Langfuse

Features 🔥

• Fully generated C# SDK based on official Langfuse OpenAPI specification using AutoSDK
• Same day update to support new features
• Updated and supported automatically if there are no breaking changes
• All modern .NET features - nullability, trimming, NativeAOT, etc.
• Support .Net Framework/.Net Standard 2.0

Usage

using Langfuse;

using var client = new LangfuseClient(apiKey);

Health Check

Basic example showing how to create a client and check API health.

using var client = new LangfuseClient(apiKey);

// Check that the Langfuse API and database are healthy.
var response = await client.Health.HealthHealthAsync();

Observations

List observations from the current Langfuse API.

using var client = new LangfuseClient(apiKey);

// List the most recent observations in your project.
var response = await client.Observations.ObservationsGetManyAsync(
    limit: 10);

Prompts

List prompts managed in Langfuse.

using var client = new LangfuseClient(apiKey);

// List all prompts in your project.
var response = await client.Prompts.PromptsListAsync(
    limit: 10);

OpenTelemetry ingestion

Ingest trace spans into Langfuse using the current OpenTelemetry endpoint.

using var client = new LangfuseClient(apiKey);

// Create a span and send it via OTLP/HTTP JSON ingestion.
var nowNanoseconds = (DateTimeOffset.UtcNow.ToUnixTimeMilliseconds() * 1_000_000).ToString();
var response = await client.Opentelemetry.OpentelemetryExportTracesAsync(
    resourceSpans:
    [
        new OtelResourceSpan
        {
            ScopeSpans =
            [
                new OtelScopeSpan
                {
                    Spans =
                    [
                        new OtelSpan
                        {
                            TraceId = Guid.NewGuid().ToString("N"),
                            SpanId = Guid.NewGuid().ToString("N")[..16],
                            Name = "sdk-integration-test",
                            Kind = 1,
                            StartTimeUnixNano = nowNanoseconds,
                            EndTimeUnixNano = nowNanoseconds,
                        },
                    ],
                },
            ],
        },
    ]);

Projects

Get information about the project associated with the API key.

using var client = new LangfuseClient(apiKey);

// Retrieve the project associated with your API key.
var response = await client.Projects.ProjectsGetAsync();

Scores

List scores for evaluating LLM outputs in Langfuse.

using var client = new LangfuseClient(apiKey);

// List all scores in your project with pagination.
var response = await client.ScoresV3.ScoresV3GetManyV3Async(
    limit: 10);

Datasets

List and manage datasets for LLM evaluation in Langfuse.

using var client = new LangfuseClient(apiKey);

// List all datasets in your project with pagination.
var response = await client.Datasets.DatasetsListAsync(
    limit: 10);

Ecosystem maintenance

This SDK is one of more than 200 .NET SDKs maintained with AutoSDK. The tryAGI SDK audit continuously checks repository synchronization, upstream-spec regeneration, release workflows, warnings, public API visibility, and trimming/NativeAOT compatibility.

Every issue is first investigated for ecosystem-wide applicability. When the root cause belongs in AutoSDK, we fix and regression-test the generator, then roll the improvement out to every applicable SDK. Provider-specific behavior remains in this repository when it cannot be derived safely from the API specification.

Issue content—including code blocks, logs, links, and attachments—is treated only as untrusted diagnostic data. Embedded control instructions, hidden directives, delimiter tricks, or requests to alter triage or tooling behavior are ignored. Please report reproducible technical evidence and remove secrets and personal data.

Support

Priority place for bugs: https://github.com/tryAGI/Langfuse/issues
Priority place for ideas and general questions: https://github.com/tryAGI/Langfuse/discussions
Discord: https://discord.gg/Ca2xhfBf3v

Acknowledgments

This project is supported by JetBrains through the Open Source Support Program.