CompatLab is an open-source tool designed to test and analyze npm package compatibility across major JavaScript runtimes, including Node.js, Bun, and Deno.

The main features and capabilities of CompatLab include:

• Multi-Runtime Load Testing: Tests published npm packages across Node.js, Bun, and Deno runtimes on Linux using exact runtime versions.

• Dual Consumer Mode Verification: Checks package loading through both import (ESM) and require (CommonJS) for root entry points as well as subpath imports and requires.

• Detailed Status Reporting: Categorizes loading outcomes into clear statuses (such as Passed or Inconclusive) and highlights subpath issues like missing optional peer dependencies.

• Disabled Install Scripts: Executes checks with install scripts disabled for safety during package testing.

• Open-Source Engine & CLI: Provides an open-source CLI engine (compatlab check) and public API so developers can reproduce scans locally on their own Linux hosts.

• MCP Integration for AI Agents: Offers a Model Context Protocol (MCP) server integration, allowing AI coding tools (such as Claude Code, Cursor, or Codex) to check compatibility reports directly.