Troubles with LangChain Code root & sub-node

I’m missing something obvious, and hopefully, someone can point me in the right direction.

I’m trying to extend the AI options using the LangChain Code nodes.

I want to build a few different LangChain nodes, but for the sake of this example, let’s use a custom Document loader.

Here’s the code (inside Supply Data) for my custom Document loader (tested and works with built-in AI nodes like In-Memory Vector Store). The output Type of this sub-node has been set to Document:

const { Document } = require("langchain/document");

class MockDocumentLoader {
  constructor(mockData) {
    this.mockData = mockData;

  async load() {
    // Construct Document objects from your mock data
    const documents = => {
        return new Document({ pageContent: data.page_content, metadata: data.metadata || {} }); 
    return documents;

const mockData = [
  { page_content: "The first document.", metadata: { source: "Wikipedia" } },
  { page_content: "Another document for testing.",  metadata: { source: "Google" }  },

return new MockDocumentLoader(mockData)

Now, in my root LangChain node, I call the custom Document loader through this code (as explained here):

const loader = (await this.getInputConnectionData("ai_document", 0))[0]
const parentDocuments = await loader.load()

The root LangChain Code node has input Type set to Main and to Document.

Now, no matter what I try, when I run this root node, the sub-node always returns the following error message: this.getMode is not a function.

Again, what surprises me is that the sub-node works just fine with the built-in AI nodes, just not (yet) with a custom LangChain Code root node.

What am I missing?

Information on your n8n setup

  • n8n version: 1.33.1
  • Database: SQLite
  • n8n EXECUTIONS_PROCESS setting: own, main
  • Running n8n via: npm
  • Operating system: Ubuntu 22.02

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  • n8n version:
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  • n8n EXECUTIONS_PROCESS setting (default: own, main):
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  • Operating system: