get_usage_metadata_callback

langchain_core.callbacks.usage.get_usage_metadata_callback(name: str = 'usage_metadata_callback') → Generator[UsageMetadataCallbackHandler, None, None]

Beta

This feature is in beta. It is actively being worked on, so the API may change.

Get usage metadata callback.

Get context manager for tracking usage metadata across chat model calls using AIMessage.usage_metadata.

Parameters:

name (str) – The name of the context variable. Defaults to "usage_metadata_callback".

Return type:

Generator[UsageMetadataCallbackHandler, None, None]

Example

from langchain.chat_models import init_chat_model
from langchain_core.callbacks import get_usage_metadata_callback

llm_1 = init_chat_model(model="openai:gpt-4o-mini")
llm_2 = init_chat_model(model="anthropic:claude-3-5-haiku-latest")

with get_usage_metadata_callback() as cb:
    llm_1.invoke("Hello")
    llm_2.invoke("Hello")
    print(cb.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-3-5-haiku-20241022': {'input_tokens': 8,
  'output_tokens': 21,
  'total_tokens': 29,
  'input_token_details': {'cache_read': 0, 'cache_creation': 0}}}

Added in version 0.3.49.