BYOK.Core 1.0.0

BYOK RX — Bring Your Own Key

One interface client, multiple providers.

Route AI requests across multiple LLM providers with automatic fallback, all through a unified IChatClient interface.

Features

• Unified interface — single IChatClient that routes to OpenAI, Anthropic, Groq, DeepSeek, Ollama, OpenRouter, and any OpenAI-compatible provider
• Automatic fallback — define fallback chains per model; if a provider fails, BYOK tries the next one
• Model aliases — friendly names like "fast" or "cheap" that resolve to real model paths
• Per-provider key rotation — each provider gets its own API key provider; keys can rotate at runtime without restart
• Function calling — built-in support through Microsoft.Extensions.AI.FunctionInvokingChatClient
• OpenTelemetry ready — providers expose ChatClientMetadata for observability instrumentation
• Dependency injection — AddBYOKClient() extension for IServiceCollection

Install

dotnet add package BYOK.Core
dotnet add package BYOK.OpenAI
dotnet add package BYOK.Anthropic

Quick Start

using Microsoft.Extensions.AI;
using BYOK.Core;
using BYOK.OpenAI;
using BYOK.Anthropic;

var openAiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? "";
var anthropicKey = Environment.GetEnvironmentVariable("ANTHROPIC_API_KEY") ?? "";
var groqKey = Environment.GetEnvironmentVariable("GROQ_API_KEY") ?? "";

var byok = BYOKClient.Create(options =>
{
    options.UseOpenAI(openAiKey);
    options.UseAnthropic(anthropicKey);
    options.UseGroq(groqKey);

    options.Routing.ForModelId("openai:gpt-5.4-mini")
        .FallbackTo("groq:llama-4-maverick");

    options.Routing.ForAlias("fast")
        .Try("anthropic:claude-sonnet-5");

    options.DefaultTimeout = TimeSpan.FromSeconds(100);
});

var messages = new List<ChatMessage>
{
    new(ChatRole.System, "You are a helpful assistant."),
    new(ChatRole.User, "Hello!")
};

var chatOptions = new ChatOptions
{
    ModelId = "openai:gpt-5.4-mini"
};

var response = await byok.GetResponseAsync(messages, chatOptions);

Console.WriteLine($"Result: {response.Text}");

Dependency injection

services.AddBYOKClient(options =>
{
    options.UseOpenAI(openAiKey);
    options.UseAnthropic(anthropicKey);

    options.Routing.ForModelId("openai:gpt-5.4-mini")
        .FallbackTo("groq:llama-4-maverick");
});

Then inject IChatClient anywhere:

public class MyService(IChatClient chatClient)
{
    public async Task RunAsync()
    {
        var response = await chatClient.GetResponseAsync(messages, new ChatOptions
        {
            ModelId = "openai:gpt-5.4-mini"
        });
    }
}

Usage

Route format

Set ModelId to "{providerName}:{modelId}" and BYOK routes to the right provider:

ModelId = "openai:gpt-5.4-mini"

The provider name must match one registered via UseOpenAICompatible(), UseAnthropicCompatible(), or one of the built-in extensions.

Built-in providers

Fallback

options.Routing.ForModelId("openai:gpt-5.4-mini")
    .FallbackTo("groq:llama-4-maverick")
    .FallbackTo("anthropic:claude-sonnet-5");

If the primary fails, BYOK tries fallbacks in order.

Aliases

options.Routing.ForAlias("fast").Try("anthropic:claude-sonnet-5");
options.Routing.ForAlias("cheap").Try("groq:deepseek-v4-flash");

Use anywhere a route is expected: ModelId = "fast".

Custom providers

options.UseOpenAICompatible(
    providerName: "myprovider"
    apiKey: openAiKey,
    configure: config =>
    {
        config.BaseUrl = "https://my-custom-endpoint.com/v1";
        config.AddHeader("X-Custom", "value");
        config.NativeOptions.ClientLoggingOptions.LogLevel = OpenAI.Diagnostics.ClientLogLevel.Informational;
    });

options.UseAnthropicCompatible(
    providerName: "myanthropic"
    apiKey: anthropicKey,
    configure: config =>
    {
        config.BaseUrl = "https://my-custom-anthropic.com";
    });

Then use ModelId = "myprovider:some-model" or ModelId = "myanthropic:some-model".

Or register any custom IChatClient with a factory:

options.UseProvider("my-custom", () => new MyChatClient(apiKey));

Streaming

await foreach (var update in byok.GetStreamingResponseAsync(messages, chatOptions))
{
    Console.Write(update.Text);
}

Function calling

var fcMessages = new List<ChatMessage>
{
    new(ChatRole.System, "You are a helpful assistant that can use tools."),
    new(ChatRole.User, "What time is it?")
};

var fcOptions = new ChatOptions
{
    ModelId = "groq:llama-4-maverick",
    Tools = [AIFunctionFactory.Create(GetCurrentTime)]
};

var response = await byok.GetResponseAsync(fcMessages, fcOptions);
Console.WriteLine($"Result: {response.Text}");

Define your function tool:

[Description("Returns the current time")]
static string GetCurrentTime() => DateTime.Now.ToString("HH:mm:ss");

Architecture

┌──────────────────────────────────────────┐
│              BYOKClient                   │
│  Routing → Provider Factory → IChatClient │
└──────────────────────────────────────────┘
         │                     │
         ▼                     ▼
  BYOK.OpenAI           BYOK.Anthropic
  OpenAICompatibleClient AnthropicChatClient
  (IChatClient)          (IChatClient)

Each provider client caches the underlying SDK client and only rebuilds when the API key changes.

License

MIT © BracoZS