATEWAY_API_KEY"], 'ai-gateway-protocol-version': '0.0.1', 'ai-speech-model-specification-version': '4', 'ai-model-id': 'openai/tts-1', 'Content-Type': 'application/json'},
)
with urllib.request.urlopen(request) as response:
    print(json.load(response))

generate-speech.sh

set -euo pipefail
 
curl --fail-with-body -X POST https://ai-gateway.vercel.sh/v4/ai/speech-model \
  -H "Authorization: Bearer $AI_GATEWAY_API_KEY" \
  -H "ai-gateway-protocol-version: 0.0.1" \
  -H "ai-speech-model-specification-version: 4" \
  -H "ai-model-id: openai/tts-1" \
  -H "Content-Type: application/json" \
  -d '{
    "text": "Hello! Thanks for trying out AI Gateway.",
    "voice": "alloy",
    "outputFormat": "mp3"
  }' | jq -r '.audio' | base64 -d > greeting.mp3
 
if [ -s greeting.mp3 ]; then echo "Saved greeting.mp3"; else exit 1; fi

The response is a JSON object with the base64-encoded audio:

response.json

{
  "audio": "SUQzBAAAAAAA...",
  "warnings": []
}

Limitations

Audio returns base64-encoded in a JSON response. Streaming audio output is not supported.
Google speech models don't support speed or language. Set pacing through instructions since the model detects the language from the text.
Microsoft speech models don't support instructions. Set the delivery with providerOptions.azure.style instead.
Microsoft speech models reject unknown voices and unsupported styles.

Last updated September 8, 2026

Cross-link map: AI Gateway Text to Speech (/docs/ai-gateway/modalities/text-to-speech)

From the Vercel docs graph (built 2026-10-09T15:41:22.984Z), spanning vercel.com docs + KB, nextjs.org, ai-sdk.dev, and other Vercel documentation sites. Full graph as JSON: https://vercel.com/docs/graph.json

Semantically closest pages

AI Gateway Speech to Text — Transcribe audio files into text with transcription models through Vercel AI Gateway.
AI Gateway Audio Input — Analyze recorded audio with AI Gateway, compare audio input with transcription and realtime voice, and choose a supporte
AI Gateway Speech Quickstart: Transcription and TTS — Generate speech and transcribe it using AI Gateway.
generateSpeech — API Reference for generateSpeech.
Speech — Learn how to generate speech from text with the AI SDK.

Prerequisites

AI Gateway — Vercel MCP tools for ai gateway.

This page links to (6)

Speech — Learn how to generate speech from text with the AI SDK.
Azure OpenAI — Learn how to use the Azure OpenAI provider for the AI SDK.
Google — Learn how to use Google Provider.
Realtime Voice with AI Gateway — Build low-latency, speech-to-speech voice agents with the AI SDK through Vercel AI Gateway.
AI Gateway Speech to Text — Transcribe audio files into text with transcription models through Vercel AI Gateway.
AI SDK for Python with AI Gateway — Build AI-powered Python applications using the AI SDK for Python with AI Gateway for unified access to 200+ models.

Pages that link here (7)

By site: vercel-changelog (2) · vercel-docs (5)

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From vercel-docs

AI Gateway Speech Quickstart: Transcription and TTS — Generate speech and transcribe it using AI Gateway.
AI Gateway Inputs and Tools — Send images, PDFs, audio, and video to AI Gateway models, and connect models to application functions with tool use.
AI Gateway Model Modalities — The inputs and outputs AI Gateway models work with: text, image, and video generation, speech to text, text to speech, r
Realtime Voice with AI Gateway — Build low-latency, speech-to-speech voice agents with the AI SDK through Vercel AI Gateway.
AI Gateway Speech to Text — Transcribe audio files into text with transcription models through Vercel AI Gateway.

Speech to Text

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