Winui Packaging Agent Skill
MSIX packaging, code signing, and distribution for WinUI 3 apps — build for release, certificate generation (winapp cert generate), certificate trust, code signing (winapp sign), self-contained deployment, CI/CD with GitHub Actions, and Microsoft Store submission. Use when preparing for release, creating MSIX installers, managing certificates, setting up CI/CD packaging, or publishing to the Microsoft Store.
Install
one command, takes just this skill from the repositorynpx skills add https://github.com/microsoft/win-dev-skills --skill winui-packagingThe instruction itself
12 sections, as written by the authorQuick Reference
| Task | Command |
|------|---------|
| Build for release | .\BuildAndRun.ps1 /p:Configuration=Release |
| Package + sign | winapp package <dir> --cert devcert.pfx |
| Generate + sign + package | winapp package <dir> --generate-cert --install-cert |
| Generate dev certificate | winapp cert generate |
| Trust certificate (admin) | winapp cert install ./devcert.pfx |
| Sign existing file | winapp sign ./app.msix ./devcert.pfx |
| Self-contained deployment | winapp package <dir> --cert devcert.pfx --self-contained |
End-to-End Workflow
Step 1: Build for Release
Use the BuildAndRun.ps1 script from the winui-dev-workflow skill to build your app in Release configuration without launching it:
.\BuildAndRun.ps1 /p:Configuration=Release -SkipRun
Step 2: Generate Certificate (one-time)
winapp cert generate --manifest .
Creates devcert.pfx (default password: password). The --manifest flag auto-matches the Publisher field in Package.appxmanifest.
Step 3: Trust Certificate (one-time, requires admin)
winapp cert install ./devcert.pfx
Adds cert to machine Trusted Root store. Persists across reboots.
Step 4: Package and Sign
winapp package <build-output-dir> --cert ./devcert.pfx
This locates appxmanifest.xml, stages the layout, generates resources.pri, creates .msix, and signs it.
Step 5: Install or Distribute
# Local install
Add-AppxPackage ./MyApp.msix
# Or double-click the .msix file
Key Rules
- Publisher must match between certificate and manifest
Identity.Publisher— usewinapp cert generate --manifestto auto-match - Prefer
winapp package --certover separatewinapp sign— one step instead of two cert installrequires admin — run terminal as Administrator- Default PFX password is
password— override with--password --timestampis critical for production — without it, signatures expire with the cert:
winapp package <dir> --cert prod.pfx --timestamp http://timestamp.digicert.com
--self-containedbundles Windows App SDK runtime — larger but no runtime dependency
CI/CD with GitHub Actions
name: Build and Package
on: [push]
jobs:
build:
runs-on: windows-latest
steps:
- uses: actions/checkout@v4
- uses: microsoft/[email protected]
- name: Build
run: dotnet build -c Release -p:Platform=x64
- name: Package
run: |
winapp cert generate --if-exists skip --quiet
winapp package ./bin/x64/Release/ --cert ./devcert.pfx --quiet
- name: Upload artifact
uses: actions/upload-artifact@v4
with:
name: msix-package
path: "*.msix"
CI/CD tips:
- Use
--quietfor clean output - Use
--if-exists skipwithcert generateto avoid failures on re-runs - Store production PFX as a repository secret
Store Submission
- Partner Center account — register at partner.microsoft.com
- Age ratings — complete the questionnaire in Partner Center
- Screenshots — capture at 1366x768 minimum resolution
- Privacy policy — required for apps that access internet or user data
- Submit: upload the signed
.msix/.msixbundleproduced bywinapp packagevia Microsoft Partner Center — Apps and games → your app → Packages. Microsoft Store submission is browser-based; there is no first-party CLI submit command yet.
Troubleshooting
| Error | Solution |
|-------|----------|
| "Publisher mismatch" | Run winapp cert generate --manifest to re-generate |
| "Certificate not trusted" | Run winapp cert install ./devcert.pfx as admin |
| "Access denied" | cert install needs admin elevation |
| "Certificate file already exists" | Use --if-exists overwrite or --if-exists skip |
| "appxmanifest.xml not found" | Run winapp init or pass --manifest <path> |
| "Package installation failed" | Trust cert first; remove stale: Get-AppxPackage <name> \| Remove-AppxPackage |
| Signature invalid after time | Re-sign with --timestamp |
References
| File | Read when... |
|------|-------------|
| references/sourcegen-patterns.md | Setting up AOT/trimming, JSON source generators, NativeAOT readiness, CsWin32 |
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How to use it
Take microsoft/winui-packaging from the repository into ~/.claude/skills for personal
use, or into .claude/skills inside a project.
The agent identifies a skill by the name field in its header. Two skills with the
same name cannot sit side by side — one of them will be ignored.