# LangSmith Stack

| Layer | Product | Role |
|-------|---------|------|
| **L4** | Blekline | Allow/block at ingress; metadata audit |
| **L3** | LangSmith | Eval, traces, datasets |

## Wiring

1. Blekline emits metadata-only events via `/api/events` (no prompt bodies by default)
2. Forward OTel labels from [Telemetry spec](/docs/reference/telemetry-spec) to LangSmith
3. Correlate traces via `requestId`

LangSmith measures quality **after** Blekline governance decisions. LangSmith is not a SIEM — use [Enterprise telemetry](/docs/enterprise/telemetry) for Splunk/Datadog.

See [LangSmith documentation](https://docs.smith.langchain.com/).

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**Next steps:** [Eval hub](/docs/integrations/eval-and-safety) · [Trust boundaries](/docs/security/trust-boundaries) · [Telemetry](/docs/enterprise/telemetry) · [Open workspace](https://app.blekline.com)