Amber is a versatile JavaScript and TypeScript runtime built with Rust and V8, designed for efficiency and reliability. It offers a single binary solution for running scripts, Jest-style tests, servers, and agent tools, all while providing an opt-in capability sandbox for enhanced security. Amber focuses on a clear, contract-tested compatibility surface, distinguishing itself from Node.js clones.

• Unified Binary: Execute scripts, tests, servers, and agent tools from a single `amber` executable.

• TypeScript Support: Run `.ts` and `.tsx` files directly, with type stripping handled by `oxc`. Stack traces point to your original `.ts` lines.

• Jest-Style Testing: Features `describe`, `test`, and `expect` for testing with zero-argument discovery and a `--watch` mode.

• HTTP Server: Export a fetch handler and `amber serve` will speak HTTP/1.1 to it, with optional `--https` support via `rustls`.

• Capability Sandbox: By default, denies file, network, environment, and process access. Allows specific paths and hosts, with an audit trail.

• Agent Tools: Export functions, print their schemas, and serve them over MCP stdio or JSON-RPC.

• Subcommand CLI: Includes `amber run`, `amber test`, `amber serve`, `amber bundle`, `amber compile`, `amber install`, `amber mcp`, and `amber repl` for a comprehensive development workflow.

• Contract-Based Compatibility: Clearly defines supported subsets of Node.js and Web platform APIs, with rigorous testing.

• Open Source: Developed under the MIT license.

Get started quickly with prebuilt archives for macOS, Linux, and Windows, or build from source using Cargo. Amber aims to provide a stable and predictable runtime environment for modern JavaScript and TypeScript development.