Send application logs

Send application logs to Braintrust to inspect events such as retries and payment failures alongside your AI traces. A log doesn’t require an LLM call, an agent, or an active trace. When a failure occurs during an agent run, you can inspect both the message and the surrounding model behavior. Get logs into Braintrust in three ways:

Send logs from the Python SDK, either by emitting messages or by forwarding standard-library logging records.
Send logs from the TypeScript SDK, either by emitting messages or by forwarding console output.
Send OpenTelemetry logs from any language that exports OTLP.

Application logs are in public preview and can change before reaching general availability.

Messages share the fields, queries, filters, and IDs used by spans. A message:

Records a point in time, with zero duration.
Has no children.
Carries a severity level.

Emit a message to record an event. Open a span to time an operation or nest other rows under it.

Send logs from the Python SDK

To send logs from Python, emit messages with a project logger’s severity methods, such as info() and error(), or forward existing records from the standard-library logging module with BraintrustLogHandler. The guide covers stored fields, message templates, and associating logs with a trace.

Send logs from the TypeScript SDK

To send logs from TypeScript, emit messages with a project logger’s severity methods, such as info() and error(), or forward existing console output with wrapConsole(). The guide covers stored fields, message templates, and associating logs with a trace.

Send OpenTelemetry logs

To forward OpenTelemetry logs, configure your exporter or Collector. You can also send Claude Code events to Braintrust as OpenTelemetry logs, including API requests, errors, and tool results.

Inspect logs

The Logs row type shows SDK messages, OTLP log records, and OpenTelemetry span events. The Traces and Spans row types also include log rows. A log that isn’t attached to a trace, such as an OTLP log record without a trace ID, appears in Traces as its own row. Log rows don’t offer scoring or human review actions.

Go to Logs in your project. In the toolbar’s row type selector, choose Logs. This loads All logs view, with Dense rows and an all-time range.
Choose a time range and use the search field to filter messages. The chart above the table groups messages by log level by default. See Explore the logs chart.
Select a message to inspect its contents:
- Output: The full message.
- Details: Log level, timestamp, span ID, and log ID.
- Metadata and Context: Additional fields, when present.

To query messages with SQL, use the Query page, the bt sql CLI, or the API. Filter on span_attributes.type = 'log' to select messages, and include a range filter on created to bound the query.

Recent messages in a project

SELECT created, output, span_attributes.log_level, metadata
FROM project_logs('<PROJECT_ID>') -- Replace with your project ID
WHERE span_attributes.type = 'log'
  AND created > NOW() - INTERVAL 1 DAY
ORDER BY created DESC
LIMIT 100

Filter by severity

In the Logs row type, select the empty search field. It suggests a filter for each severity level, such as span_attributes.log_level = 'warn' or span_attributes.log_level = 'error'. Choose one to apply it.

To filter on a message’s own level, open the menu beside Log level in Details and select Filter by this value.

Error and fatal messages

SELECT created, output, error, metadata
FROM project_logs('<PROJECT_ID>') -- Replace with your project ID
WHERE span_attributes.type = 'log'
  AND span_attributes.log_level IN ('error', 'fatal')
  AND created > NOW() - INTERVAL 7 DAY
ORDER BY created DESC
LIMIT 100

Messages without a span_attributes.log_level value don’t match a severity filter. For OpenTelemetry logs and span events, see how Braintrust derives log levels.

View logs in a trace

To inspect a message in context, select it in its trace’s hierarchy or Timeline. Log icons and timeline markers reflect the recorded severity, when present.Older messages can lack a preview in the trace hierarchy until you open them. The full message remains available in Output.

Messages emitted during one trace

SELECT created, output, span_attributes.log_level, span_id
FROM project_logs('<PROJECT_ID>') -- Replace with your project ID
WHERE span_attributes.type = 'log'
  AND root_span_id = '<ROOT_SPAN_ID>' -- Replace with the trace's root span ID
ORDER BY created

Next steps

Filter and search to find records from a specific operation.
Examine traces to inspect the operations surrounding a message.
Send logs from the Python SDK to emit messages or forward logging records.
Send logs from the TypeScript SDK to emit messages or forward console output.
Configure OpenTelemetry to connect existing instrumentation to Braintrust.

Start

Instrument

Observe

Annotate

Evaluate

Deploy

Admin

Best practices

Send application logs

Send logs from the Python SDK

Send logs from the TypeScript SDK

Send OpenTelemetry logs

Inspect logs

Filter by severity

View logs in a trace

Next steps

​Send logs from the Python SDK

​Send logs from the TypeScript SDK

​Send OpenTelemetry logs

​Inspect logs

​Filter by severity

​View logs in a trace

​Next steps

Send logs from the Python SDK

Send logs from the TypeScript SDK

Send OpenTelemetry logs

Inspect logs

Filter by severity

View logs in a trace

Next steps