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LangWatch provides automatic instrumentation for the official openai-go client library through a dedicated middleware that captures detailed information about your OpenAI API calls.

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Installation

go get github.com/langwatch/langwatch/sdk-go github.com/openai/openai-go

​
Usage

Set LANGWATCH_API_KEY and OPENAI_API_KEY environment variables before running.
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 OpenAI client with LangWatch middleware
	client := openai.NewClient(
		oaioption.WithAPIKey(os.Getenv("OPENAI_API_KEY")),
		oaioption.WithMiddleware(otelopenai.Middleware("my-app",
			otelopenai.WithCaptureInput(),
			otelopenai.WithCaptureOutput(),
		)),
	)

	response, err := client.Chat.Completions.New(ctx, openai.ChatCompletionNewParams{
		Model: openai.ChatModelGPT5,
		Messages: []openai.ChatCompletionMessageParamUnion{
			openai.SystemMessage("You are a helpful assistant."),
			openai.UserMessage("Hello, OpenAI!"),
		},
	})
	if err != nil {
		log.Fatalf("Chat completion failed: %v", err)
	}

	log.Printf("Response: %s", response.Choices[0].Message.Content)
}
The middleware automatically captures request/response content, token usage, and model information. Streaming responses are fully supported and automatically accumulated.
The defer tp.Shutdown(ctx) call is essential. Without it, traces buffered in memory will be lost when your application exits.