Openrouter integration to langchain

[wonhs91]

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Feature request

I am using models from OpenRouter via ChatOpenAI. This works for invoking and streaming, however tool calling functionality does not work.
It would be great if there is a ChatOpenRouter plugin that will help integrate OpenRouter to my langgraph project.

Motivation

I wanted to use OpenRouter, but it is not available. At least not without specific tunings that I don't know about.

Proposal (If applicable)

No response

[brycepg]

Here's the workaround (works with bind tools):

pip install langchain_openai python-dotenv

Set OPENROUTER_API_KEY in .env

import os
from typing import Optional

from dotenv import load_dotenv
from langchain_core.utils.utils import secret_from_env
from langchain_openai import ChatOpenAI
from pydantic import Field, SecretStr

load_dotenv()

class ChatOpenRouter(ChatOpenAI):
    openai_api_key: Optional[SecretStr] = Field(
        alias="api_key", default_factory=secret_from_env("OPENROUTER_API_KEY", default=None)
    )
    @property
    def lc_secrets(self) -> dict[str, str]:
        return {"openai_api_key": "OPENROUTER_API_KEY"}

    def __init__(self,
                 openai_api_key: Optional[str] = None,
                 **kwargs):
        openai_api_key = openai_api_key or os.environ.get("OPENROUTER_API_KEY")
        super().__init__(base_url="https://openrouter.ai/api/v1", openai_api_key=openai_api_key, **kwargs)


openrouter_model = ChatOpenRouter(model_name="anthropic/claude-3.7-sonnet:thinking")

Set the model_name argument to ChatOpenRouter to the specific model you want on openrouter