Skip to main content

​
Langfuse Setup

The simplest Langfuse setup uses:
  • LangfuseConfig
  • LangfuseHttpTransport
  • LangfuseExporter
  • Telemetry

​
Minimal Example

use Cognesy\Telemetry\Adapters\Langfuse\LangfuseConfig;
use Cognesy\Telemetry\Adapters\Langfuse\LangfuseExporter;
use Cognesy\Telemetry\Adapters\Langfuse\LangfuseHttpTransport;
use Cognesy\Telemetry\Application\Registry\TraceRegistry;
use Cognesy\Telemetry\Application\Telemetry;

$telemetry = new Telemetry(
    registry: new TraceRegistry(),
    exporter: new LangfuseExporter(
        transport: new LangfuseHttpTransport(new LangfuseConfig(
            baseUrl: $_ENV['LANGFUSE_BASE_URL'],
            publicKey: $_ENV['LANGFUSE_PUBLIC_KEY'],
            secretKey: $_ENV['LANGFUSE_SECRET_KEY'],
        )),
    ),
);
// @doctest id="4954"

​
Environment Variables

The examples use:
  • LANGFUSE_BASE_URL
  • LANGFUSE_PUBLIC_KEY
  • LANGFUSE_SECRET_KEY
See:
  • examples/_support/langfuse.php

​
Agent Runtime Example

The working agent example is:
  • examples/D05_AgentTroubleshooting/TelemetryLangfuse/run.php
That example shows the full pattern:
  1. create telemetry
  2. create a shared event dispatcher
  3. attach RuntimeEventBridge
  4. install runtime projectors
  5. execute the agent
  6. call $hub->flush()

​
Subagent Example

For nested telemetry across parent and child agents, see:
  • examples/D05_AgentTroubleshooting/SubagentTelemetryLangfuse/run.php

​
Notes

  • Langfuse uses the base URL and sends traces to /api/public/otel/v1/traces
  • request-scoped traces can fall back to request ids as session.id
  • if you get a 4xx response, check the base URL and keys first