What causes "OPENAI_API_KEY is not set." in microsoft/semantic-kernel?

Set OPENAI_API_KEY to your OpenAI API key

microsoft/semantic-kernel · error · InvalidOperationException

OPENAI_API_KEY is not set.

Error message

OPENAI_API_KEY is not set.

What it means

The OpenAI DependencyInjection migration sample throws InvalidOperationException when OPENAI_API_KEY is null. This sample shows DI-based agent registration against the direct OpenAI API, comparing SK's Kernel-dependent ChatCompletionAgent with AF's keyed-singleton AIAgent. The key is needed at composition time to build the chat client registered in the container.

Source

Thrown at dotnet/samples/AgentFrameworkMigration/OpenAI/Step03_DependencyInjection/Program.cs:10

// Copyright (c) Microsoft. All rights reserved.

using Microsoft.Agents.AI;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.SemanticKernel;
using Microsoft.SemanticKernel.Agents;
using OpenAI;
using OpenAI.Chat;

var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new InvalidOperationException("OPENAI_API_KEY is not set.");
var model = System.Environment.GetEnvironmentVariable("OPENAI_MODEL") ?? "gpt-4o";
var userInput = "Tell me a joke about a pirate.";

Console.WriteLine($"User Input: {userInput}");

await SKAgentAsync();
await SKAgent_As_AFAgentAsync();
await AFAgentAsync();

async Task SKAgentAsync()
{
    Console.WriteLine("\n=== SK Agent ===\n");

    var serviceCollection = new ServiceCollection();
    serviceCollection.AddKernel().AddOpenAIChatClient(model, apiKey);
    serviceCollection.AddTransient((sp) => new ChatCompletionAgent()
    {
        Kernel = sp.GetRequiredService<Kernel>(),

View on GitHub (pinned to c028a0c7dc)

Solutions

Set OPENAI_API_KEY to your OpenAI API key
Optionally set OPENAI_MODEL (defaults to gpt-4o)
If using VS, add the variable to Properties/launchSettings.json
Consider using .NET user secrets for local dev: dotnet user-secrets set OPENAI_API_KEY 'sk-...'

Example fix

// before
var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new InvalidOperationException("OPENAI_API_KEY is not set.");

// after
var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
if (string.IsNullOrWhiteSpace(apiKey))
    throw new InvalidOperationException(
        "OPENAI_API_KEY is not set. See README.md Environment Variables section.");

Defensive patterns

Strategy: validation

Validate before calling

var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
if (string.IsNullOrWhiteSpace(apiKey))
{
    Console.Error.WriteLine("OPENAI_API_KEY is not set. Required for DI samples.");
    return;
}

Type guard

static bool IsOpenAIKeyConfigured() =>
    !string.IsNullOrWhiteSpace(Environment.GetEnvironmentVariable("OPENAI_API_KEY"));

Try / catch

try
{
    var apiKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY")
        ?? throw new InvalidOperationException("OPENAI_API_KEY is not set.");
}
catch (InvalidOperationException ex) when (ex.Message.Contains("OPENAI_API_KEY"))
{
    Console.Error.WriteLine(ex.Message);
    return;
}

Prevention

DI samples read env vars directly — use user secrets (dotnet user-secrets) or launchSettings.json
Do not assume IConfiguration or appsettings.json provides the key
Validate the key at the top of Program.cs before building the DI container
Never commit API keys to source control — use .gitignore for .env files

When it happens

Trigger: Running OpenAI/Step03_DependencyInjection without OPENAI_API_KEY. The throw at line 10 fires before any ServiceCollection is built or agents registered.

Common situations: DI samples read env vars directly rather than user secrets or IConfiguration; the key is in a .env file that the console host doesn't auto-load; running from VS without the env var in launchSettings.json.

Related errors

AI-assisted analysis of microsoft/semantic-kernel@c028a0c7dc (2026-08-13). Data as JSON: /api/errors/bd2d1daa6e7caee1. Report an issue: GitHub.