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Tracing forwards every LLM call Onyx makes to an external observability platform so you can monitor latency, token usage, and cost, and evaluate response quality. Onyx supports Braintrust and Langfuse.
Tracing is available on self-hosted deployments. It is not configurable on Onyx Cloud.

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Connect a provider

1

Navigate to the Tracing dashboard

Click your user profile icon, select Admin Panel, and open the Tracing tab under the Usage section of the sidebar.
2

Connect Braintrust and/or Langfuse

You can connect either or both providers — traces are sent to every connected provider.
Create an API key in the Braintrust dashboard under Settings → API Keys.In Onyx, click Connect on the Braintrust card and fill in:
  • API Key — your Braintrust API key.
  • Project Name (optional) — the Braintrust project traces are logged to. Defaults to Onyx.
  • API URL (optional) — only needed for self-hosted Braintrust or non-default regions. Defaults to https://api.braintrust.dev.
Onyx validates the credentials before saving. Once connected, the card shows Connected and traces begin flowing within about 30 seconds — no restart required.

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Disconnect a provider

Open the provider card, click the disconnect button, and confirm. Onyx stops sending new traces to that provider immediately. Traces already delivered are unaffected.

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Configuring with environment variables

Configuring tracing from the Admin Panel is the recommended approach, but Onyx also honors environment variables for backwards compatibility. A provider configured through the UI takes precedence over its environment variables.
ProviderVariableDescription
BraintrustBRAINTRUST_API_KEYAPI key. Enables Braintrust tracing when set.
BraintrustBRAINTRUST_PROJECTProject name traces are logged to. Defaults to Onyx.
BraintrustBRAINTRUST_API_URLCustom API URL for self-hosted / non-default regions.
LangfuseLANGFUSE_SECRET_KEYSecret key. Required (with the public key) to enable Langfuse.
LangfuseLANGFUSE_PUBLIC_KEYPublic key. Required (with the secret key) to enable Langfuse.
LangfuseLANGFUSE_HOSTBase URL for a non-default region or self-hosted Langfuse.
Providers configured through environment variables appear in the Tracing dashboard as configured via environment. You can adopt them into UI-managed configuration by connecting the provider from the Admin Panel.