diff --git a/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.test.ts b/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.test.ts
new file mode 100644
index 0000000000..1331fdd3f9
--- /dev/null
+++ b/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.test.ts
@@ -0,0 +1,42 @@
+import { mockDeep } from 'jest-mock-extended';
+import type { IExecuteFunctions, INode } from 'n8n-workflow';
+import { NodeApiError } from 'n8n-workflow';
+
+import * as audio from './audio';
+import { router } from './router';
+
+describe('OpenAI router', () => {
+	const mockExecuteFunctions = mockDeep<IExecuteFunctions>();
+	const mockAudio = jest.spyOn(audio.transcribe, 'execute');
+
+	beforeEach(() => {
+		jest.clearAllMocks();
+	});
+
+	it('should handle NodeApiError undefined error chaining', async () => {
+		const errorNode: INode = {
+			id: 'error-node-id',
+			name: 'ErrorNode',
+			type: 'test.error',
+			typeVersion: 1,
+			position: [100, 200],
+			parameters: {},
+		};
+		const nodeApiError = new NodeApiError(
+			errorNode,
+			{ message: 'API error occurred', error: { error: { message: 'Rate limit exceeded' } } },
+			{ itemIndex: 0 },
+		);
+
+		mockExecuteFunctions.getNodeParameter.mockImplementation((parameter) =>
+			parameter === 'resource' ? 'audio' : 'transcribe',
+		);
+		mockExecuteFunctions.getInputData.mockReturnValue([{ json: {} }]);
+		mockExecuteFunctions.getNode.mockReturnValue(errorNode);
+		mockExecuteFunctions.continueOnFail.mockReturnValue(false);
+
+		mockAudio.mockRejectedValue(nodeApiError);
+
+		await expect(router.call(mockExecuteFunctions)).rejects.toThrow(NodeApiError);
+	});
+});
diff --git a/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.ts b/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.ts
index 2b64993e2d..876dd88cb1 100644
--- a/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.ts
+++ b/packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/router.ts
@@ -62,7 +62,7 @@ export async function router(this: IExecuteFunctions) {
 
 			if (error instanceof NodeApiError) {
 				// If the error is a rate limit error, we want to handle it differently
-				const errorCode: string | undefined = (error.cause as any).error?.error?.code;
+				const errorCode: string | undefined = (error.cause as any)?.error?.error?.code;
 				if (errorCode) {
 					const customErrorMessage = getCustomErrorMessage(errorCode);
 					if (customErrorMessage) {