winui-setup

Purpose

Install and verify the prerequisites every other winui-* skill assumes. WinApp CLI 0.7 owns WinUI template discovery and installation through winapp new; do not install the template pack separately. The project's target framework may require a newer .NET SDK than the CLI's minimum.

[!IMPORTANT] Install per-user prerequisites (WinApp CLI) without asking, and tell the user what changed. Ask before anything that needs admin rights (UAC) or a large toolchain — the .NET SDK, Developer Mode, and Native AOT build tools. Windows Sandbox enablement is the user's to do.

This skill is idempotent: detect everything first, install or upgrade only what is needed, and print one final summary.

Steps

Detect everything

Run these checks together so the user sees the full state before anything changes:

$minimumDotNet = [version]'8.0.100'
$minimumWinApp = [version]'0.7.0'

# .NET SDK — project-mode winapp run requires SDK 8.0.100+
$dotnetSdks = @(& dotnet --list-sdks 2>$null) | ForEach-Object {
    $text = ($_ -replace ' \[.*$','').Trim()
    $parsed = $null
    if ([version]::TryParse(($text -split '-')[0], [ref]$parsed)) { $parsed }
}
$dotnetVersion = $dotnetSdks |
    Where-Object { $_ -ge $minimumDotNet } |
    Sort-Object -Descending |
    Select-Object -First 1
$dotnetOk = $null -ne $dotnetVersion

# WinApp CLI — require released 0.7+ for the migrated workflows
$winappCmd = Get-Command winapp -ErrorAction SilentlyContinue
$winappVersion = $null
$winappPrerelease = $false
if ($winappCmd) {
    foreach ($line in @(& winapp --version 2>$null)) {
        $match = [regex]::Match(
            [string]$line,
            '^\s*v?(?<version>\d+\.\d+\.\d+)(?:-(?<prerelease>[0-9A-Za-z.-]+))?(?:\+[0-9A-Za-z.-]+)?\s*$'
        )
        if ($match.Success) {
            $parsed = $null
            if ([version]::TryParse($match.Groups['version'].Value, [ref]$parsed)) {
                $winappVersion = $parsed
                $winappPrerelease = $match.Groups['prerelease'].Success
            }
        }
    }
}
$winappOk = ($winappVersion -ge $minimumWinApp) -and -not $winappPrerelease

# Developer Mode
$devModeOk = ((Get-ItemProperty `
    -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock' `
    -Name AllowDevelopmentWithoutDevLicense -ErrorAction SilentlyContinue
).AllowDevelopmentWithoutDevLicense) -eq 1

Print a one-shot status table:

.NET SDK >= 8.0.100     [OK] found 10.0.100
WinApp CLI >= 0.7.0     [!] found 0.6.0 — will upgrade
Developer Mode          [X] disabled — needs admin to enable

Install what's missing

.NET SDK (ask first)

The SDK installer is machine-wide and triggers UAC. Ask the user first. When they agree and no SDK at or above 8.0.100 was found, install the recommended SDK:

winget install --id Microsoft.DotNet.SDK.10 --exact --silent --accept-package-agreements --accept-source-agreements

Do not install another SDK when one already satisfies both the CLI minimum and the requested project's target framework / global.json. The CLI's minimum does not let an 8.x SDK build a net10.0-windows app. If the base check passed but the requested project needs another SDK, report that requirement and offer to install its matching SDK rather than declaring the project ready. If the user declines, print the command for later use.

WinApp CLI (no admin needed)

WinApp CLI is a per-user MSIX package, so install or upgrade it without asking and tell the user what changed. If winapp is missing, install it. If it is below released 0.7.0, upgrade it. Skip both when the installed version already meets the minimum:

# When winapp is missing
winget install --id Microsoft.WinAppCli --exact --silent --accept-package-agreements --accept-source-agreements

# When winapp does not meet the released 0.7.0 minimum
winget upgrade --id Microsoft.WinAppCli --exact --silent --accept-package-agreements --accept-source-agreements

Refresh PATH after any winget install or upgrade:

$env:Path = [Environment]::GetEnvironmentVariable('Path','Machine') + ';' +
            [Environment]::GetEnvironmentVariable('Path','User')

Run the version detection again. If a released 0.7.0 or later is still unavailable, report the actual version and mark setup blocked; do not fall back to older commands. A prerelease doesn't meet the requirement unless the user asks for preview validation.

Developer Mode (ask first)

Developer Mode requires admin elevation. Ask the user before triggering UAC. Only if they agree, elevate this one operation:

Start-Process powershell -Verb RunAs -ArgumentList @(
    '-NoProfile','-Command',
    "New-Item -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock' -Force | Out-Null; " +
    "Set-ItemProperty -Path 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\AppModelUnlock' " +
    "-Name AllowDevelopmentWithoutDevLicense -Type DWord -Value 1"
) -Wait

If the user declines or dismisses UAC, continue to the summary and print the command for later use.

Additional requirements for the requested workflow

Report these separately from the base toolchain. winapp target snapshot sandbox --json inspects an existing guest without starting or repairing it; "no target running" alone does not mean the Windows feature is unavailable. winui-ui-testing Step 1 defines what to do when Windows Sandbox is unavailable.

Enabling Windows Sandbox is a user action (admin plus a reboot): ask the user to open Turn Windows features on or off, select Windows Sandbox, and restart if prompted. Hardware virtualization must be enabled; a VM may also require nested virtualization. See Microsoft's supported editions and installation steps.

Final summary

Always print a single summary:

==== winui-setup summary ====
.NET SDK >= 8.0.100     [>] already present (10.0.100)
WinApp CLI >= 0.7.0     [OK] upgraded to 0.7.0
Developer Mode          [OK] enabled

Only report readiness for the workflows whose requirements passed. If the current harness exposes the winui-dev orchestrator agent, start a fresh session with that agent and ask it to build a WinUI app. Otherwise, start a fresh session in the current harness and ask it to perform the WinUI task; it will load the relevant winui-* skills on demand.

For GitHub Copilot CLI, for example:

copilot --agent winui:winui-dev -p "build me a WinUI 3 markdown editor"

Things to NOT do

• Do not install Visual Studio; it is optional. Native AOT needs only the MSVC C++ build tools, a separate, explicitly approved setup.
• Do not install or upgrade the user's AI coding harness; this skill manages Windows/WinUI development prerequisites only.
• Do not elevate the entire session; request elevation only for the specific approved setup operation.
• Do not silently retry failed installs.