microsoft/autogen · error · Exception

Please set OPENAI_API_KEY environment variable.

Error message

Please set OPENAI_API_KEY environment variable.

What it means

Guard in GetStartCodeSnippet.CodeSnippet1 ('get started' example): OPENAI_API_KEY is null, so it throws before OpenAIClient is constructed with an empty key. The snippet then builds an OpenAIChatAgent on gpt-4o-mini, so a valid key is mandatory.

Source

Thrown at dotnet/samples/AgentChat/AutoGen.Basic.Sample/CodeSnippet/GetStartCodeSnippet.cs:17

// Copyright (c) Microsoft Corporation. All rights reserved.
// GetStartCodeSnippet.cs

#region snippet_GetStartCodeSnippet
using AutoGen;
using AutoGen.Core;
using AutoGen.OpenAI;
using AutoGen.OpenAI.Extension;
using OpenAI;
#endregion snippet_GetStartCodeSnippet

public class GetStartCodeSnippet
{
    public async Task CodeSnippet1()
    {
        #region code_snippet_1
        var openAIKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY") ?? throw new Exception("Please set OPENAI_API_KEY environment variable.");
        var openAIClient = new OpenAIClient(openAIKey);
        var model = "gpt-4o-mini";

        var assistantAgent = new OpenAIChatAgent(
            name: "assistant",
            systemMessage: "You are an assistant that help user to do some tasks.",
            chatClient: openAIClient.GetChatClient(model))
            .RegisterMessageConnector()
            .RegisterPrintMessage(); // register a hook to print message nicely to console

        // set human input mode to ALWAYS so that user always provide input
        var userProxyAgent = new UserProxyAgent(
            name: "user",
            humanInputMode: HumanInputMode.ALWAYS)
            .RegisterPrintMessage();

        // start the conversation
        await userProxyAgent.InitiateChatAsync(

View on GitHub (pinned to 027ecf0a37)

Solutions

1. export OPENAI_API_KEY=sk-... (or set it in launchSettings.json) and rerun dotnet run.
2. Restart the IDE so newly set variables are visible to the debug process.
3. For tests, set the variable in the test runner environment or filter out live-API tests.
4. Ensure no trailing whitespace/quotes when exporting the key.

var openAIKey = Environment.GetEnvironmentVariable("OPENAI_API_KEY");
if (string.IsNullOrWhiteSpace(openAIKey))
{
    Console.Error.WriteLine("Please set OPENAI_API_KEY environment variable.");
    return;
}

When it happens

Trigger: Running the get-started sample without OPENAI_API_KEY; running the snippet-executing tests in AutoGen.Basic.Sample on a machine without credentials.

Common situations: First-run experience: developer clones the repo, runs samples, hasn't exported the key yet; terminal/IDE environment mismatch; key set after the process started.

Related errors

• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set OPENAI_API_KEY environment variable.
• Please set ANTHROPIC_API_KEY environment variable.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/e91f6f70aef59b28. Report an issue: GitHub.