n8n-io/n8n · warning

INVALID_EXPRESSION_PATH

INVALID_EXPRESSION_PATH

Error message

'${nodeName}' parameter '${paramPath}' uses $json.${fieldPathStr} but no predecessor outputs this field.

What it means

Warning-level validator issue (code INVALID_EXPRESSION_PATH) emitted when an expression in parameter paramPath references $json.<fieldPath> but NONE of the predecessor nodes' output shapes contain that field. The field will resolve to undefined at runtime, so the validator flags it. Message interpolates nodeName, paramPath, and the dotted field path.

Source

Thrown at packages/@n8n/workflow-sdk/src/workflow-builder/plugins/validators/expression-path-validator.ts:106

	const validIn: string[] = [];
	const invalidIn: string[] = [];

	for (const pred of predecessors) {
		const shape = outputShapes.get(pred);
		if (shape) {
			if (hasPath(shape, fieldPath)) {
				validIn.push(pred);
			} else {
				invalidIn.push(pred);
			}
		}
	}

	const fieldPathStr = fieldPath.join('.');

	if (invalidIn.length > 0 && validIn.length === 0) {
		issues.push({
			code: 'INVALID_EXPRESSION_PATH',
			message: `'${nodeName}' parameter '${paramPath}' uses $json.${fieldPathStr} but no predecessor outputs this field.`,
			severity: 'warning',
			nodeName,
			parameterPath: paramPath,
		});
	} else if (invalidIn.length > 0 && validIn.length > 0) {
		issues.push({
			code: 'PARTIAL_EXPRESSION_PATH',
			message: `'${nodeName}' parameter '${paramPath}' uses $json.${fieldPathStr} - exists in [${validIn.join(', ')}] but NOT in [${invalidIn.join(', ')}].`,
			severity: 'warning',
			nodeName,
			parameterPath: paramPath,
		});
	}
}

/**
 * Validate that $('NodeName').item.json.path references a valid field

View on GitHub (pinned to 5ac6606e81)

Solutions

1. Verify the upstream node actually outputs the referenced field (check its output shape).
2. Correct the field name in the expression to match the real output.
3. Add a Set/code node upstream that produces the required field.

Example fix

// before
'={{ $json.emailAddress }}' // upstream outputs 'email'
// after
'={{ $json.email }}'

function fieldExistsInAllPreds(fieldPath: string[], predShapes: Map<string, Record<string, unknown>>): boolean {
  for (const shape of predShapes.values()) {
    if (!hasPath(shape, fieldPath)) return false;
  }
  return true;
}
if (!fieldExistsInAllPreds(fieldPath, predShapes)) {
  // warn: $json.field not provided by any predecessor
}

When it happens

Trigger: Writing '={{ $json.email }}' when no upstream node outputs an 'email' field; renaming an upstream field without updating downstream expressions.

Common situations: Stale expressions after a schema change; typos in field names; assuming a field exists because an example item had it.

Related errors

• PARTIAL_EXPRESSION_PATH
• AGENT_STATIC_PROMPT
• AGENT_STATIC_PROMPT
• INVALID_DATE_METHOD
• MISSING_EXPRESSION_PREFIX

AI-assisted analysis of n8n-io/n8n@5ac6606e81 (2026-08-12). Data as JSON: /api/errors/7e5a84b5a320b5ab. Report an issue: GitHub.