How to use DI with Semantic Kernel plugins?

Question

I'm trying out Microsoft's Semantic Kernel for chat completion in a Blazor app. I added a service that uses EF Core:

public interface ISearchService
{
    Task<string?> GetCustomerAsync(string surname);
}

This is the interface. The implementation is straightforward. I then created a plugin class:

[Description("Representats customer data")]
public class SearchPlugin(ISearchService searchService)
{
    [KernelFunction("GetCustomer"), Description("Get customer details by their surname")]
    [return: Description("Customer details")]
    public async Task<string?> GetCustomer([Description("Customer surname")] string surname)
        => await searchService.GetCustomerAsync(surname);
}

I register the service as Scoped:

services.AddScoped<ISearchService, SearchService>();

And register the kernel:

services.AddSemanticKernel(configuration)
    .Plugins.AddFromType<SearchPlugin>();

Where AddSemanticKernel is an extension method:

public static IKernelBuilder AddSemanticKernel(this IServiceCollection services, IConfiguration configuration)
{
    var modelId = "llama3.2:3b";
    var endpoint = new Uri("http://localhost:11424");

    services.AddOllamaChatCompletion(modelId, endpoint);

    return services.AddKernel();
}

However, when I start the app, I get the following exception:

System.InvalidOperationException: Cannot resolve scoped service 'MyApp.Services.Interfaces.ISearchService' from root provider.

What am I doing wrong?

provide serviceProvider directly, I have something like: kernel.Plugins.AddFromType<TesterTools>(pluginName: "Tester", serviceProvider: sp) — dododo
– dododo, Commented Aug 24 at 16:44
i think it's services.AddKernel().AddOllamaChatCompletion() — jeb
– jeb, Commented Aug 25 at 10:02

Michał Turczyn · Accepted Answer · 2025-08-25 12:05:24Z

0

Unforutnately, plugins and Kernel have own DI system, separated from the application one.

So you need to actually register types you want to use in plugins with KernelBuilder:

var kernel = services.AddKernel();
kernel.Services.AddScoped<ISearchService, SearchService>();
return kernel;

Here's related GitHub discussion

There's another GitHub issue, suggesting you could create Kernel with application's service provider:

services.AddSingleton<Kernel>(serviceProvider =>
{
    Kernel k = new(serviceProvider);
    k.Plugins.AddFromType<SearchPlugin>();
    return k;
});

answered Aug 25 at 12:05

Michał Turczyn

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Comments

dododo · Accepted Answer · 2025-08-25 20:58:38Z

As pointed by @Michał Turczyn, the Kernel has own DI collection, but combining them easy to do for example with AddKernel method:

using var host = Host.CreateDefaultBuilder(args)
    .ConfigureServices(services =>
    {
        // Model & key
        var openAiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");

        // Register Semantic Kernel via IServiceCollection
        var kernelBuilder = services.AddKernel();
        kernelBuilder.AddOpenAIChatCompletion(modelId: "gpt-4o-mini", apiKey: openAiKey);
        kernelBuilder.Plugins.AddFromType<CodeGenTool>(); // expose your tool
        // use a regular DI
        services.AddScoped<ISearchService, MockSearchService>();
    })
    .Build();

since AddKernel provides regular DI collection as argument to KernelBuilder:

public static IKernelBuilder AddKernel(this IServiceCollection services)
{
    services.AddTransient<KernelPluginCollection>();
    services.AddTransient<Kernel>();
    return new KernelBuilder(services);
}

where CodeGenTool is:

public class CodeGenTool(ISearchService searchService)
...

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