mason4agents

TL;DR: if you have ever used mason.nvim, this is it for coding agents.

Mason Registry powered tool installer for coding agents.

mason4agents downloads and manages LSP servers, formatters, linters, and other development tools from the Mason Registry — the same registry used by mason.nvim. It installs tools into the user's home directory and makes them available via PATH to coding agents such as oh-my-pi.

It currently supports oh-my-pi. Future versions may support Claude Code, Codex CLI, Copilot, OpenCode, and others.

Why

Installing tools such as LSP servers, linters, and formatters is inconvenient. Many of them are not included in native OS package managers, so users have to download and install them manually. This introduces maintenance burden.

Another problem is you may not know what tools are available for your project. This tool includes a (primitive) suggestion function. It scans your project, prefers oh-my-pi's built-in LSP defaults, and falls back to information from LazyVim to suggest relevant tools.

Features

• Mason Registry compatible — consumes the same registry, package schema, and release assets as mason.nvim
• OMP/Pi extension — /mason interactive package manager, CLI-backed slash subcommands, 7 LLM-callable tools, automatic PATH injection
• XDG Base Directory — data, config, cache, and state follow $XDG_* conventions
• Safe by default — no build script execution without --allow-build-scripts, zip-slip protection, path traversal rejection, sandboxed temp directories with atomic rename
• JSON protocol — all CLI commands support --json final envelopes; long operations stream stderr NDJSON progress with byte totals, percent complete, and current speed when available
• Cross-platform — Linux, macOS, Windows (Unix symlinks on *nix, .cmd wrappers on Windows)
• No shell profile modification — mason4agents env outputs export PATH=... for manual sourcing

Prerequisites

• Rust toolchain (stable, edition 2021) — for building from source
• Bun (v1.x) — for the TypeScript OMP/Pi adapter
• oh-my-pi (OMP) or Pi CLI — for extension integration
• External package managers (optional, per source type):
  • npm — for npm-based packages
  • python3 + pip — for PyPI packages
  • cargo — for crates.io packages
  • go — for Go packages
  • gem — for Ruby packages
  • composer — for PHP packages
  • luarocks — for Lua packages
  • nuget — for NuGet packages

Run mason4agents doctor to check which managers are available on your system.

Installation

From source

git clone <repo-url>
cd mason4agents
cargo build --release
# binary at target/release/mason4agents

Via npm package in oh-my-pi (OMP) / Pi

# Install with oh-my-pi (OMP)
omp plugin install mason4agents

# Or install with Pi
pi install npm:mason4agents

# Test locally with OMP without publishing
omp --extension ./dist/pi/extension.js
# or
pi --offline -e dist/pi/extension.js

Binary resolution order

The npm shim and OMP/Pi extension locate the Rust binary by checking (in order):

1. MASON4AGENTS_BIN environment variable
2. Bundled native/mason4agents-{platform}-{arch} or dist/native/... (local/source builds and old packages)
3. Installed native optional dependency package, for example mason4agents-linux-x64-gnu
4. Development target/debug/mason4agents / target/release/mason4agents (after cargo build)

Quick Start

CLI

# Refresh the Mason Registry cache
mason4agents refresh

# Search for packages
mason4agents search lua
mason4agents search --category LSP --language TypeScript

# Install a package
mason4agents install stylua
mason4agents install typescript-language-server

# List installed packages
mason4agents list --installed

# Check which directory a binary was installed to
mason4agents which stylua

# Get shell PATH setup
eval "$(mason4agents env --shell bash)"

# Run diagnostics
mason4agents doctor

# Uninstall
mason4agents uninstall stylua

Pi Extension

Open the interactive package manager in OMP/Pi:

/mason

The panel opens as a host-width, theme-aware TUI with visible tabs at the top (list, suggested, installed, check update, refresh, doctor) and a width-aware table area below. The suggested tab scans the local project, prefers OMP built-in LSP defaults as its LSP recommendation source, and falls back to locally cached LazyVim curated suggestions for languages OMP does not cover. Table views show installed status directly, keep a highlighted current row, and support Tab/←/→ to switch tabs, / local filtering, ↑/↓ row selection, Enter for an in-place package detail popup, and state-aware package actions: i for missing packages, u/d for installed packages. Long operations (install, update, uninstall, refresh) show a modal progress panel, block additional Mason operations while the CLI runs, enter a 30s no-progress warning state where q/Esc closes the panel without killing the CLI, and keep the final result in that panel.

Run CLI-backed slash subcommands directly when you do not need the panel. /mason with no arguments opens the TUI; pressing Tab after the bare /mason prompt shows all subcommands, and typing a prefix narrows the subcommand suggestions with per-command argument shapes before you press Enter:

/mason search stylua --language Lua
/mason installed
/mason list --outdated
/mason install stylua
/mason uninstall stylua
/mason doctor
/mason register --omp

Direct non-long slash-command results are rendered as human-readable tables or summaries, not raw JSON. Direct long commands (/mason install, /mason update, /mason uninstall, /mason refresh) use the same progress panel when custom UI is available and fall back to the final rendered result otherwise.

Use the following tools from OMP/Pi (they call the Rust CLI under the hood):

Tool	Description
mason_list	List installed/outdated packages
mason_search	Search registry with query, category, language filters
mason_install	Install one or more packages
mason_uninstall	Uninstall packages
mason_update	Update packages (all or specific)
mason_which	Resolve an installed binary path
mason_env	Generate shell PATH setup

CLI Commands

The npm package/Pi TypeScript shim exposes this command surface. A native Rust binary built directly from source (for example, target/release/mason4agents) supports the same commands except register --omp, which is implemented by the shim to update OMP/Pi registration.

mason4agents refresh [--registry <url|file>]
mason4agents search [query] [--category <category>] [--language <lang>] [--registry <url|file>]
mason4agents list [--installed|--outdated] [--registry <url|file>]
mason4agents install <pkg[@version]>... [--registry <url|file>] [--allow-build-scripts]
mason4agents uninstall <pkg>...
mason4agents update [pkg...] [--registry <url|file>] [--allow-build-scripts]
mason4agents which <executable>
mason4agents bin-dir
mason4agents env --shell bash|zsh|fish|powershell|cmd|json
mason4agents doctor
mason4agents register --omp

By default, all commands output human-readable text. Add --json for a final structured JSON envelope wrapped in {"ok": true, "data": ...}; for long operations, progress events are written to stderr as NDJSON objects with kind: "progress" while stdout remains the final envelope only. Download progress events include total_bytes, downloaded_bytes, download_percent, and bytes_per_second when the remote source reports a content length. Package-changing commands run through the OMP/Pi extension or npm CLI refresh OMP LSP registration after successful installs, updates, and uninstalls. Run mason4agents register --omp from the npm package/Pi shim to register already-installed Mason LSP tools with oh-my-pi manually; do not use that subcommand with a native Rust CLI built directly from source.

Example text output:

$ mason4agents doctor
mason4agents doctor
  Bin dir:         /home/user/.local/share/mason4agents/bin
  Bin dir exists:  ✓
  Data writable:   ✓
  Registry cache:  1200 packages
  PATH contains:   ✓
  PATH is first:   ✓
  Managers:
    npm           ✓ installed
    cargo         ✓ installed
    ...
  Overall:         ✓ ok

$ mason4agents which stylua
/home/user/.local/share/mason4agents/bin/stylua

$ mason4agents install stylua
 ✓ stylua v2.5.2  bins: stylua

$ mason4agents env --shell bash
export PATH='/home/user/.local/share/mason4agents/bin':"$PATH"

Building

The package has three delivered pieces: the Rust CLI (core), the npm shim, and the OMP/Pi extension (TypeScript).

Build everything (recommended)

bun run build

This runs:

1. bun run build:js to bundle the TypeScript npm shim (dist/bin/mason4agents.js) and OMP/Pi extension (dist/pi/extension.js)
2. bun run build:native to run cargo build --release
3. Copies the current-platform release binary into native/ for local resolver fallback and native-package staging

Build components separately

# Rust CLI only
cargo build --release                          # binary: target/release/mason4agents
cargo build                                    # debug binary: target/debug/mason4agents

# JS entries only
bun run build:js

# Rust CLI plus native/ staging copy for the current platform
bun run build:native

Output artifacts

Artifact	Path	Used by
Rust CLI	target/release/mason4agents	Direct shell usage
Rust CLI (dev)	target/debug/mason4agents	OMP/Pi extension dev fallback
Local native binary	native/mason4agents-{platform}-{arch}	Bundled/local resolver fallback
Release native artifact	native/mason4agents-linux-x64-gnu, native/mason4agents-win32-x64.exe, etc.	Platform-specific npm native packages
npm shim	dist/bin/mason4agents.js	npx mason4agents
OMP/Pi extension	dist/pi/extension.js	omp --extension ./dist/pi/extension.js / pi --offline -e dist/pi/extension.js

Package, CI, and publish

# Build current-platform tarballs for local install testing
bun run pack:local

# Alias for the same local tarball flow
bun run publish:local

# Publish from prebuilt multi-platform artifacts (normally only in GitHub release CI)
bun run publish:npm

The published npm layout uses a small root package (mason4agents) plus platform native optional dependencies: mason4agents-linux-x64-gnu, mason4agents-linux-arm64-gnu, mason4agents-darwin-x64, mason4agents-darwin-arm64, mason4agents-win32-x64, and mason4agents-win32-arm64. The native packages contain only package.json, LICENSE, and bin/mason4agents or bin/mason4agents.exe, and they do not declare their own bin field.

GitHub Actions has two workflows:

• ci.yml runs on branch pushes and pull requests. It runs the Rust/TypeScript/Bun quality gate and builds/smoke-tests native CLI artifacts for Linux, macOS, and Windows on x64 and arm64.
• release.yml runs on v* tags. It rebuilds from the tag, uploads the six native artifacts, stages npm packages, validates npm pack --dry-run --json contents, publishes all native packages first, then publishes the root package.

Tag releases should use vX.Y.Z, and the tag must match package.json's version. First-time publishing of the six native child packages requires npm bootstrap (local login or temporary NPM_TOKEN) because npm Trusted Publishing can only be configured for packages that already exist. After bootstrap, configure Trusted Publishing for mason4agents and all six native packages against .github/workflows/release.yml, then remove the temporary token.

Tests

Rust

cargo test                         # Rust test suite
cargo test cli_fixture             # CLI integration tests only
cargo test -- --ignored            # including network smoke test

TypeScript

bun test                           # TypeScript test suite

Full verification

cargo fmt --check && cargo clippy --all-targets -- -D warnings && cargo test && ./node_modules/.bin/tsc --noEmit && bun test

XDG Directory Layout

~/.config/mason4agents/              # Configuration
~/.local/share/mason4agents/
  bin/                               # Symlinks to installed tools (on PATH)
  packages/<name>/...                # Installed package contents
  share/                             # Mason share links
  opt/                               # Mason opt links
~/.cache/mason4agents/
  registry/                          # Cached registry index + checksum
  downloads/                         # Downloaded archives (cacheable)
  logs/                              # Install logs
~/.local/state/mason4agents/
  installed.json                     # Install state database
  locks/                             # Install/update lock files

Override any directory via MASON4AGENTS_CONFIG_HOME, MASON4AGENTS_DATA_HOME, MASON4AGENTS_CACHE_HOME, MASON4AGENTS_STATE_HOME.

Source Types Requiring External Managers

The following Mason source types are installed via external package managers (mason4agents doctor reports their availability):

• npm, pypi, cargo, golang, gem, composer, luarocks, nuget

Build scripts (source.build.run) are disabled by default and require explicit --allow-build-scripts.

What is NOT currently included

• Claude Code, Codex CLI, GitHub Copilot CLI, OpenCode adapters
• Automatic shell profile modification
• Neovim/mason.nvim integration or dependency

License

MIT