n8n-io/n8n · error · NodeOperationError

A non-empty prompt is required.

Error message

A non-empty prompt is required.

What it means

The Generate Image operation requires a non-empty prompt. After reading the 'prompt' parameter, the code checks prompt.trim(). If the prompt is blank or whitespace-only, it throws a NodeOperationError before calling the OpenAI image generation API. This prevents sending an empty generation request.

Source

Thrown at packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/v1/actions/image/generate.operation.ts:259

			},
		],
	},
];

const displayOptions = {
	show: {
		operation: ['generate'],
		resource: ['image'],
	},
};

export const description = updateDisplayOptions(displayOptions, properties);

export async function execute(this: IExecuteFunctions, i: number): Promise<INodeExecutionData[]> {
	const model = this.getNodeParameter('model', i) as string;
	const prompt = this.getNodeParameter('prompt', i) as string;
	if (!prompt.trim()) {
		throw new NodeOperationError(this.getNode(), 'A non-empty prompt is required.', {
			itemIndex: i,
		});
	}
	const options = this.getNodeParameter('options', i, {});
	let response_format = 'b64_json';
	let binaryPropertyOutput = 'data';

	if (options.returnImageUrls) {
		response_format = 'url';
	}

	if (options.binaryPropertyOutput) {
		binaryPropertyOutput = options.binaryPropertyOutput as string;
		delete options.binaryPropertyOutput;
	}

	if (options.dalleQuality) {
		options.quality = options.dalleQuality;

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Enter a descriptive prompt for image generation
2. If using an expression, add a fallback: {{$json["description"] || 'A serene landscape'}}, or use an IF node to filter empty prompts
3. Validate upstream data has the prompt field populated before this node

Example fix

// before — prompt: ''
// after  — prompt: 'A futuristic city skyline at sunset, digital art style'

const prompt = this.getNodeParameter('prompt', i) as string;
if (!prompt || !prompt.trim()) {
  throw new UserError('A non-empty prompt is required for image generation.');
}

function isNonEmptyPrompt(value: unknown): value is string {
  return typeof value === 'string' && value.trim().length > 0;
}

When it happens

Trigger: The 'prompt' parameter in the Generate Image operation is empty, contains only whitespace, or resolves to empty via an expression. The trim() check catches whitespace-only values.

Common situations: Prompt field left empty; expression like {{$json["description"]}} resolves to empty from upstream data; user expects a default prompt but none is configured.

Related errors

• A non-empty prompt is required.
• A non-empty prompt is required.
• A non-empty prompt is required.
• A non-empty prompt is required.
• A non-empty prompt is required.

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/11863e6cc7190fa2. Report an issue: GitHub.