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

# Observability

VeADK provides application logs and traces to diagnose model calls, tools, and agent execution. Logs record individual events; traces connect operations within a request so you can inspect timing and relationships

Tracing uses [OpenTelemetry](https://opentelemetry.io/docs/specs/semconv/registry/attributes/gen-ai/) spans and generative AI attributes. Coverage depends on the instrumentation provided by the runtime and tools. External backends also require compatible protocols, endpoints, and credentials

See [Application logging](/productions/veadk/preview/en/components/observability/logging) for log levels and formatting

## Core concepts

### span

A span is a traceable unit of execution that records a name, start/end times, attributes, and parent-child relationships. VeADK builds a tree of spans for each request, covering nodes such as agent runs, model calls, and tool executions, and annotates them per the generative-AI semantic conventions with attributes like `gen_ai.operation.name` and `gen_ai.span.kind`.

### The tracer `OpentelemetryTracer`

`OpentelemetryTracer` is the unified tracing entry point. It holds a list of exporters, wires each one into the tracing pipeline on initialization, and automatically attaches an in-memory exporter for local retention and dumping.

### exporter

An exporter sends span data to a specific backend platform. Each exporter targets one backend and can be used alone or combined. VeADK ships the following exporters:

| Exporter | Class | Target platform | Docs |
| :- | :- | :- | :- |
| APMPlus | `APMPlusExporter` | Volcengine APMPlus, traces and metrics | [APMPlus](/productions/veadk/preview/en/components/observability/apmplus) |
| Cozeloop | `CozeloopExporter` | Cozeloop, trace observation and evaluation | [Cozeloop](/productions/veadk/preview/en/components/observability/cozeloop) |
| TLS | `TLSExporter` | Volcengine TLS log service | [TLS](/productions/veadk/preview/en/components/observability/tls) |
| In-memory | `InMemoryExporter` | In-process memory, local debugging and dumping | [In-memory exporter](/productions/veadk/preview/en/components/observability/inmemory) |

<Warning>
  Traces may contain user input, model responses, and tool data. Before enabling external exporters, confirm the destination, access controls, and retention policy. `force_export()` requests a flush; it does not prove that the backend received the data
</Warning>

## Attaching a tracer to an agent

Complete [model configuration](/productions/veadk/preview/en/components/agent/model) first. This example stores traces locally and does not require an external observability backend. Running it prints a model response and the path to a JSON trace file

```python title="app.py" lines theme={null}
import asyncio
from pathlib import Path

from veadk import Agent, Runner
from veadk.tracing.telemetry.opentelemetry_tracer import OpentelemetryTracer

tracer = OpentelemetryTracer()
agent = Agent(name="trace_demo", tracers=[tracer])
runner = Runner(agent=agent, app_name="trace_demo", user_id="demo-user")
response = asyncio.run(
    runner.run("Explain the purpose of an agent in one sentence", session_id="demo-session")
)
print(response)
Path("traces").mkdir(exist_ok=True)
path = tracer.dump(user_id="demo-user", session_id="demo-session", path="traces")
print(path)
```

After configuring each backend's endpoint, credentials, and target resource, one tracer can report to multiple platforms. This configuration fragment replaces the tracer above:

```python lines theme={null}
from veadk.tracing.telemetry.exporters.apmplus_exporter import APMPlusExporter
from veadk.tracing.telemetry.exporters.cozeloop_exporter import CozeloopExporter
from veadk.tracing.telemetry.exporters.tls_exporter import TLSExporter
from veadk.tracing.telemetry.opentelemetry_tracer import OpentelemetryTracer

tracer = OpentelemetryTracer(
    exporters=[APMPlusExporter(), CozeloopExporter(), TLSExporter()]
)
```

### Tracer parameters

`OpentelemetryTracer` accepts the following fields:

| Parameter | Type | Default | Description |
| :- | :- | :- | :- |
| `name` | `str` | `veadk_opentelemetry_tracer` | Tracer identifier, used for logging and naming dump files. |
| `exporters` | `list[BaseExporter]` | `[]` | List of exporters. `InMemoryExporter` may not be added explicitly, or validation fails; the in-memory exporter is attached automatically. |
| `apmplus_managed_externally` | `bool` | — | Read-only property. Whether a global `TracerProvider` already existed at initialization. When `True`, VeADK reuses the external provider instead of overriding it and skips registering the APMPlus span processor; this does not establish that the external provider reports to APMPlus. |

<Note>
  `InMemoryExporter` is managed automatically by `OpentelemetryTracer` and retains completed, sampled spans. Do not add it to the `exporters` list manually, or initialization fails.
</Note>

### Reusing a preconfigured global TracerProvider

By default, `OpentelemetryTracer` creates and sets the global `TracerProvider` during initialization. If a global `TracerProvider` already exists at that point (for example, set by another library or the application itself), VeADK reuses it instead of overriding it.

When a global provider already exists, the `APMPlusExporter` object remains in the exporter list, but its span processor is not registered by this tracer. Cozeloop, TLS, and in-memory exporters are still attached. This also applies to exporters created with `ENABLE_APMPLUS=true`

`apmplus_managed_externally` only indicates that a provider already existed at initialization. It does not inspect that provider's destination or confirm delivery to APMPlus. If your application already configures OpenTelemetry, configure the APMPlus destination there and verify the Trace ID in the backend

## Enabling exporters via environment variables

Besides constructing exporters explicitly, `Agent` attaches the matching exporter at runtime based on the following environment variables (enabled when set to `true`). If the agent provides no `tracers`, an `OpentelemetryTracer` is created automatically:

| Environment variable | Exporter enabled |
| :- | :- |
| `ENABLE_APMPLUS` | `APMPlusExporter` |
| `ENABLE_COZELOOP` | `CozeloopExporter` |
| `ENABLE_TLS` | `TLSExporter` |

<Tip>
  When all three variables are `false` (the default), `Agent` creates no tracer. To trace in that case, construct an `OpentelemetryTracer` explicitly and pass it via `tracers`.
</Tip>

## Content tracing

By default, spans record the input and output content of the agent, model, and tools. In scenarios involving sensitive data, you can disable content capture and reduce content captured by VeADK. This is controlled by `OpenTelemetryConfig.trace_content`.

| Config | Environment variable | Type | Default | Description |
| :- | :- | :- | :- | :- |
| `trace_content` | `OBSERVABILITY_OPENTELEMETRY_TRACE_CONTENT` | `bool` | `True` | Whether to write prompt, completion, and tool input/output content into spans. Set to `false` to disable these content fields; configure third-party instrumentation and application logs separately. |

```bash lines theme={null}
# Disable content capture
export OBSERVABILITY_OPENTELEMETRY_TRACE_CONTENT=false
```

## Local dumping

The in-memory exporter built into `OpentelemetryTracer` retains spans by `session_id`. Call `dump` to export the current session's spans to a local JSON file for offline analysis:

```python lines theme={null}
path = tracer.dump(user_id="demo-user", session_id="demo-session", path="traces")
print(f"trace written to {path}")
```

The exported JSON contains, for each span, its name, `span_id`, `trace_id`, start/end times, attributes, and parent span. See [In-memory exporter](/productions/veadk/preview/en/components/observability/inmemory) for details.