Voicebox is a local-first, open-source desktop application for AI voice cloning, text-to-speech (TTS), speech-to-text (STT), and dictation. It provides a full voice I/O stack that runs entirely on the user's machine, supporting multiple TTS engines (Qwen3-TTS, Chatterbox, Kokoro, TADA, LuxTTS, etc.) with zero-shot voice cloning from short audio samples. The application is built as a Tauri v2 desktop shell (Rust) wrapping a React/TypeScript frontend and a Python FastAPI backend with SQLite storage. Key features include global dictation with auto-paste, voice profile management with effects chains, a multi-track story editor, MCP server integration for AI agents, and GPU acceleration (CUDA, ROCm, MLX, DirectML). The architecture follows a service-oriented pattern with a backend factory for pluggable TTS/STT engines, SSE-based progress streaming, and a platform abstraction layer for cross-platform compatibility. The codebase is well-structured with extensive documentation, CI/CD pipelines, and a large community.