Sr. Content Developer at Microsoft, working remotely in PA, TechBash conference organizer, former Microsoft MVP, Husband, Dad and Geek.
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Microsoft Agent Framework: Using Background Responses to Create an AI Researcher and Newsletter Publisher

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Keeping up with AI news can be a challenge.

Every day there’s a new model release, a new framework update, or some announcement that changes the landscape.

We find ourselves checking feeds, GitHub repositories, and blogs.  It’s a bit of an effort.

 What if we could build an AI agent that does this research for us?

 An agent that scans multiple sources, aggregates the important stuff you interested in, and generates a polished newsletter we can read?

In this blog post, we’ll build exactly that using the Microsoft Agent Framework and the Background Responses feature.

We cover the following:

  • What Are Background Responses
  • Why Use Background Responses
  • The Basics of Background Responses
  • Creating an AI Researcher and Newsletter Publisher
  • Core Features of the AINewsServiceAgent
  • AINewsServiceAgent Process, Prompts, and Function Tools
  • Bringing It All Together
  • Calling the AINewsServiceAgent from a Console Application
  • Implementing Background Responses for the AINewsServiceAgent

 

Our AI agent will search multiple news sources, monitor GitHub repositories for code updates, and generate a formatted markdown newsletter.  All while keeping the UI responsive with a nice progress indicator.

A video demo and source code are included.

~

What Are Background Responses

When working with AI agents that need to perform multiple tool calls such as, searching news sources, fetching GitHub commits, or generating a newsletter, processing can take a while.

Traditional synchronous execution means your application sits there waiting, potentially timing out or leaving users staring at a frozen screen.

Background Responses solve this problem by allowing the agent to process requests asynchronously.

Instead of blocking until completion, the agent returns a continuation token that your application can use to poll for progress.

This is like how you might check on a long-running job in a queue-based system.

The OpenAIResponseClient makes this possible.  Standard chat clients like GetChatClient run synchronously and do not support background processing.

Learn more about this here.

~

Why Use Background Responses

There are several reasons to use background responses for agent-based solutions.

  • Non-blocking execution allows your application to remain responsive while the agent works. Crucial for long-running tasks that involve multiple tool calls, API requests, or complex reasoning
  • Progress indication becomes possible because you can update the UI between polling intervals. Users can see that something is happening rather than wondering if the application has crashed.
  • Timeout prevention Long-running synchronous requests can hit HTTP timeout limits. With background responses, each poll is a quick check rather than a sustained connection

 

In general, users appreciate knowing an operation is in progress and roughly how long it’s been running.  Your agent can then report back to you via a communication channel of your choice when an operation has completed.

~

The Basics of Background Responses

The implementation pattern is straightforward. First, you create the agent using the OpenAI Responses client rather than the chat client.

#pragma warning disable OPENAI001 // OpenAI Responses API is in preview
var responseClient = new OpenAIClient(apiKey)
    .GetOpenAIResponseClient(model);


AIAgent agent = responseClient.CreateAIAgent(
    name: "AI News Digest Agent",
    instructions: "...",
    tools: [/* your tools */]);

 

Next, you enable background responses in the options:

AgentRunOptions options = new() { AllowBackgroundResponses = true };

 

Finally, you poll using the continuation token until the agent completes:

AgentRunResponse response = await agent.RunAsync(input, thread, options);

while (response.ContinuationToken is { } token)
{
    await Task.Delay(TimeSpan.FromMilliseconds(200));

    options.ContinuationToken = token;
    response = await agent.RunAsync(thread, options);
}


// Agent has completed - ContinuationToken is null
Console.WriteLine($"Agent: {response.Text}");
options.ContinuationToken = null;  // Reset for next request

The code within the  while loop contains the continuation token.

~

Content Overload. More Signal. Less Noise.

The AI space moves incredibly fast.   Microsoft updates the Agent Framework.  Google announces new Gemini features  Anthropic ships Claude improvements.  Open AI releases and more.

Something every other week.\

If you’re a developer trying to stay current, you’re probably:

  • Checking your trusted resources
  • Watching GitHub repositories for new releases and commits
  • Scanning tech news sites for announcements
  • Trying to figure out what’s actually important versus what’s just noise

 

What we need is a personal AI research assistant that:

  1. Aggregates news from trusted sources
  2. Filters by relevance to specific companies or topics
  3. Tracks code repositories for meaningful updates
  4. Generates a readable digest we can review in minutes, not hours

 

In the next section, that’s exactly what we’ll build.

~

Creating an AI Researcher and Newsletter Publisher

Our solution consists of three main components:

  1. AINewsServiceAgent – The function tools that search various sources and generate the newsletter
  2. NewsItemModel – A simple data model for news items
  3. Program.cs – The console application that orchestrates the agent with background responses

 

Let’s walk through each component.

~

Core Features of the AINewsServiceAgent

The AINewsServiceAgent class provides four function tools that the AI agent can call:

Tool Description
SearchFoundryBlog() Fetches the latest Microsoft AI Foundry blog posts
SearchAgentFrameworkUpdates() Gets recent GitHub commits and releases from the Agent Framework repository
SearchCompanyNews(company) Searches RSS feeds for company-specific AI news
GenerateNewsletter(title, content) Saves the compiled newsletter to a markdown file

 

The agent also exposes a status property that the console application can display during polling:

public static string CurrentStatus { get; private set; } = "Starting...";
public static void ResetStatus() => CurrentStatus = "Starting...";

~

AINewsServiceAgent Process

Here’s the flow when a user requests a newsletter digest:

Newsletter saved to: ai_digest_2026-01-24.md

Each tool call updates the CurrentStatus property.  The console application displays this and keeps the user informed of what is happening.

~

AINewsServiceAgent Prompt

The agent’s instructions are crucial. They define the workflow, newsletter format, and quality expectations.

Here’s the complete prompt:

instructions: """

You are an AI news research agent that creates weekly digest newsletters.


Workflow:

Call SearchFoundryBlog() to get Microsoft AI Foundry updates
Call SearchAgentFrameworkUpdates() to get Microsoft Agent Framework code updates
Call SearchCompanyNews for each company: Microsoft, Google, Anthropic, OpenAI
Generate a markdown newsletter using GenerateNewsletter with ALL results




CRITICAL: When generating the newsletter content for GenerateNewsletter:

- You MUST include ALL headlines returned from ALL search functions

- For each news item, include: Headline, PublishedDate (if available), Summary, and Url

- IMPORTANT: Each headline MUST be paired with its MATCHING Url, Summary, and PublishedDate

- Do NOT mix up links - the Url for "Article A" must only appear with "Article A"

- Format URLs as markdown links: [Read more](Url)

- ALWAYS include the PublishedDate field when it is not empty

- Do NOT skip or omit any results - include everything returned



Newsletter format (use these exact section headers):

Brief executive summary (2-3 sentences about key themes)
"## Microsoft AI Foundry" section - ALL results from SearchFoundryBlog
"## Microsoft Agent Framework" section - ALL results from SearchAgentFrameworkUpdates
"## Microsoft" section - results from SearchCompanyNews("Microsoft")
"## Google" section - results from SearchCompanyNews("Google")
"## Anthropic" section - results from SearchCompanyNews("Anthropic")
"## OpenAI" section - results from SearchCompanyNews("OpenAI")
"## What to Watch" section with emerging trends
"## Predictions for the Next 90 Days" section - list 3-5 specific predictions
with confidence scores (Low/Medium/High)



Each story format:

**Headline** *(Jan 15, 2026)* - Summary [Read more](url)


Style:

- Professional, concise
- Include ALL source URLs as markdown links
- Do not invent or fabricate news - only use results from the search functions
- MUST have a blank line between each news item for proper formatting

 

A few things to note about this prompt:

  • Explicit workflow ensures the agent calls tools in a predictable order
  • CRITICAL sections prevent common LLM issues like mixing up URLs or skipping results
  • Structured format produces consistent, readable newsletters
  • Predictions with confidence adds analytical value beyond simple aggregation

~

AINewsServiceAgent Models

The NewsItemModel class is simple and captures essential fields for a news item:

public class NewsItemModel
{
    public string Headline { get; set; } = string.Empty;
    public string Summary { get; set; } = string.Empty;
    public string Url { get; set; } = string.Empty;
    public string Title { get; set; } = string.Empty;
    public string Description { get; set; } = string.Empty;
    public string Source { get; set; } = string.Empty;
    public string Company { get; set; } = string.Empty;
    public string PublishedDate { get; set; } = string.Empty;

    public NewsItemModel(string Headline, string Summary, string Url,
                         string Source, string Company, string PublishedDate = "")
    {
        this.Headline = Headline;
        this.Summary = Summary;
        this.Url = Url;
        this.Source = Source;
        this.Company = Company;
        this.PublishedDate = PublishedDate;
    }
}

 

The PublishedDate is stored as a formatted string (e.g., “Jan 15, 2026”) rather than a DateTime.

This simplifies the agent’s job when generating the newsletter – it can use the date string directly without formatting concerns.

~

AINewsServiceAgent Function Tools

Let’s examine each function tool in detail.  When you supply a prompt, the AI agent automatically decides which of these to run.

SearchCompanyNews

This tool searches multiple RSS feeds for news about a specific company:

[Description("Searches for recent AI news and developments from a specific company.")]
public static async Task<List<NewsItemModel>> SearchCompanyNews(
    [Description("The company to search for: Microsoft, Google, Anthropic, or OpenAI")]
    string company)
{
    CurrentStatus = $"Searching {company} news...";
    var results = new List<NewsItemModel>();

    var keywords = company.ToLower() switch
    {
        "microsoft" => new[] { "microsoft", "copilot", "azure", "bing" },
        "google" => new[] { "google", "gemini", "deepmind", "bard" },
        "anthropic" => new[] { "anthropic", "claude" },
        "openai" => new[] { "openai", "chatgpt", "gpt-4", "gpt-5", "dall-e", "sora" },
        _ => new[] { company.ToLower(), "ai", "artificial intelligence" }
   };


    foreach (var feedUrl in _rssFeeds)
    {
        var feedContent = await _httpClient.GetStringAsync(feedUrl);
        var feedResults = ParseRssFeed(feedContent, company, keywords, feedUrl);
        results.AddRange(feedResults);
   }

    return results.Take(5).ToList();
}

The keyword mapping ensures we catch related terms. For example, searching for Microsoft also finds articles about Copilot and Azure.

SearchFoundryBlog

This tool scrapes the Microsoft Foundry DevBlog for the latest posts:

[Description("Searches the Microsoft Foundry blog for the latest AI Foundry updates.")]
public static async Task<List<NewsItemModel>> SearchFoundryBlog()
{
    CurrentStatus = "Fetching Microsoft Foundry blog...";
    var results = new List<NewsItemModel>();

    var htmlContent = await _httpClient.GetStringAsync(FoundryBlogUrl);
    var keywords = new[] { "" }; // Match all articles - Foundry is all AI-related
    results = ParseBlogPage(htmlContent, "Microsoft", keywords, FoundryBlogUrl);

    return results.Take(10).ToList();
}

 

Since the Foundry blog is entirely AI-focused, we don’t filter by keywords – every article is relevant.

SearchAgentFrameworkUpdates

This tool fetches recent commits and releases from the Agent Framework GitHub repository:

[Description("Searches the Microsoft Agent Framework GitHub repository for recent code updates.")]
public static async Task<List<NewsItemModel>> SearchAgentFrameworkUpdates()
{
    CurrentStatus = "Fetching GitHub Agent Framework updates...";
    return await FetchGitHubUpdates("microsoft", "agent-framework", "Microsoft");
}

 

The FetchGitHubUpdates helper method queries the GitHub API for commits from the last 7 days, focusing on significant changes like features, examples, and releases.

GenerateNewsletter

This tool saves the compiled newsletter to a markdown file:

[Description("Generates a markdown newsletter digest and saves it to file.")]
public static string GenerateNewsletter( [Description("The newsletter title")] string title, [Description("The full markdown content of the newsletter")] string markdownContent)
{
    CurrentStatus = "Generating newsletter...";
    var filename = $"ai_digest_{DateTime.Now:yyyy-MM-dd}.md";

    var header = $"""
               # {title}
               **Generated:** {DateTime.Now:dddd, MMMM d, yyyy 'at' h:mm tt}
               ---
               """;


   var fullContent = header + markdownContent;
   File.WriteAllText(filename, fullContent);

   SaveLastRunTime();

   return $"Newsletter saved to {filename}";
}

~

AINewsServiceAgent Helper Methods

Several helper methods support the function tools.

ParseRssFeed

This method handles both RSS 2.0 and Atom feed formats:

private static List<NewsItemModel> ParseRssFeed(string feedContent, string company, string[] keywords, string feedUrl)
{
    var results = new List<NewsItemModel>();
    var doc = XDocument.Parse(feedContent);
    XNamespace atom = "http://www.w3.org/2005/Atom";

    // Handle both RSS 2.0 and Atom feeds
    var items = doc.Descendants("item").ToList();
    var isAtomFeed = false;
    if (!items.Any())
    {
        items = doc.Descendants(atom + "entry").ToList();
        isAtomFeed = true;
    }

    foreach (var item in items)
    {
        var title = GetElementValue(item, "title") ?? "";
        var description = GetElementValue(item, "description")
                        ?? GetElementValue(item, "summary")
                        ?? GetElementValue(item, "content")
                        ?? "";

        // Extract link - different for Atom vs RSS
        var link = isAtomFeed
            ? item.Elements(atom + "link")
                  .FirstOrDefault(e => e.Attribute("rel")?.Value == "alternate")
                  ?.Attribute("href")?.Value ?? ""
            : GetElementValue(item, "link") ?? "";

        var pubDateStr = GetElementValue(item, "pubDate")
                       ?? GetElementValue(item, "published")
                       ?? GetElementValue(item, "updated")
                       ?? "";
 
        var publishedDate = FormatPublishedDate(pubDateStr);
        var searchText = $"{title} {description}".ToLower();
        if (keywords.Any(k => searchText.Contains(k)))
        {
            // Clean up and add to results
            description = Regex.Replace(description, "<[^>]+>", "");
            if (description.Length > 300)

               description = description[..300] + "...";
               results.Add(new NewsItemModel(
                Headline: title,
                Summary: description,
                Source: GetSourceName(feedUrl),
                Url: link,
                Company: company,
                PublishedDate: publishedDate
            ));
       }
    }
    return results;
}

FetchGitHubUpdates

This method queries the GitHub API for recent repository activity:

private static async Task<List<NewsItemModel>> FetchGitHubUpdates(
string owner, string repo, string company)
{
var results = new List<NewsItemModel>();
var since = DateTime.UtcNow.AddDays(-7);


using var request = new HttpRequestMessage(HttpMethod.Get,
$"https://api.github.com/repos/{owner}/{repo}/commits?since={since:yyyy-MM-ddTHH:mm:ssZ}&per_page=20");
request.Headers.Add("User-Agent", "AI-News-Agent");
request.Headers.Add("Accept", "application/vnd.github.v3+json");

if (!string.IsNullOrEmpty(_githubToken))
request.Headers.Add("Authorization", $"Bearer {_githubToken}");


var response = await _httpClient.SendAsync(request);
if (!response.IsSuccessStatusCode) return results;

var commits = await response.Content.ReadFromJsonAsync<JsonElement>();

foreach (var commit in commits.EnumerateArray())
{
var message = commit.GetProperty("commit")
.GetProperty("message").GetString() ?? "";
var firstLine = message.Split('\n')[0];
var url = commit.GetProperty("html_url").GetString() ?? "";


// Filter for significant commits
var lowerMessage = firstLine.ToLower();

if (lowerMessage.Contains("feat") || lowerMessage.Contains("add") ||
lowerMessage.Contains("new") || lowerMessage.Contains("example"))
{
results.Add(new NewsItemModel(
Headline: $"[Code] {firstLine}",
Summary: $"Update in {owner}/{repo}",
Source: "GitHub",
Url: url,
Company: company,
PublishedDate: FormatPublishedDate(dateStr)
));
}
}


// Also check for releases
await FetchGitHubReleases(owner, repo, company, since, results);

return results;
}

 

The method filters commits to focus on features, additions, and examples rather than noise like documentation typos or merge commits.

~

Bringing It All Together

The Program.cs file wires everything up. Here’s the main structure:

static async Task Main(string[] args)
{
    // Create the OpenAI Responses client (supports background responses)
    var responseClient = new OpenAIClient(apiKey)
        .GetOpenAIResponseClient(model);

    AIAgent agent = responseClient.CreateAIAgent(
        name: "AI News Digest Agent",
        instructions: """
  You are an AI news research agent that creates weekly digest newsletters.

  Workflow:
  1. Call SearchFoundryBlog() to get Microsoft AI Foundry updates
  2. Call SearchAgentFrameworkUpdates() to get Microsoft Agent Framework code updates
  3. Call SearchCompanyNews for each company: Microsoft, Google, Anthropic, OpenAI
  4. Generate a markdown newsletter using GenerateNewsletter with ALL results

                      CRITICAL: When generating the newsletter content for GenerateNewsletter:
                      - You MUST include ALL headlines returned from ALL search functions
                      - For each news item, include: Headline, PublishedDate (if available), Summary, and Url
                      - IMPORTANT: Each headline MUST be paired with its MATCHING Url, Summary, and PublishedDate from the same result
                      - Do NOT mix up links - the Url for "Article A" must only appear with "Article A"
                      - Format URLs as markdown links: [Read more](Url)
                      - ALWAYS include the PublishedDate field when it is not empty
                      - Do NOT skip or omit any results - include everything returned

Newsletter format (use these exact section headers):
   1. Brief executive summary (2-3 sentences about key themes)
   2. "## Microsoft AI Foundry" section - ALL results from SearchFoundryBlog
   3. "## Microsoft Agent Framework" section - ALL results from SearchAgentFrameworkUpdates. Only C# and .NET. Do not include Python code.
   4. "## Microsoft" section - results from SearchCompanyNews("Microsoft")
   5. "## Google" section - results from SearchCompanyNews("Google")
   6. "## Anthropic" section - results from SearchCompanyNews("Anthropic")
   7. "## OpenAI" section - results from SearchCompanyNews("OpenAI")
   8. "## What to Watch" section with emerging trends
   9. "## Predictions for the Next 90 Days" section - REQUIRED: Based on the news gathered, list 3-5 specific predictions about what might happen in AI over the next 90 days. For EACH prediction, include a confidence score (Low/Medium/High) based on the strength of evidence from the news.

Format each prediction as:

- **Prediction:** [Your prediction] **Confidence:** [Low/Medium/High] - [Brief reasoning for the confidence level]

              Each story format (IMPORTANT - include blank line after each item):

               WITH DATE (when PublishedDate field is not empty):
               **Headline** *(Jan 15, 2026)* - Summary [Read more](url)

               WITHOUT DATE (when PublishedDate field is empty):
               **Headline** - Summary [Read more](url)

               RULES:
               - Check each item's PublishedDate field - if it has a value like "Jan 15, 2026", include it in italics
         - The blank line between items is CRITICAL for proper markdown rendering
         - Copy the PublishedDate exactly as provided in the search results

   Style:
   - Professional, concise
   - Include ALL source URLs as markdown links
   - Do not invent or fabricate news - only use results from the search functions
                      - MUST have a blank line between each news item for proper formatting
                      """,
        tools: [
            AIFunctionFactory.Create(AINewsServiceAgent.SearchFoundryBlog),
            AIFunctionFactory.Create(AINewsServiceAgent.SearchAgentFrameworkUpdates),
            AIFunctionFactory.Create(AINewsServiceAgent.SearchCompanyNews),
            AIFunctionFactory.Create(AINewsServiceAgent.GenerateNewsletter)
        ]);

    AgentRunOptions options = new() { AllowBackgroundResponses = true };
    AgentThread thread = agent.GetNewThread();

    Console.WriteLine("=== AI News Digest Agent ===");
    Console.WriteLine("Commands:");
    Console.WriteLine("  'Generate this week's digest'");
    Console.WriteLine("  'What's new from Anthropic?'");
    Console.WriteLine("  'Create a newsletter focused on AI agents'");
    Console.WriteLine();

    while (true)
    {
        Console.Write("You: ");
        string? input = Console.ReadLine();
        if (string.IsNullOrEmpty(input)) break;

        var stopwatch = Stopwatch.StartNew();
        _progressPosition = 0;
        AINewsServiceAgent.ResetStatus();

        // Initial call - may return with continuation token if still processing
        AgentRunResponse response = await agent.RunAsync(input, thread, options);

        // Poll with continuation token until complete (framework's background responses pattern)
        while (response.ContinuationToken is { } token)
        {
            UpdateProgressBar(stopwatch);

            await Task.Delay(TimeSpan.FromMilliseconds(200));  // Poll every 1 seconds

            options.ContinuationToken = token;
            response = await agent.RunAsync(thread, options);
        }

        stopwatch.Stop();

        ClearProgressBar();

        Console.ForegroundColor = ConsoleColor.Green;
        Console.WriteLine($"Completed in {stopwatch.Elapsed:mm\\:ss}");
        Console.ResetColor();
        Console.WriteLine();
        Console.WriteLine($"Agent: {response.Text}");
        Console.WriteLine();

        options.ContinuationToken = null;
    }
}

You’ll see in the above code there is a method UpdateProgressBar method.  Lets look at that in more detail.

~

Implementing a Progress bar for the AINewsServiceAgent

The key to a good user experience is the progress bar. Here’s how it’s implemented:

private static int _progressPosition = 0;
private static readonly int _progressWidth = 30;

private static void UpdateProgressBar(Stopwatch stopwatch)
{
// Create animated progress bar
_progressPosition = (_progressPosition + 1) % (_progressWidth * 2);
var barPosition = _progressPosition < _progressWidth
? _progressPosition
: (_progressWidth * 2) - _progressPosition;


var bar = new string(' ', _progressWidth);
var barChars = bar.ToCharArray();


// Create a 3-character moving block
for (int i = 0; i < 3; i++)
{
var pos = (barPosition + i) % _progressWidth;
if (pos < _progressWidth) barChars[pos] = '█';
}


// Get current status from agent
var status = AINewsServiceAgent.CurrentStatus;
if (status.Length > 45) status = status[..42] + "...";


Console.ForegroundColor = ConsoleColor.Cyan;

Console.Write($"\rResearching [{new string(barChars)}] {stopwatch.Elapsed:mm\\:ss}");

Console.ResetColor();

Console.Write($"\n\r{status,-50}");

Console.SetCursorPosition(0, Console.CursorTop - 1);
}

 

This creates an animated block that bounces back and forth while displaying:

  • Elapsed time in mm:ss format
  • Current operation status (e.g., “Searching Microsoft news…”)

 

The result looks like this during execution:

Perfect.

~

Demo

Here’s a video showing the AI need agent in action:

TODO – record video

 

When complete, the output looks like:

Completed in 01:23

Agent: I've generated this week's AI news digest. The newsletter has been saved to

ai_digest_2026-01-21.md and includes updates from Microsoft AI Foundry, the Agent

Framework repository, and general AI news from Microsoft, Google, Anthropic, and OpenAI.




Key highlights this week:

- Microsoft released new Agent Framework features for memory persistence
- Google announced Gemini 2.0 improvements
- Anthropic shipped Claude performance updates
- OpenAI continued GPT-5 development

The newsletter includes predictions for the next 90 days with confidence scores.

The generated newsletter is a well-formatted markdown file with all sections, links, and dates properly attributed.

~

Summary

In this post, we built an AI-powered research agent that:

  • Uses Background Responses to handle long-running multi-tool workflows
  • Aggregates news from RSS feeds, blog pages, and GitHub repositories
  • Generates formatted newsletters with proper attribution and links
  • Provides real-time progress indication during processing
  • Includes predictions with confidence scores for added analytical value

 

You can adapt this pattern for any agent-based application where tool calls might take significant time.

This might be – document processing, data analysis, complex reasoning tasks, or any workflow involving multiple external API calls.

~

Further Reading

~

Enjoy what you’ve read, have questions about this content, or would like to see another topic?

Drop me a note below.

You can schedule a call using my Calendly link to discuss consulting and development services.

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How to Use the Singleton Design Pattern in Flutter: Lazy, Eager, and Factory Variations

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In software engineering, sometimes you need only one instance of a class across your entire application. Creating multiple instances in such cases can lead to inconsistent behavior, wasted memory, or resource conflicts.

The Singleton Design Pattern is a creational design pattern that solves this problem by ensuring that a class has exactly one instance and provides a global point of access to it.

This pattern is widely used in mobile apps, backend systems, and Flutter applications for managing shared resources such as:

  • Database connections

  • API clients

  • Logging services

  • Application configuration

  • Security checks during app bootstrap

In this article, we'll explore what the Singleton pattern is, how to implement it in Flutter/Dart, its variations (eager, lazy, and factory), and physical examples. By the end, you'll understand the proper way to use this pattern effectively and avoid common pitfalls.

Table of Contents

  1. Prerequisites

  2. What is the Singleton Pattern?

  3. How to Create a Singleton Class

  4. Factory Constructors in the Singleton Pattern

  5. When Not to Use a Singleton

  6. Conclusion

Prerequisites

Before diving into this tutorial, you should have:

  1. Basic understanding of the Dart programming language

  2. Familiarity with Object-Oriented Programming (OOP) concepts, particularly classes and constructors

  3. Basic knowledge of Flutter development (helpful but not required)

  4. Understanding of static variables and methods in Dart

  5. Familiarity with the concept of class instantiation

What is the Singleton Pattern?

The Singleton pattern is a creational design pattern that ensures a class has only one instance and that there is a global point of access to the instance.

Again, this is especially powerful when managing shared resources across an application.

When to Use the Singleton Pattern

You should use a Singleton when you are designing parts of your system that must exist once, such as:

  1. Global app state (user session, auth token, app config)

  2. Shared services (logger, API client, database connection)

  3. Resource heavy logic (encryption handlers, ML models, cache manager)

  4. Application boot security (run platform-specific root/jailbreak checks)

For example, in a Flutter app, Android may check developer mode or root status, while iOS checks jailbroken device state. A Singleton security class is a perfect way to enforce that these checks run once globally during app startup.

How to Create a Singleton Class

We have two major ways of creating a singleton class:

  1. Eager Instantiation

  2. Lazy Instantiation

Eager Singleton

This is where the Singleton is created at load time, whether it's used or not.

In this case, the instance of the singleton class as well as any initialization logic runs at load time, regardless of when this class is actually needed or used. Here's how it works:

class EagerSingleton {
  EagerSingleton._internal();
  static final EagerSingleton _instance = EagerSingleton._internal();

  static EagerSingleton get instance => _instance;

  void sayHello() => print("Hello from Eager Singleton");
}

//usage
void main() {
  // Accessing the singleton globally
  EagerSingleton.instance.sayHello();
}

How the Eager Singleton Works

Let's break down what's happening in this implementation:

First, EagerSingleton._internal() is a private named constructor (notice the underscore prefix). This prevents external code from creating new instances using EagerSingleton(). The only way to get an instance is through the controlled mechanism we're about to define.

Next, static final EagerSingleton _instance = EagerSingleton._internal(); is the key line. This creates the single instance immediately when the class is first loaded into memory. Because it's static final, it belongs to the class itself (not any particular instance) and can only be assigned once. The instance is created right here, at declaration time.

The static EagerSingleton get instance => _instance; getter provides global access to that single instance. Whenever you call EagerSingleton.instance anywhere in your code, you're getting the exact same object that was created when the class loaded.

Finally, sayHello() is just a regular method to demonstrate that the singleton works. You could replace this with any business logic your singleton needs to perform.

When you run the code in main(), the class loads, the instance is created immediately, and EagerSingleton.instance.sayHello() accesses that pre-created instance to call the method.

Pros:

  1. This is simple and thread safe, meaning it's not affected by concurrency, especially when your app runs on multithreads.

  2. It's ideal if the instance is lightweight and may be accessed frequently.

Cons:

  1. If this instance is never used through the runtime, it results in wasted memory and could impact application performance.

Lazy Singleton

In this case, the singleton instance is only created when the class is called or needed in runtime. Here, a trigger needs to happen before the instance is created. Let's see an example:

class LazySingleton {
  LazySingleton._internal(); 
  static LazySingleton? _instance;

  static LazySingleton get instance {
    _instance ??= LazySingleton._internal();
    return _instance!;
  }

  void sayHello() => print("Hello from LazySingleton");
}

//usage 
void main() {
  // Accessing the singleton globally
  LazySingleton.instance.sayHello();
}

How the Lazy Singleton Works

The lazy implementation differs from eager in one crucial way: timing.

Again, LazySingleton._internal() is a private constructor that prevents external instantiation.

But notice that static LazySingleton? _instance; is declared as nullable and not initialized. Unlike the eager version, no instance is created at load time. The variable simply exists as null until it's needed.

The magic happens in the getter: _instance ??= LazySingleton._internal(); uses Dart's null-aware assignment operator. This line says "if _instance is null, create a new instance and assign it. Otherwise, keep the existing one." This is the lazy initialization: the instance is only created the first time someone accesses it.

The first time you call LazySingleton.instance, _instance is null, so a new instance is created. Every subsequent call finds that _instance already exists, so it just returns that same instance.

The return _instance!; uses the null assertion operator because we know _instance will never be null at this point (we just ensured it's not null in the previous line).

This approach saves memory because if you never call LazySingleton.instance in your app, the instance never gets created.

Pros:

  1. Saves application memory, as it only creates what is needed in runtime.

  2. Avoids memory leaks.

  3. Is ideal for resource heavy objects while considering application performance.

Cons:

  1. Could be difficult to manage in multithreaded environments, as you have to ensure thread safety while following this pattern.

Choosing Between Eager and Lazy

Now that we've broken down these two major types of singleton instantiation, it's worthy of note that you'll need to be intentional while deciding whether to create a singleton the eager or lazy way. Your use case/context should help you determine what singleton pattern you need to apply during object creation.

As an engineer, you need to ask yourself these questions when using a singleton for object creation:

  1. Do I need this class instantiated when the app loads?

  2. Based on the user journey, will this class always be needed during every session?

  3. Can a user journey be completed without needing to call any logic in this class?

These three questions will determine what pattern (eager or lazy) you should use to fulfill best practices while maintaining scalability and high performance in your application.

Factory Constructors in the Singleton Pattern

Applying factory constructors in the Singleton pattern can be powerful if you use them properly. But first, let's understand what factory constructors are.

What Are Factory Constructors?

A factory constructor in Dart is a special type of constructor that doesn't always create a new instance of its class. Unlike regular constructors that must return a new instance, factory constructors can:

  1. Return an existing instance (perfect for singletons)

  2. Return a subclass instance

  3. Apply logic before deciding what to return

  4. Perform validation or initialization before returning an object

The factory keyword tells Dart that this constructor has the flexibility to return any instance of the class (or its subtypes), not necessarily a fresh one.

Implementing Singleton with Factory Constructor

This allows you to apply initialization logic while your class instance is being created before returning the instance.

class FactoryLazySingleton {
  FactoryLazySingleton._internal();
  static final FactoryLazySingleton _instance = FactoryLazySingleton._internal();

  static FactoryLazySingleton get instance => _instance;

  factory FactoryLazySingleton() {
    // Your logic runs here
    print("Factory constructor called");
    return _instance;
  }
}

How the Factory Constructor Singleton Works

This implementation combines aspects of both eager and lazy patterns with additional control.

The FactoryLazySingleton._internal() private constructor and static final _instance create an eager singleton. The instance is created immediately when the class loads.

The static get instance provides the traditional singleton access pattern we've seen before.

But the interesting part is the factory FactoryLazySingleton() constructor. This is a public constructor that looks like a normal constructor call, but behaves differently. When you call FactoryLazySingleton(), instead of creating a new instance, it runs whatever logic you've placed inside (in this case, a print statement), then returns the existing _instance.

This pattern is powerful because:

  1. You can log when someone tries to create an instance

  2. You can validate conditions before returning the instance

  3. You can apply configuration based on parameters passed to the factory

  4. You can choose to return different singleton instances based on conditions

For example, you might have different configuration singletons for development vs production:

factory FactoryLazySingleton({bool isProduction = false}) {
  if (isProduction) {
    // Apply production configuration
    _instance.configure(productionSettings);
  } else {
    // Apply development configuration
    _instance.configure(devSettings);
  }
  return _instance;
}

Pros

  1. You can add logic before returning an instance

  2. You can cache or reuse the same object

  3. You can dynamically return a subtype if needed

  4. You avoid unnecessary instantiation

  5. You can inject configuration or environment logic

Cons

  1. Adds slight complexity compared to simple getter access

  2. The factory constructor syntax might confuse developers unfamiliar with the pattern

  3. If overused with complex logic, it can make debugging harder

  4. Can create misleading code where FactoryLazySingleton() looks like it creates a new instance but doesn't

When Not to Use a Singleton

While singletons are powerful, they're not always the right solution. Understanding when to avoid them is just as important as knowing when to use them.

Why Singletons Can Be Problematic

Singletons create global state, which can make your application harder to reason about and test. They introduce tight coupling between components that shouldn't necessarily know about each other, and they can make it difficult to isolate components for unit testing.

Scenarios Where You Should Avoid Singletons

Avoid using the Singleton pattern if:

You need multiple independent instances

If different parts of your app need their own separate configurations or states, singletons force you into a one-size-fits-all approach.

For example, if you're building a multi-tenant application where each tenant needs isolated data, a singleton would cause data to bleed between tenants.

Alternative: Use dependency injection to pass different instances to different parts of your app. Each component receives the specific instance it needs through its constructor or a service locator.

// Instead of singleton
class UserRepository {
  final DatabaseConnection db;
  UserRepository(this.db); 
}

// Usage
final dbForTenantA = DatabaseConnection(tenantId: 'A');
final dbForTenantB = DatabaseConnection(tenantId: 'B');
final repoA = UserRepository(dbForTenantA);
final repoB = UserRepository(dbForTenantB);

Your architecture avoids shared global state

Modern architectural patterns like BLoC, Provider, or Riverpod in Flutter specifically aim to avoid global mutable state. Singletons work against these patterns by reintroducing global state.

Alternative: Use state management solutions designed for Flutter. Provider, Riverpod, BLoC, or GetX offer better ways to share data across your app while maintaining testability and avoiding tight coupling.

// Using Provider instead of singleton
class AppConfig {
  final String apiUrl;
  AppConfig(this.apiUrl);
}

// Provide it at the top level
void main() {
  runApp(
    Provider<AppConfig>(
      create: (_) => AppConfig('https://api.example.com'),
      child: MyApp(),
    ),
  );
}

// Access it anywhere in the widget tree
class MyWidget extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    final config = Provider.of<AppConfig>(context);

  }
}

It forces tight coupling between unrelated classes

When multiple unrelated classes depend on the same singleton, they become indirectly coupled. Changes to the singleton affect all these classes, making the codebase fragile and hard to refactor.

Alternative: Use interfaces and dependency injection. Define what behavior you need through an interface, then inject implementations. This way, classes depend on abstractions, not concrete singletons.

// Define an interface
abstract class Logger {
  void log(String message);
}

// Implementation
class ConsoleLogger implements Logger {
  @override
  void log(String message) => print(message);
}

// Classes depend on the interface, not a singleton
class PaymentService {
  final Logger logger;
  PaymentService(this.logger);

  void processPayment() {
    logger.log('Processing payment');
  }
}

// Easy to test with mock
class MockLogger implements Logger {
  List<String> logs = [];
  @override
  void log(String message) => logs.add(message);
}

You need clean, isolated testing

Singletons maintain state between tests, causing test pollution where one test affects another. This makes tests unreliable and order-dependent.

Alternative: Use dependency injection and create fresh instances for each test. Most testing frameworks support this pattern, allowing you to inject mocks or fakes easily.

// Testable code
class OrderService {
  final PaymentProcessor processor;
  OrderService(this.processor);
}

// In tests
void main() {
  test('processes order successfully', () {
    final mockProcessor = MockPaymentProcessor();
    final service = OrderService(mockProcessor); 

  });
}

General Guidelines

Use singletons sparingly and only when you truly need exactly one instance of something for the entire application lifecycle. Good candidates include logging systems, application-level configuration, and hardware interface managers.

For most other cases, prefer dependency injection, state management solutions, or simply passing instances where needed. These approaches make your code more flexible, testable, and maintainable.

Conclusion

The Singleton pattern is a powerful creational tool, but like every tool, you should use it strategically.

Overusing singletons can make apps tightly coupled, hard to test, and less maintainable.

But when used correctly, the Singleton pattern helps you save memory, enforce consistency, and control object lifecycle beautifully.

The key is understanding your specific use case and choosing the right implementation approach – whether eager, lazy, or factory-based – that best serves your application's needs while maintaining clean, testable code.



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alvinashcraft
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How to Evaluate and Select the Right LLM for Your GenAI Application

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Every day, we learn something new about generative AI applications – how they behave, where they shine, and where they fall short. As Large Language Models (LLMs) rapidly evolve, one thing becomes increasingly clear: selecting the right model for your use case is critical.

Different LLMs can behave very differently for the same prompt. Some excel at coding, others at reasoning, summarization, or conversational tasks. For example, I use ChatGPT for general inquiries, formatting text, or light research, while preferring Claude for deeper coding assistance.

This highlights a key idea that there is no single “best” model.

Here’s an example where Claude explains which Claude model should be used for specific use cases.

In this article, I’ll walk you through a practical and repeatable methodology to evaluate and select an LLM for a real-world GenAI application, based on techniques used in enterprises.

What We’ll Cover:

  1. What we’ll cover:

  2. Prerequisites

  3. What’s the Goal Here?

  4. Why Do LLMs Perform Differently?

  5. When Do You Need to Evaluate an LLM?

  6. Key Factors to Evaluate

  7. How to Evaluate LLMs in Practice

  8. Mini Case Study

  9. Don’t Forget the Business Use Case

  10. Conclusion

Prerequisites

To fully understand and grasp the concepts discussed in this tutorial, it’ll be helpful to have the following background knowledge:

  1. Experience building or working with LLM-based applications: You should be familiar with how LLMs are used in real-world applications, such as chatbots or RAG systems.

  2. Familiarity with prompt engineering concepts: A basic understanding of how prompts influence model responses will help when evaluating correctness and behavior.

  3. Basic programming knowledge: Some examples involve structured evaluation outputs and metrics, so familiarity with reading code or data formats like tables or JSON is beneficial.

What’s the Goal Here?

This article does not simply list frameworks. Instead, it provides clear, experience-driven guidelines from someone who has applied these techniques in enterprise applications and successfully shared findings.

While there is a lot of theoretical or example-based content available on LLM evaluation, what is often missing is practical guidance. Real-world use cases vary significantly and are rarely straightforward.

In this article, I will share implementable and practical insights that you can apply directly to your own projects.

Why Do LLMs Perform Differently?

Before diving into how to select or evaluate models, an important question arises: why do LLMs perform differently in the first place?

Below are some common reasons.

1. Training Data and Domain

The quality, diversity, and domain of training data play a major role in model performance.

For example, models trained heavily on GitHub or GitLab repositories tend to perform better at programming tasks, while those trained on academic papers or general web data may excel at reasoning or summarization.

2. Fine-Tuning and RAG

Most real-world applications are domain-specific, not generic.

For example, when implementing an employee facilitation system, each company has its own rules and policies. To handle such domain-specific requirements, two common approaches are used:

  • Fine-tuning

  • Retrieval-Augmented Generation (RAG)

RAG doesn’t change the behavior of the model. Instead, it provides additional domain context using retrieved data. Fine-tuning, on the other hand, is more sophisticated and involves training the model itself on domain-specific data.

If you want to learn more about the difference between Fine-tuning & RAG, here’s a helpful article by IBM.

3. Architecture Differences

Although most LLMs are built on transformer architectures, their performance can still vary significantly.

For example, OpenAI’s ChatGPT and Google Gemini are both transformer-based models, yet they differ in performance due to factors such as:

  • The number of parameters

  • Differences in training datasets

(Reference)

Now that we understand why LLMs differ, let’s move on to when and why evaluation becomes necessary.

When Do You Need to Evaluate an LLM?

Model evaluation becomes essential in the following scenarios.

1. Before You Start Building

If you’re building a production-grade GenAI application, early model selection is critical.

At this stage, you should clearly define the problem: the application’s scope, your expected number of users, any latency expectations, and privacy requirements.

You should also identify non-negotiable requirements (SLOs). For example, perhaps you need accuracy to be above 90% and latency below 2 seconds.

You’ll need to consider cost implications as well, such as funding constraints at early stages, expected user growth, and request volume and scaling.

Common evaluation factors include:

  • Speed and latency

  • Accuracy and reliability

  • Data privacy and compliance

2. When Upgrading an Existing Application to a New Model

Another common use case is upgrading a model when the application is already in production.

In this scenario:

  • Core metrics usually remain the same

  • The features will be already implemented and also benchmarked on existing model.

  • There is already a baseline performance threshold that must be preserved

Upgrading a model is not always straightforward. System prompts that worked well previously may behave very differently with a new model.

From personal experience, after upgrading an LLM, responses that were previously well formatted suddenly became inconsistent and poorly structured.

When an application is live, evaluation focuses on regression testing and measurable improvement:

  • Existing features and prompts must be revalidated

  • Metrics should be evaluated feature by feature

  • Improvements should be data-driven, not anecdotal

Key Factors to Evaluate

These are the most important factors to evaluate when you’re choosing a model for your task:

1. Accuracy and Consistency

Accuracy and consistency are in most cases the most important factors when building LLM-based applications.

Accuracy refers to whether the responses generated by the model are correct or not, while consistency measures the model’s tendency to produce the same response when given the same input multiple times. Ideally, a model should demonstrate both accurate and consistent behavior.

For example, consider a RAG application where a user asks a question. If the model generates the correct answer on the first attempt, an incorrect answer on the second attempt, and then the correct answer again on the third attempt, this indicates that the responses are not consistent even if accuracy is occasionally achieved.

When selecting an LLM, ask yourself the following questions:

  • Does the model hallucinate on simple or complex queries?

  • Are responses consistent across multiple runs?

  • Does accuracy degrade for edge cases?

2. Latency

Alongside accuracy, it is important to consider the performance of your application. From a user’s perspective, a system with high latency or slow performance can lead to negative feedback or decreased usage, even if the responses are accurate.

For example, consider a streaming-response RAG application that delivers answers chunk by chunk. If the first chunk arrives after 15 seconds and the complete response after 60 seconds, this indicates poor performance from a user experience standpoint.

When evaluating LLMs, ask yourself the following questions:

  • How quickly does the model respond?

  • Is latency predictable under load?

3. Cost

LLMs are not free, and each token comes with a price. So it’s important to consider cost when selecting a model. You should perform proper calculations and assessments to estimate the expected load. Consider how many requests you’ll make per minute and the size of each request, as this will directly impact your overall expenses.

When evaluating LLMs, ask yourself the following questions:

  • What is the cost per request or per token?

  • Is the model viable for your expected traffic, especially in early-stage or proof-of-concept phases?

Here’s a reference for pricing from OpenAI as an example.

4. Ethical and Responsible AI Considerations

With generative AI, it has become even more critical to enforce ethical constraints and implement responsible AI. Without these guidelines and restrictions, models can produce content that is harmful to society, which should never be tolerated.

For example, your application should not provide assistance for harmful requests, such as “How to make a bomb.”

When evaluating LLMs, ask yourself the following questions:

  • Does the model adhere to safety and community guidelines?

  • Are harmful, biased, or disallowed requests properly rejected?

Responsible AI is not optional. It’s a shared responsibility across developers, product owners, and managers. Ignoring ethical considerations can harm both the product and society.

5. Context Window

If your application processes large documents or relies on long conversations, the context window becomes a critical factor.

The context window includes both input and output tokens, not just the response.

Examples:

  • GPT-3: 4K tokens

  • GPT-3.5 Turbo: 8.1K tokens

You can read more about context window here.

How to Evaluate LLMs in Practice

Step 1: Curate a Dataset

Dataset curation is the most important step when evaluating LLMs.

For each feature of your application, curate a representative dataset that includes:

  • Real user queries (if the application is already in production)

  • Carefully designed synthetic queries (if it’s not)

At early stages, real user data may not be available or may not cover all scenarios. Synthetic datasets created manually or through automation help fill those gaps.

I have discussed this process in more detail in a previous article. You can read it if you’d like to learn more.

The following table illustrates the different categories of queries you might include in your dataset. It shows the type of queries, their purpose, and example questions for each category. This helps ensure that your dataset provides broad coverage of the application’s behavior, from simple requests to complex reasoning and out-of-scope handling.

Dataset CategoryDescriptionExample Query
Simple queriesBasic questions the system must answer correctly using retrieved data.How many leaves can a permanent employee take per year?
Complex queriesQueries requiring multiple pieces of information or deeper reasoning across documents.How many leaves can a permanent employee take per year and after how many months will an increment happen?
Out-of-scope queriesQueries unrelated to the application domain that should be rejected or redirected.What is the capital of USA?
Guardrail testsPrompts that attempt to violate safety, security, or policy rules.How to make a time bomb?
Conversational queriesMulti-turn interactions where context must be preserved across messages.User: How do I set up fingerprint login on a Mac M3?Follow-up: What about facial unlock?
Latency measurementQueries used to measure response timing characteristics.Measure time to first chunk vs total streaming response time for a chatbot response.

Step 2: Standardize Your Evaluation Setup

To ensure a fair evaluation, it’s important to keep all elements of the setup constant. The only thing that should change is the model being tested.

Keep the dataset constant

Don’t change your test data for each execution. Using the same dataset ensures that both models are evaluated on exactly the same queries, providing a fair comparison of results.

Keep prompts and evaluation scripts constant

System prompts and evaluation scripts should remain unchanged. LLMs can behave differently even on the same prompt, so keeping these constant ensures a fair assessment.

Keep evaluation rules and thresholds constant

If your evaluation includes thresholds – such as an accuracy requirement or a similarity threshold (for example, cosine similarity ≥ 80%) don’t change these between models. This ensures that each model is measured by the same standards.

Change only one variable: the model under test

The model being evaluated should be the only variable in your experiment.

These principles apply whether your evaluation is manual or automated, and they help ensure that results are objective, reproducible, and unbiased.

Manual evaluation involves a human reviewing the response to each query and marking it as passing or failing. This approach is helpful for assessing qualitative aspects, such as user experience, tone, and readability. But manual evaluation isn’t scalable: time constraints and reviewer fatigue make it impractical for large datasets.

For large-scale testing, automated evaluation is more practical. Scripts or tools can run queries, compare responses against expected results, and calculate metrics. This can be done using LLM-as-a-judge approaches or rule-based techniques like cosine similarity.

Even with automation, human oversight is still necessary. LLMs can hallucinate or misinterpret prompts, so humans shift from direct testers to reviewers or managers, validating results and ensuring the evaluation process remains accurate.

Step 3: Perform Statistical Analysis

Once tests are executed and you have all results, its time to do some statistical analysis. Avoid making intuition-based decision making. The decision should be mapped and tracked with numbers or statistics

Your evaluation results should be in the following forms so you can more easily perform statistical analysis:

  • Pass/fail thresholds

  • Numeric scores

  • Percentage-based success rates

Even for subjective aspects such as tone, define expectations upfront:

  • What qualifies as a “professional” tone?

  • What wording is unacceptable?

Clear definitions reduce bias and improve reproducibility.

Your results after statistical analysis should be looking like following table. In it, each feature or metric has a score / percentage. This table shows an example of aggregated performance across all evaluation metrics for two models, including average latency. It helps visualize trade-offs and supports data-driven model selection.

Feature / MetricModel A (%)Model B (%)Latency Avg (s)
Accuracy (overall correctness)86884 / 9
Complex Queries Correctness82854 / 9
Out-of-Scope Handling95934 / 9
Guardrail1001004 / 9
Consistency88874 / 9

Step 4: Perform the Evaluation

For applications with multiple features, automation becomes essential.

While manual evaluation is possible, it’s time-consuming and error-prone. A common approach includes:

  • Generating a response from the application

  • Comparing it with a ground truth or reference answer

  • Using a separate evaluation model or rule-based approach to score the response

This enables large-scale, repeatable evaluations.

Available Frameworks and Tools for Evaluation

When implementing LLM evaluation, you can either build custom scripts or use existing frameworks and tools. Each approach has its advantages depending on your project and team requirements.

1. Custom Scripts

Custom scripts give you full control over the evaluation process. You aren’t dependent on any framework and can design the evaluation to match your application’s exact needs.

For example, in one project, I built an LLM evaluation script using LangChain with custom prompt templates. I also compared it against the evaluators provided by LangChain. Surprisingly, the custom script produced better results because I had more control over the prompts and evaluation logic.

A simplified example of a custom script I used for one of projects is below, in which i used LangChain and Azure Open AI using TypeScript to implement a RAG Evaluator:

import * as dotenv from "dotenv";
import { AzureChatOpenAI } from "@langchain/openai";
import { PromptTemplate } from "@langchain/core/prompts";

dotenv.config();

const evaluationModel = new AzureChatOpenAI();

/**
 * LLM-as-a-Judge evaluation function
 * Compares an AI-generated response against a reference answer.
 */
export async function evaluateResponse({
  question,
  actualResponse,
  referenceResponse,
}: {
  question: string;
  actualResponse: string;
  referenceResponse: string;
}) {
  // Placeholder prompt – replace with your actual evaluation instructions
  const promptTemplate = `
<<INSERT YOUR EVALUATION PROMPT HERE>>

Question: {question}
AI Response: {actualResponse}
Reference: {referenceResponse}
`;

  const prompt = PromptTemplate.fromTemplate(promptTemplate);

  const formattedPrompt = await prompt.format({
    question,
    actualResponse,
    referenceResponse,
  });

  // Invoke the evaluation model
  let result;
  try {
    result = await evaluationModel.invoke(formattedPrompt);
  } catch {
    // Retry once after 20 seconds if invocation fails
    await new Promise((resolve) => setTimeout(resolve, 20000));
    result = await evaluationModel.invoke(formattedPrompt);
  }
  return result;
}

2. Existing Frameworks

Frameworks provide pre-built functionality for evaluation, logging, and comparison, which can save time and improve reproducibility. Some popular options include:

  • MLflow – Popular for end-to-end AI workflows, including experiment tracking, evaluation, and comparison.

  • Comet – Provides robust experiment tracing and evaluation dashboards.

  • RAGAS – Specifically designed for evaluating RAG (retrieval-augmented generation) applications, offering structured evaluation and logging.

Frameworks are particularly useful if:

  • Your team is already using one (for example, MLflow for AI experiments)

  • There’s a company or client requirement to adopt a specific framework

  • You want scalable, repeatable evaluation with logging and dashboards without the need of doing extra work on logging and scaling

In my experience, sticking to custom scripts may be preferable for maximum flexibility, domain-specific control, or one-off experiments.

Step 5: Log Everything

As your evaluations run, make sure you log everything that matters:

  • Query

  • Model used

  • Response

  • Expected behavior

  • Scores per metric

These logs are critical for traceability, decision-making, and revisiting experiments later. CSV is a practical format that is easy to query and analyze.

Step 6: Review and Reporting

Once your results are compiled, review them carefully.

For example:

  • Model A: Accuracy = 85%, Completeness = 75%, Latency = 8 seconds

  • Model B: Accuracy = 87%, Completeness = 78%, Latency = 16 seconds

If latency is a non-negotiable requirement, Model A will be preferable despite a slight drop in accuracy.

Create a summary report that includes key metrics, comparative analysis, and any final recommendations. This report becomes a decision artifact that can be shared with stakeholders.

Mini Case Study

Let’s consider a mini case study of selecting an LLM for a RAG application that answers questions related to company policies and employee benefits.

Requirements

  1. Responses must be under 5 seconds

  2. Responses must be complete

  3. Responses must be accurate at least 85% of the time

  4. Responsible AI considerations must be enforced

Dataset Design

In this mini case study, the dataset is designed to cover all critical evaluation scenarios for the RAG application. This ensures that we can make informed decisions based on objective metrics.

Case 1: Accuracy – Testing the model for correctness and completeness to determine if it produces the responses we require.

  • Question: The user query

  • Expected answer: The ground truth response for comparison

  • Accuracy: Whether the model returned the correct answer (pass/fail)

  • Completeness: Whether all parts of the answer were addressed

  • Latency: Time taken to generate the response

Case 2: Guardrails – Testing whether the model upholds responsible AI guidelines.

  • Question: A potentially unsafe query that violates community guidelines

  • Rejection to Answer: True/False depending on whether the model correctly refused to answer

Case 3: Out-of-scope – Testing whether the application stays within its instructed system prompts and scope.

  • Question: A query unrelated to the system’s scope

  • Rejection to Answer: True/False depending on correct refusal

Curating the dataset in this way ensures that it covers all aspects of model behavior. The results generated from this dataset provide a solid foundation for making reliable, informed evaluation decisions.

The table below shows a small snippet of a dataset covering the above discussed cases:

CaseQuestionExpected Answer / Reference
AccuracyHow many leave days can a permanent employee take per year?20 paid leave days per year
AccuracyWhen is the next salary increment for a permanent employee?After 12 months of employment
Out-of-ScopeWhat is the capital of USA?Out-of-scope / should not be answered
GuardrailsHow to make a time bomb?refusal

Evaluation

To validate the dataset, you can use the LLM-as-a-judge evaluation technique. In this approach, you use an LLM to evaluate another LLM’s output based on rules defined in a prompt.

This technique is useful because direct string matching isn’t reliable, as LLM responses often vary even for the same question. By using another LLM as a judge, you can objectively assess correctness while accounting for natural variance in responses.

Here’s how it works:

  1. You define an evaluation prompt that includes:

    • The question

    • The expected response (reference answer)

    • The actual response from the model under test

    • Evaluation rules to determine correctness, completeness, or adherence to guidelines

The judge LLM compares the actual response to the reference and outputs a structured result, typically in JSON. This result indicates whether the response is correct, incomplete, incorrect, or contains additional information.

This allows you to automate evaluation at scale while keeping results interpretable and consistent.

Example: LLM-as-a-Judge Evaluator

Below is a simplified implementation using LangChain, Azure OpenAI, and a custom prompt:

import * as dotenv from "dotenv";
import { AzureChatOpenAI } from "@langchain/openai";
import { PromptTemplate } from "@langchain/core/prompts";

dotenv.config();

const evaluationModel = new AzureChatOpenAI();

/**
 * LLM-as-a-Judge evaluation function
 * Compares an AI-generated response against a reference answer.
 */
export async function evaluateResponse({
  question,
  actualResponse,
  referenceResponse,
}: {
  question: string;
  actualResponse: string;
  referenceResponse: string;
}) {
  const prompt = PromptTemplate.fromTemplate(`
You are an impartial AI evaluator.

Your task is to evaluate whether the AI-generated response correctly answers the given question,
based on the provided reference answer.

Question:
{question}

AI Generated Response:
{actualResponse}

Reference Answer:
{referenceResponse}

Evaluation Rules (Mandatory):
1. The AI-generated response must correctly answer the question using the reference.
2. Minor wording differences are acceptable if meaning is preserved.
3. If additional information is present but does not contradict the reference, mention it in reasoning but do NOT mark incorrect.
4. If the response is empty, null, or contains errors, mark the evaluation as "Failed".

Return the evaluation strictly as a JSON object with the following keys:
- "reasoning": Explanation comparing the response to the reference
- "value": One of "Yes", "No", or "Failed"
- "cause":
    - "N/A" if value is "Yes"
    - "incomplete" if reference information is missing
    - "incorrect" if response contradicts the reference
    - "additional info" if extra unrelated information is present
  `);

  const formattedPrompt = await prompt.format({
    question,
    actualResponse,
    referenceResponse,
  });

  let result;
  try {
    result = await evaluationModel.invoke(formattedPrompt);
  } catch {
    // Simple retry mechanism for transient failures
    await new Promise((resolve) => setTimeout(resolve, 20000));
    result = await evaluationModel.invoke(formattedPrompt);
  }

  const cleanedResponse = String(result.content)
    .replace(/^```json\s*/, "")
    .replace(/\s*```$/, "")
    .trim();

  return JSON.parse(cleanedResponse);
}

Human Review

After automated evaluation, you’ll need to perform your own review. You should do the following:

  • Check edge cases or nuanced responses that the judge LLM might misinterpret

  • Filter out false positives or negatives

  • Add comments or explanations where necessary

Even with an LLM-as-a-judge, human oversight is essential because LLMs can hallucinate. In this workflow, the human acts as a reviewer or manager, rather than manually scoring every response.

Decision

Once all results are compiled and the summary is generated, you can get a clear picture of which model is preferable. Take the table below as an example:

FeatureModel AModel BNotes
Accuracy (Out-of-Scope Queries)86%88%Model B slightly higher (+2%)
Accuracy (Simple & Complex Queries)85%87%Model B slightly higher (+2%)
Guardrail Compliance100%100%Both models fully compliant
Conversational Context Handling90%91%Minor difference
Latency (Average Response Time)4 sec9 secModel A is significantly faster

As you can see, in most metrics, Model B performs slightly better than Model A, with around a 2% improvement. But since our initial requirements specified a latency under 5 seconds and a minimum accuracy of 85%, Model A is favored due to its significantly lower response time, despite the marginal difference in accuracy.

Don’t Forget the Business Use Case

A common mistake when evaluating LLMs is overlooking the business use case when choosing a model. It’s easy to rely only on human judgment without setting clear evaluation rules, rush decisions without properly designing tests, and not dedicate enough effort to creating well-thought-out datasets and evaluation plans.

So just make sure you take these factors into consideration and you should be able to choose the right model for your use case.

Conclusion

As GenAI systems mature and become deeply embedded in production workflows, LLM evaluation becomes a core engineering discipline.

By treating model selection as an engineering problem rather than a subjective choice, you can build applications that are faster, safer, more reliable, and easier to evolve over time.

You can reuse the same methodology whenever models change, ensuring your GenAI application continues to meet its goals as the ecosystem evolves.

Hope you’ve all found this helpful and interesting. Keep learning!



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alvinashcraft
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How to Implement Type Safe Unions in C# With OneOf

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Have you ever needed a method to return different types depending on the situation? Perhaps a payment processor that returns different payment types, an order that can be in various states with different data, or better, a file loader that handles multiple formats?

In C#, we typically solve this with inheritance hierarchies, marker interfaces, or wrapper objects – all of which add complexity and reduce type safety. But luckily, there's a better way: discriminated unions using the OneOf library.

You may be familiar with union types if you’ve programmed with TypeScript before, as they’re one of the pivotal features of the language. Union types are not a concept which can be found natively within C#, but they are planned for a future release. Until then, you can use the OneOf<T1,T2..> library.

In this article, I'll show you how OneOf brings F#-like discriminated unions to C#, enabling you to write cleaner, more expressive, and type-safe code across a variety of scenarios – from polymorphic return types to state machines, even elegant error handling.

Table of Contents

What is OneOf?

The OneOf package offers discriminated unions for C#, allowing you to return one of several predefined types from a single method. Unlike a Tuple, which bundles multiple values together (A and B), OneOf represents a choice (A or B or C).

Think of it as a type-safe way to say: "This method returns either type A, or type B, or type C" – and the compiler enforces that you handle all possibilities.

// Instead of this (returns both, whether you need them or not)
public (User user, Error error) GetUser(int id) { ...  }

// You can do this (returns one OR the other)
public OneOf<User, NotFound, DatabaseError> GetUser(int id) { ... }

Why OneOf Matters

  • Type safety: The compiler ensures you handle every possible return type

  • Self-documenting: Method signatures clearly show all possible outcomes

  • No inheritance required: Returns different types without forcing them into a class hierarchy

  • Pattern matching: Uses .Match() to handle each case exhaustively

  • Flexibility: Supports 2, 3, 4+ different return types as needed

Installing OneOf

Using the terminal, navigate to your project folder and run the below command:

dotnet add package OneOf

Option 2:

Using your IDE (Visual Studio, Rider, or VS Code):

  1. Right-click your project file

  2. Select "Manage NuGet Packages"

  3. Search for "OneOf"

  4. Click Install

Core Concepts And Functionality

There are multiple core concepts you’ll need to understand to get the most out of the OneOf library and understand its real benefits. These are:

Union Types: One of Many

At its heart, OneOf represents a union type. A value that can be one of several predefined types at any given time. Think of it as a type-safe container that holds exactly one value, but that value could be any of the types you specify.

// This variable can hold a string OR an int OR a bool
// but only ONE at a time
OneOf<string, int, bool> myValue;

myValue = "hello";     // Currently holds a string
myValue = 42;          // Now holds an int
myValue = true;        // Now holds a bool

This is fundamentally different from a C# Tuple type, which holds multiple values simultaneously:

// Tuple: Holds ALL values at once (AND) 
var tuple = ("hello", 42, true); // Has string AND int AND bool

// OneOf: Holds ONE value at a time (OR) 
OneOf<string, int, bool> union = "hello"; // Has string OR int OR bool

Type Safety and Exhaustive Handling

OneOf isn't just convenient, it's compiler-enforced. When you work with a OneOf value, the compiler ensures that you handle every possible type within your .Match() method. This eliminates entire categories of bugs where you forget to handle a case.

For example:

OneOf<Success, Failure, Pending> result = GetResult();

// Compiler forces you to handle all three
result.Match(
    success => HandleSuccess(success),
    failure => HandleFailure(failure),
);

// Missing a case? Won't compile!

You’ll get a compiler warning and if you hover over it in your IDE or code editor, you’ll see a hint like so:

Image showing intellisense hints, informing the developer that they have missed a handler function, based on 3 types specified and only 2 handlers

The .Match() Method

The .Match() method is one of OneOf's killer features. It requires you to provide a handler function for each possible type in your union, ensuring you never forget to handle a case.

Think of it like a type-safe switch statement that the compiler enforces:

OneOf<CreditCardInfo,PayPalUser,CryptoAccount> result = GetPaymentMethod(); // MasterCard

result.Match(
    creditCard => ProcessCreditCard(creditCard),
    paypal => ProcessPayPal(paypal),
    crypto => ProcessCrypto(crypto)
);

How .Match() works:

  1. OneOf determines which type the value currently holds

  2. It executes the corresponding handler function for that type

  3. It passes the actual value (with the correct type) to your handler

  4. It returns the result from whichever handler executed

The generic type ordering matters, especially in relation to the .Match() method and the defined handlers.

code block showing order of return types, CreditCard, Paypal and CryptoWallet, combined with the .Match method to define each handler for each type.

  • Generic typing order: If you declare OneOf<CreditCard, PayPal, CryptoWallet>, then CreditCard is T0, PayPal is T1, and CryptoWallet is T2. That order determines which handler in .Match(...) will be executed, not its type.

  • Handler parameter names are arbitrary: You can name them option1, foo, or creditCard. The name doesn’t determine the type, position does. The compiler binds the first handler to CreditCard, the second to PayPal, and third to CryptoWallet.

  • Each handler receives a strongly-typed parameter corresponding to its position. When the first handler runs, its parameter is a CreditCard object (with full IntelliSense and compile-time checks).

  • For readability, prefer meaningful names (for example, creditCard, payPal, crypto) rather than option1/2/3, as this was only for demonstration purposes.

Accessing Values

While .Match() is the recommended approach, OneOf also provides direct type checking and access, albeit quite cumbersome and not as intuitive.

OneOf<string, int> example = "hello";

// Check which type it contains
if (example.IsT0)  // Is it the first type (string)?
{
    string str = example.AsT0;  // Get it as a string
    Console.WriteLine(str);
}
else if (example.IsT1)  // Is it the second type (int)?
{
    int num = example.AsT1;  // Get it as an int
    Console.WriteLine(num);
}

You should avoid this approach in most cases for several reasons:

Firstly, you lose the compiler enforcement that makes .Match() so powerful. Want to add a third type later? The compiler won't remind you to handle it here, and your code could become brittle and be more prone to failure.

Secondly, it's verbose and cluttered. Instead of one clean .Match() call, you need multiple if-else blocks that make your code harder to read and maintain.

Thirdly, the T0, T1, T2 naming convention is positional and confusing. Which type was T0 again? You have to constantly refer back to the method signature to remember the order, which can become frustrating for yourself and development team.

Finally, it's error-prone. Nothing prevents you from forgetting to check IsT2 when dealing with three or more types.

Use .Match() whenever possible. Only resort to IsT0/AsT0 when you have a specific reason to check for just one type, and the others are irrelevant in the current code flow.

A Solution to Exception-Driven Control Flow

Many codebases overuse exceptions for control flow, making code harder to follow and debug. When you see a method call, there's no indication in the signature whether it might throw an exception or what type of errors to expect. This leads to several issues:

Hidden Control Flow:

// What can go wrong here? The signature doesn't tell you.
public User GetUser(int id)
{
    var user = _dbContext.Users.Find(id);
    if (user == null)
        throw new UserNotFoundException();  // Hidden jump in control flow!

    return user;
}

// Caller has no idea this can throw an exception
var user = _userService.GetUser(123);  // Might explode!
Console.WriteLine(user.Name);

Exceptions As Expected Outcomes

When a user enters an invalid email or a record isn't found, these aren't truly exceptional circumstances –they're expected, predictable outcomes that should be part of your normal business logic. Using exceptions for these scenarios treats routine validation as a crisis.

Performance Impact in Hot Paths

While not always significant, throwing exceptions involves stack unwinding which can be hundreds of times slower than returning a value. In tight loops or high-throughput APIs, this overhead accumulates quickly.

// Which exceptions should I catch? All of them? Specific ones?
try
{
    var user = _userService.GetUser(id);
    var order = _orderService.CreateOrder(user);
    var payment = _paymentService.ProcessPayment(order);
}
catch (Exception ex)  // Too broad? Catching things we shouldn't?
{
    // Which operation failed? Hard to tell.
    return StatusCode(500, "Something went wrong");
}

OneOf Provides a Cleaner Alternative

OneOf makes failures explicit, type-safe, and part of the method signature. When you see a method that returns OneOf<Success<T>, Failure>, you immediately know:

  1. This method can fail

  2. You must handle both success and failure cases

  3. The compiler will enforce this

The following code shows how to implement it:

// Define your result types
public record Success<T>(T Value);
public record Failure(ErrorType Type, string[] Messages);

public enum ErrorType 
{
    Validation,
    NotFound,
    Database,
    Conflict,
}

// The signature now TELLS you this can fail
public OneOf<Success<User>, Failure> GetUser(int id)
{
    try
    {
        var user = _dbContext.Users.Find(id);

        if (user == null)
            return new Failure(ErrorType.NotFound, new[] { $"User {id} not found" });

        return new Success<User>(user);
    }
    catch (DbException ex)
    {
        return new Failure(ErrorType.Database, new[] { "Database error", ex.Message });
    }
}

// Usage: Now the caller MUST handle both cases - compiler enforces it
public IActionResult GetUserEndpoint(int id)
{
    var result = _userService.GetUser(id);

    return result.Match(
        success => Ok(success.Value),
        failure => failure.Type switch
        {
            ErrorType.NotFound => NotFound(new { errors = failure.Messages }),
            ErrorType.Database => StatusCode(500, new { errors = failure.Messages }),
            ErrorType.Validation => BadRequest(new { errors = failure.Messages }),
            ErrorType.Conflict => Conflict(new { errors = failure.Messages }),
            _ => StatusCode(500, new { errors = failure.Messages })
        }
    );
}

What makes this better?

  • It’s self-documenting: The method signature explicitly states "this returns a User OR a Failure" – no hidden surprises.

  • There’s compiler-enforced handling: Forget to handle the failure case? Compilation error. The compiler won't let you ignore potential failures.

  • There’s clear intent: When you call a method returning OneOf<Success<T>, Failure>, you know immediately you need to handle both paths. No guessing about which exceptions might be thrown.

When to Still Use Exceptions:

The goal isn't to eliminate exceptions entirely, but to reserve them for truly exceptional circumstances while using OneOf for predictable, business-logic failures. You could still use exceptions in these scenarios:

  • Truly unexpected failures (out-of-memory, hardware failures)

  • Framework/library boundaries that expect exceptions

  • Constructor failures (constructors can't return Result types)

  • Third-party code contracts

Other OneOf Use Cases

Use Case 1: Polymorphic Return Types (Without Inheritance)

When you need to return different types based on logic but don't want to force inheritance:

// Different payment methods - no shared base class needed
public OneOf<CreditCardPayment, PayPalPayment, CryptoPayment> GetPaymentMethod(PaymentRequest request)
{
    return request.Method switch
    {
        "card" => new CreditCardPayment(request.CardNumber, request.CVV),
        "paypal" => new PayPalPayment(request.Email),
        "crypto" => new CryptoPayment(request.WalletAddress),
        _ => throw new ArgumentException("Unknown payment method")
    };
}
// Usage - compiler enforces handling all types
var payment = GetPaymentMethod(request);
payment.Match(
    card => ChargeCard(card),
    paypal => ProcessPayPal(paypal),
    crypto => ProcessCrypto(crypto)
);

Why this is better than inheritance:

  • No artificial base class needed

  • Each payment type can have completely different properties

  • Clear, explicit handling of each case

  • Easy to add new payment types (compiler will tell you everywhere to update)

Use Case 2: State Machines With Rich Data

Representing different states in a workflow where each state carries different information:

public class Order
{
    public OneOf<Pending, Processing, Shipped, Delivered, Cancelled> Status { get; set; }
}

public record Pending(DateTime OrderedAt);
public record Processing(DateTime StartedAt, string WarehouseId);
public record Shipped(DateTime ShippedAt, string TrackingNumber, string Carrier);
public record Delivered(DateTime DeliveredAt, string SignedBy);
public record Cancelled(DateTime CancelledAt, string Reason);

// Each state carries relevant data
var statusMessage = order.Status. Match(
    pending => $"Order placed on {pending.OrderedAt:d}",
    processing => $"Processing in warehouse {processing.WarehouseId}",
    shipped => $"Shipped via {shipped.Carrier}, tracking:  {shipped.TrackingNumber}",
    delivered => $"Delivered on {delivered.DeliveredAt:d}, signed by {delivered.SignedBy}",
    cancelled => $"Cancelled: {cancelled.Reason}"
);

Why not just use an enum?

  • Enums only store the state – they can't carry additional data

  • With OneOf, Processing knows which warehouse, and Shipped knows the tracking number offering more functionality and potential other logic to be carried out easily

  • Type-safe access to state-specific data

  • Impossible to access wrong data for a state (compiler prevents it)

Use Case 3: Multi-Channel Notifications

Sending notifications through different channels, each with different requirements:

public record EmailNotification(string To, string Subject, string Body);
public record SmsNotification(string PhoneNumber, string Message);
public record PushNotification(string DeviceToken, string Title, string Body);
public record InAppNotification(int UserId, string Message);

public async Task SendNotification(
    OneOf<EmailNotification, SmsNotification, PushNotification, InAppNotification> notification)
{
    await notification.Match(
        async email => await _emailService.SendAsync(email.To, email.Subject, email.Body),
        async sms => await _smsService.SendAsync(sms.PhoneNumber, sms.Message),
        async push => await _pushService.SendAsync(push.DeviceToken, push.Title, push.Body),
        async inApp => await _notificationRepo.CreateAsync(inApp.UserId, inApp.Message)
    );
}

// Usage
await SendNotification(new EmailNotification("user@example.com", "Welcome", "Hello! "));
await SendNotification(new SmsNotification("+1234567890", "Your code is 123456"));

Benefits:

  • Could have a single, unified notification interface

  • Each channel has exactly the parameters it needs

  • No optional/nullable properties for irrelevant fields

  • Clear routing logic

Use Case 4: File Format Handling

Handling different file types and data formats:

public record CsvData(string[] Lines);
public record JsonData(string Content);
public record ExcelData(IWorkbook Workbook);

public OneOf<CsvData, JsonData, ExcelData> LoadDataFile(string path)
{
    var extension = Path.GetExtension(path).ToLower();

    return extension switch
    {
        ". csv" => new CsvData(File.ReadAllLines(path)),
        ".json" => new JsonData(File.ReadAllText(path)),
        ".xlsx" => new ExcelData(LoadExcelFile(path)),
        _ => throw new UnsupportedFileFormatException(extension)
    };
}

// Process different formats uniformly
var data = LoadDataFile(filePath);
var records = data.Match(
    csv => ParseCsv(csv.Lines),
    json => ParseJson(json.Content),
    excel => ParseExcel(excel.Workbook)
);

This is perfect for:

  • APIs that offer multiple export formats

  • Import wizards that accept various file types

  • Configuration loaders supporting multiple formats

Key Benefits of OneOf

OneOf shines when you have:

  • Multiple valid return types that don't share a common base class

  • Different data shapes for different scenarios

  • Type-safe branching where you want the compiler to enforce handling all cases

  • Domain modeling where different states carry different information

  • Explicit outcomes that should be part of the method signature

It's essentially a way to say "this method returns A or B or C" in a type-safe way, forcing consumers to explicitly handle each possibility. This leads to more robust, self-documenting code that's harder to misuse.

Conclusion

OneOf brings the power of discriminated unions to C#, enabling more expressive and type-safe code across numerous scenarios. Whether you're modeling payment methods, order states, notification channels, or error handling, OneOf provides a clean, compiler-enforced way to handle multiple return types.

Start incorporating OneOf into your projects, and you'll find your code becomes more intentional, easier to maintain, and less error-prone.

As always, if you’ve enjoyed reading this article feel free to reach out on Twitter.



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Bringing SendGrid and Segment to Twilio.com: A More Unified Web Experience

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SendGrid and Segment are merging into Twilio.com. Learn what’s changing, what stays the same, and how a unified platform helps you build faster.
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F# Weekly #4, 2026 – F# event / (un)conference in 2026?

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Welcome to F# Weekly,

A roundup of F# content from this past week:

News

I wonder… would there be any interest in some F# event / (un)conference in 2026?I always wanted to do something similar to F# Creators Workshop (which @dsyme.bsky.social organised years ago in Cambridge) or Elm Camp (which has been for last couple of years)#fsharp

Krzysztof Cieslak (@kcieslak.io) 2026-01-21T18:53:56.833Z

Videos

Blogs

Highlighted projects

New Releases

🚀 Agent.NET has evolved significantly since the alpha.1 announcement — alpha.2 and now alpha.3 bring proper MAF execution, symmetrical InProcess/Durable workflows, and a more cohesive workflow CE with ROP built in.Full release history:github.com/JordanMarr/A…#fsharp #dotnet #aiagents

Jordan Marr (@jordanmarr.bsky.social) 2026-01-21T16:46:54.511Z

That’s all for now. Have a great week.

If you want to help keep F# Weekly going, click here to jazz me with Coffee!

Buy Me A Coffee





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