Read before writing or changing WinUI 3 XAML: choosing controls, pages and navigation, layout, Fluent Design, theming, accessibility, x:Bind, real samples, and checking that APIs exist with winapp find-api. Not for WPF or WinForms UI, even if the app uses the Windows App SDK.
Install
npx skills add microsoft/winappCli --skill winui-designnpx skills add microsoft/winappCli --skill winui-design -a claude-code -gnpx skills add microsoft/winappCli --skill winui-design -a codex -ggemini skills install https://github.com/microsoft/winappCli.git --path plugins/winui/agent-plugin/skills/winui-designgh skill install microsoft/winappCli winui-designgit clone --depth 1 https://github.com/microsoft/winappCli /tmp/microsoft__winappCli
mkdir -p ~/.claude/skills ~/.agents/skills
cp -R /tmp/microsoft__winappCli/plugins/winui/agent-plugin/skills/winui-design ~/.claude/skills/winui-design # Claude Code
cp -R /tmp/microsoft__winappCli/plugins/winui/agent-plugin/skills/winui-design ~/.agents/skills/winui-design # Codex, Cursor, Gemini CLI, Copilot, OpenCode