n8n-io/n8n · error · Error

Flag requires a value

Error message

Flag ${flag} requires a value

What it means

CLI argument-parsing error from the ensureValue helper. It fires when a flag that takes a value (e.g. --prompt, --dataset) is the last token or is not followed by another token, so no value can be consumed. Generic guard shared by all value-taking flags in parseCli.

Solutions

1. Provide the value after the flag, e.g. --prompt "..." or --max-examples 5.
2. If the value starts with a dash, quote it or use the flag's inline form if supported.
3. Check the printed help for flags that require values.

When it happens

Trigger: Thrown at packages/@n8n/ai-workflow-builder.ee/evaluations/cli/argument-parser.ts:398 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/3dae175ff4cb0535. Report an issue: GitHub.

Appendix: source

Thrown at packages/@n8n/ai-workflow-builder.ee/evaluations/cli/argument-parser.ts:398

		lines.push('');
	}

	lines.push('Examples:');
	lines.push('  pnpm eval --verbose');
	lines.push('  pnpm eval --prompt "Create a Slack notification workflow"');
	lines.push('  pnpm eval --prompts-csv my-prompts.csv --max-examples 5');
	lines.push('  pnpm eval:langsmith --dataset "workflow-builder-canvas-prompts" --name "test-run"');

	return lines.join('\n');
}

export function printHelp(): void {
	console.log(formatHelp());
}

function ensureValue(argv: string[], i: number, flag: string): string {
	const value = argv[i + 1];
	if (value === undefined) throw new Error(`Flag ${flag} requires a value`);
	return value;
}

function splitFlagToken(token: string): { flag: string; inlineValue?: string } {
	if (!token.startsWith('--')) return { flag: token };
	const equalsIndex = token.indexOf('=');
	if (equalsIndex === -1) return { flag: token };
	return { flag: token.slice(0, equalsIndex), inlineValue: token.slice(equalsIndex + 1) };
}

function isStringArray(value: unknown): value is string[] {
	return Array.isArray(value) && value.every((v): v is string => typeof v === 'string');
}

function parseCli(argv: string[]): {
	values: Partial<Record<CliKey, unknown>>;
	seenKeys: Set<CliKey>;
} {

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