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June 17, 2026

Web Callouts

Nimar Blume

Call any HTTP endpoint from your trace, observation, or session views to trigger external workflows from Langfuse.

Web Callouts allow you to call an HTTP endpoint from any trace, observation, or session view to trigger external workflows from Langfuse.

For example, trigger agent re-runs from Langfuse: after you find a specific trace, click the configured callout to post the specific observation/trace ID to your backend. You can also integrate with your support tool to attach a trace to a customer case.

Project admins configure the endpoint, toast text and encrypted request headers under Project Settings > Integrations > Web Callouts. Users then see the callout in the three dots menu when viewing a trace, observation, or session.

Langfuse will POST a JSON payload to your configured endpoint with the following format:

{
  "version": 1,
  "items": [
    {
      "projectId": "project-id",
      "traceId": "trace-id",
      "observationId": "observation-id",
      "sessionId": "session-id"
    }
  ]
}

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