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Using OpenRouter with LangChain

Using LangChain

LangChain provides a standard interface for working with chat models. You can use OpenRouter with LangChain by setting the base_url parameter to point to OpenRouter’s API. For more details on LangChain’s model interface, see the LangChain Models documentation.

Resources:

1import { ChatOpenAI } from "@langchain/openai";
2import { HumanMessage, SystemMessage } from "@langchain/core/messages";
3
4const chat = new ChatOpenAI(
5  {
6    model: '<model_name>',
7    temperature: 0.8,
8    streaming: true,
9    apiKey: '${API_KEY_REF}',
10  },
11  {
12    baseURL: 'https://openrouter.ai/api/v1',
13    defaultHeaders: {
14      'HTTP-Referer': '<YOUR_SITE_URL>', // Optional. Site URL for rankings on openrouter.ai.
15      'X-Title': '<YOUR_SITE_NAME>', // Optional. Site title for rankings on openrouter.ai.
16    },
17  },
18);
19
20// Example usage
21const response = await chat.invoke([
22  new SystemMessage("You are a helpful assistant."),
23  new HumanMessage("Hello, how are you?"),
24]);