observability-pydantic-validation--keyerror-tool-call-id-during-pydantic-v2-validatio-cd5a2489

THEN Update the `coerce_args` method in `langchain_core/messages/tool.py` to use `values.get("tool_call_id")` instead of `values["tool_call_id"]` to gracefully handle missing keys. Alternatively, as a temporary workaround, remove the explicit Union type for chat_history in the InputChat Pydantic model (e.g., use `List` instead of `List[Union[...]]`) to bypass strict validation.

In `langchain_core/messages/tool.py` line 122, change:
```python
tool_call_id = values["tool_call_id"]
```
to:
```python
tool_call_id = values.get("tool_call_id")
```