Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain.js documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain.js rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

The following code:

import { ChatWebLLM } from '@langchain/community/chat_models/webllm';

webllmModel = new ChatWebLLM({
	model: 'Phi2-q4f32_1',
	chatOptions: {
		temperature: 0.1
	}
});
await webllmModel.initialize();

Error Message and Stack Trace (if applicable)

Uncaught (in promise) TypeError: (void 0) is not a constructor
at ChatWebLLM.initialize (@langchain_community_chat_models_webllm.js?v=b8d3d037:13507:19)
at worker.ts:156:22

Description

I'm trying to use ChatWebLLM via web workers following the documentation and the end-to-end example referenced in the docs.

I expect the web llm engine to be initialized when I call ChatWebLLM.initialize; however, the error above occurs instead.

After studying the source code, I figured that in a recent commit, the developers of web-llm renamed the Engine class to MLCEngine. This results in a failed constructor call on this line:

Fixing the web-llm version to 0.2.35 (where the class was not renamed yet) works for now.

System Info

Node version: v22.1.0
langchain version: 0.2.4
@langchain/community version: 0.2.5
@mlc-ai/web-llm version: 0.2.41