feat(google-cloud): add Google Cloud Text-to-Speech plugin

[mshivam019]

Summary

• Adds @livekit/agents-plugin-google-cloud using the @google-cloud/text-to-speech client library
• gRPC bidirectional streaming: SynthesizeStream via TextToSpeechClient.streamingSynthesize() with sentence tokenization
• REST one-shot synthesis: ChunkedStream via TextToSpeechClient.synthesizeSpeech() with LINEAR16 WAV -> PCM extraction
• updateOptions() for runtime voice/language/gender changes
• Credentials follow the standard Google Cloud auth chain: credentials object -> keyFilename -> GOOGLE_APPLICATION_CREDENTIALS -> ADC

Why this plugin vs the existing google.beta.TTS

The existing google.beta.TTS (Gemini TTS) uses @google/genai which does not support streaming synthesis. This plugin uses the @google-cloud/text-to-speech client which supports gRPC bidirectional streaming — needed for Gemini Flash TTS models like gemini-3.1-flash-tts-preview as well as classic models (Journey, Chirp 3, Standard, WaveNet).

The LiveKit docs show "Available in: [ ] Node.js, [x] Python" — this closes the Node.js gap.

Credentials

// Option 1: credentials object
const tts = new TTS({
  credentials: { client_email: '...', private_key: '...' },
});

// Option 2: key file path
const tts = new TTS({
  keyFilename: '/path/to/service-account.json',
});

// Option 3: GOOGLE_APPLICATION_CREDENTIALS env var or gcloud ADC (auto-detected)
const tts = new TTS();

Streaming synthesis

• Uses TextToSpeechClient.streamingSynthesize() for gRPC bidirectional streaming
• Input text sentence-tokenized via tokenize.basic.SentenceTokenizer
• Audio decoded via AudioByteStream, emitted as SynthesizedAudio frames
• Proper abort signal handling: cleans up gRPC call via call.cancel()/call.destroy()
• AudioByteStream.flush() called on stream end to prevent trailing audio truncation

Files changed

File	Change
plugins/google-cloud/package.json	New package: @livekit/agents-plugin-google-cloud
plugins/google-cloud/src/tts.ts	TTS, SynthesizeStream, ChunkedStream classes
plugins/google-cloud/src/models.ts	TTSModel, TTSGender, TTSLanguage types
plugins/google-cloud/src/index.ts	Plugin registration + exports
plugins/google-cloud/tsconfig.json	Extends root tsconfig
plugins/google-cloud/tsup.config.ts	Extends root tsup config
plugins/google-cloud/api-extractor.json	Extends shared API extractor config
plugins/google-cloud/README.md	Installation, auth, usage docs
.changeset/google-cloud-tts-plugin.md	Changeset entry
pnpm-lock.yaml	Lock @google-cloud/text-to-speech dependency

Usage

import { TTS } from '@livekit/agents-plugin-google-cloud';

// Streaming synthesis with Gemini Flash TTS
const tts = new TTS({
  modelName: 'gemini-3.1-flash-tts-preview',
  voiceName: 'Zephyr',
  language: 'en-IN',
});

// Non-streaming with standard voices
const tts = new TTS({
  language: 'en-US',
  voiceName: 'en-US-Standard-H',
  streaming: false,
});

Verification

• tsc --noEmit — zero errors
• eslint src/**/*.ts — zero errors
• tsup build — CJS + ESM bundles compile cleanly

[changeset-bot]

🦋 Changeset detected

Latest commit: cca2c86

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 35 packages

Name	Type
@livekit/agents-plugin-google-cloud	Patch
@livekit/agents	Patch
@livekit/agents-plugin-anam	Patch
@livekit/agents-plugin-assemblyai	Patch
@livekit/agents-plugin-baseten	Patch
@livekit/agents-plugin-bey	Patch
@livekit/agents-plugin-cartesia	Patch
@livekit/agents-plugin-cerebras	Patch
@livekit/agents-plugin-deepgram	Patch
@livekit/agents-plugin-elevenlabs	Patch
@livekit/agents-plugin-fishaudio	Patch
@livekit/agents-plugin-google	Patch
@livekit/agents-plugin-hedra	Patch
@livekit/agents-plugin-hume	Patch
@livekit/agents-plugin-inworld	Patch
@livekit/agents-plugin-lemonslice	Patch
@livekit/agents-plugin-liveavatar	Patch
@livekit/agents-plugin-livekit	Patch
@livekit/agents-plugin-minimax	Patch
@livekit/agents-plugin-mistral	Patch
@livekit/agents-plugin-mistralai	Patch
@livekit/agents-plugin-neuphonic	Patch
@livekit/agents-plugin-openai	Patch
@livekit/agents-plugin-perplexity	Patch
@livekit/agents-plugin-phonic	Patch
@livekit/agents-plugin-resemble	Patch
@livekit/agents-plugin-rime	Patch
@livekit/agents-plugin-runway	Patch
@livekit/agents-plugin-sarvam	Patch
@livekit/agents-plugin-silero	Patch
@livekit/agents-plugin-soniox	Patch
@livekit/agents-plugin-tavus	Patch
@livekit/agents-plugins-test	Patch
@livekit/agents-plugin-trugen	Patch
@livekit/agents-plugin-xai	Patch

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