feat(speechify): add Speechify TTS plugin

[luke-speechify]

Summary

Adds @livekit/agents-plugin-speechify — a Speechify text-to-speech plugin with streaming synthesis and word-level timestamps, built on Speechify's official @speechify/api SDK. It follows the existing plugin conventions and mirrors the cartesia package layout.

Features

• Streaming TTS with word-level timestamps. Uses Speechify's /v1/audio/stream/with-timestamps endpoint (Server-Sent Events) via client.audio.streamWithTimestamps(), so audio and aligned speech marks arrive incrementally while the audio is still being generated. Declares capabilities: { streaming: true, alignedTranscript: true }.
• SynthesizeStream chunks streamed input into sentences and streams one request per sentence; ChunkedStream handles one-shot synthesize(). Both defer final: true to the last frame of the stream and attach each request's word timestamps to a frame (speech-mark times are absolute milliseconds, converted to seconds).
• 24 kHz mono PCM output (pcm_24000).
• Configurable voice, model, language, and loudness/text normalization via TTSOptions. Defaults to the dominic_32 voice and the simba-3.2 model.
• Reads the API key from the apiKey option or the SPEECHIFY_API_KEY environment variable.

Custom headers

Every request carries two custom headers so Speechify can attribute API usage to this integration per release:

• Speechify-Caller: livekit-typescript
• Speechify-Caller-Version: <plugin version>

They are set on the SDK client and merged into every request; the SDK sets no caller of its own, and per-request options do not clobber them.

Tests

• Deterministic unit tests mock the SSE endpoint and cover one-shot + streaming synthesis, audio framing, word-timestamp conversion, and the attribution headers.
• A gated end-to-end test (via @livekit/agents-plugins-test) runs when SPEECHIFY_API_KEY and OPENAI_API_KEY are set.
• pnpm build (ESM + CJS + type declarations) and api-extractor pass.

Notes

• New files carry SPDX/REUSE headers; public options and methods are documented for TypeDoc.
• Added to the root README plugin table and the turbo.json env allowlist (SPEECHIFY_API_KEY).

Usage

import * as speechify from '@livekit/agents-plugin-speechify';

const tts = new speechify.TTS({ voiceId: 'dominic_32', model: 'simba-3.2' });

[changeset-bot]

🦋 Changeset detected

Latest commit: faef238

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

This PR includes changesets to release 39 packages

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

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