The "Show preview" setting (`ShowCustomPreview`) controls whether AI-generated results are displayed in a preview window before pasting. **The preview feature does not consume additional AI credits**—the preview displays the same AI response that was already generated, cached locally from a single API call.
The implementation flow:
1. User initiates "Paste with AI" action
2. A single AI API call is made via `ExecutePasteFormatAsync`
3. The result is cached in `GeneratedResponses`
4. If preview is enabled, the cached result is displayed in the preview UI
5. User can paste the cached result without any additional API calls
See the `ExecutePasteFormatAsync(PasteFormat, PasteActionSource)` method in `OptionsViewModel.cs` for the implementation.
Advanced Paste is an unpackaged, self-contained WinUI 3 app (`PowerToys.AdvancedPaste.exe`). To call Windows AI APIs (Phi Silica / `Microsoft.Windows.AI.Text.LanguageModel`) it acquires **package identity** at runtime via a shared sparse MSIX package (`Microsoft.PowerToys.SparseApp`).
### Running and attaching the debugger
1. Set the **Runner** project (`src/runner`) as the startup project in Visual Studio.
2. Launch the Runner (F5). This starts the PowerToys tray icon and loads all module interfaces.
3. Open Settings (right-click tray icon → Settings) and enable the **Advanced Paste** module if it isn't already. The module launches `PowerToys.AdvancedPaste.exe` in the background immediately.
4. In Visual Studio, go to **Debug → Attach to Process** (`Ctrl+Alt+P`) and attach to `PowerToys.AdvancedPaste.exe` (select **Managed (.NET Core)** debugger).
Alternatively, use the VS Code launch configuration **"Run AdvancedPaste"** from [.vscode/launch.json](/.vscode/launch.json) to launch the exe directly — but note that without the Runner, IPC and hotkeys won't work.
### Sparse package identity (local development)
#### Why is this needed?
- The `LanguageModel` API requires a Limited Access Feature (LAF) unlock, which only succeeds when the calling process has a matching package identity.
- Advanced Paste is an unpackaged, self-contained WinUI 3 app. The sparse package grants it identity without converting it to a full MSIX.
- The csproj uses `<ProjectPriFileName>PowerToys.AdvancedPaste.pri</ProjectPriFileName>` (matching the convention of other WinUI3 apps like ImageResizer). This requires WindowsAppSDK Foundation >= 2.0.22 ([PR #6376](https://github.com/microsoft/WindowsAppSDK/pull/6376)) which fixes MRT PRI lookup under sparse identity so `Application.LoadComponent` resolves custom-named PRI files instead of hard-coding `resources.pri`.
1. Generates a dev certificate under `src/PackageIdentity/.user/` (first run only).
2. Auto-imports that certificate into `CurrentUser\TrustedPeople` and `CurrentUser\Root` so the OS grants sparse identity to AP (without trust, `GetPackageFamilyName` returns `APPMODEL_ERROR_NO_PACKAGE` and LAF unlock silently fails).
3. Removes any prior registration.
4. Rewrites the publisher in a temp copy of `AppxManifest.xml` to match the dev cert subject.
5. Registers via `Add-AppxPackage -Register … -ExternalLocation X:\…\<Platform>\<Config>\WinUI3Apps`.
Re-register after rebuilding AP, changing `src/PackageIdentity/AppxManifest.xml`, or switching platforms/configurations by re-running the same command. Unregister with `-Unregister`.
#### Troubleshooting
| Problem | Cause | Fix |
|---------|-------|-----|
| `GetPackageFamilyName` returns `APPMODEL_ERROR_NO_PACKAGE` (15700) at runtime; LAF unlock returns `Unavailable` | Dev certificate not trusted (or sparse package not registered) | Re-run `BuildSparsePackage.ps1 -DevRegister` — auto-imports the cert into `TrustedPeople` and `Root`. |
| `Microsoft.UI.Xaml.dll` crash with `0xC000027B` (class-not-registered) on AP or Settings startup | `<Application>``Executable` path in `src/PackageIdentity/AppxManifest.xml` does not resolve under the registered `ExternalLocation` (`<Config>\WinUI3Apps\`) | Confirm every `Executable` is relative to `WinUI3Apps\` (per #47177) and the file exists under the build output. |
| AP launches but never shows a window when triggered via hotkey | Runner's pipe-server wait timed out before AP's cold-start finished bootstrapping WinAppSDK + DI host | Already mitigated by the 15 s pipe timeout in `AdvancedPasteProcessManager.cpp`; warm-start launches connect in well under 1 s. |
| `XamlParseException` / `ms-appx:///Microsoft.UI.Xaml/Themes/…` not found | WindowsAppSDK Foundation < 2.0.22; MRT can't resolve custom PRI name under sparse identity | Ensure `Microsoft.WindowsAppSDK.Foundation` >= 2.0.22 in `Directory.Packages.props`. |
### How Settings UI checks Phi Silica availability
Settings UI does not have sparse package identity. To check whether Phi Silica is available, it launches Advanced Paste as a short-lived subprocess:
```
PowerToys.AdvancedPaste.exe --check-phi-silica
```
`Program.Main` recognizes this flag, calls `PhiSilicaLafHelper.TryUnlock()` + `LanguageModel.GetReadyState()`, prints one of `Available` / `NotReady` / `NotSupported` to stdout, and exits with the matching code (0/1/2). Settings reads stdout with a 10 s wait. Because each call is a fresh process, transient `Unavailable` results are not cached across checks.
### See also
- [Phi Silica local testing & troubleshooting guide](advancedpaste-phisilica-local-testing.md) — layer-by-layer diagnostics for Phi Silica availability
- [`src/PackageIdentity/readme.md`](/src/PackageIdentity/readme.md) — full sparse package documentation
- [microsoft/microsoft-ui-xaml#10856](https://github.com/microsoft/microsoft-ui-xaml/issues/10856) — original WinUI sparse-identity PRI bug
- [microsoft/WindowsAppSDK#6376](https://github.com/microsoft/WindowsAppSDK/pull/6376) — MRT sparse PRI fix (Foundation >= 2.0.22)
