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Creating a Phi Silica addon for Electron

This guide shows you how to create a C# native addon that uses the Phi Silica AI model to summarize text on-device in your Electron app. Phi Silica is a small language model that runs locally on Windows 11 devices with NPUs.

Prerequisites

Note

Phi Silica requires a Copilot+ PC with NPU support. The API will return an error on devices without NPU support.

Step 1: Create a C# native addon

npx winapp node create-addon --template cs --name csAddon

This creates a csAddon/ folder with:

  • addon.cs - Your C# code that will call Windows APIs
  • csAddon.csproj - Project file with references to Windows SDK and Windows App SDK
  • README.md - Documentation

The command also adds a build-addon script to your package.json.

Build the addon:

npm run build-addon

Step 2: Add Phi Silica code

Open csAddon/addon.cs and add the Phi Silica summarization code:

using Microsoft.JavaScript.NodeApi;
using Microsoft.Windows.AI.Generative;

namespace CsAddon;

[JSExport]
public static class Addon
{
    public static async Task<string> SummarizeText(string text)
    {
        var session = await LanguageModel.CreateAsync();
        var result = await session.GenerateResponseAsync($"Summarize: {text}");
        return result.Response;
    }
}

Step 3: Build the addon

npm run build-addon

This compiles your C# code using Native AOT (Ahead-of-Time compilation), which creates a .node binary that requires no .NET runtime on target machines.

Step 4: Test the addon

Open src/index.js and load the addon:

const csAddon = require('../csAddon/dist/csAddon.node');

Add a test function:

const callPhiSilica = async () => {
  console.log('Summarizing with Phi Silica: ')
  const result = await csAddon.Addon.summarizeText("The Windows App Development CLI is a powerful tool that bridges cross-platform development with Windows-native capabilities.");
  console.log('Summary:', result);
};

Call it in createWindow():

callPhiSilica();

Step 5: Add required capability

Open appxmanifest.xml and add the systemAIModels capability:

<Capabilities>
  <rescap:Capability Name="runFullTrust" />
  <rescap:Capability Name="systemAIModels" />
</Capabilities>

Step 6: Update debug identity

After modifying appxmanifest.xml, update the debug identity:

npx winapp node add-electron-debug-identity

Run the app:

npm start

Check the console output for the Phi Silica summary.

Note

There is a known Windows bug with sparse packaging Electron applications that can cause crashes or blank windows. See the setup guide for the workaround.

Next steps

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