Vapi

AssemblyAI's Voice Agent API is an API for building real-time voice agents. It connects speech-to-text, an LLM, and text-to-speech through a single WebSocket, with built-in turn detection and interruption handling.

Vertex AI is Google Cloud’s managed platform for developing and deploying machine-learning and generative-AI applications. It provides hosted models and APIs that applications, including agents, can call at runtime, along with tools for model training, evaluation, and serving.

Voicebox is a local-first, open-source AI voice studio developed in the jamiepine/voicebox repository. It combines voice cloning, text-to-speech, speech-to-text dictation, voice profiles, audio effects, and agent voice output in a desktop application. It generates speech through seven switchable TTS engines, including Qwen3-TTS, Qwen CustomVoice, LuxTTS, Chatterbox, HumeAI TADA, and Kokoro, and supports voice cloning from reference audio, preset voices, multilingual generation, automatic text chunking, crossfading, and multi-track story editing. Whisper-based transcription powers global dictation, in-app recording, and the transcription API; an optional local Qwen3 LLM can refine dictation or rewrite text according to a voice profile's persona. The application exposes REST endpoints for speech generation, agent speech, transcription, and profile management, plus a built-in MCP server with tools for speaking, transcribing, and browsing captures and profiles. It runs models and stores voice data locally, using Tauri with a React/TypeScript frontend and FastAPI backend; platform backends include MLX on Apple Silicon and PyTorch on CUDA, ROCm, XPU, DirectML, or CPU. The repository is licensed under the MIT License and provides macOS, Windows, and Docker distribution, with Linux build-from-source instructions.

ElevenLabs is an AI voice and audio platform offering text-to-speech, voice generation and cloning, speech-to-text transcription, dubbing, music generation, and voice agents. Its transcription capability produces timing information for video cuts, subtitles, and synchronized animations. It provides more than 5,000 voices across more than 90 languages, supports custom voice clones, and offers secure APIs and SDKs through ElevenAPI. ElevenCreative supports content creation, while ElevenAgents supports customer-experience applications.