# R3 Reactive Extensions

Build reactive/event-driven C# with R3 (Cysharp's modern reimplementation of Reactive...

- Repository: https://github.com/Aaronontheweb/dotnet-skills (1244 stars)
- Category: Business
- License: MIT
- Last updated: 2026-10-28
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add Aaronontheweb/dotnet-skills --skill r3-reactive-extensions -g -a claude-code -y`
Codex: `npx skills add Aaronontheweb/dotnet-skills --skill r3-reactive-extensions -g -a codex -y`
Cursor: `npx skills add Aaronontheweb/dotnet-skills --skill r3-reactive-extensions -g -a cursor -y`
Gemini CLI: `npx skills add Aaronontheweb/dotnet-skills --skill r3-reactive-extensions -g -a gemini-cli -y`
Claude Code plugin marketplace: `/plugin marketplace add Aaronontheweb/dotnet-skills`

## Description

Build reactive/event-driven C# with R3 (Cysharp's modern reimplementation of Reactive Extensions). Covers the Observable<T>/Observer<T> model, the OnErrorResume error contract, async dispatch with AwaitOperation, Task/IAsyncEnumerable integration, TimeProvider/FrameProvider scheduling, the concurrency contract, and how R3 differs from System.Reactive (Rx.NET).

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# R3: Modern Reactive Extensions for .NET

R3 is [Cysharp's](https://github.com/Cysharp/R3) ground-up reimplementation of Reactive
Extensions, "the new future of dotnet/reactive and UniRx." It keeps the LINQ-over-events
programming model but rebuilds the core types, error contract, and scheduler to fix
long-standing problems in `System.Reactive` (Rx.NET). Use this skill when composing event
streams, UI input, timers, or push-based pipelines in C#.

**Canonical sources** (link to these from code and docs):
- Repository: https://github.com/Cysharp/R3
- README (full operator reference): https://github.com/Cysharp/R3/blob/main/README.md
- Author's design rationale: https://neuecc.medium.com/r3-a-new-modern-reimplementation-of-reactive-extensions-for-c-cf29abcc5826

## When to Use This Skill

Use this skill when:
- Composing **events** over time, UI input, sensor/feed updates, websocket messages, domain events
- You need operators like debounce, throttle, merge, combine-latest, distinct-until-changed
- Building **MVVM** state with `ReactiveProperty` / `BindableReactiveProperty`
- Bridging push-based streams with `Task` / `async` and `IAsyncEnumerable`
- Migrating from `System.Reactive`, UniRx, or `IObservable<T>` code
- You hit Rx pain points: subscriptions dying on exceptions, scheduler overhead, or leak hunting

**Not the right tool for:** request/response I/O (use `async/await`), bounded producer/consumer
with **backpressure** (use `System.Threading.Channels`), or server-side stream processing with
batching/backpressure (use Akka.NET Streams). R3, like all Rx, is **push-based with no
backpressure**. See the `csharp-concurrency-patterns` skill for choosing between these.

## Reference Files

The rest: https://github.com/Aaronontheweb/dotnet-skills/blob/HEAD/skills/r3-reactive-extensions/SKILL.md