# LangChain

[LangChain](https://www.langchain.com/) is a framework for building and deploying applications powered by large language models (LLMs), streamlining the entire lifecycle from development to production. 

It offers open-source components and integrations for building applications, LangGraph for creating stateful agents with streaming and human-in-the-loop support, and LangSmith for inspecting, monitoring, and evaluating performance to ensure optimization. 

Finally, with LangGraph Platform, developers can deploy their applications as production-ready APIs and Assistants.

This guide will walk you through the setup.

{% hint style="info" %}
*Before you begin: Make sure you have generated your Cortecs API key. If not, check out our* [*QuickStart*](https://docs.cortecs.ai/quickstart) *guide.*
{% endhint %}

## 1. Install LangChain 

LangChain offers both [Python](https://python.langchain.com/docs/how_to/installation/) and [JavaScript](https://js.langchain.com/docs/how_to/installation/) libraries.

To get started quickly, follow the installation instructions in the documentation for your preferred language.

Once the framework is installed, you can begin building applications by connecting to an external provider.

## 2. Connect to cortecs

Cortecs provides **OpenAI-compatible API endpoints**, making it easy to integrate with LangChain and many other tools.

To connect and use the LLM, create an `ChatOpenAI` object, with the following settings:

– `api_key`: Your API Key\
– `base_url`:  <code class="expression">space.vars.DEFAULT\_API\_BASE\_URL</code>\
– `model`: <code class="expression">space.vars.DEFAULT\_CHAT\_MODEL</code> (feel free to pick another one from the [catalogue](https://cortecs.ai/serverlessModels))\
– (optional) `extra_body`: `{"preference": "balanced"}`

```python
from langchain_openai import ChatOpenAI
from pydantic import SecretStr

llm = ChatOpenAI(
    model="gpt-5-mini",
    # you also can use env vars to configure base_url and api_key
    api_key=SecretStr("eyJhbG***"),
    base_url="https://api.cortecs.ai/v1",
    extra_body= {"preference": "balanced"}
)

print(llm.invoke("Hi").content)
```

### 2.1. Embedding Model

To create embeddings and use LangChain with vector databases, you can instantiate an `OpenAIEmbeddings` object with the following settings:

– `api_key`: Your API Key\
– `base_url`:  <code class="expression">space.vars.DEFAULT\_API\_BASE\_URL</code>\
– `model`: <code class="expression">space.vars.DEFAULT\_EMBEDDING\_MODEL</code> (feel free to pick another embedding model from the [catalogue](https://cortecs.ai/serverlessModels))\
– (optional) `model_kwargs`: `{"extra_body": {"preference": "balanced"}}`

```python
from langchain_openai import OpenAIEmbeddings
from pydantic import SecretStr

embedding_model = OpenAIEmbeddings(
    model="text-embedding-3-large",
    api_key=SecretStr("eyJhbG***"),
    base_url="https://api.cortecs.ai/v1",
    model_kwargs= {"extra_body": {"preference": "balanced"}}
)

print(embedding_model.embed_query("Hi"))
```

Enjoy your **privacy-preserving LLM applications** with the power of Cortecs and LangChain. Explore other models, tweak the setup to your needs, and join the conversation on our [Discord](https://discord.com/invite/bPFEFcWBhp) to share feedback 👩‍💻👨‍💻