README

dotnet add package PostHog.AI

using PostHog;
using PostHog.AI;
using OpenAI;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;

var builder = Host.CreateApplicationBuilder(args);

// 1. Configure PostHog
builder.Services.AddPostHog(options =>
{
    options.ProjectToken = "YOUR_PROJECT_TOKEN";
    options.HostUrl = new Uri("https://us.i.posthog.com"); // or eu.i.posthog.com
});

// 2. Register OpenAI Client with PostHog integration
// This registers OpenAIClient as a Singleton and configures it to use the PostHog interceptor.
// You can also chain additional HTTP handlers here (e.g., for resilience).
builder.Services.AddPostHogOpenAIClient("YOUR_OPENAI_API_KEY", options => 
{
    // Optional: Configure OpenAIClientOptions here
});

var host = builder.Build();

// 3. Inject and use OpenAIClient
var openAIClient = host.Services.GetRequiredService<OpenAIClient>();
// ... use client

using PostHog.AI;
using OpenAI;
using System.ClientModel;
using System.ClientModel.Primitives;

// 1. Register PostHog AI services
builder.Services.AddPostHogAI();

// 2. Configure OpenAI Client with the intercepting handler manually
builder.Services.AddHttpClient("PostHogOpenAI") // Named client
    .AddPostHogOpenAIHandler();

builder.Services.AddSingleton<OpenAIClient>(sp =>
{
    var httpClientFactory = sp.GetRequiredService<IHttpClientFactory>();
    var httpClient = httpClientFactory.CreateClient("PostHogOpenAI");
    
    // Explicitly set the transport
    var options = new OpenAIClientOptions
    {
        Transport = new HttpClientPipelineTransport(httpClient)
    };
    
    return new OpenAIClient(new ApiKeyCredential("YOUR_OPENAI_API_KEY"), options);
});

using PostHog.AI;

// Begin a scope with context
using (PostHogAIContext.BeginScope(
    distinctId: "user-123",
    traceId: "trace-abc",
    sessionId: "session-xyz",
    spanId: "span-1",
    spanName: "summarize_text",
    parentId: null))
{
    // All OpenAI API calls within this scope will include the context
    var chatClient = openAIClient.GetChatClient("gpt-4");
    var response = await chatClient.CompleteChatAsync("Summarize this text");
}
// Context is automatically restored when the scope ends

using PostHog.AI;

// Parent span
using (PostHogAIContext.BeginScope(
    traceId: "trace-123",
    spanId: "span-parent",
    spanName: "process_document"))
{
    // Child span 1
    using (PostHogAIContext.BeginScope(
        traceId: "trace-123", // Same trace
        spanId: "span-child-1",
        spanName: "extract_summary",
        parentId: "span-parent")) // Link to parent
    {
        // First AI call
        var chatClient = openAIClient.GetChatClient("gpt-4");
        await chatClient.CompleteChatAsync("Summarize the document");
    }

    // Child span 2
    using (PostHogAIContext.BeginScope(
        traceId: "trace-123",
        spanId: "span-child-2",
        spanName: "extract_keywords",
        parentId: "span-parent"))
    {
        // Second AI call
        var chatClient = openAIClient.GetChatClient("gpt-4");
        await chatClient.CompleteChatAsync("Extract keywords from the document");
    }
}

using PostHog.AI;

var customProperties = new Dictionary<string, object>
{
    { "workflow_id", "workflow-123" },
    { "feature_flag", "new-model-v2" },
    { "$ai_session_id", "override-session" } // Can override context properties
};

using (PostHogAIContext.BeginScope(
    sessionId: "default-session",
    properties: customProperties))
{
    // Properties dictionary takes precedence over context properties
    // In this case, $ai_session_id will be "override-session"
    var chatClient = openAIClient.GetChatClient("gpt-4");
    await chatClient.CompleteChatAsync("Hello");
}