strictcli

Strict CLI framework for TypeScript — declare everything, infer nothing.

strictcli takes the opposite stance from convention-over-configuration CLI libraries: every command, flag, argument, type, default, and help string is declared explicitly, and anything left unstated is a hard error at registration time. No implicit defaults, no guessed types, no silently ignored input. The result is a CLI whose behavior is fully determined by its declaration.

This package is the native TypeScript implementation: pure ESM, Node >= 22, with full static type inference from flag declarations all the way to handler arguments — declare flag("count", t.int, { required: true }) and your handler's args.count is a bigint, checked by the compiler.

Install

npm install strictcli

Usage

Types are carriers (t.str, t.bool, t.int, t.float, plus t.list(...) and t.dict(...)) that bind the schema, the runtime parser, and the inferred TypeScript type in one value, so they cannot drift apart:

import { arg, command, createApp, flag, t } from "strictcli";

const build = command("build", {
	help: "Build the project",
	flags: [
		flag("dry-run", t.bool, { help: "Print actions without running", default: true }),
		flag("count", t.int, { help: "How many times to build", required: true }),
	],
	args: [arg("values", t.float, { help: "Input values", variadic: true })],
	handler: (args, ctx) => {
		// Inferred: args.dry_run is boolean, args.count is bigint, args.values is number[]
		ctx.info(`building ${args.count} time(s), dry-run=${args.dry_run}`);
		return 0;
	},
});

const app = createApp("myapp", {
	version: "1.0.0",
	help: "my cool app",
	commands: [build],
});

app.run(process.argv.slice(2));

Features

• Strict four-type system — str, bool, int, float, with int backed by bigint for full 64-bit signed integer range and strict parsing (no whitespace, no overflow wraparound).
• Static handler-arg inference — dash-named flags (--dry-run) arrive as underscore keys (dry_run) with exact types and true optional-key modifiers, derived entirely from the declarations.
• Mandatory help everywhere — missing help text on any app, group, command, flag, or argument is a registration-time error.
• Env var and JSON config file resolution — explicit precedence: CLI > env > config > default, with auto-registered config show/set/path/edit subcommands.
• First-class check system — TOML-declared checks with double-entry registration, tag DSL selection, DAG-ordered execution.
• MCP server integration — expose commands as Model Context Protocol tools.
• Schema dump — every app answers --dump-schema with a machine-readable JSON description of its full structure.
• Groups, passthrough commands, deprecation notices, mutex/co-required/implies dependencies — the complete strictcli surface.

Sibling implementations

strictcli is developed in the smm-h/strictcli monorepo alongside first-class Python (PyPI: strictcli) and Go implementations. All implementations are kept byte-identical in behavior — same error messages, same help output, same parsing rules — enforced by a shared cross-language conformance suite.

License

MIT