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Introduction

The Telemetry package is the shared tracing layer for Instructor PHP runtimes. It does not generate runtime events on its own. Runtime packages such as agents, agent-ctrl, instructor, polyglot, and http-client emit events, and telemetry projectors turn those events into correlated spans and logs. At the center is Cognesy\Telemetry\Application\Telemetry. You give it:
  • a TraceRegistry to keep active spans in memory
  • an exporter such as OtelExporter, LogfireExporter, or LangfuseExporter
Then runtime projectors write observations into that shared telemetry instance.

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Main Pieces

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Telemetry

Telemetry is the main application service. It opens spans, records logs, closes spans, stores pending metrics, and flushes exporters. Common methods:
  • openRoot(string $key, string $name)
  • openChild(string $key, string $parentKey, string $name)
  • log(string $key, string $name)
  • complete(string $key)
  • fail(string $key)
  • flush()

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TraceRegistry

TraceRegistry tracks active spans by key during the current process. The key is local to your app. It can be an execution id, request id, or any stable name you use while the run is active.

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Exporters

The package ships with three main exporters:
  • OtelExporter for generic OTEL payloads
  • LogfireExporter for Logfire OTLP export
  • LangfuseExporter for Langfuse OTLP export
You can combine them with CompositeTelemetryExporter.

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Where Runtime Wiring Happens

Projectors live in the packages that own the events, not in packages/telemetry. Typical examples:
  • Cognesy\Agents\Telemetry\AgentsTelemetryProjector
  • Cognesy\AgentCtrl\Telemetry\AgentCtrlTelemetryProjector
  • Cognesy\Instructor\Telemetry\InstructorTelemetryProjector
  • Cognesy\Polyglot\Telemetry\PolyglotTelemetryProjector
  • Cognesy\Http\Telemetry\HttpClientTelemetryProjector
Use RuntimeEventBridge to attach those projectors to a shared event bus.
  1. 02-basic-setup.md
  2. 03-runtime-wiring.md
  3. 04-troubleshooting.md
  4. 05-langfuse.md
  5. 06-logfire.md