Implementation:BerriAI Litellm Braintrust Logger

Attribute	Value
Sources	`litellm/integrations/braintrust_logging.py`
Domains	Logging, Observability, Evaluation, Integrations
Last Updated	2026-02-15 16:00 GMT

Overview

The BraintrustLogger sends LLM success events (completions, embeddings, image generations) to the Braintrust evaluation and observability platform.

Description

BraintrustLogger extends CustomLogger to post LLM call data as spans to the Braintrust project logs API (/project_logs/{project_id}/insert). It supports both sync and async logging, automatic project creation, project ID caching, span hierarchies (via span_id, root_span_id, span_parents metadata), custom span names, tags from langfuse_default_tags, and token usage metrics. The logger also supports a mock mode for testing (controlled by the BRAINTRUST_MOCK environment variable).

Usage

Import and register BraintrustLogger when you need to send LLM telemetry to Braintrust for evaluation, tracing, or monitoring. Requires BRAINTRUST_API_KEY in the environment or passed directly.

Code Reference

Source Location

litellm/integrations/braintrust_logging.py

Signature

class BraintrustLogger(CustomLogger):
    def __init__(
        self, api_key: Optional[str] = None, api_base: Optional[str] = None
    ) -> None

Import

from litellm.integrations.braintrust_logging import BraintrustLogger

I/O Contract

Inputs

Parameter	Type	Required	Description
`api_key`	`Optional[str]`	No	Braintrust API key. Falls back to `BRAINTRUST_API_KEY` env var.
`api_base`	`Optional[str]`	No	Braintrust API base URL. Falls back to `BRAINTRUST_API_BASE` env var or `"https://api.braintrustdata.com/v1"`.

Key Methods

Method	Returns	Description
`log_success_event(kwargs, response_obj, start_time, end_time)`	`None`	Synchronous success event logging.
`async_log_success_event(kwargs, response_obj, start_time, end_time)`	`None`	Asynchronous success event logging.
`get_project_id_sync(project_name: str)`	`str`	Get or create project by name (sync), with caching.
`get_project_id_async(project_name: str)`	`str`	Get or create project by name (async), with caching.

Outputs

Output	Type	Description
Side effect	HTTP POST	Posts span events to `/project_logs/{project_id}/insert` on the Braintrust API.

Usage Examples

import litellm

# Set the callback
litellm.success_callback = ["braintrust"]

# Make a completion call - events are automatically logged
response = litellm.completion(
    model="gpt-4",
    messages=[{"role": "user", "content": "Hello"}],
    metadata={
        "project_name": "my-project",
        "span_name": "user-query",
    },
)

# Direct instantiation
from litellm.integrations.braintrust_logging import BraintrustLogger

logger = BraintrustLogger(api_key="my-braintrust-key")

Related Pages

BerriAI_Litellm_Argilla_Logger - another observability integration for data annotation
BerriAI_Litellm_MLflow_Logger - another evaluation/tracing integration
BerriAI_Litellm_PostHog_Logger - another analytics integration

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Principle

Implementation

Heuristic

Environment