FileCallbackHandler can't resolve name in on_chain_start (same as #26588)

[mirskiy]

Checked other resources

• I added a very descriptive title to this issue.
• I searched the LangChain documentation with the integrated search.
• I used the GitHub search to find a similar question and didn't find it.
• I am sure that this is a bug in LangChain rather than my code.
• The bug is not resolved by updating to the latest stable version of LangChain (or the specific integration package).

Example Code

#!/usr/bin/env python3
from langchain_core.callbacks import FileCallbackHandler, StdOutCallbackHandler
from langchain.chat_models import init_chat_model
from langchain_community.utilities import SQLDatabase
from langchain_community.agent_toolkits import create_sql_agent
from sqlalchemy import create_engine

logfile = "output.log"
handlier = FileCallbackHandler(logfile)

engine = create_engine("sqlite:///titanic.db")
db = SQLDatabase(engine=engine)
llm = init_chat_model("gpt-4o-mini", model_provider="openai")
agent_executor = create_sql_agent(
        llm, db=db,
        agent_type="openai-tools",
        agent_executor_kwargs={"callbacks": [handlier]},
        verbose=True)
agent_executor.invoke({"input": "test"})

Error Message and Stack Trace (if applicable)

Error in FileCallbackHandler.on_chain_start callback: AttributeError("'NoneType' object has no attribute 'get'")

Description

Same issue as #26588
FileCallbackHandler.on_chain_start doesn't resolve name from kwargs.

System Info

System Information

OS: Linux
OS Version: #167~18.04.1-Ubuntu SMP Wed May 24 00:51:42 UTC 2023
Python Version: 3.13.2 (main, Feb 22 2025, 11:11:40) [GCC 7.5.0]

Package Information

langchain_core: 0.3.37
langchain: 0.3.19
langchain_community: 0.3.18
langsmith: 0.3.10
langchain_openai: 0.3.6
langchain_text_splitters: 0.3.6
langgraph_sdk: 0.1.53

Optional packages not installed

langserve

Other Dependencies

aiohttp<4.0.0,>=3.8.3: Installed. No version info available.
async-timeout<5.0.0,>=4.0.0;: Installed. No version info available.
dataclasses-json<0.7,>=0.5.7: Installed. No version info available.
httpx: 0.28.1
httpx-sse<1.0.0,>=0.4.0: Installed. No version info available.
jsonpatch<2.0,>=1.33: Installed. No version info available.
langchain-anthropic;: Installed. No version info available.
langchain-aws;: Installed. No version info available.
langchain-cohere;: Installed. No version info available.
langchain-community;: Installed. No version info available.
langchain-core<1.0.0,>=0.3.34: Installed. No version info available.
langchain-core<1.0.0,>=0.3.35: Installed. No version info available.
langchain-core<1.0.0,>=0.3.37: Installed. No version info available.
langchain-deepseek;: Installed. No version info available.
langchain-fireworks;: Installed. No version info available.
langchain-google-genai;: Installed. No version info available.
langchain-google-vertexai;: Installed. No version info available.
langchain-groq;: Installed. No version info available.
langchain-huggingface;: Installed. No version info available.
langchain-mistralai;: Installed. No version info available.
langchain-ollama;: Installed. No version info available.
langchain-openai;: Installed. No version info available.
langchain-text-splitters<1.0.0,>=0.3.6: Installed. No version info available.
langchain-together;: Installed. No version info available.
langchain-xai;: Installed. No version info available.
langchain<1.0.0,>=0.3.19: Installed. No version info available.
langsmith-pyo3: Installed. No version info available.
langsmith<0.4,>=0.1.125: Installed. No version info available.
langsmith<0.4,>=0.1.17: Installed. No version info available.
numpy<2,>=1.26.4;: Installed. No version info available.
numpy<3,>=1.26.2;: Installed. No version info available.
openai<2.0.0,>=1.58.1: Installed. No version info available.
orjson: 3.10.15
packaging<25,>=23.2: Installed. No version info available.
pydantic: 2.10.6
pydantic-settings<3.0.0,>=2.4.0: Installed. No version info available.
pydantic<3.0.0,>=2.5.2;: Installed. No version info available.
pydantic<3.0.0,>=2.7.4: Installed. No version info available.
pydantic<3.0.0,>=2.7.4;: Installed. No version info available.
pytest: Installed. No version info available.
PyYAML>=5.3: Installed. No version info available.
requests: 2.32.3
requests-toolbelt: 1.0.0
requests<3,>=2: Installed. No version info available.
rich: 13.9.4
SQLAlchemy<3,>=1.4: Installed. No version info available.
tenacity!=8.4.0,<10,>=8.1.0: Installed. No version info available.
tenacity!=8.4.0,<10.0.0,>=8.1.0: Installed. No version info available.
tiktoken<1,>=0.7: Installed. No version info available.
typing-extensions>=4.7: Installed. No version info available.
zstandard: 0.23.0

[mirskiy]

Propsed fix in #29942, let me know if this is acceptable.