UsageMetadataCallbackHandler(
self,
)Whether to ignore retry callbacks.
Callback Handler that tracks AIMessage.usage_metadata.
Example:
from langchain.chat_models import init_chat_model
from langchain_core.callbacks import UsageMetadataCallbackHandler
llm_1 = init_chat_model(model="openai:gpt-5.5")
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