# Symptom
```
ImportError: cannot import name 'ChatOpenAI' from 'langchain'
```
## Confirm
Run `python -c "import langchain; print(langchain.__version__)"`. If it is 1.x, the old import path is gone by design, not by accident.
## Cause
LangChain v1 shrank the `langchain` namespace to agents, messages, tools, chat models (init functions), and embeddings. Model classes moved to provider packages. Training data and old tutorials still teach the pre-v1 paths.
## Fix
```python
from langchain_openai import ChatOpenAI # needs pip install langchain-openai
```
or provider-agnostic:
```python
from langchain.chat_models import init_chat_model
model = init_chat_model("openai:gpt-5.5")
```
## Verify
Import the class and construct it. Then grep the codebase for other stale imports from `langchain` (`langchain.chat_models` classes, `langchain.llms`, `langchain.embeddings` classes); they fail the same way and it is cheaper to fix them all now.