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Show HN: Crust – A CLI framework for TypeScript and Bun

(github.com)
33
6
16h

by jellyotsiro

We've been building Crust (https://crustjs.com/), a TypeScript-first, Bun-native CLI framework with zero dependencies. It's been powering our core product internally for a while, and we're now open-sourcing it.

The problem we kept running into: existing CLI frameworks in the JS ecosystem are either minimal arg parsers where you wire everything yourself, or heavyweight frameworks with large dependency trees and Node-era assumptions. We wanted something in between.

What Crust does differently:

- Full type inference from definitions — args and flags are inferred automatically. No manual type annotations, no generics to wrangle. You define a flag as type: "string" and it flows through to your handler.

- Compile-time validation — catches flag alias collisions and variadic arg mistakes before your code runs, not at runtime.

- Zero runtime dependencies — @crustjs/core is ~3.6kB gzipped (21kB install). For comparison: yargs is 509kB, oclif is 411kB.

- Composable modules — core, plugins, prompts, styling, validation, and build tooling are all separate packages. Install only what you need.

- Plugin system — middleware-based with lifecycle hooks (preRun/postRun). Official plugins for help, version, and shell autocompletion.

- Built for Bun — no Node compatibility layers, no legacy baggage.

Quick example:

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

  const main = new Crust("greet")
    .args([{ name: "name", type: "string", default: "world" }])
    .flags({ shout: { type: "boolean", short: "s" } })
    .use(helpPlugin())
    .use(versionPlugin("1.0.0"))
    .run(({ args, flags }) => {
      const msg = `Hello, ${args.name}!`;
      console.log(flags.shout ? msg.toUpperCase() : msg);
    });

  await main.execute();
Scaffold a new project:

  bun create crust my-cli
Site: https://crustjs.com GitHub: https://github.com/chenxin-yan/crust

Happy to answer any questions about the design decisions or internals.

camkego
2h

This looks useful. But, it's interesting how the backend-world and front-end world keep diverging. I must admit, I had no idea what this was from the title. "CLI framework"? But in backend-land, these would typically be called "argument parsers" or "command line argument parsers". But maybe I am missing some of the functionality.

jellyotsiro
2h

good point.

we’re using “framework” intentionally because it goes beyond argument parsing. crust handles parsing, but also:

type inference across args + flags end to end compile-time validation (so mistakes fail before runtime) plugin system with lifecycle hooks (help, version, autocomplete, etc.) composable modules (prompts, styling, validation, build tooling) auto-generates agent skills and modules from the CLI definitions

so it sits a layer above a traditional arg parser like yargs or commander, closer to something like oclif, but much lighter and bun-native.

bennettpompi1
2h

this is cool! i'd recommend fleshing out the README. Clicked on the link before the discussion and was a tad confused.

jellyotsiro
2h

will fix in the next hour!

rgbrgb
2h

nice, congrats on launch. To get an idea... what's the size of a standalone hello world cli binary?

jellyotsiro
1h

tens of KBs (v small)

rgbrgb
42m

Isn't a standalone Bun binary like 50MB because it has to bundle the runtime? How could this get smaller?

matt_kantor
3h

> Versions before 1.0 do not strictly follow semantic versioning.

Sorry for being nitpicky, but yes they do. Semantic versioning[0] allows arbitrary changes while the major version is 0:

> Major version zero (0.y.z) is for initial development. Anything MAY change at any time. The public API SHOULD NOT be considered stable.

[0]: https://semver.org/

jellyotsiro
3h

thanks for the catch, what we meant is that we’re not committing to strict stability guarantees yet, so APIs may still change as we iterate toward 1.0.

matt_kantor
3h

I understand, but that's already implied by a 0.y.z version number.

landl0rd
3h

Is there an examples section? Would be helpful to see a demo

jellyotsiro
3h

one of the examples would be trynia.ai (search and index api for ai agents)

here is github: github.com/nozomio-labs/nia-cli

dnlzro
2h

Psst, the GitHub link in your post is broken (it should be https://github.com/chenxin-yan/crust).

dang
49m

Fixed above. Thanks for the heads-up!

jellyotsiro
2h

thanks for flagging! the post itself works, just the link at the bottom

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