Callback Handler that tracks AIMessage.usage_metadata.
UsageMetadataCallbackHandler(
self,
)Example:
from langchain.chat_models import init_chat_model
from langchain_core.callbacks import UsageMetadataCallbackHandler
llm_1 = init_chat_model(model="openai:gpt-4o-mini")
llm_2 = init_chat_model(model="anthropic:claude-haiku-4-5-20251001")
callback = UsageMetadataCallbackHandler()
result_1 = llm_1.invoke("Hello", config={"callbacks": [callback]})
result_2 = llm_2.invoke("Hello", config={"callbacks": [callback]})
callback.usage_metadata{'gpt-4o-mini-2024-07-18': {'input_tokens': 8,
'output_tokens': 10,
'total_tokens': 18,
'input_token_details': {'audio': 0, 'cache_read': 0},
'output_token_details': {'audio': 0, 'reasoning': 0}},
'claude-haiku-4-5-20251001': {'input_tokens': 8,
'output_tokens': 21,
'total_tokens': 29,
'input_token_details': {'cache_read': 0, 'cache_creation': 0}}}Whether to raise an error if an exception occurs.
Whether to ignore LLM callbacks.
Whether to ignore retry callbacks.
Whether to ignore chain callbacks.
Whether to ignore agent callbacks.
Whether to ignore retriever callbacks.
Whether to ignore chat model callbacks.
Ignore custom event.