# F# Weekly #20, 2026 - .NET 11 Preview 4 and SwaggerProvider 4.0

**URL:** <https://forums.fsharp.org/t/f-weekly-20-2026-net-11-preview-4-and-swaggerprovider-4-0/5127>\
**Category:** General\
**Created:** [May 16, 2026, 6:30pm UTC](https://forums.fsharp.org/t/f-weekly-20-2026-net-11-preview-4-and-swaggerprovider-4-0/5127 "2026-05-16T18:30:40Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![sergey\_tihon](https://yyz2.discourse-cdn.com/flex030/user_avatar/forums.fsharp.org/sergey_tihon/32/25_2.png) [@sergey\_tihon](https://forums.fsharp.org/u/sergey_tihon)\
**Post date:** [May 16, 2026, 6:30pm UTC](https://forums.fsharp.org/t/f-weekly-20-2026-net-11-preview-4-and-swaggerprovider-4-0/5127/1 "2026-05-16T18:30:40Z")

</div>

Welcome to F# Weekly,

A roundup of F# content from this past week:

**News**

- [[System.Text.Json] now understands F# discriminated unions out of the box](https://github.com/dotnet/core/blob/main/release-notes/11.0/preview/preview4/libraries.md#systemtextjson-improvements)
- [SwaggerProvider v4.0.0](https://fsprojects.github.io/SwaggerProvider/)

> **[Jon Sagara (@jonsagara.com)](https://bsky.app/profile/jonsagara.com/post/3mlqmshzs3c2m)**
>
> "\[System.Text.Json\] now understands F# discriminated unions out of the box" https://github.com/dotnet/core/blob/main/release-notes/11.0/preview/preview4/libraries.md#systemtextjson-improvements

**Microsoft News**

- [.NET 11 Preview 4 is now available!](https://devblogs.microsoft.com/dotnet/dotnet-11-preview-4/)
- [.NET and .NET Framework May 2026 servicing releases updates](https://devblogs.microsoft.com/dotnet/dotnet-and-dotnet-framework-may-2026-servicing-updates/)
- [Process API Improvements in .NET 11](https://devblogs.microsoft.com/dotnet/process-api-improvements-in-dotnet-11/)
- [.NET MAUI Moves to CoreCLR in .NET 11](https://devblogs.microsoft.com/dotnet/dotnet-maui-moves-to-coreclr-in-dotnet-11/)
- [From beta to stable: Announcing the Azure SDK for Rust 🎉🦀 - Azure SDK Blog](https://devblogs.microsoft.com/azure-sdk/from-beta-to-stable-announcing-the-azure-sdk-for-rust-ga/)
- [WebAssembly Data Processing at the Edge with Azure IoT Operations - ISE Developer Blog](https://devblogs.microsoft.com/ise/wasm-edge-data-processing/)
- [Visual Studio Code 1.120](https://code.visualstudio.com/updates/v1_120) with Agents window
- [Agent Skills in Visual Studio: Teach Copilot How Your Team Works - Visual Studio Blog](https://devblogs.microsoft.com/visualstudio/agent-skills-in-visual-studio/)
- [Introducing WinUI agent plugin for GitHub Copilot and Claude Code - #ifdef Windows](https://devblogs.microsoft.com/ifdef-windows/build-native-windows-apps-with-ai-agents-for-winui-and-windows-app-sdk/)

**Videos**

- [Yapping about GUIs, F# and Lisp](https://www.youtube.com/watch?v=e0gAJ7rgROU&t=2s)
- [Blazor Community Standup: E2E Component Testing for Blazor](https://www.youtube.com/watch?v=C1e1_7G1VaE)

**Blogs**

- [ragingHungryPanda: Shared Postgres Test Container with Expecto in F#](https://blog.keyboardvagabond.com/programming/shared-postgres-test-container-with-expecto-in-fsharp)
- [brandewinder: Computing lighting and shadows of mountains from above in F#](https://hachyderm.io/@brandewinder/116548190004590128)
- [Event Sourcing: compensation – the simple way out when things go wrong – planetgeek.ch](https://www.planetgeek.ch/2026/05/12/event-sourcing-compensation-the-simple-way-out-when-things-go-wrong/)

**Highlighted projects**

- [Azizs2162/fyper](https://github.com/Azizs2162/fyper) — Build type-safe Cypher queries in F# with plain records, query expressions, and automatic parameterization
- [agentruntimecontrolprotocol/fsharp-sdk](https://github.com/agentruntimecontrolprotocol/fsharp-sdk) — F# / .NET reference SDK for ARCP (Agent Runtime Control Protocol) with durable execution and human-in-the-loop support
- [MagnusOpera/FScript](https://github.com/MagnusOpera/FScript) — Functional language interpreter inspired by F#/ML, with type inference and LSP support
- [goswinr/Euclid](https://github.com/goswinr/Euclid) — A 2D and 3D geometry library for F# (and JavaScript via Fable)
- [elekvk/FocusQuest](https://github.com/elekvk/FocusQuest) — Gamified productivity web app built with F#, Bolero and ASP.NET Core

**New Releases**

- [FSharp.Data 8.1.14](https://www.nuget.org/packages/FSharp.Data/8.1.14)
- [FSharp.Compiler.Service 43.12.204](https://www.nuget.org/packages/FSharp.Compiler.Service)
- [WebSharper 10.1.4.673](https://www.nuget.org/packages/WebSharper)
- [Feliz 3.3.2](https://www.nuget.org/packages/Feliz)
- [Feliz.UseElmish 5.0.0](https://www.nuget.org/packages/Feliz.UseElmish)
- [Feliz.CompilerPlugins 3.2.0](https://www.nuget.org/packages/Feliz.CompilerPlugins)
- [SwaggerProvider 4.0.0](https://www.nuget.org/packages/SwaggerProvider)
- [SageFs 0.6.273](https://www.nuget.org/packages/SageFs)
- [FSharp.Formatting 22.0.1](https://www.nuget.org/packages/FSharp.Formatting)
- [fsdocs-tool 22.0.1](https://www.nuget.org/packages/fsdocs-tool)
- [RProvider 3.0.0](https://www.nuget.org/packages/RProvider)
- [FSharp.Idioms 1.5.10](https://www.nuget.org/packages/FSharp.Idioms)

> **[Sergey Tihon 🦔🦀 (@sergeytihon.com)](https://bsky.app/profile/sergeytihon.com/post/3mlyhvesyvk2a)**
>
> SwaggerProvider v4.0.0 is live! 🎉 #fsharp
> 
> Overhauled for speed, cleaner code gen, and better developer ergonomics.
> ⚡ Blazing fast zero-allocation hot paths
> 📅 Native DateOnly & TimeOnly support
> 📝 Richer IDE docs via inline XmlDoc
> ⚠️ Breaking: Legacy...

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

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