---
url: https://docs.freetheai.org/sdks/langchain.md
description: >-
  Use FreeTheAI models in LangChain through the OpenAI-compatible ChatOpenAI
  class in Python and JavaScript, with streaming and tool binding.
---

# LangChain

LangChain's `ChatOpenAI` talks to any OpenAI-compatible API, so it works with FreeTheAI by setting the base URL, your key, and an `fta/` model ID.

## Python

```bash
pip install langchain-openai
```

```python
import os
from langchain_openai import ChatOpenAI

llm = ChatOpenAI(
    model="fta/zai/glm-5.3",
    base_url="https://api.freetheai.org/v1",
    api_key=os.environ["FTAI_KEY"],
    max_retries=2,
)

reply = llm.invoke("Give me three names for a bakery.")
print(reply.content)

for chunk in llm.stream("Write a two-line poem about coffee."):
    print(chunk.content, end="", flush=True)
```

### Tools

```python
from langchain_core.tools import tool

@tool
def get_weather(city: str) -> str:
    """Get the current weather for a city."""
    return f"It is 21°C and sunny in {city}."

llm_with_tools = llm.bind_tools([get_weather])
reply = llm_with_tools.invoke("What's the weather in Madrid?")
print(reply.tool_calls)
```

Use a model that can call tools, such as `fta/zai/glm-5.3` or `fta/kimi/k3`. The `fta/dog/` and `fta/lion/` models cannot.

## JavaScript and TypeScript

```bash
npm install @langchain/openai @langchain/core
```

```ts
import { ChatOpenAI } from '@langchain/openai'

const llm = new ChatOpenAI({
  model: 'fta/zai/glm-5.3',
  apiKey: process.env.FTAI_KEY,
  configuration: { baseURL: 'https://api.freetheai.org/v1' },
})

const reply = await llm.invoke('Give me three names for a bakery.')
console.log(reply.content)
```

## Notes

* Free accounts run one request at a time. Chains that fan out in parallel (`batch`, `RunnableParallel`, agents that call tools in parallel) will see `429` on the extra requests; set `max_concurrency=1` in the run config, or call one at a time.
* LangChain may print a warning that it does not know the model's context size. That is expected for `fta/` models and harmless.
* Errors are raised as the OpenAI SDK's exceptions; see [Errors](/errors).