> ## Documentation Index
> Fetch the complete documentation index at: https://braintrust.dev/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Strip OTel attributes from metadata

export const plans_0 = "Any"

export const deployments_0 = "Any"

export const data_plane_version_0 = undefined

export const use_case_0 = undefined

<Note>
  **Applies to:**

  * Plan - {plans_0}
  * Deployment - {deployments_0}
  * {data_plane_version_0}
  * {use_case_0}
</Note>

## Summary

When OTel spans are ingested into Braintrust, attributes such as `ai.prompt`, `gen_ai.input.messages`, and `llm.input_messages` are parsed into the span's structured `input` and `output` fields. Historically, those same raw attributes were also kept on the span's `metadata`, which duplicated large payloads.

Braintrust now supports an option that strips parsed attributes from `metadata` so each payload is stored only once, on the structured field it was parsed into.

* **Braintrust-hosted:** this option is enabled. Parsed OTel attributes no longer appear in `metadata`.
* **Self-hosted:** the option is off by default. There is no change to your data until you opt in.
* **Per-span escape hatch:** set the `braintrust.otel.preserve_attributes` attribute to `true` on any span where you need the raw attributes preserved on `metadata` for forensics or debugging.

## What changes for Braintrust-hosted customers

For spans ingested via OTel, attribute keys that Braintrust successfully parses into structured fields are removed from `metadata`. The data is not lost. It is available on the parsed field (`input`, `output`, `metrics`, `expected`, `tags`, `span_attributes`, or `origin`).

Examples of attributes that are parsed and therefore stripped:

* Vercel AI SDK: `ai.prompt`, `ai.prompt.messages`, `ai.prompt.format`, `ai.response.text`
* OpenInference / generic Gen AI: `gen_ai.input.messages`, `gen_ai.output.messages`
* LlamaIndex / OpenInference: `llm.input_messages`, `llm.output_messages`
* Traceloop, CrewAI, Pydantic AI, LiveKit, and other supported integrations: their parsed attributes are stripped as well.

Attributes that Braintrust does not parse are unaffected and remain on `metadata` as before.

## Escape hatch: preserve raw attributes per span

If you need the raw OTel attributes on `metadata` for a specific code path, for example to compare what an upstream library actually emitted against what Braintrust parsed, set the attribute `braintrust.otel.preserve_attributes` to `true` on that span. The override is evaluated per-span, so you can scope it to one suspect call without changing the rest of your tracing.

Both the boolean `true` and the string `"true"` are accepted.

```python theme={"theme":{"light":"github-light","dark":"github-dark-dimmed"}}
from opentelemetry import trace

tracer = trace.get_tracer(__name__)

with tracer.start_as_current_span("debug-llm-call") as span:
    span.set_attribute("braintrust.otel.preserve_attributes", True)
    # ... your instrumented LLM call ...
```

When this attribute is set, Braintrust skips the strip step for that span and writes all raw attributes to `metadata` exactly as before.

## Self-hosted: enabling the feature

Self-hosted deployments default to the prior behavior (raw attributes are kept on `metadata`). To opt in, set `STRIP_OTEL_ATTRIBUTES_FROM_METADATA=true` on the `api-ts` service through your deployment configuration.

The per-span `braintrust.otel.preserve_attributes` escape hatch works the same way once the env var is enabled.

## Verifying the behavior

1. Send a known OTel span (for example, a Vercel AI SDK call producing `ai.prompt`) to Braintrust.
2. Open the resulting log row. The parsed payload should appear in `input` / `output`, and the corresponding attribute keys should be absent from `metadata`.
3. Re-run the same call after setting the `braintrust.otel.preserve_attributes` attribute to `true` on the span. The raw attribute keys should reappear in `metadata` while still being parsed into `input` / `output`.