zodline

Build type-safe command-line interfaces with Zod. Declare your commands, options and arguments as schemas — validation, TypeScript types and help output come for free.

📚 Documentation · Quickstart · API reference

Features

• 🛡️ Type-safe: options and args are inferred from your schemas. Rename a field and every call site fails to compile.
• 📋 Declarative: A command is a plain object — description, schemas, action. No builder chains.
• ✅ Validation included: Coercion, defaults, refinements, unions — anything Zod can express, your CLI can accept.
• 🚫 Strict by default: Unknown flags are errors, not silently ignored keys. Typos surface immediately.
• ❓ Generated help: --help and --version are handled for you, including per-command help.
• 🚀 Zero dependencies: Only Zod, which you already have.

Requirements

• Node.js 16 or later
• Zod 4 (peer dependency)
• An ESM project — zodline ships no CommonJS build

Installation

npm install zodline zod

Quickstart

import { z } from 'zod';
import { defineCommand, defineConfig, defineOptions, processConfig } from 'zodline';

const greet = defineCommand({
  description: 'Greet someone',
  options: defineOptions(
    z.object({
      name: z.string().describe('Name to greet'),
      loud: z.boolean().default(false).describe('Use uppercase'),
    }),
    { n: 'name', l: 'loud' }, // Short aliases
  ),
  action: async (options) => {
    // options is typed as { name: string; loud: boolean }
    const greeting = `Hello, ${options.name}!`;
    console.log(options.loud ? greeting.toUpperCase() : greeting);
  },
});

const config = defineConfig({
  meta: {
    name: 'my-cli',
    version: '1.0.0',
    description: 'A simple CLI example',
  },
  commands: { greet },
});

const result = processConfig(config, process.argv.slice(2));
await result.command.action(result.options, result.args);

Run it:

$ my-cli greet --name Alice
Hello, Alice!

$ my-cli greet -n Bob --loud
HELLO, BOB!

Help is generated from the same schemas:

$ my-cli --help

A simple CLI example (my-cli v1.0.0)

USAGE my-cli <command>

COMMANDS

  greet    Greet someone

Use my-cli <command> --help for more information about a command.

$ my-cli greet --help

Greet someone (my-cli greet v1.0.0)

USAGE my-cli greet [OPTIONS]

OPTIONS

  --name, -n    Name to greet
  --loud, -l    Use uppercase (default: false)

Usage

Commands

Commands are a flat record of name to definition. Group related commands with a separator in the name:

const config = defineConfig({
  meta: { name: 'my-app', version: '1.0.0' },
  commands: {
    start: startCommand,
    'apps:list': appsListCommand,
    'apps:create': appsCreateCommand,
  },
});

Use a space as the separator to get subcommands. The longest matching name wins and the remaining positional arguments become args:

const config = defineConfig({
  meta: { name: 'my-app', version: '1.0.0' },
  commands: {
    'config set': configSetCommand,
    'config get': configGetCommand,
  },
});

• my-app config set theme dark runs configSetCommand with the args ['theme', 'dark']
• my-app config --help lists only the config commands

Set defaultCommand to run a command when none is given:

const config = defineConfig({
  meta: { name: 'my-app', version: '1.0.0' },
  commands: { start: startCommand, build: buildCommand },
  defaultCommand: startCommand,
});

• my-app runs startCommand
• my-app build runs buildCommand
• my-app --help still shows the help message

Options

defineOptions takes a Zod object schema and an optional map from short alias to schema key. The .describe() text becomes the option's help line, and .default() is shown in help.

const options = defineOptions(
  z.object({
    port: z.coerce.number().min(1).max(65535).default(3000).describe('Port to listen on'),
    files: z.array(z.string()).describe('Input files'),
    tags: z.array(z.string()).optional().describe('Tags to apply'),
  }),
  { p: 'port', f: 'files' },
);

Everything from the command line arrives as a string, so use z.coerce for numbers and other non-string types.

A single value for an array field is wrapped automatically, so both of these produce ['a.txt']:

--files a.txt
--files a.txt --files b.txt   # ['a.txt', 'b.txt']

Arguments

Positional arguments are validated by a single schema that receives the whole array. Use z.tuple for a fixed shape and z.array for a variable number:

const copy = defineCommand({
  description: 'Copy a file',
  args: z.tuple([z.string().describe('Source file'), z.string().describe('Destination file')]),
  options: defineOptions(z.object({ verbose: z.boolean().default(false) }), { v: 'verbose' }),
  action: async (options, args) => {
    const [source, destination] = args; // [string, string]
    console.log(`Copying ${source} to ${destination}`);
  },
});

Flag syntax

| Form | Example | Result | | --- | --- | --- | | Long flag | --verbose | verbose: true | | Long flag with value | --port 3000, --port=3000 | port: '3000' | | Short flag | -v, -p 3000 | resolved through the alias map | | Clustered short flags | -abc | a: true, b: true, c: true | | Kebab-case | --max-retries | matches the schema key maxRetries | | Repeated flag | --file a.txt --file b.txt | file: ['a.txt', 'b.txt'] |

A flag whose next argument starts with -, or which is last, becomes true.

Help and version

• <cli> --help prints the command list, <cli> <command> --help prints that command's options.
• <cli> --version prints meta.version. It is only handled when no command is given and meta.version is set.

Both paths print to stdout and call process.exit(0). Keep that in mind when calling processConfig from tests.

Error handling

processConfig validates and returns — it never invokes your action. That keeps parsing and execution separate, so commands stay testable.

import { z } from 'zod';
import { processConfig, ZodlineError } from 'zodline';

try {
  const result = processConfig(config, process.argv.slice(2));
  await result.command.action(result.options, result.args);
} catch (error) {
  if (error instanceof ZodlineError) {
    // Unknown command, unknown option, or no command specified
    console.error(error.message);
  } else if (error instanceof z.ZodError) {
    // An option failed schema validation
    console.error(z.prettifyError(error));
  } else {
    throw error;
  }
  process.exit(1);
}

Positional argument failures are currently thrown as a plain Error prefixed with Argument validation failed:.

API

| Export | Description | | --- | --- | | defineOptions(schema, aliases?) | Pairs a Zod object schema with an optional short-alias map. | | defineCommand(definition) | Defines a command from a description, examples, options, args and action. | | defineConfig(config) | Defines the CLI from meta, commands and an optional defaultCommand. | | processConfig(config, argv) | Parses and validates argv, returning { command, options, args }. | | ZodlineError | Thrown for unknown commands and unknown options. |

See the API reference for full signatures and types.

Comparison

| | zodline | commander | yargs | | --- | --- | --- | --- | | Validation | Zod schemas | custom parser functions | built-in coercions | | Option types | inferred from the schema | manual type annotations | inferred from the builder chain | | Runtime dependencies | 0 | 0 | 6 | | Module format | ESM only | CJS and ESM | CJS and ESM | | Parsing and execution | separate | coupled | coupled |

Dependency counts as of commander 15 and yargs 18. Both cover more surface than zodline — nested subcommands, shell completion, i18n. zodline is deliberately smaller and leans on Zod for everything it can.

Used By

• Capawesome Team CLI — the Capawesome Cloud CLI to manage Live Updates and more.

Contributing

npm install
npm test
npm run build
npm run lint

Bug reports and feature requests are welcome in the issue tracker.

Migration

zodline was previously published as @robingenz/zli. To migrate:

1. Replace the dependency:

   npm uninstall @robingenz/zli
   npm install zodline

2. Update import specifiers:

   - import { ... } from '@robingenz/zli';
   + import { ... } from 'zodline';

3. Rename the ZliError export to ZodlineError (the public API is otherwise unchanged):

   - import { ZliError } from '@robingenz/zli';
   + import { ZodlineError } from 'zodline';

Changelog

See CHANGELOG.md.

License

See LICENSE.