Vx Usage

VX - Universal Development Tool Manager

One-sentence summary: vx = prefix any dev tool command with vx → it auto-installs the tool and runs it.

vx is a universal development tool manager that automatically installs and manages development tools (Node.js, Python/uv, Go, Rust, etc.) with zero configuration.

Core Concept

Instead of requiring users to manually install tools, prefix any command with vx:

vx node --version      # Auto-installs Node.js if needed
vx uv pip install x    # Auto-installs uv if needed
vx go build .          # Auto-installs Go if needed
vx cargo build         # Auto-installs Rust if needed
vx just test           # Auto-installs just if needed

vx is fully transparent - same commands, same arguments, just add vx prefix.

Essential Commands

Tool Execution (most common)

vx <tool> [args...]           # Run any tool (auto-installs if missing)
vx node app.js                # Run Node.js
vx python script.py           # Run Python (via uv)
vx npm install                # Run npm
vx npx create-react-app app   # Run npx
vx cargo test                 # Run cargo
vx just build                 # Run just (task runner)
vx git status                 # Run git

Tool Management

vx install node@22            # Install specific version
vx install uv go rust         # Install multiple tools at once
vx list                       # List all available tools
vx list --installed           # List installed tools only
vx versions node              # Show available versions
vx switch node@20             # Switch active version
vx uninstall go@1.21          # Remove a version

Project Management

vx init                       # Initialize vx.toml for project
vx sync                       # Install all tools from vx.toml
vx setup                      # Full project setup (sync + hooks)
vx dev                        # Enter dev environment with all tools
vx run test                   # Run project scripts from vx.toml
vx check                      # Verify tool constraints
vx lock                       # Generate vx.lock for reproducibility

Environment & Config

vx env list                   # List environments
vx config show                # Show configuration
vx cache info                 # Show cache usage
vx search <query>             # Search available tools
vx info                       # System info and capabilities

Project Configuration (vx.toml)

Projects use vx.toml in the root directory:

[tools]
node = "22"         # Major version
go = "1.22"         # Minor version
uv = "latest"       # Always latest
rust = "1.80"       # Specific version
just = "*"          # Any version

[scripts]
dev = "npm run dev"
test = "cargo test"
lint = "npm run lint && cargo clippy"
build = "just build"

[hooks]
pre_commit = ["vx run lint"]
post_setup = ["npm install"]

Using --with for Multi-Runtime

When a command needs additional runtimes available:

vx --with bun node app.js     # Node.js + Bun in PATH
vx --with deno npm test        # npm + Deno available

Package Aliases

vx supports package aliases — short commands that automatically route to ecosystem packages:

# These are equivalent:
vx vite              # Same as: vx npm:vite
vx vite@5.0          # Same as: vx npm:vite@5.0
vx rez               # Same as: vx uv:rez
vx pre-commit        # Same as: vx uv:pre-commit
vx meson             # Same as: vx uv:meson
vx release-please    # Same as: vx npm:release-please

Benefits:

• Simpler commands without remembering ecosystem prefixes
• Automatic runtime dependency management (node/python installed as needed)
• Respects project vx.toml version configuration

Available Aliases:

Companion Tool Environment Injection

When vx.toml includes tools like MSVC, vx automatically injects discovery environment variables into all subprocess environments. This allows any tool needing a C/C++ compiler to discover the vx-managed installation.

# vx.toml — MSVC env vars injected for ALL tools
[tools]
node = "22"
cmake = "3.28"
rust = "1.82"

[tools.msvc]
version = "14.42"
os = ["windows"]

Now tools like node-gyp, CMake, Cargo (cc crate) automatically find MSVC:

# node-gyp finds MSVC via VCINSTALLDIR
vx npx node-gyp rebuild

# CMake discovers the compiler
vx cmake -B build -G "Ninja"

# Cargo cc crate finds MSVC for C dependencies
vx cargo build

Injected Environment Variables (MSVC example):

MSVC Build Tools (Windows)

Microsoft Visual C++ compiler for Windows development:

# Install MSVC Build Tools
vx install msvc@latest
vx install msvc 14.40       # Specific version

# Using MSVC tools via namespace
vx msvc cl main.cpp -o main.exe
vx msvc link main.obj
vx msvc nmake

# Direct aliases
vx cl main.cpp              # Same as: vx msvc cl
vx nmake                    # Same as: vx msvc nmake

# Version-specific usage
vx msvc@14.40 cl main.cpp

Available MSVC Tools:

Supported Tools (114 Providers)

Provider System (Starlark DSL)

All 114 providers are defined using provider.star (Starlark DSL) — a declarative, zero-compilation approach. Each provider lives in crates/vx-providers/<name>/provider.star.

vx uses a two-phase execution model (inspired by Buck2):

1. Analysis Phase (Starlark): provider.star runs as pure computation, returning descriptor dicts. No I/O.
2. Execution Phase (Rust): The Rust runtime interprets descriptors for actual downloads, installs, and process execution.

How to add a new tool

# crates/vx-providers/mytool/provider.star
load("@vx//stdlib:provider.star", "runtime_def", "github_permissions")
load("@vx//stdlib:provider_templates.star", "github_rust_provider")

name        = "mytool"
description = "My awesome tool"
ecosystem   = "custom"

runtimes = [runtime_def("mytool", aliases=["mt"])]
permissions = github_permissions()

# Use a template — covers 90% of tools
_p = github_rust_provider("owner", "mytool",
    asset = "mytool-{vversion}-{triple}.{ext}")
fetch_versions   = _p["fetch_versions"]
download_url     = _p["download_url"]
install_layout   = _p["install_layout"]
store_root       = _p["store_root"]
get_execute_path = _p["get_execute_path"]
environment      = _p["environment"]

Available templates

Template Placeholders

Starlark Standard Library (14 modules)

Located in crates/vx-starlark/stdlib/. The main entry point is provider.star which re-exports everything:

# Import everything from the unified facade
load("@vx//stdlib:provider.star",
     "runtime_def", "bundled_runtime_def", "dep_def",
     "github_permissions", "platform_map",
     "env_set", "env_prepend",
     "archive_layout", "binary_layout")

Key modules:

• provider.star — Unified facade (re-exports all)
• runtime.star — runtime_def, bundled_runtime_def, dep_def
• platform.star — platform_map, platform_select, rust_triple, go_os_arch
• env.star — env_set, env_prepend, env_append, env_unset
• layout.star — archive_layout, binary_layout, bin_subdir_layout, hooks
• provider_templates.star — High-level templates (4 templates)
• permissions.star — github_permissions, system_permissions
• system_install.star — winget_install, brew_install, apt_install

Important Rules for AI Agents

1. Always use vx prefix when running tools in vx-managed projects
2. Use vx just instead of just for task runner commands
3. Use vx npm instead of npm directly
4. Use vx cargo instead of cargo directly
5. Check vx.toml first to understand project tool requirements
6. Use vx run <script> for project-defined scripts
7. Never suggest manual tool installation - vx handles it automatically
8. Commands like vx install are for explicit pre-installation; normal usage auto-installs
9. Use correct terminology: Runtime (not Tool), Provider (not Plugin), provider.star (not provider config)
10. Provider development: New tools are added via provider.star Starlark DSL in crates/vx-providers/<name>/
11. Tests go in tests/ dirs — never inline #[cfg(test)] in source files

Version Resolution Priority

vx resolves tool versions in this order (highest to lowest):

1. Command-line override: vx node@22 app.js
2. Project vx.toml: [tools] node = "22"
3. Parent directory vx.toml (traverses up to root)
4. User global config: ~/.config/vx/config.toml
5. Provider default: latest stable version

MCP Integration

vx is MCP-ready — replace npx/uvx with vx in MCP server configurations. This eliminates the "install Node.js/Python first" requirement for all MCP servers.

Configuration Pattern

{
  "mcpServers": {
    "example-server": {
      "command": "vx",
      "args": ["npx", "-y", "@example/mcp-server@latest"]
    },
    "python-server": {
      "command": "vx",
      "args": ["uvx", "some-python-mcp-server@latest"]
    }
  }
}

Real-World MCP Examples

{
  "mcpServers": {
    "filesystem": {
      "command": "vx",
      "args": ["npx", "-y", "@modelcontextprotocol/server-filesystem", "/path/to/dir"]
    },
    "github": {
      "command": "vx",
      "args": ["npx", "-y", "@modelcontextprotocol/server-github"],
      "env": { "GITHUB_TOKEN": "<token>" }
    },
    "sqlite": {
      "command": "vx",
      "args": ["uvx", "mcp-server-sqlite", "--db-path", "/path/to/db.sqlite"]
    }
  }
}

Migration Pattern

Benefits for AI Agents

• Zero-config: No need to check if Node.js/Python is installed before starting MCP servers
• Version consistency: MCP servers always use the version specified in vx.toml
• Cross-platform: Same MCP config works on Windows, macOS, and Linux
• CI/CD ready: MCP servers in CI pipelines just work with vx

GitHub Actions Integration

vx provides a GitHub Action (action.yml) for CI/CD workflows. Use it in .github/workflows/ files:

Basic Usage

- uses: loonghao/vx@main
  with:
    version: 'latest'           # vx version (default: latest)
    github-token: ${{ secrets.GITHUB_TOKEN }}

Pre-install Tools

- uses: loonghao/vx@main
  with:
    tools: 'node go uv'         # Space-separated tools to pre-install
    cache: 'true'               # Enable tool caching (default: true)

Project Setup (vx.toml)

- uses: loonghao/vx@main
  with:
    setup: 'true'               # Run `vx setup --ci` for vx.toml projects

Full Example

name: CI
on: [push, pull_request]

jobs:
  build:
    runs-on: ${{ matrix.os }}
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]

    steps:
      - uses: actions/checkout@v6

      - uses: loonghao/vx@main
        with:
          tools: 'node@22 uv'
          setup: 'true'
          cache: 'true'

      - run: vx node --version
      - run: vx npm test

Action Inputs

Action Outputs

Container Image Support

vx also provides a container image for containerized workflows, and it can be consumed from Podman-compatible environments:

# Use vx as base image
FROM ghcr.io/loonghao/vx:latest

# Tools are auto-installed on first use
RUN vx node --version
RUN vx uv pip install mypackage

Multi-stage Build with vx

FROM ghcr.io/loonghao/vx:latest AS builder
RUN vx node --version && vx npm ci && vx npm run build

FROM nginx:alpine
COPY --from=builder /home/vx/dist /usr/share/nginx/html

GitHub Actions Container Jobs

jobs:
  build:
    runs-on: ubuntu-latest
    container:
      image: ghcr.io/loonghao/vx:latest
    steps:
      - uses: actions/checkout@v6
      - run: vx node --version
      - run: vx npm test