# Observability for Quarkus LangChain4j with Opik

[Quarkus LangChain4j](https://docs.quarkiverse.io/quarkus-langchain4j/dev/index.html) uses Quarkus OpenTelemetry configuration in `application.properties`.

## When this guide applies

Use this if your app is Quarkus + LangChain4j and you want OTEL traces to land in Opik.

## Opik OTLP endpoint modes

For full endpoint/header details, see [Opik OpenTelemetry overview](/guides/multi-language-opentelemetry).

- Cloud endpoint: `https://www.comet.com/opik/api/v1/private/otel`
- Enterprise endpoint: `https://<comet-deployment-url>/opik/api/v1/private/otel`
- Self-hosted endpoint: `http://localhost:5173/api/v1/private/otel`

## Example (`application.properties`)

Intent:
Configure Quarkus OTEL trace exporter to target Opik directly.

Applies when:
You are using Quarkus-native OTEL exporter settings.

Required fields:

- `quarkus.otel.enabled=true`
- `quarkus.otel.traces.enabled=true`
- `quarkus.otel.exporter.otlp.traces.endpoint`
- `quarkus.otel.exporter.otlp.traces.protocol=http/protobuf`

Optional fields:

- `quarkus.otel.exporter.otlp.traces.headers` (`projectName` strongly recommended)
- `quarkus.application.name` (for `service.name` attribution)

Minimal valid setup:

```properties
quarkus.otel.enabled=true
quarkus.otel.traces.enabled=true
quarkus.otel.exporter.otlp.traces.endpoint=https://www.comet.com/opik/api/v1/private/otel
quarkus.otel.exporter.otlp.traces.protocol=http/protobuf
quarkus.otel.exporter.otlp.traces.headers=Authorization=<your-api-key>,Comet-Workspace=<your-workspace>,projectName=<your-project-name>
```

## Validation

1. Start your Quarkus app with OTEL enabled.
2. Trigger a LangChain4j-backed endpoint/action.
3. Confirm spans with your configured `service.name` and project headers arrive in Opik.

## Source references

- [Quarkus OpenTelemetry guide](https://quarkus.io/guides/opentelemetry)
- [Quarkus LangChain4j docs](https://docs.quarkiverse.io/quarkus-langchain4j/dev/index.html)
- [Opik OpenTelemetry overview](/guides/multi-language-opentelemetry)

## Related pages

- [.NET](./net-index.md)
- [Administration](./administration-index.md)
- [AI Coding Assistants](./ai-coding-assistants-index.md)
- [Changelog](../changelog.md)
- [Configuration](./configuration-index.md)
- [Contributing](./contributing-index.md)
- [Development](./development-index.md)
- [Evaluation](./evaluation-index.md)
- [Getting Started](./getting-started-index.md)
- [Guardrails](./guardrails-index.md)

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