vv-synth

日本語版

vv-synth is a small CLI that sends text to VOICEVOX Engine and writes the synthesized audio as a local WAV file.

The project intentionally stays thin:

• vv-synth talks to a separately prepared VOICEVOX Engine over HTTP.
• VOICEVOX Engine, voice libraries, model files, Docker images, official binaries, and generated WAV files are not bundled in this repository.
• Runtime behavior is centered in vv_synth/engine_client.py, vv_synth/output_paths.py, and main.py.

Documentation

• Users: Quick Start / Usage
• VOICEVOX terms: OSS Publication And VOICEVOX Terms
• Maintainers: Architecture / Maintenance
• AI coding agents (Codex CLI / Claude Code recommended): AGENTS.md / CLAUDE.md / .claude/rules/ / skills/README.md
• Agent Skills: skills/vv-synth/ for portable TTS, skills/vv-synth-dev/ for this repository

Requirements

Requirement	Purpose
Python 3.14+	Runtime
uv	Dependency and tool management
Docker	Optional way to run VOICEVOX Engine
VOICEVOX Engine	HTTP API on http://127.0.0.1:50021, prepared with Docker or an official binary

Windows is supported as long as Python, uv, and a reachable VOICEVOX Engine are available. For Windows NVIDIA GPU usage, see Windows + NVIDIA GPU.

VOICEVOX CORE (voicevox_core/) is not required by vv-synth.

OSS Publication And VOICEVOX Terms

vv-synth is open source under the MIT License and contains only the small HTTP client CLI. It does not vendor VOICEVOX Engine itself, voice libraries, model files, Docker images, official Windows/macOS/Linux binaries, or generated WAV files.

Users are responsible for checking and following the latest official VOICEVOX terms. Using generated audio requires credit identifying VOICEVOX and compliance with each voice library / speaker's own terms. The required credit may be omitted only where an applicable license explicitly permits it. If generated audio is embedded in an application or redistributed, the final distribution must also satisfy those terms and credit requirements.

When granting others permission to use generated audio, you must require them to comply with the applicable voice library terms and to pass on these same obligations whenever they grant further permission to use the audio, as required by items 2 and 3 of the official VOICEVOX software terms.

References:

• VOICEVOX official software terms
• voicevox/voicevox_engine on Docker Hub
• VOICEVOX Engine Releases
• VOICEVOX Q&A

Maintainer checklist for every change and release:

• Confirm the code license in LICENSE (MIT) matches the pyproject.toml license metadata.
• Confirm version in pyproject.toml, metadata.version in both skills/*/SKILL.md files, and the release tag v<version> (created by gh skill publish --tag) match.
• Confirm the VOICEVOX official links in this README are current.
• Confirm VOICEVOX Engine, voice libraries, model files, and generated WAV files are not tracked by Git.
• If sample audio is ever distributed, confirm speaker-specific terms and credit notation first.

Prepare VOICEVOX Engine

vv-synth only needs an HTTP Engine listening on http://127.0.0.1:50021. The VOICEVOX desktop GUI is not required.

Docker users should use the official image. If you do not want Docker, use an official Engine binary from VOICEVOX Engine Releases.

Sources: voicevox/voicevox_engine on Docker Hub, Docker Desktop GPU support, VOICEVOX Q&A

Docker CPU

Pull the image:

docker pull voicevox/voicevox_engine:cpu-latest

Run in the foreground:

docker run --rm -it -p '127.0.0.1:50021:50021' voicevox/voicevox_engine:cpu-latest

Run in the background:

docker run --rm -d -p '127.0.0.1:50021:50021' voicevox/voicevox_engine:cpu-latest

Stop a background container with docker ps, then docker stop <id>.

Windows + NVIDIA GPU (Docker Desktop)

Windows GPU usage with Docker requires:

• Windows 10 / 11 with an NVIDIA GPU
• Docker Desktop with the WSL2 backend enabled
• A current NVIDIA driver that supports WSL2 GPU usage
• A current WSL2 Linux kernel (wsl --update in PowerShell)

Check whether Docker can see the GPU:

docker run --rm -it --gpus=all nvcr.io/nvidia/k8s/cuda-sample:nbody nbody -gpu -benchmark

Run the NVIDIA GPU Engine image:

docker pull voicevox/voicevox_engine:nvidia-latest
docker run --rm -it --gpus all -p '127.0.0.1:50021:50021' voicevox/voicevox_engine:nvidia-latest

Background:

docker run --rm -d --gpus all -p '127.0.0.1:50021:50021' voicevox/voicevox_engine:nvidia-latest

After the Engine is listening, vv-synth usage is the same as CPU mode. GPU selection is an Engine concern; vv-synth does not need a GPU-specific option.

Official Engine Binaries

If you do not use Docker, download an official binary for your OS from VOICEVOX Engine Releases. Windows builds include CPU, GPU/DirectML, and GPU/CUDA variants.

Once http://127.0.0.1:50021/version responds, vv-synth can use the binary Engine exactly like the Docker Engine. If you change the port, pass --engine-url or set VOICEVOX_ENGINE_URL.

Verify The Engine

In another terminal:

curl -sSf http://127.0.0.1:50021/version

If JSON is returned, the Engine is ready. Speaker style IDs are available from /speakers in http://127.0.0.1:50021/docs.

Engine Troubleshooting

Symptom	Check
Cannot connect to the Docker daemon	Start Docker Desktop, or use an official Engine binary
port is already allocated on 50021	Stop other Engine containers or the VOICEVOX desktop app
GPU container cannot select a driver	Confirm Docker Desktop WSL2 backend, NVIDIA driver, and wsl --update
vv-synth cannot connect	Confirm curl .../version works and the port is 127.0.0.1:50021
HTTP 4xx for speaker	Pick a valid style ID from /speakers

Do not run multiple Engines on port 50021 at the same time.

Quick Start

git clone https://github.com/ru-461/vv-synth.git
cd vv-synth
uv sync
uv run vv-synth --help

After starting VOICEVOX Engine with Docker or an official binary:

uv run vv-synth "こんにちは、音声合成のテストです。"

The default output is output/YYYYMMDD-HHMMSS.wav (local time) under the directory where you run the command. The output/ directory is created automatically on first run. Set VV_SYNTH_OUTPUT_DIR to change the default directory globally.

Global Install

Install directly from GitHub (no clone needed):

uv tool install git+https://github.com/ru-461/vv-synth

From a local clone (editable):

uv tool install --editable .

Two commands are installed and behave identically:

• vv-synth — the canonical name
• vvs — short alias

If ~/.local/bin is not on PATH:

uv tool update-shell
# or
export PATH="$HOME/.local/bin:$PATH"

Uninstall:

uv tool uninstall vv-synth

If you installed in editable mode and the repository path changed, reinstall:

uv tool uninstall vv-synth
cd /path/to/vv-synth
uv tool install --editable .

Agent Skill Local Install

The portable vv-synth Agent Skill lets coding agents use this CLI from other projects. gh skill is the recommended installation path; npx skills (Vercel Labs) is a supported alternative.

Recommended: gh skill

Requires GitHub CLI v2.90+:

cd /path/to/vv-synth
gh skill install . vv-synth --from-local --scope user --agent universal

Use a specific agent target if you only want the skill installed for one host:

gh skill install . vv-synth --from-local --scope user --agent codex
gh skill install . vv-synth --from-local --scope user --agent claude-code

Preview the published skill before installing (reads from GitHub; in a local clone, read skills/vv-synth/SKILL.md directly):

gh skill preview ru-461/vv-synth vv-synth

Alternative: npx skills

Requires Node.js; no global install needed. --global targets your user directory (omit it for the current project only):

cd /path/to/vv-synth
npx skills@latest add . --skill vv-synth --global

Target one agent, or list the repository's skills before installing:

npx skills@latest add . --skill vv-synth --global --agent claude-code
npx skills@latest add . --list

See skills/README.md for publishing, updates, and project-scoped installs.

Usage

vv-synth MESSAGE [OPTIONS]

vv-synth --help is written in English.

A successful run prints INFO: wrote <absolute-path> to stdout. Synthesis and file I/O errors print one English line to stderr and exit with code 1. Invalid arguments or options produce a Typer usage error on stderr and exit with code 2.

Option	Short	Default	Description
MESSAGE	-	required	Text to synthesize
--output	-o	automatic timestamp	Output WAV file name or path
--output-dir	-	output	Directory for WAV files when --output is a basename; can also be set with VV_SYNTH_OUTPUT_DIR
--speaker	-s	2	VOICEVOX speaker style ID
--speed	-	1.0	Finite speech speed from 0.01 to 10.0 (1.0 is normal; larger is faster)
--engine-url	-	http://127.0.0.1:50021	Engine URL; can also be set with VOICEVOX_ENGINE_URL

Examples:

vv-synth "テストです" -o hello.wav
vv-synth "テストです" --output-dir artifacts
vv-synth "テストです" -s 3 --speed 1.5

Speaker style IDs: http://127.0.0.1:50021/docs, /speakers

Architecture

Component Layout

Keep this diagram aligned with the implementation when module boundaries change.

flowchart TB
  subgraph cli["vv-synth CLI"]
    main["main.py\nTyper"]
    paths["vv_synth/output_paths.py"]
    client["vv_synth/engine_client.py"]
  end

  subgraph external["External"]
    engine["VOICEVOX Engine\nDocker or binary / :50021"]
  end

  subgraph fs["Filesystem"]
    outdir["./output/\n(current working directory)"]
  end

  user(["User / Agent"]) --> main
  main --> paths
  main --> client
  paths --> outdir
  client -->|"POST /audio_query"| engine
  client -->|"POST /synthesis"| engine
  client --> outdir

Path	Responsibility
main.py	Typer CLI and vv-synth entry point
vv_synth/output_paths.py	Output path resolution (output/, -o, timestamp names)
vv_synth/engine_client.py	Engine HTTP calls, speech rate, WAV saving

Synthesis Flow

Update this sequence if the Engine API call order changes.

sequenceDiagram
  actor U as User
  participant M as main.py
  participant P as output_paths
  participant C as engine_client
  participant E as VOICEVOX Engine

  U->>M: vv-synth MESSAGE [options]
  M->>P: resolve_output_file()
  P-->>M: Path
  M->>C: synthesize_text_to_file()
  C->>E: POST /audio_query?text&speaker
  E-->>C: AudioQuery (JSON)
  C->>C: apply_speed_scale()
  C->>E: POST /synthesis?speaker
  E-->>C: WAV bytes
  C->>C: save_wav()
  C-->>M: Path
  M-->>U: INFO wrote path (stdout)

Project Layout

vv-synth/
├── main.py
├── vv_synth/
│   ├── engine_client.py
│   └── output_paths.py
├── tests/               # pytest suite (Engine mocked; no running Engine needed)
├── output/              # Git-ignored WAV output, except .gitkeep
├── docs/                # Japanese project overview (OVERVIEW.ja.md)
├── skills/              # Agent Skills (vv-synth, vv-synth-dev)
├── .claude/rules/       # Agent rules referenced by AGENTS.md
├── .github/             # CI workflow, Dependabot, issue / PR templates, and Code of Conduct
├── pyproject.toml       # vv-synth package and [project.scripts]
├── AGENTS.md            # Shared agent guidance
├── CLAUDE.md            # Claude Code summary
├── CONTRIBUTING.md      # Contribution guide
├── SECURITY.md          # Security policy
├── README.md            # English main README
├── README.ja.md         # Japanese README
├── LICENSE              # MIT (code only; generated audio follows VOICEVOX terms)
└── uv.lock

Output Directory

By default, WAV files are written under output/ relative to the command's current working directory.

Invocation	Output example
no -o	output/20260521-143052.wav
-o hello.wav	output/hello.wav
-o path/to/a.wav	path/to/a.wav
--output-dir artifacts	artifacts/...

VOICEVOX CORE

vv-synth only uses the VOICEVOX Engine HTTP API. VOICEVOX CORE, voice libraries, and model files are not bundled with this CLI and are not part of its setup flow.

Maintenance

Environment

uv sync --group dev

Start VOICEVOX Engine with Docker or an official binary, then confirm:

curl -sSf http://127.0.0.1:50021/version

Change Map

Change	Primary files	Also update
CLI options/help	main.py	Usage, vv-synth --help wording
Output path rules	vv_synth/output_paths.py	Output Directory
Engine API/speed/errors	vv_synth/engine_client.py	Mermaid diagrams
Global command name	pyproject.toml [project.scripts]	install instructions
Dependency versions	pyproject.toml	uv lock / uv.lock
Agent rules/boundaries	AGENTS.md, CLAUDE.md, .claude/rules/*.md	Architecture tables
Engine setup or VOICEVOX terms guidance	README files, skills/*/SKILL.md	official links and Docker/binary parity

Mermaid Updates

The canonical architecture diagrams live in this README. Update them when:

• modules are added, renamed, or change responsibility;
• Engine API endpoints or call order change;
• CLI dependencies on the filesystem or external services change.

Keep the copies in README.ja.md and docs/OVERVIEW.ja.md aligned when diagram content changes.

Quality Checks

uv run ruff check .
uv run ruff format .
uv run ty check
uv run pytest

pytest runs the unit test suite in tests/. Tests mock the Engine over urllib, so no running VOICEVOX Engine is required.

Manual smoke test with Engine running:

uv run vv-synth "maintenance smoke test"
ls -la output/

If package entry points changed:

uv tool install --editable .
vv-synth --help

Documentation Sync Checklist

• README.md and README.ja.md describe the same user-facing behavior.
• Mermaid diagrams match the implementation.
• AGENTS.md / CLAUDE.md and Agent Skills are current.
• CLI option tables match vv-synth --help.
• VOICEVOX Engine / voice library terms links and the "do not vendor external assets" policy remain intact.
• LICENSE and the pyproject.toml license metadata still match.

Commit Policy

• Commit only when explicitly requested.
• Use an English one-line message: prefix: message.
• Examples: feat: add pitch option, docs: update engine setup.
• Do not commit output/*.wav, voicevox_core/, download, VOICEVOX Engine binaries, models, voice libraries, or virtual environments.

Troubleshooting

Symptom	Check
command not found: vv-synth	uv tool install --editable . and PATH (~/.local/bin)
Connection refused	Start Engine with Docker or an official binary; confirm port 50021
HTTP 4xx	Check the --speaker style ID
WAV is not saved	Current working directory, --output-dir, and write permissions
Mermaid does not render	Markdown fence must be ```mermaid