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

# Anthropic (Claude) Integration

> Instrument Anthropic Claude API calls in Go using LangWatch to track performance, detect errors, and improve AI agent testing.

LangWatch supports tracing Anthropic Claude API calls using the same `otelopenai` middleware used for OpenAI. Configure the client to point to Anthropic's API endpoint.

## Installation

```bash  theme={null}
go get github.com/langwatch/langwatch/sdk-go github.com/openai/openai-go
```

## Usage

<Info>
  Set `LANGWATCH_API_KEY` and `ANTHROPIC_API_KEY` environment variables before running.
</Info>

```go  theme={null}
package main

import (
	"context"
	"log"
	"os"

	langwatch "github.com/langwatch/langwatch/sdk-go"
	otelopenai "github.com/langwatch/langwatch/sdk-go/instrumentation/openai"
	"github.com/openai/openai-go"
	oaioption "github.com/openai/openai-go/option"
	"go.opentelemetry.io/otel"
	sdktrace "go.opentelemetry.io/otel/sdk/trace"
)

func main() {
	ctx := context.Background()

	// Set up LangWatch exporter
	exporter, err := langwatch.NewDefaultExporter(ctx)
	if err != nil {
		log.Fatalf("failed to create exporter: %v", err)
	}
	tp := sdktrace.NewTracerProvider(sdktrace.WithBatcher(exporter))
	otel.SetTracerProvider(tp)
	defer tp.Shutdown(ctx) // Critical: ensures traces are flushed

	// Create Anthropic client via OpenAI-compatible API
	client := openai.NewClient(
		oaioption.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")),
		oaioption.WithBaseURL(os.Getenv("ANTHROPIC_BASE_URL")),
		oaioption.WithMiddleware(otelopenai.Middleware("my-app",
			otelopenai.WithCaptureInput(),
			otelopenai.WithCaptureOutput(),
			otelopenai.WithGenAISystem("anthropic"),
		)),
	)

	response, err := client.Chat.Completions.New(ctx, openai.ChatCompletionNewParams{
		Model: "claude-4-5-sonnet",
		Messages: []openai.ChatCompletionMessageParamUnion{
			openai.SystemMessage("You are a helpful assistant."),
			openai.UserMessage("Hello, Claude!"),
		},
	})
	if err != nil {
		log.Fatalf("Chat completion failed: %v", err)
	}

	log.Printf("Response: %s", response.Choices[0].Message.Content)
}
```

<Warning>
  The `defer tp.Shutdown(ctx)` call is essential. Without it, traces buffered in memory will be lost when your application exits.
</Warning>

## Related

* [Capturing RAG](/integration/python/tutorials/capturing-rag) - Learn how to capture RAG data from retrievers and tools
* [Capturing Metadata and Attributes](/integration/python/tutorials/capturing-metadata) - Add custom metadata and attributes to your traces and spans
* [Capturing Evaluations & Guardrails](/integration/python/tutorials/capturing-evaluations-guardrails) - Log evaluations and implement guardrails in your Anthropic applications