uno-platform

A guide to Uno Platform, a .NET framework for building apps for Windows, phones, macOS, Linux, and browsers from shared C# and XAML code. It covers platform-specific behavior, rendering choices, and common application patterns.

In plain words
What is it for?
Use it when starting or migrating a cross-platform app, building shared XAML interfaces, supporting WebAssembly or mobile targets, or adapting Windows UI code to other platforms.
Why use it?
It helps developers share most of an app across several operating systems while accounting for differences in rendering and native platform APIs.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/managedcode/dotnet-skills/uno-platform
Any agent
npx skills add managedcode/dotnet-skills --skill uno-platform
Clone the repo
git clone --depth 1 https://github.com/managedcode/dotnet-skills

Made for: Claude Code, Codex.

Per session 129 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,820 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00129 $0.01820
Opus 5 $0.00064 $0.00910
Sonnet 5 $0.00026 $0.00364
Haiku 4.5 $0.00013 $0.00182

Measured 2d ago against content hash 9652a051deaf, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

uno-platform scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

catalog/Frameworks/Uno-Platform/skills/uno-platform/SKILL.md · 256 lines

How it starts

The opening of the file, as written. The whole thing — 256 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Uno Platform

Trigger On

  • building cross-platform apps from a single C# and XAML codebase
  • targeting WebAssembly, iOS, Android, macOS, Linux, and Windows simultaneously
  • migrating WPF or UWP applications to cross-platform
  • implementing pixel-perfect UI across all platforms
  • using WinUI/UWP APIs on non-Windows platforms

Documentation

References

See detailed examples in the references/ folder:

  • patterns.md — MVUX, XAML, navigation, and performance patterns

Platform Support

Platform Rendering Notes
Windows WinUI 3 Native Windows App SDK
WebAssembly Skia/Canvas Runs in browser
iOS Skia/Metal Native iOS app
Android Skia/OpenGL Native Android app
macOS Skia/Metal Mac Catalyst or AppKit
Linux Skia/X11 GTK or Framebuffer

Workflow

  1. Choose the right template — Uno Platform offers various templates for different scenarios
  2. Understand rendering modes — Skia vs native rendering affects performance and fidelity
  3. Apply MVVM or MVUX patterns — keep views dumb, logic in ViewModels
  4. Handle platform differences — use conditional XAML or partial classes
  5. Test on all target platforms — behavior varies across platforms

Project Structure

MyApp/
├── MyApp/                    # Shared code
│   ├── App.xaml              # Application entry
│   ├── MainPage.xaml         # Main page
│   ├── Presentation/         # ViewModels (MVUX/MVVM)
│   ├── Business/             # Business logic
│   └── Services/             # Platform services
├── MyApp.Wasm/               # WebAssembly head
├── MyApp.Mobile/             # iOS and Android head
├── MyApp.Skia.Gtk/           # Linux head
├── MyApp.Skia.WPF/           # Windows Skia head
└── MyApp.Windows/            # Native WinUI head

Read the full file on GitHub · 256 lines

Files

What ships with it

2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 256 lines · 129 tokens per session scan A 9652a051deaf

Subscribe to this mod's changes

uno-platform is a skill published in the GitHub repository managedcode/dotnet-skills (477 stars, last pushed 2d ago), licensed MIT. It adds 129 tokens to every session and 1,820 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.