n8n-io/n8n · error

ARRAY_INPUT_COLLAPSED_TO_FIRST_ITEM

ARRAY_INPUT_COLLAPSED_TO_FIRST_ITEM

Error message

Code node reads the first input item (e.g. $input.first().json / items[0].json) and applies an array operation to it, but its upstream HTTP Request node "${httpParent}" splits a top-level array into one item per element. The first item is a single element, not the whole array, so the rest are dropped. Read every item with $input.all().map(i => i.json) (or iterate the items) instead.

What it means

Error "Code node reads the first input item (e.g. $input.first().json / items[0].json) and applies an array operation to it, but its upstream HTTP Request node "${httpParent}" splits a top-level array into one item per element. The first item is a single element, not the whole array, so the rest are dropped. Read every item with $input.all().map(i => i.json) (or iterate the items) instead." thrown in n8n-io/n8n.

Solutions

1. Replace $input.first().json / items[0].json with $input.all().map(i => i.json) so the whole array is consumed
2. If the Code node must see the full array, disable output splitting (response format 'text' or 'all items in one item') on the upstream HTTP Request node

When it happens

Trigger: Thrown at packages/@n8n/instance-ai/src/tools/workflows/detect-array-input-collapse.ts:95 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/c0625e34b5c9b75b. Report an issue: GitHub.

Appendix: source

Thrown at packages/@n8n/instance-ai/src/tools/workflows/detect-array-input-collapse.ts:95

 */
export function detectArrayInputCollapse(json: WorkflowJSON): ValidationWarning[] {
	const warnings: ValidationWarning[] = [];
	const typeByName = nodeTypeByName(json);

	for (const node of json.nodes ?? []) {
		if (node.type !== CODE_NODE_TYPE) continue;
		const params = node.parameters;
		const jsCode = isRecord(params) && typeof params.jsCode === 'string' ? params.jsCode : '';
		if (!jsCode || !treatsJsonAsArray(jsCode)) continue;

		const httpParent =
			typeof node.name === 'string'
				? mainInputSources(json, node.name).find((s) => typeByName.get(s)?.includes('httpRequest'))
				: undefined;
		if (!httpParent) continue;

		warnings.push({
			code: 'ARRAY_INPUT_COLLAPSED_TO_FIRST_ITEM',
			nodeName: typeof node.name === 'string' ? node.name : undefined,
			message:
				'Code node reads the first input item (e.g. $input.first().json / items[0].json) and applies an array ' +
				`operation to it, but its upstream HTTP Request node "${httpParent}" splits a top-level array into one ` +
				'item per element. The first item is a single element, not the whole array, so the rest are dropped. ' +
				'Read every item with $input.all().map(i => i.json) (or iterate the items) instead.',
		});
	}

	return warnings;
}

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