Kernel Builder Integration

UseClaudeCodeChatCompletion() is the primary extension point. It registers an IChatCompletionService backed by Claude Code authentication into the Semantic Kernel service collection.

Availability: net8.0 and net10.0 only. netstandard2.0 targets can use AddClaudeCodeAuthentication and build the kernel manually.

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Overloads

Auto-resolved session (no arguments)

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion()
    .Build();

Reads credentials via the full resolution chain. Defaults to model claude-sonnet-4-6.

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Custom model

using JD.SemanticKernel.Connectors.ClaudeCode;

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(ClaudeModels.Opus)
    .Build();

The modelId parameter is the first positional argument. Well-known constants are available via ClaudeModels:

Constant	Model ID	Description
ClaudeModels.Opus	claude-opus-4-6	Most capable, 1M context
ClaudeModels.Sonnet	claude-sonnet-4-6	Balanced (default)
ClaudeModels.Haiku	claude-haiku-4-5-20251001	Fastest, lowest cost
ClaudeModels.Default	claude-sonnet-4-6	Alias for Sonnet

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Explicit API key override

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(apiKey: "sk-ant-api...")
    .Build();

Skips credential file and environment variable lookup entirely.

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Explicit OAuth token override

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(apiKey: "sk-ant-oat...")
    .Build();

The handler detects the sk-ant-oat prefix and switches to Bearer + CLI header authentication automatically.

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Custom options via delegate

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(configure: o =>
    {
        o.CredentialsPath = "/run/secrets/claude-credentials.json";
    })
    .Build();

The configure delegate receives a ClaudeCodeSessionOptions instance. It runs after apiKey is applied, so you can combine both:

var kernel = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(
        modelId:   "claude-opus-4-6",
        apiKey:    Environment.GetEnvironmentVariable("MY_CLAUDE_KEY"),
        configure: o => o.CredentialsPath = "/custom/path")
    .Build();

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What the extension registers

Internally, UseClaudeCodeChatCompletion performs the following steps:

1. Builds a ClaudeCodeSessionOptions from the supplied arguments.
2. Creates a ClaudeCodeSessionProvider (not registered in DI — it is owned by the handler).
3. Creates an HttpClient with ClaudeCodeSessionHttpHandler as the message handler.
4. Constructs an AnthropicClient with a placeholder key (the handler strips and replaces it at request time).
5. Wraps the client with ChatClientBuilder (enabling automatic function invocation).
6. Calls .AsChatCompletionService() to bridge Microsoft.Extensions.AI.IChatClient → SK's IChatCompletionService.
7. Registers the result as a singleton IChatCompletionService in builder.Services.

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Using the registered service

Once the kernel is built, retrieve the service via SK's standard APIs:

var chat = kernel.GetRequiredService<IChatCompletionService>();
var history = new ChatHistory();
history.AddUserMessage("Hello Claude!");
var response = await chat.GetChatMessageContentsAsync(history);

Or use InvokePromptAsync for simple one-shot calls:

var result = await kernel.InvokePromptAsync("Summarise the Liskov Substitution Principle.");

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Chaining with other builder calls

UseClaudeCodeChatCompletion returns IKernelBuilder so it chains naturally:

var builder = Kernel.CreateBuilder()
    .UseClaudeCodeChatCompletion(ClaudeModels.Sonnet, apiKey: myKey);

builder.Plugins.AddFromType<MyPlugin>();

var kernel = builder.Build();