Vox — Claude Code Skill

Project Overview

Vox is a lightweight voice MCP server (~1,500 lines of Rust) providing local text-to-speech (Kokoro) and speech-to-text (Moonshine Base) via the MCP protocol. It runs as a stdio subprocess per MCP client, or as a shared HTTP daemon.

Build & Test

cargo check                    # type-check only
cargo test                     # run all unit tests (84 tests across 10 modules)
cargo clippy -- -D warnings    # lint — must pass with zero warnings
cargo build --release          # optimized build (LTO + single codegen unit)
cargo bench -- resample        # benchmark resampling

All of cargo test, cargo clippy -- -D warnings, and cargo fmt --check must pass before submitting changes.

Architecture

| Module | Purpose | |--------|---------| | main.rs | Entry point, config loading, model download, stdio/daemon startup | | cli.rs | Clap CLI parser: daemon, config, download-models subcommands | | server.rs | MCP tool handlers (say, listen, converse), streaming TTS pipeline | | tts.rs | Kokoro TTS engine wrapper, voice name → speaker ID resolution, sentence splitting | | audio.rs | cpal-based mic capture and speaker playback, Lanczos-3 sinc resampling | | stt.rs | Moonshine Base STT engine wrapper | | vad.rs | Voice activity detection (Silero ONNX) | | config.rs | TOML config loading, env var overrides (VOX_* prefix), path resolution | | daemon.rs | HTTP daemon lifecycle: daemonize, PID file, start/stop/status/log | | models.rs | Model readiness checks and download/extraction | | lib.rs | Public re-exports for benchmarks (audio, config, error, tts) | | error.rs | VoiceError enum with thiserror derives |

Transport Modes

• Stdio (default): rmcp::transport::stdio(). One process per MCP client.
• Daemon (vox daemon start [--port PORT]): StreamableHttpService via rmcp. Single process, models loaded once, multiple clients connect over HTTP/SSE. Factory closure creates a VoiceMcpServer per session with shared Arc<Mutex<TtsEngine>> and Arc<Mutex<SttEngine>>.

Config System

Precedence (highest wins):

1. Environment variables: VOX_SPEED, VOX_VOICE, VOX_MODEL_DIR, VOX_LOG_LEVEL, VOX_PORT
2. TOML file: $XDG_CONFIG_HOME/vox/config.toml
3. Compiled defaults (Config::default())

CLI management: vox config get [key], vox config set <key> <value>, vox config path

MCP Tools

| Tool | Description | |------|-------------| | say | Speak text aloud through speakers (TTS only) | | listen | Record from microphone and transcribe (STT only) | | converse | Speak text then listen for response (TTS + STT round-trip) |

Available Voices

American female (af_*): heart, alloy, aoede, bella, jessica, kore, nicole, nova, river, sarah, sky American male (am_*): adam, echo, eric, liam, michael, onyx, puck, santa British female (bf_*): alice, emma, lily British male (bm_*): daniel, fable, george, lewis

Default: af_heart (ID 0). Voices can be specified by name or numeric ID.

Code Conventions

• Edition 2024 — uses let chains (if let Ok(x) = ... && let Ok(y) = ...)
• Visibility: pub(crate) for test-only exposure, not fully pub
• Clippy: treat all warnings as errors (-D warnings)
• Tests: inline #[cfg(test)] mod tests per module, tempfile for filesystem tests
• unsafe impl Send: TtsEngine and CaptureHandle have manual Send impls due to non-Send cpal/sherpa internals confined to dedicated threads

Dev Workflow

1. Make changes
2. cargo test — verify all 84 tests pass
3. cargo clippy -- -D warnings — zero warnings
4. cargo fmt --check — formatting
5. If touching audio.rs resampling: cargo bench -- resample