hardkoded/vercel-ai-sdk-dotnet/vercel-ai-dotnet

Vercel AI SDK for .NET

Unofficial port of vercel/ai. Apache-2.0. Not an official Vercel product. Parity target is Language Model specification V4.

Map JavaScript names to C#

• generateText → GenerateTextAsync
• streamText → StreamTextAsync (returns StreamTextResult)
• AbortSignal → CancellationToken
• tool() → Tool.Function(name, description, jsonSchema, execute)
• stopWhen: isStepCount(n) → StopWhen.IsStepCount(n)
• "openai/gpt-4.1-mini" → GenerateTextOptions.ModelId (Gateway) or a provider’s LanguageModel

Generate text

var model = OpenAIProvider.Create().LanguageModel("gpt-4.1-mini");
var result = await client.GenerateTextAsync(new GenerateTextOptions
{
    Model = model,
    Prompt = "Summarize this incident in one sentence.",
    Tools = new[]
    {
        Tool.Function("lookup", "Lookup a host", "{\"type\":\"object\"}", (args, ct) => Task.FromResult("{\"ok\":true}")),
    },
    StopWhen = StopWhen.IsStepCount(4),
    Output = OutputSpec.Object("{\"type\":\"object\"}", "report"),
});

result.Text is the last step. result.Output is the parsed JSON object when Output is set. The default stop condition is one model step; tools from that step still execute.

Stream

StreamTextResult.TextStream yields text deltas. Stream yields every part. In ASP.NET Core, result.ToUIMessageStreamResult() writes text/event-stream for a JavaScript useChat client. Pass keepAliveMs to write : stream-open immediately and : keep-alive comments while the next part is still pending. Do not add a React or Razor chat component for that protocol.

Providers

Each package exposes CreateXxx() / AddXxx() and reads the same environment variable as the JavaScript provider. Gateway uses AI_GATEWAY_API_KEY and https://ai-gateway.vercel.sh/v4/ai. OpenAI-compatible providers share Vercel.AI.OpenAICompatible.

Register the client with services.AddAiSdk(). Add services.AddAiSdkOpenTelemetry() to record spans on the Vercel.AI activity source.

Tests

Mock HttpMessageHandler. Use TestLanguageModel from Vercel.AI.Testing when the test does not care about HTTP. Skip live tests unless the provider key is set.