> ## Documentation Index
> Fetch the complete documentation index at: https://docs.instructorphp.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Telemetry

# Telemetry Cheatsheet

Namespace:

* `Cognesy\\Telemetry\\`

Minimal usage:

```php theme={null}
use Cognesy\Telemetry\Adapters\OTel\OtelExporter;
use Cognesy\Telemetry\Application\Registry\TraceRegistry;
use Cognesy\Telemetry\Application\Telemetry;

$telemetry = new Telemetry(
    registry: new TraceRegistry(),
    exporter: new OtelExporter(),
);

$telemetry->openRoot('run', 'demo.run');
$telemetry->log('run', 'demo.step');
$telemetry->complete('run');
$telemetry->flush();
```

Core concepts:

* `TraceContext`
* `SpanReference`
* `Observation`
* `MetricMeasurement`
* `TelemetryContinuation`
* `InstrumentationProfile`

Application services:

* `Telemetry`
* `TraceRegistry`
* `CompositeTelemetryExporter`

Exporter setup:

* `Telemetry` takes `new TraceRegistry()` plus an exporter
* use `CompositeTelemetryExporter([...])` when you want to fan out to multiple backends
* call `flush()` after the run to send buffered observations and metrics

## Live Interop Suite

Run the live backend interop suite from the monorepo root:

```bash theme={null}
TELEMETRY_INTEROP_ENABLED=1 composer test:telemetry-interop
```

Notes:

* tests live under `packages/telemetry/tests/Integration`
* the suite is opt-in and skips cleanly when disabled
* backend contract tests cover direct exporter write/read interop
* runtime smoke tests cover inference, streaming, agent, and AgentCtrl paths
* inference, streaming, and agent runtime smoke coverage also require `OPENAI_API_KEY`
* AgentCtrl smoke coverage also requires a usable `codex` CLI with working auth/config

## Logfire

Basic setup:

```php theme={null}
use Cognesy\Telemetry\Adapters\Logfire\LogfireConfig;
use Cognesy\Telemetry\Adapters\Logfire\LogfireExporter;
use Cognesy\Telemetry\Application\Registry\TraceRegistry;
use Cognesy\Telemetry\Application\Telemetry;

$telemetry = new Telemetry(
    registry: new TraceRegistry(),
    exporter: new LogfireExporter(new LogfireConfig(
        endpoint: 'https://logfire-eu.pydantic.dev',
        serviceName: 'my-service',
        headers: ['Authorization' => $token],
    )),
);
```

Notes:

* `endpoint` is the base OTLP URL, not the full `/v1/traces` path
* `LogfireExporter` requires either `LogfireConfig` or a custom transport
* practical examples:
  * `examples/A03_Troubleshooting/TelemetryLogfire/run.php`
  * `examples/D05_AgentTroubleshooting/TelemetryLogfire/run.php`
  * `examples/D05_AgentTroubleshooting/SubagentTelemetryLogfire/run.php`

## Langfuse

Basic setup:

```php theme={null}
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: $baseUrl,
            publicKey: $publicKey,
            secretKey: $secretKey,
        )),
    ),
);
```

Notes:

* Langfuse traces are sent to `/api/public/otel/v1/traces`
* request-scoped traces fall back to request ids as `session.id` values
* practical examples:
  * `examples/A03_Troubleshooting/TelemetryLangfuse/run.php`
  * `examples/D05_AgentTroubleshooting/TelemetryLangfuse/run.php`
  * `examples/D05_AgentTroubleshooting/SubagentTelemetryLangfuse/run.php`

## Runtime wiring

For runtime packages, telemetry is usually attached to an event bus through `RuntimeEventBridge`
and one or more projectors:

```php theme={null}
use Cognesy\Agents\Telemetry\AgentsTelemetryProjector;
use Cognesy\Http\Telemetry\HttpClientTelemetryProjector;
use Cognesy\Polyglot\Telemetry\PolyglotTelemetryProjector;
use Cognesy\Telemetry\Application\Projector\CompositeTelemetryProjector;
use Cognesy\Telemetry\Application\Projector\RuntimeEventBridge;

(new RuntimeEventBridge(new CompositeTelemetryProjector([
    new AgentsTelemetryProjector($telemetry),
    new PolyglotTelemetryProjector($telemetry),
    new HttpClientTelemetryProjector($telemetry),
])))->attachTo($events);
```

Runtime notes:

* runtime packages own their local projectors and emit serialized `data['telemetry']` envelopes
* telemetry core rehydrates the envelope and correlates spans centrally
* `AgentCtrlTelemetryProjector` correlates `agent-ctrl` by `executionId`
* `agent_ctrl.session_id` is continuation metadata, not the primary trace key
* request-scoped traces fall back to request ids as `session.id` values for Langfuse
* use the Integration suite when you need live backend proof, not just local payload inspection

Adapter namespaces:

* `Cognesy\\Telemetry\\Adapters\\OTel`
* `Cognesy\\Telemetry\\Adapters\\Logfire`
* `Cognesy\\Telemetry\\Adapters\\Langfuse`