What is Crust?

Why Crust?

Most CLI tools in the JavaScript ecosystem are either minimal arg parsers that leave you wiring everything together, or heavyweight frameworks that bring more complexity than you need.

Crust sits in the sweet spot: more structured than a bare parser, lighter than a full framework, and designed so you only pull in what you actually use.

Chainable builder API — Immutable, type-safe builder pattern with full TypeScript inference
TypeScript-first — Args and flags are fully inferred from your definitions. No manual type annotations, just autocomplete that works.
Composable, not monolithic — Every capability ships as its own module. Install only what you need — @crustjs/core for the framework, @crustjs/plugins for official plugins, @crustjs/crust for build tooling.
Built for Bun — Targets the Bun runtime from the ground up. No Node compatibility layers, no legacy baggage.

Features

Compile-time validation catches flag alias collisions and variadic arg mistakes before your code runs
Zero runtime dependencies — Core modules have no external dependencies
Subcommand routing — Nested command trees with automatic resolution
Plugin system — Middleware-based architecture with lifecycle hooks
Flag inheritance — Share flags across subcommands with inherit: true

Quick Example

src/cli.ts

import { Crust } from "@crustjs/core";
import { helpPlugin, versionPlugin } from "@crustjs/plugins";

const main = new Crust("greet")
  .meta({ description: "A friendly greeter CLI" })
  .use(versionPlugin("1.0.0"))
  .use(helpPlugin())
  .args([
    {
      name: "name",
      type: "string",
      description: "Who to greet",
      default: "world",
    },
  ])
  .flags({
    shout: { type: "boolean", description: "SHOUT the greeting", short: "s" },
  })
  .run(({ args, flags }) => {
    const message = `Hello, ${args.name}!`;
    console.log(flags.shout ? message.toUpperCase() : message);
  });

await main.execute();

$ bun run src/cli.ts world --shout
HELLO, WORLD!

$ bun run src/cli.ts --help
greet - A friendly greeter CLI

USAGE:
  greet [name] [options]

ARGS:
  [name]            Who to greet

OPTIONS:
  -s, --shout       SHOUT the greeting
  -h, --help        Show help
  -v, --version     Show version number