Add trace and logs

.github/actions/spell-check/expect.txt

@@ -886,7 +886,6 @@ Ldr
 LEFTALIGN
 LEFTSCROLLBAR
 LEFTTEXT
-leftclick
 LError
 LEVELID
 LExit
@@ -1012,7 +1011,6 @@ MENUITEMINFO
 MENUITEMINFOW
 MERGECOPY
 MERGEPAINT
-Metacharacter
 metadatamatters
 Metadatas
 metafile

.github/instructions/common-libraries.instructions.md

@@ -1,61 +0,0 @@
----
-description: 'Guidelines for shared libraries including logging, IPC, settings, DPI, telemetry, and utilities consumed by multiple modules'
-applyTo: 'src/common/**'
----
-
-# Common Libraries – Shared Code Guidance
-
-Guidelines for modifying shared code in `src/common/`. Changes here can have wide-reaching impact across the entire PowerToys codebase.
-
-## Scope
-
-- Logging infrastructure (`src/common/logger/`)
-- IPC primitives and named pipe utilities
-- Settings serialization and management
-- DPI awareness and scaling utilities
-- Telemetry helpers
-- General utilities (JSON parsing, string helpers, etc.)
-
-## Guidelines
-
-### API Stability
-
-- Avoid breaking public headers/APIs; if changed, search & update all callers
-- Coordinate ABI-impacting struct/class layout changes; keep binary compatibility
-- When modifying public interfaces, grep the entire codebase for usages
-
-### Performance
-
-- Watch perf in hot paths (hooks, timers, serialization)
-- Avoid avoidable allocations in frequently called code
-- Profile changes that touch performance-sensitive areas
-
-### Dependencies
-
-- Ask before adding third-party deps or changing serialization formats
-- New dependencies must be MIT-licensed or approved by PM team
-- Add any new external packages to `NOTICE.md`
-
-### Logging
-
-- C++ logging uses spdlog (`Logger::info`, `Logger::warn`, `Logger::error`, `Logger::debug`)
-- Initialize with `init_logger()` early in startup
-- Keep hot paths quiet – no logging in tight loops or hooks
-
-## Acceptance Criteria
-
-- No unintended ABI breaks
-- No noisy logs in hot paths
-- New non-obvious symbols briefly commented
-- All callers updated when interfaces change
-
-## Code Style
-
-- **C++**: Follow `.clang-format` in `src/`; use Modern C++ patterns per C++ Core Guidelines
-- **C#**: Follow `src/.editorconfig`; enforce StyleCop.Analyzers
-
-## Validation
-
-- Build: `tools\build\build.cmd` from `src/common/` folder
-- Verify no ABI breaks: grep for changed function/struct names across codebase
-- Check logs: ensure no new logging in performance-critical paths

.github/instructions/runner-settings-ui.instructions.md

@@ -1,68 +0,0 @@
----
-description: 'Guidelines for Runner and Settings UI components that communicate via named pipes and manage module lifecycle'
-applyTo: 'src/runner/**,src/settings-ui/**'
----
-
-# Runner & Settings UI – Core Components Guidance
-
-Guidelines for modifying the Runner (tray/module loader) and Settings UI (configuration app). These components communicate via Windows Named Pipes using JSON messages.
-
-## Runner (`src/runner/`)
-
-### Scope
-
-- Module bootstrap, hotkey management, settings bridge, update/elevation handling
-
-### Guidelines
-
-- If IPC/JSON contracts change, mirror updates in `src/settings-ui/**`
-- Keep module discovery in `src/runner/main.cpp` in sync when adding/removing modules
-- Keep startup lean: avoid blocking/network calls in early init path
-- Preserve GPO & elevation behaviors; confirm no regression in policy handling
-- Ask before modifying update workflow or elevation logic
-
-### Acceptance Criteria
-
-- Stable startup, consistent contracts, no unnecessary logging noise
-
-## Settings UI (`src/settings-ui/`)
-
-### Scope
-
-- WinUI/WPF UI, communicates with Runner over named pipes; manages persisted settings schema
-
-### Guidelines
-
-- Don't break settings schema silently; add migration when shape changes
-- If IPC/JSON contracts change, align with `src/runner/**` implementation
-- Keep UI responsive: marshal to UI thread for UI-bound operations
-- Reuse existing styles/resources; avoid duplicate theme keys
-- Add/adjust migration or serialization tests when changing persisted settings
-
-### Acceptance Criteria
-
-- Schema integrity preserved, responsive UI, consistent contracts, no style duplication
-
-## Shared Concerns
-
-### IPC Contract Changes
-
-When modifying the JSON message format between Runner and Settings UI:
-
-1. Update both `src/runner/` and `src/settings-ui/` in the same PR
-2. Preserve backward compatibility where possible
-3. Add migration logic for settings schema changes
-4. Test both directions of communication
-
-### Code Style
-
-- **C++ (Runner)**: Follow `.clang-format` in `src/`
-- **C# (Settings UI)**: Follow `src/.editorconfig`, use StyleCop.Analyzers
-- **XAML**: Use XamlStyler or run `.\.pipelines\applyXamlStyling.ps1 -Main`
-
-## Validation
-
-- Build Runner: `tools\build\build.cmd` from `src/runner/`
-- Build Settings UI: `tools\build\build.cmd` from `src/settings-ui/`
-- Test IPC: Launch both Runner and Settings UI, verify communication works
-- Schema changes: Run serialization tests if settings shape changed

AGENTS.md

@@ -1,165 +0,0 @@
----
-description: 'Top-level AI contributor guidance for developing PowerToys - a collection of Windows productivity utilities'
-applyTo: '**'
----
-
-# PowerToys – AI Contributor Guide
-
-This is the top-level guidance for AI contributions to PowerToys. Keep changes atomic, follow existing patterns, and cite exact paths in PRs.
-
-## Overview
-
-PowerToys is a set of utilities for power users to tune and streamline their Windows experience.
-
-| Area | Location | Description |
-|------|----------|-------------|
-| Runner | `src/runner/` | Main executable, tray icon, module loader, hotkey management |
-| Settings UI | `src/settings-ui/` | WinUI/WPF configuration app communicating via named pipes |
-| Modules | `src/modules/` | Individual PowerToys utilities (each in its own subfolder) |
-| Common Libraries | `src/common/` | Shared code: logging, IPC, settings, DPI, telemetry, utilities |
-| Build Tools | `tools/build/` | Build scripts and automation |
-| Documentation | `doc/devdocs/` | Developer documentation |
-| Installer | `installer/` | WiX-based installer projects |
-
-For architecture details and module types, see [Architecture Overview](doc/devdocs/core/architecture.md).
-
-## Conventions
-
-For detailed coding conventions, see:
-- [Coding Guidelines](doc/devdocs/development/guidelines.md) – Dependencies, testing, PR management
-- [Coding Style](doc/devdocs/development/style.md) – Formatting, C++/C#/XAML style rules
-- [Logging](doc/devdocs/development/logging.md) – C++ spdlog and C# Logger usage
-
-### Component-Specific Instructions
-
-These instruction files are automatically applied when working in their respective areas:
-- [Runner & Settings UI](.github/instructions/runner-settings-ui.instructions.md) – IPC contracts, schema migrations
-- [Common Libraries](.github/instructions/common-libraries.instructions.md) – ABI stability, shared code guidelines
-
-## Build
-
-### Prerequisites
-
-- Visual Studio 2022 17.4+
-- Windows 10 1803+ (April 2018 Update or newer)
-- Initialize submodules once: `git submodule update --init --recursive`
-
-### Build Commands
-
-| Task | Command |
-|------|---------|
-| First build / NuGet restore | `tools\build\build-essentials.cmd` |
-| Build current folder | `tools\build\build.cmd` |
-| Build with options | `build.ps1 -Platform x64 -Configuration Release` |
-
-### Build Discipline
-
-1. One terminal per operation (build → test). Do not switch or open new ones mid-flow
-2. After making changes, `cd` to the project folder that changed (`.csproj`/`.vcxproj`)
-3. Use scripts to build: `tools/build/build.ps1` or `tools/build/build.cmd`
-4. For first build or missing NuGet packages, run `build-essentials.cmd` first
-5. **Exit code 0 = success; non-zero = failure** – treat this as absolute
-6. On failure, read the errors log: `build.<config>.<platform>.errors.log`
-7. Do not start tests or launch Runner until the build succeeds
-
-### Build Logs
-
-Located next to the solution/project being built:
-- `build.<configuration>.<platform>.errors.log` – errors only (check this first)
-- `build.<configuration>.<platform>.all.log` – full log
-- `build.<configuration>.<platform>.trace.binlog` – for MSBuild Structured Log Viewer
-
-For complete details, see [Build Guidelines](tools/build/BUILD-GUIDELINES.md).
-
-## Tests
-
-### Test Discovery
-
-- Find test projects by product code prefix (e.g., `FancyZones`, `AdvancedPaste`)
-- Look for sibling folders or 1-2 levels up named `<Product>*UnitTests` or `<Product>*UITests`
-
-### Running Tests
-
-1. **Build the test project first**, wait for exit code 0
-2. Run via VS Test Explorer (`Ctrl+E, T`) or `vstest.console.exe` with filters
-3. **Avoid `dotnet test`** in this repo – use VS Test Explorer or vstest.console.exe
-
-### Test Types
-
-| Type | Requirements | Setup |
-|------|--------------|-------|
-| Unit Tests | Standard dev environment | None |
-| UI Tests | WinAppDriver v1.2.1, Developer Mode | Install from [WinAppDriver releases](https://github.com/microsoft/WinAppDriver/releases/tag/v1.2.1) |
-| Fuzz Tests | OneFuzz, .NET 8 | See [Fuzzing Tests](doc/devdocs/tools/fuzzingtesting.md) |
-
-### Test Discipline
-
-1. Add or adjust tests when changing behavior
-2. If tests skipped, state why (e.g., comment-only change, string rename)
-3. New modules handling file I/O or user input **must** implement fuzzing tests
-
-### Special Requirements
-
-- **Mouse Without Borders**: Requires 2+ physical computers (not VMs)
-- **Multi-monitor utilities**: Test with 2+ monitors, different DPI settings
-
-For UI test setup details, see [UI Tests](doc/devdocs/development/ui-tests.md).
-
-## Boundaries
-
-### Ask for Clarification When
-
-- Ambiguous spec after scanning relevant docs
-- Cross-module impact (shared enum/struct) is unclear
-- Security, elevation, or installer changes involved
-- GPO or policy handling modifications needed
-
-### Areas Requiring Extra Care
-
-| Area | Concern | Reference |
-|------|---------|-----------|
-| `src/common/` | ABI breaks | [Common Libraries Instructions](.github/instructions/common-libraries.instructions.md) |
-| `src/runner/`, `src/settings-ui/` | IPC contracts, schema | [Runner & Settings UI Instructions](.github/instructions/runner-settings-ui.instructions.md) |
-| Installer files | Release impact | Careful review required |
-| Elevation/GPO logic | Security | Confirm no regression in policy handling |
-
-### What NOT to Do
-
-- Don't merge incomplete features into main (use feature branches)
-- Don't break IPC/JSON contracts without updating both runner and settings-ui
-- Don't add noisy logs in hot paths
-- Don't introduce third-party deps without PM approval and `NOTICE.md` update
-
-## Validation Checklist
-
-Before finishing, verify:
-
-- [ ] Build clean with exit code 0
-- [ ] Tests updated and passing locally
-- [ ] No unintended ABI breaks or schema changes
-- [ ] IPC contracts consistent between runner and settings-ui
-- [ ] New dependencies added to `NOTICE.md`
-- [ ] PR is atomic (one logical change), with issue linked
-
-## Documentation Index
-
-### Core Architecture
-- [Architecture Overview](doc/devdocs/core/architecture.md)
-- [Runner](doc/devdocs/core/runner.md)
-- [Settings System](doc/devdocs/core/settings/readme.md)
-- [Module Interface](doc/devdocs/modules/interface.md)
-
-### Development
-- [Coding Guidelines](doc/devdocs/development/guidelines.md)
-- [Coding Style](doc/devdocs/development/style.md)
-- [Logging](doc/devdocs/development/logging.md)
-- [UI Tests](doc/devdocs/development/ui-tests.md)
-- [Fuzzing Tests](doc/devdocs/tools/fuzzingtesting.md)
-
-### Build & Tools
-- [Build Guidelines](tools/build/BUILD-GUIDELINES.md)
-- [Tools Overview](doc/devdocs/tools/readme.md)
-
-### Instructions (Auto-Applied)
-- [Runner & Settings UI](.github/instructions/runner-settings-ui.instructions.md)
-- [Common Libraries](.github/instructions/common-libraries.instructions.md)

Directory.Packages.props

@@ -63,7 +63,7 @@
     <PackageVersion Include="Microsoft.SemanticKernel.Connectors.MistralAI" Version="1.66.0-alpha" />
     <PackageVersion Include="Microsoft.SemanticKernel.Connectors.Ollama" Version="1.66.0-alpha" />
     <PackageVersion Include="Microsoft.Toolkit.Uwp.Notifications" Version="7.1.2" />
-    <PackageVersion Include="Microsoft.Web.WebView2" Version="1.0.3179.45" />
+    <PackageVersion Include="Microsoft.Web.WebView2" Version="1.0.3405.78" />
     <!-- Package Microsoft.Win32.SystemEvents added as a hack for being able to exclude the runtime assets so they don't conflict with 8.0.1. This is a dependency of System.Drawing.Common but the 8.0.1 version wasn't published to nuget. -->
     <PackageVersion Include="Microsoft.Win32.SystemEvents" Version="9.0.10" />
     <PackageVersion Include="Microsoft.WindowsPackageManager.ComInterop" Version="1.10.340" />
@@ -77,10 +77,8 @@
     <PackageVersion Include="Microsoft.Windows.CsWinRT" Version="2.2.0" />
     <PackageVersion Include="Microsoft.Windows.ImplementationLibrary" Version="1.0.231216.1"/>
     <PackageVersion Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.26100.6901" />
-    <PackageVersion Include="Microsoft.WindowsAppSDK" Version="1.8.251106002" />
-    <PackageVersion Include="Microsoft.WindowsAppSDK.Foundation" Version="1.8.251104000" />
-    <PackageVersion Include="Microsoft.WindowsAppSDK.AI" Version="1.8.39" />
-    <PackageVersion Include="Microsoft.WindowsAppSDK.Runtime" Version="1.8.251106002" />
+    <PackageVersion Include="Microsoft.WindowsAppSDK" Version="2.0.0-experimental4" />
+    <PackageVersion Include="Microsoft.WindowsAppSDK.AI" Version="2.0.130-experimental" />
     <PackageVersion Include="Microsoft.Xaml.Behaviors.WinUI.Managed" Version="2.0.9" />
     <PackageVersion Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.1.39" />
     <PackageVersion Include="ModernWpfUI" Version="0.9.4" />

SEMANTIC_SEARCH_API_SUMMARY.md

@@ -0,0 +1,244 @@
+# Windows App SDK Semantic Search API 总结
+
+## 1. 环境与依赖
+
+| 项目 | 版本/值 |
+|------|---------|
+| **Windows App SDK** | `2.0.0-experimental3` |
+| **.NET** | `net9.0-windows10.0.26100.0` |
+| **AI Search NuGet** | `Microsoft.WindowsAppSDK.AI` (2.0.57-experimental) |
+| **命名空间** | `Microsoft.Windows.AI.Search.Experimental.AppContentIndex` |
+| **应用类型** | WinUI 3 MSIX 打包应用 |
+
+---
+
+## 2. 核心 API
+
+### 2.1 索引管理
+```csharp
+// 创建/打开索引
+var result = AppContentIndexer.GetOrCreateIndex("indexName");
+if (result.Succeeded) {
+    _indexer = result.Indexer;
+    // result.Status: CreatedNew | OpenedExisting
+}
+
+// 等待索引能力就绪
+await _indexer.WaitForIndexCapabilitiesAsync();
+
+// 等待索引空闲（建索引完成）
+await _indexer.WaitForIndexingIdleAsync(TimeSpan.FromSeconds(120));
+
+// 清理
+_indexer.RemoveAll();  // 删除所有索引
+_indexer.Remove(id);   // 删除单个
+_indexer.Dispose();
+```
+
+### 2.2 添加内容到索引
+```csharp
+// 索引文本 → 自动建立 TextLexical + TextSemantic 索引
+IndexableAppContent textContent = AppManagedIndexableAppContent.CreateFromString(id, text);
+_indexer.AddOrUpdate(textContent);
+
+// 索引图片 → 自动建立 ImageSemantic + ImageOcr 索引
+IndexableAppContent imageContent = AppManagedIndexableAppContent.CreateFromBitmap(id, softwareBitmap);
+_indexer.AddOrUpdate(imageContent);
+```
+
+### 2.3 查询
+```csharp
+// 文本查询
+TextQueryOptions options = new TextQueryOptions {
+    Language = "en-US",                          // 可选
+    MatchScope = QueryMatchScope.Unconstrained,  // 匹配范围
+    TextMatchType = TextLexicalMatchType.Fuzzy   // Fuzzy | Exact
+};
+AppIndexTextQuery query = _indexer.CreateTextQuery(searchText, options);
+IReadOnlyList<TextQueryMatch> matches = query.GetNextMatches(5);
+
+// 图片查询
+ImageQueryOptions imgOptions = new ImageQueryOptions {
+    MatchScope = QueryMatchScope.Unconstrained,
+    ImageOcrTextMatchType = TextLexicalMatchType.Fuzzy
+};
+AppIndexImageQuery imgQuery = _indexer.CreateImageQuery(searchText, imgOptions);
+IReadOnlyList<ImageQueryMatch> imgMatches = imgQuery.GetNextMatches(5);
+```
+
+### 2.4 能力检查（只读）
+```csharp
+IndexCapabilities capabilities = _indexer.GetIndexCapabilities();
+
+bool textLexicalOK = capabilities.GetCapabilityState(IndexCapability.TextLexical)
+    .InitializationStatus == IndexCapabilityInitializationStatus.Initialized;
+bool textSemanticOK = capabilities.GetCapabilityState(IndexCapability.TextSemantic)
+    .InitializationStatus == IndexCapabilityInitializationStatus.Initialized;
+bool imageSemanticOK = capabilities.GetCapabilityState(IndexCapability.ImageSemantic)
+    .InitializationStatus == IndexCapabilityInitializationStatus.Initialized;
+bool imageOcrOK = capabilities.GetCapabilityState(IndexCapability.ImageOcr)
+    .InitializationStatus == IndexCapabilityInitializationStatus.Initialized;
+```
+
+---
+
+## 3. 四种索引能力
+
+| 能力 | 说明 | 触发方式 |
+|------|------|----------|
+| `TextLexical` | 词法/关键词搜索 | CreateFromString() 自动 |
+| `TextSemantic` | AI 语义搜索 (Embedding) | CreateFromString() 自动 |
+| `ImageSemantic` | 图像语义搜索 | CreateFromBitmap() 自动 |
+| `ImageOcr` | 图片 OCR 文字搜索 | CreateFromBitmap() 自动 |
+
+---
+
+## 4. 可控选项（有限）
+
+### TextQueryOptions
+| 属性 | 类型 | 说明 |
+|------|------|------|
+| `Language` | string | 查询语言（可选，如 "en-US"）|
+| `MatchScope` | QueryMatchScope | Unconstrained / Region / ContentItem |
+| `TextMatchType` | TextLexicalMatchType | **Fuzzy** / Exact（仅影响 Lexical）|
+
+### ImageQueryOptions
+| 属性 | 类型 | 说明 |
+|------|------|------|
+| `MatchScope` | QueryMatchScope | Unconstrained / Region / ContentItem |
+| `ImageOcrTextMatchType` | TextLexicalMatchType | **Fuzzy** / Exact（仅影响 OCR）|
+
+### 枚举值说明
+
+**QueryMatchScope:**
+- `Unconstrained` - 无约束，同时使用 Lexical + Semantic
+- `Region` - 限制在特定区域
+- `ContentItem` - 限制在单个内容项
+
+**TextLexicalMatchType:**
+- `Fuzzy` - 模糊匹配，允许拼写错误、近似词
+- `Exact` - 精确匹配，必须完全一致
+
+---
+
+## 5. 关键限制 ⚠️
+
+| 限制 | 说明 |
+|------|------|
+| **不能单独指定 Semantic/Lexical** | 系统自动同时使用所有可用能力 |
+| **Fuzzy/Exact 只影响 Lexical** | 对 Semantic 搜索无效 |
+| **能力检查是只读的** | `GetIndexCapabilities()` 只能查看，不能控制 |
+| **无相似度阈值** | 不能设置 Semantic 匹配的阈值 |
+| **无结果排序控制** | 无法指定按相关度或其他方式排序 |
+| **语言需手动传** | 不会自动检测，需开发者指定 |
+| **无相关度分数** | 查询结果不返回匹配分数 |
+
+---
+
+## 6. 典型使用流程
+
+```
+┌─────────────────────────────────────────────────────────┐
+│                    App 启动时                           │
+├─────────────────────────────────────────────────────────┤
+│ 1. GetOrCreateIndex("name")     // 创建/打开索引        │
+│ 2. WaitForIndexCapabilitiesAsync()  // 等待能力就绪     │
+│ 3. GetIndexCapabilities()        // 检查可用能力        │
+│ 4. IndexAll()                    // 索引所有数据        │
+│    ├─ CreateFromString() × N                           │
+│    └─ CreateFromBitmap() × N                           │
+│ 5. WaitForIndexingIdleAsync()    // 等待索引完成        │
+└─────────────────────────────────────────────────────────┘
+                         ↓
+┌─────────────────────────────────────────────────────────┐
+│                    运行时查询                            │
+├─────────────────────────────────────────────────────────┤
+│ 1. CreateTextQuery(text, options)   // 创建查询         │
+│ 2. query.GetNextMatches(N)          // 获取结果         │
+│ 3. 处理 TextQueryMatch / ImageQueryMatch               │
+└─────────────────────────────────────────────────────────┘
+                         ↓
+┌─────────────────────────────────────────────────────────┐
+│                    App 退出时                           │
+├─────────────────────────────────────────────────────────┤
+│ 1. _indexer.RemoveAll()             // 清理索引         │
+│ 2. _indexer.Dispose()               // 释放资源         │
+└─────────────────────────────────────────────────────────┘
+```
+
+---
+
+## 7. 查询结果处理
+
+```csharp
+// 文本查询结果
+foreach (var match in textMatches)
+{
+    if (match.ContentKind == QueryMatchContentKind.AppManagedText)
+    {
+        AppManagedTextQueryMatch textResult = (AppManagedTextQueryMatch)match;
+        string contentId = match.ContentId;      // 内容 ID
+        int offset = textResult.TextOffset;      // 匹配文本偏移
+        int length = textResult.TextLength;      // 匹配文本长度
+    }
+}
+
+// 图片查询结果
+foreach (var match in imageMatches)
+{
+    if (match.ContentKind == QueryMatchContentKind.AppManagedImage)
+    {
+        AppManagedImageQueryMatch imageResult = (AppManagedImageQueryMatch)match;
+        string contentId = imageResult.ContentId;  // 图片 ID
+    }
+}
+```
+
+---
+
+## 8. 能力变化监听
+
+```csharp
+// 监听索引能力变化
+_indexer.Listener.IndexCapabilitiesChanged += (indexer, capabilities) =>
+{
+    // 重新检查能力状态，更新 UI
+    LoadAppIndexCapabilities();
+};
+```
+
+---
+
+## 9. 结论
+
+这是一个**高度封装的黑盒 API**：
+
+### 优点 ✅
+- 简单易用，几行代码即可实现搜索
+- 自动处理 Lexical + Semantic
+- 支持文本和图片多模态搜索
+- 系统级集成，无需额外部署模型
+
+### 缺点 ❌
+- 无法精细控制搜索类型
+- 不能只用 Semantic Search
+- 选项有限，缺乏高级配置
+- 实验性 API，可能变更
+
+### 替代方案
+**如果需要纯 Semantic Search（向量搜索）**，建议：
+- 直接使用 Embedding 模型生成向量
+- 配合向量数据库（Azure Cosmos DB、FAISS、Qdrant 等）
+
+---
+
+## 10. 相关 NuGet 包
+
+```xml
+<PackageReference Include="Microsoft.WindowsAppSDK" Version="2.0.0-experimental3" />
+<PackageReference Include="Microsoft.WindowsAppSDK.AI" Version="2.0.57-experimental" />
+```
+
+---
+
+*文档生成日期: 2026-01-21*

doc/specs/common-search-library.md

@@ -0,0 +1,496 @@
+# Common.Search Library Specification
+
+## Overview
+
+本文档描述 `Common.Search` 库的重构设计，目标是提供一个通用的、可插拔的搜索框架，支持多种搜索引擎实现（Fuzzy Match、Semantic Search 等）。
+
+## Goals
+
+1. **解耦** - 搜索引擎与数据源完全解耦
+2. **可插拔** - 支持替换不同的搜索引擎实现
+3. **泛型** - 不绑定特定业务类型（如 SettingEntry）
+4. **可组合** - 支持多引擎组合（即时 Fuzzy + 延迟 Semantic）
+5. **可复用** - 可被 PowerToys 多个模块使用
+
+## Architecture
+
+```
+┌─────────────────────────────────────────────────────────────────┐
+│                      Consumer (e.g., Settings.UI)               │
+├─────────────────────────────────────────────────────────────────┤
+│  SettingsDataProvider        ← 业务特定的数据加载               │
+│  SettingsSearchService       ← 业务特定的搜索服务               │
+│  SettingEntry : ISearchable  ← 业务实体实现搜索契约             │
+└─────────────────────────────────────────────────────────────────┘
+                              │ uses
+                              ▼
+┌─────────────────────────────────────────────────────────────────┐
+│                      Common.Search (Library)                    │
+├─────────────────────────────────────────────────────────────────┤
+│                                                                 │
+│  ┌─────────────────────────────────────────────────────────┐   │
+│  │                    Core Abstractions                     │   │
+│  ├─────────────────────────────────────────────────────────┤   │
+│  │  ISearchable              ← 可搜索内容契约               │   │
+│  │  ISearchEngine<T>         ← 搜索引擎接口                 │   │
+│  │  SearchResult<T>          ← 统一结果模型                 │   │
+│  │  SearchOptions            ← 搜索选项                     │   │
+│  └─────────────────────────────────────────────────────────┘   │
+│                                                                 │
+│  ┌─────────────────────────────────────────────────────────┐   │
+│  │                    Implementations                       │   │
+│  ├─────────────────────────────────────────────────────────┤   │
+│  │  FuzzSearch/                                             │   │
+│  │  ├── FuzzSearchEngine<T>  ← 内存 Fuzzy 搜索              │   │
+│  │  ├── StringMatcher        ← 现有的模糊匹配算法           │   │
+│  │  └── MatchResult          ← Fuzzy 匹配结果               │   │
+│  │                                                          │   │
+│  │  SemanticSearch/                                         │   │
+│  │  ├── SemanticSearchEngine ← Windows AI Search 封装       │   │
+│  │  └── SemanticSearchCapabilities                          │   │
+│  │                                                          │   │
+│  │  CompositeSearch/                                        │   │
+│  │  └── CompositeSearchEngine<T> ← 多引擎组合               │   │
+│  └─────────────────────────────────────────────────────────┘   │
+│                                                                 │
+└─────────────────────────────────────────────────────────────────┘
+```
+
+## Core Interfaces
+
+### ISearchable
+
+定义可搜索内容的最小契约。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// Defines a searchable item that can be indexed and searched.
+/// </summary>
+public interface ISearchable
+{
+    /// <summary>
+    /// Gets the unique identifier for this item.
+    /// </summary>
+    string Id { get; }
+
+    /// <summary>
+    /// Gets the primary searchable text (e.g., title, header).
+    /// </summary>
+    string SearchableText { get; }
+
+    /// <summary>
+    /// Gets optional secondary searchable text (e.g., description).
+    /// Returns null if not available.
+    /// </summary>
+    string? SecondarySearchableText { get; }
+}
+```
+
+### ISearchEngine&lt;T&gt;
+
+搜索引擎核心接口。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// Defines a pluggable search engine that can index and search items.
+/// </summary>
+/// <typeparam name="T">The type of items to search, must implement ISearchable.</typeparam>
+public interface ISearchEngine<T> : IDisposable
+    where T : ISearchable
+{
+    /// <summary>
+    /// Gets a value indicating whether the engine is ready to search.
+    /// </summary>
+    bool IsReady { get; }
+
+    /// <summary>
+    /// Gets the engine capabilities.
+    /// </summary>
+    SearchEngineCapabilities Capabilities { get; }
+
+    /// <summary>
+    /// Initializes the search engine.
+    /// </summary>
+    Task InitializeAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Indexes a single item.
+    /// </summary>
+    Task IndexAsync(T item, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Indexes multiple items in batch.
+    /// </summary>
+    Task IndexBatchAsync(IEnumerable<T> items, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Removes an item from the index by its ID.
+    /// </summary>
+    Task RemoveAsync(string id, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Clears all indexed items.
+    /// </summary>
+    Task ClearAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Searches for items matching the query.
+    /// </summary>
+    Task<IReadOnlyList<SearchResult<T>>> SearchAsync(
+        string query,
+        SearchOptions? options = null,
+        CancellationToken cancellationToken = default);
+}
+```
+
+### SearchResult&lt;T&gt;
+
+统一的搜索结果模型。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// Represents a search result with the matched item and scoring information.
+/// </summary>
+public sealed class SearchResult<T>
+    where T : ISearchable
+{
+    /// <summary>
+    /// Gets the matched item.
+    /// </summary>
+    public required T Item { get; init; }
+
+    /// <summary>
+    /// Gets the relevance score (higher is more relevant).
+    /// </summary>
+    public required double Score { get; init; }
+
+    /// <summary>
+    /// Gets the type of match that produced this result.
+    /// </summary>
+    public required SearchMatchKind MatchKind { get; init; }
+
+    /// <summary>
+    /// Gets the match details for highlighting (optional).
+    /// </summary>
+    public IReadOnlyList<MatchSpan>? MatchSpans { get; init; }
+}
+
+/// <summary>
+/// Represents a span of matched text for highlighting.
+/// </summary>
+public readonly record struct MatchSpan(int Start, int Length);
+
+/// <summary>
+/// Specifies the kind of match that produced a search result.
+/// </summary>
+public enum SearchMatchKind
+{
+    /// <summary>Exact text match.</summary>
+    Exact,
+
+    /// <summary>Fuzzy/approximate text match.</summary>
+    Fuzzy,
+
+    /// <summary>Semantic/AI-based match.</summary>
+    Semantic,
+
+    /// <summary>Combined match from multiple engines.</summary>
+    Composite,
+}
+```
+
+### SearchOptions
+
+搜索配置选项。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// Options for configuring search behavior.
+/// </summary>
+public sealed class SearchOptions
+{
+    /// <summary>
+    /// Gets or sets the maximum number of results to return.
+    /// Default is 20.
+    /// </summary>
+    public int MaxResults { get; set; } = 20;
+
+    /// <summary>
+    /// Gets or sets the minimum score threshold (0.0 to 1.0).
+    /// Results below this score are filtered out.
+    /// Default is 0.0 (no filtering).
+    /// </summary>
+    public double MinScore { get; set; } = 0.0;
+
+    /// <summary>
+    /// Gets or sets the language hint for the search (e.g., "en-US").
+    /// </summary>
+    public string? Language { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether to include match spans for highlighting.
+    /// Default is false.
+    /// </summary>
+    public bool IncludeMatchSpans { get; set; } = false;
+}
+```
+
+### SearchEngineCapabilities
+
+引擎能力描述。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// Describes the capabilities of a search engine.
+/// </summary>
+public sealed class SearchEngineCapabilities
+{
+    /// <summary>
+    /// Gets a value indicating whether the engine supports fuzzy matching.
+    /// </summary>
+    public bool SupportsFuzzyMatch { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports semantic search.
+    /// </summary>
+    public bool SupportsSemanticSearch { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine persists the index to disk.
+    /// </summary>
+    public bool PersistsIndex { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports incremental indexing.
+    /// </summary>
+    public bool SupportsIncrementalIndex { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports match span highlighting.
+    /// </summary>
+    public bool SupportsMatchSpans { get; init; }
+}
+```
+
+## Implementations
+
+### FuzzSearchEngine&lt;T&gt;
+
+基于现有 StringMatcher 的内存搜索引擎。
+
+**特点：**
+- 纯内存，无持久化
+- 即时响应（毫秒级）
+- 支持 match spans 高亮
+- 基于字符的模糊匹配
+
+**Capabilities：**
+```csharp
+new SearchEngineCapabilities
+{
+    SupportsFuzzyMatch = true,
+    SupportsSemanticSearch = false,
+    PersistsIndex = false,
+    SupportsIncrementalIndex = true,
+    SupportsMatchSpans = true,
+}
+```
+
+### SemanticSearchEngine
+
+基于 Windows App SDK AI Search API 的语义搜索引擎。
+
+**特点：**
+- 系统管理的持久化索引
+- AI 驱动的语义理解
+- 需要模型初始化（可能较慢）
+- 可能不可用（依赖系统支持）
+
+**Capabilities：**
+```csharp
+new SearchEngineCapabilities
+{
+    SupportsFuzzyMatch = true,  // API 同时提供 lexical + semantic
+    SupportsSemanticSearch = true,
+    PersistsIndex = true,
+    SupportsIncrementalIndex = true,
+    SupportsMatchSpans = false,  // API 不返回详细位置
+}
+```
+
+**注意：** SemanticSearchEngine 不是泛型的，因为它需要将内容转换为字符串存入系统索引。实现时通过 `ISearchable` 接口提取文本。
+
+### CompositeSearchEngine&lt;T&gt;
+
+组合多个搜索引擎，支持 fallback 和结果合并。
+
+```csharp
+namespace Common.Search;
+
+/// <summary>
+/// A search engine that combines results from multiple engines.
+/// </summary>
+public sealed class CompositeSearchEngine<T> : ISearchEngine<T>
+    where T : ISearchable
+{
+    /// <summary>
+    /// Strategy for combining results from multiple engines.
+    /// </summary>
+    public enum CombineStrategy
+    {
+        /// <summary>Use first ready engine only.</summary>
+        FirstReady,
+
+        /// <summary>Merge results from all ready engines.</summary>
+        MergeAll,
+
+        /// <summary>Use primary, fallback to secondary if primary not ready.</summary>
+        PrimaryWithFallback,
+    }
+}
+```
+
+**典型用法：** Fuzzy 作为即时响应，Semantic 准备好后增强结果。
+
+## Directory Structure
+
+```
+src/common/Common.Search/
+├── Common.Search.csproj
+├── GlobalSuppressions.cs
+├── ISearchable.cs
+├── ISearchEngine.cs
+├── SearchResult.cs
+├── SearchOptions.cs
+├── SearchEngineCapabilities.cs
+├── SearchMatchKind.cs
+├── MatchSpan.cs
+│
+├── FuzzSearch/
+│   ├── FuzzSearchEngine.cs
+│   ├── StringMatcher.cs         (existing)
+│   ├── MatchOption.cs           (existing)
+│   ├── MatchResult.cs           (existing)
+│   └── SearchPrecisionScore.cs  (existing)
+│
+├── SemanticSearch/
+│   ├── SemanticSearchEngine.cs
+│   ├── SemanticSearchCapabilities.cs
+│   └── SemanticSearchAdapter.cs  (adapts ISearchable to Windows API)
+│
+└── CompositeSearch/
+    └── CompositeSearchEngine.cs
+```
+
+## Consumer Usage (Settings.UI)
+
+### SettingEntry 实现 ISearchable
+
+```csharp
+// Settings.UI.Library/SettingEntry.cs
+public struct SettingEntry : ISearchable
+{
+    // Existing properties...
+
+    // ISearchable implementation
+    public string Id => ElementUid ?? $"{PageTypeName}|{ElementName}";
+    public string SearchableText => Header ?? string.Empty;
+    public string? SecondarySearchableText => Description;
+}
+```
+
+### SettingsSearchService
+
+```csharp
+// Settings.UI/Services/SettingsSearchService.cs
+public sealed class SettingsSearchService : IDisposable
+{
+    private readonly ISearchEngine<SettingEntry> _engine;
+
+    public SettingsSearchService(ISearchEngine<SettingEntry> engine)
+    {
+        _engine = engine;
+    }
+
+    public async Task InitializeAsync(IEnumerable<SettingEntry> entries)
+    {
+        await _engine.InitializeAsync();
+        await _engine.IndexBatchAsync(entries);
+    }
+
+    public async Task<List<SettingEntry>> SearchAsync(string query, CancellationToken ct = default)
+    {
+        var results = await _engine.SearchAsync(query, cancellationToken: ct);
+        return results.Select(r => r.Item).ToList();
+    }
+}
+```
+
+### Startup Configuration
+
+```csharp
+// Option 1: Fuzzy only (default, immediate)
+var engine = new FuzzSearchEngine<SettingEntry>();
+
+// Option 2: Semantic only (requires Windows AI)
+var engine = new SemanticSearchAdapter<SettingEntry>("PowerToysSettings");
+
+// Option 3: Composite (best of both worlds)
+var engine = new CompositeSearchEngine<SettingEntry>(
+    primary: new SemanticSearchAdapter<SettingEntry>("PowerToysSettings"),
+    fallback: new FuzzSearchEngine<SettingEntry>(),
+    strategy: CombineStrategy.PrimaryWithFallback
+);
+
+var searchService = new SettingsSearchService(engine);
+await searchService.InitializeAsync(settingEntries);
+```
+
+## Migration Plan
+
+### Phase 1: Core Abstractions
+1. 创建 `ISearchable`, `ISearchEngine<T>`, `SearchResult<T>` 等核心接口
+2. 保持现有 FuzzSearch 代码不变
+
+### Phase 2: FuzzSearchEngine&lt;T&gt;
+1. 创建泛型 `FuzzSearchEngine<T>` 实现
+2. 内部复用现有 `StringMatcher`
+
+### Phase 3: SemanticSearchEngine
+1. 完善现有 `SemanticSearchEngine` 实现
+2. 创建 `SemanticSearchAdapter<T>` 桥接泛型接口
+
+### Phase 4: Settings.UI Migration
+1. `SettingEntry` 实现 `ISearchable`
+2. 创建 `SettingsSearchService`
+3. 迁移 `SearchIndexService` 到新架构
+4. 保持 API 兼容，逐步废弃旧方法
+
+### Phase 5: CompositeSearchEngine (Optional)
+1. 实现组合引擎
+2. 支持 Fuzzy + Semantic 混合搜索
+
+## Open Questions
+
+1. **是否需要支持图片搜索？** 当前 SemanticSearchEngine 支持 `IndexImage`，但 `ISearchable` 只有文本。如果需要图片，可能需要 `IImageSearchable` 扩展。
+
+2. **结果去重策略？** CompositeEngine 合并结果时，同一个 Item 可能被多个引擎匹配，如何去重和合并分数？
+
+3. **异步 vs 同步？** FuzzSearch 完全可以同步执行，但接口统一用 `Task` 是否合适？考虑提供同步重载？
+
+4. **索引更新策略？** 当 Settings 内容变化时（例如用户切换语言），如何高效更新索引？
+
+---
+
+*Document Version: 1.0*
+*Last Updated: 2026-01-21*

src/PackageIdentity/AppxManifest.xml

@@ -29,6 +29,7 @@
   </Resources>
   <Dependencies>
     <TargetDeviceFamily Name="Windows.Desktop" MinVersion="10.0.19000.0" MaxVersionTested="10.0.26226.0" />
+    <PackageDependency Name="Microsoft.WindowsAppRuntime.2.0-experimental3" MinVersion="0.676.658.0" Publisher="CN=Microsoft Corporation, O=Microsoft Corporation, L=Redmond, S=Washington, C=US" />
   </Dependencies>
   <Capabilities>
     <Capability Name="internetClient" />

src/common/Common.Search/Common.Search.csproj

@@ -4,5 +4,16 @@
 
   <PropertyGroup>
     <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <WarningsNotAsErrors>$(WarningsNotAsErrors);CS8305</WarningsNotAsErrors>
   </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.WindowsAppSDK" />
+    <PackageReference Include="Microsoft.WindowsAppSDK.AI" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\ManagedCommon\ManagedCommon.csproj" />
+  </ItemGroup>
 </Project>

src/common/Common.Search/FuzzSearch/FuzzSearchEngine`1.cs

@@ -0,0 +1,306 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Concurrent;
+using System.Globalization;
+using System.Text;
+
+namespace Common.Search.FuzzSearch;
+
+/// <summary>
+/// A search engine that uses fuzzy string matching for search.
+/// </summary>
+/// <typeparam name="T">The type of items to search.</typeparam>
+public sealed class FuzzSearchEngine<T> : ISearchEngine<T>
+    where T : ISearchable
+{
+    private readonly object _lockObject = new();
+    private readonly Dictionary<string, T> _itemsById = new();
+    private readonly Dictionary<string, (string PrimaryNorm, string? SecondaryNorm)> _normalizedCache = new();
+    private bool _isReady;
+    private bool _disposed;
+
+    /// <inheritdoc/>
+    public bool IsReady
+    {
+        get
+        {
+            lock (_lockObject)
+            {
+                return _isReady;
+            }
+        }
+    }
+
+    /// <inheritdoc/>
+    public SearchEngineCapabilities Capabilities { get; } = new()
+    {
+        SupportsFuzzyMatch = true,
+        SupportsSemanticSearch = false,
+        PersistsIndex = false,
+        SupportsIncrementalIndex = true,
+        SupportsMatchSpans = true,
+    };
+
+    /// <inheritdoc/>
+    public Task InitializeAsync(CancellationToken cancellationToken = default)
+    {
+        lock (_lockObject)
+        {
+            _isReady = true;
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task IndexAsync(T item, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(item);
+        ThrowIfDisposed();
+
+        lock (_lockObject)
+        {
+            _itemsById[item.Id] = item;
+            _normalizedCache[item.Id] = (
+                NormalizeString(item.SearchableText),
+                item.SecondarySearchableText != null ? NormalizeString(item.SecondarySearchableText) : null
+            );
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task IndexBatchAsync(IEnumerable<T> items, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(items);
+        ThrowIfDisposed();
+
+        lock (_lockObject)
+        {
+            foreach (var item in items)
+            {
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    break;
+                }
+
+                _itemsById[item.Id] = item;
+                _normalizedCache[item.Id] = (
+                    NormalizeString(item.SearchableText),
+                    item.SecondarySearchableText != null ? NormalizeString(item.SecondarySearchableText) : null
+                );
+            }
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task RemoveAsync(string id, CancellationToken cancellationToken = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(id);
+        ThrowIfDisposed();
+
+        lock (_lockObject)
+        {
+            _itemsById.Remove(id);
+            _normalizedCache.Remove(id);
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task ClearAsync(CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+
+        lock (_lockObject)
+        {
+            _itemsById.Clear();
+            _normalizedCache.Clear();
+        }
+
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task<IReadOnlyList<SearchResult<T>>> SearchAsync(
+        string query,
+        SearchOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+
+        if (string.IsNullOrWhiteSpace(query))
+        {
+            return Task.FromResult<IReadOnlyList<SearchResult<T>>>(Array.Empty<SearchResult<T>>());
+        }
+
+        options ??= new SearchOptions();
+        var normalizedQuery = NormalizeString(query);
+
+        List<KeyValuePair<string, T>> snapshot;
+        lock (_lockObject)
+        {
+            if (_itemsById.Count == 0)
+            {
+                return Task.FromResult<IReadOnlyList<SearchResult<T>>>(Array.Empty<SearchResult<T>>());
+            }
+
+            snapshot = _itemsById.ToList();
+        }
+
+        var bag = new ConcurrentBag<SearchResult<T>>();
+        var po = new ParallelOptions
+        {
+            CancellationToken = cancellationToken,
+            MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount - 1),
+        };
+
+        try
+        {
+            Parallel.ForEach(snapshot, po, kvp =>
+            {
+                var (primaryNorm, secondaryNorm) = GetNormalizedTexts(kvp.Key);
+
+                var primaryResult = StringMatcher.FuzzyMatch(normalizedQuery, primaryNorm);
+                double score = primaryResult.Score;
+                List<int>? matchData = primaryResult.MatchData;
+
+                if (!string.IsNullOrEmpty(secondaryNorm))
+                {
+                    var secondaryResult = StringMatcher.FuzzyMatch(normalizedQuery, secondaryNorm);
+                    if (secondaryResult.Success && secondaryResult.Score * 0.8 > score)
+                    {
+                        score = secondaryResult.Score * 0.8;
+                        matchData = null; // Secondary matches don't have primary text spans
+                    }
+                }
+
+                if (score > options.MinScore)
+                {
+                    var result = new SearchResult<T>
+                    {
+                        Item = kvp.Value,
+                        Score = score,
+                        MatchKind = SearchMatchKind.Fuzzy,
+                        MatchSpans = options.IncludeMatchSpans && matchData != null
+                            ? ConvertToMatchSpans(matchData)
+                            : null,
+                    };
+
+                    bag.Add(result);
+                }
+            });
+        }
+        catch (OperationCanceledException)
+        {
+            return Task.FromResult<IReadOnlyList<SearchResult<T>>>(Array.Empty<SearchResult<T>>());
+        }
+
+        var results = bag
+            .OrderByDescending(r => r.Score)
+            .Take(options.MaxResults)
+            .ToList();
+
+        return Task.FromResult<IReadOnlyList<SearchResult<T>>>(results);
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        lock (_lockObject)
+        {
+            _itemsById.Clear();
+            _normalizedCache.Clear();
+            _isReady = false;
+        }
+
+        _disposed = true;
+    }
+
+    private (string PrimaryNorm, string? SecondaryNorm) GetNormalizedTexts(string id)
+    {
+        lock (_lockObject)
+        {
+            if (_normalizedCache.TryGetValue(id, out var cached))
+            {
+                return cached;
+            }
+        }
+
+        return (string.Empty, null);
+    }
+
+    private static IReadOnlyList<MatchSpan> ConvertToMatchSpans(List<int> matchData)
+    {
+        if (matchData == null || matchData.Count == 0)
+        {
+            return Array.Empty<MatchSpan>();
+        }
+
+        // Convert individual match indices to spans
+        var spans = new List<MatchSpan>();
+        var sortedIndices = matchData.OrderBy(i => i).ToList();
+
+        int start = sortedIndices[0];
+        int length = 1;
+
+        for (int i = 1; i < sortedIndices.Count; i++)
+        {
+            if (sortedIndices[i] == sortedIndices[i - 1] + 1)
+            {
+                // Consecutive index, extend the span
+                length++;
+            }
+            else
+            {
+                // Gap found, save current span and start new one
+                spans.Add(new MatchSpan(start, length));
+                start = sortedIndices[i];
+                length = 1;
+            }
+        }
+
+        // Add the last span
+        spans.Add(new MatchSpan(start, length));
+
+        return spans;
+    }
+
+    private static string NormalizeString(string? input)
+    {
+        if (string.IsNullOrEmpty(input))
+        {
+            return string.Empty;
+        }
+
+        var normalized = input.ToLowerInvariant().Normalize(NormalizationForm.FormKD);
+        var sb = new StringBuilder(normalized.Length);
+
+        foreach (var c in normalized)
+        {
+            var category = CharUnicodeInfo.GetUnicodeCategory(c);
+            if (category != UnicodeCategory.NonSpacingMark)
+            {
+                sb.Append(c);
+            }
+        }
+
+        return sb.ToString();
+    }
+
+    private void ThrowIfDisposed()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+    }
+}

src/common/Common.Search/FuzzSearch/StringMatcher.cs

@@ -25,9 +25,9 @@ public class StringMatcher
     /// 6. Move onto the next substring's characters until all substrings are checked.
     /// 7. Consider success and move onto scoring if every char or substring without whitespaces matched
     /// </summary>
-    public static MatchResult FuzzyMatch(string query, string stringToCompare, MatchOption opt = null)
+    public static MatchResult FuzzyMatch(string query, string stringToCompare, MatchOption? opt = null)
     {
-        opt = opt ?? new MatchOption();
+        opt ??= new MatchOption();
 
         if (string.IsNullOrEmpty(stringToCompare))
         {

src/common/Common.Search/GlobalSuppressions.cs

@@ -11,6 +11,10 @@ using System.Diagnostics.CodeAnalysis;
 [assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.MatchResult._rawScore")]
 [assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.StringMatcher._defaultMatchOption")]
 [assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.StringMatcher._instance")]
+[assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.SemanticSearch.SemanticSearchIndex._indexName")]
+[assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.SemanticSearch.SemanticSearchIndex._indexer")]
+[assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.SemanticSearch.SemanticSearchIndex._disposed")]
+[assembly: SuppressMessage("StyleCop.CSharp.NamingRules", "SA1309:Field names should not begin with underscore", Justification = "coding style", Scope = "member", Target = "~F:Common.Search.SemanticSearch.SemanticSearchIndex._capabilities")]
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1101:Prefix local calls with this", Justification = "coding style", Scope = "member", Target = "~M:Common.Search.MatchResult.#ctor(System.Boolean,Common.Search.SearchPrecisionScore)")]
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1101:Prefix local calls with this", Justification = "coding style", Scope = "member", Target = "~M:Common.Search.MatchResult.#ctor(System.Boolean,Common.Search.SearchPrecisionScore,System.Collections.Generic.List{System.Int32},System.Int32)")]
 [assembly: SuppressMessage("Compiler", "CS8618:Non-nullable field must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring as nullable.", Justification = "Coding style", Scope = "member", Target = "~F:Common.Search.StringMatcher._instance")]

src/common/Common.Search/ISearchEngine`1.cs

@@ -0,0 +1,73 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Defines a pluggable search engine that can index and search items.
+/// </summary>
+/// <typeparam name="T">The type of items to search, must implement ISearchable.</typeparam>
+public interface ISearchEngine<T> : IDisposable
+    where T : ISearchable
+{
+    /// <summary>
+    /// Gets a value indicating whether the engine is ready to search.
+    /// </summary>
+    bool IsReady { get; }
+
+    /// <summary>
+    /// Gets the engine capabilities.
+    /// </summary>
+    SearchEngineCapabilities Capabilities { get; }
+
+    /// <summary>
+    /// Initializes the search engine.
+    /// </summary>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task representing the async operation.</returns>
+    Task InitializeAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Indexes a single item.
+    /// </summary>
+    /// <param name="item">The item to index.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task representing the async operation.</returns>
+    Task IndexAsync(T item, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Indexes multiple items in batch.
+    /// </summary>
+    /// <param name="items">The items to index.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task representing the async operation.</returns>
+    Task IndexBatchAsync(IEnumerable<T> items, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Removes an item from the index by its ID.
+    /// </summary>
+    /// <param name="id">The ID of the item to remove.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task representing the async operation.</returns>
+    Task RemoveAsync(string id, CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Clears all indexed items.
+    /// </summary>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A task representing the async operation.</returns>
+    Task ClearAsync(CancellationToken cancellationToken = default);
+
+    /// <summary>
+    /// Searches for items matching the query.
+    /// </summary>
+    /// <param name="query">The search query.</param>
+    /// <param name="options">Optional search options.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A list of search results ordered by relevance.</returns>
+    Task<IReadOnlyList<SearchResult<T>>> SearchAsync(
+        string query,
+        SearchOptions? options = null,
+        CancellationToken cancellationToken = default);
+}

src/common/Common.Search/ISearchable.cs

@@ -0,0 +1,27 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Defines a searchable item that can be indexed and searched.
+/// </summary>
+public interface ISearchable
+{
+    /// <summary>
+    /// Gets the unique identifier for this item.
+    /// </summary>
+    string Id { get; }
+
+    /// <summary>
+    /// Gets the primary searchable text (e.g., title, header).
+    /// </summary>
+    string SearchableText { get; }
+
+    /// <summary>
+    /// Gets optional secondary searchable text (e.g., description).
+    /// Returns null if not available.
+    /// </summary>
+    string? SecondarySearchableText { get; }
+}

src/common/Common.Search/MatchSpan.cs

@@ -0,0 +1,12 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Represents a span of matched text for highlighting.
+/// </summary>
+/// <param name="Start">The starting index of the match.</param>
+/// <param name="Length">The length of the match.</param>
+public readonly record struct MatchSpan(int Start, int Length);

src/common/Common.Search/SearchEngineCapabilities.cs

@@ -0,0 +1,36 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Describes the capabilities of a search engine.
+/// </summary>
+public sealed class SearchEngineCapabilities
+{
+    /// <summary>
+    /// Gets a value indicating whether the engine supports fuzzy matching.
+    /// </summary>
+    public bool SupportsFuzzyMatch { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports semantic search.
+    /// </summary>
+    public bool SupportsSemanticSearch { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine persists the index to disk.
+    /// </summary>
+    public bool PersistsIndex { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports incremental indexing.
+    /// </summary>
+    public bool SupportsIncrementalIndex { get; init; }
+
+    /// <summary>
+    /// Gets a value indicating whether the engine supports match span highlighting.
+    /// </summary>
+    public bool SupportsMatchSpans { get; init; }
+}

src/common/Common.Search/SearchError.cs

@@ -0,0 +1,134 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Represents an error that occurred during a search operation.
+/// </summary>
+public sealed class SearchError
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SearchError"/> class.
+    /// </summary>
+    /// <param name="code">The error code.</param>
+    /// <param name="message">The error message.</param>
+    /// <param name="details">Optional additional details.</param>
+    /// <param name="exception">Optional exception that caused the error.</param>
+    public SearchError(SearchErrorCode code, string message, string? details = null, Exception? exception = null)
+    {
+        Code = code;
+        Message = message;
+        Details = details;
+        Exception = exception;
+        Timestamp = DateTime.UtcNow;
+    }
+
+    /// <summary>
+    /// Gets the error code.
+    /// </summary>
+    public SearchErrorCode Code { get; }
+
+    /// <summary>
+    /// Gets the error message.
+    /// </summary>
+    public string Message { get; }
+
+    /// <summary>
+    /// Gets additional details about the error.
+    /// </summary>
+    public string? Details { get; }
+
+    /// <summary>
+    /// Gets the exception that caused the error, if any.
+    /// </summary>
+    public Exception? Exception { get; }
+
+    /// <summary>
+    /// Gets the timestamp when the error occurred.
+    /// </summary>
+    public DateTime Timestamp { get; }
+
+    /// <summary>
+    /// Creates an error for initialization failure.
+    /// </summary>
+    /// <param name="indexName">The name of the index.</param>
+    /// <param name="details">Optional details.</param>
+    /// <param name="exception">Optional exception.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError InitializationFailed(string indexName, string? details = null, Exception? exception = null)
+        => new(SearchErrorCode.InitializationFailed, $"Failed to initialize search index '{indexName}'.", details, exception);
+
+    /// <summary>
+    /// Creates an error for indexing failure.
+    /// </summary>
+    /// <param name="contentId">The ID of the content that failed to index.</param>
+    /// <param name="details">Optional details.</param>
+    /// <param name="exception">Optional exception.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError IndexingFailed(string contentId, string? details = null, Exception? exception = null)
+        => new(SearchErrorCode.IndexingFailed, $"Failed to index content '{contentId}'.", details, exception);
+
+    /// <summary>
+    /// Creates an error for search query failure.
+    /// </summary>
+    /// <param name="query">The search query that failed.</param>
+    /// <param name="details">Optional details.</param>
+    /// <param name="exception">Optional exception.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError SearchFailed(string query, string? details = null, Exception? exception = null)
+        => new(SearchErrorCode.SearchFailed, $"Search query '{query}' failed.", details, exception);
+
+    /// <summary>
+    /// Creates an error for engine not ready.
+    /// </summary>
+    /// <param name="operation">The operation that was attempted.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError EngineNotReady(string operation)
+        => new(SearchErrorCode.EngineNotReady, $"Search engine is not ready. Operation '{operation}' cannot be performed.");
+
+    /// <summary>
+    /// Creates an error for capability unavailable.
+    /// </summary>
+    /// <param name="capability">The capability that is unavailable.</param>
+    /// <param name="details">Optional details.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError CapabilityUnavailable(string capability, string? details = null)
+        => new(SearchErrorCode.CapabilityUnavailable, $"Search capability '{capability}' is not available.", details);
+
+    /// <summary>
+    /// Creates an error for timeout.
+    /// </summary>
+    /// <param name="operation">The operation that timed out.</param>
+    /// <param name="timeout">The timeout duration.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError Timeout(string operation, TimeSpan timeout)
+        => new(SearchErrorCode.Timeout, $"Operation '{operation}' timed out after {timeout.TotalSeconds:F1} seconds.");
+
+    /// <summary>
+    /// Creates an error for an unexpected error.
+    /// </summary>
+    /// <param name="operation">The operation that failed.</param>
+    /// <param name="exception">The exception that occurred.</param>
+    /// <returns>A new SearchError instance.</returns>
+    public static SearchError Unexpected(string operation, Exception exception)
+        => new(SearchErrorCode.Unexpected, $"Unexpected error during '{operation}'.", exception.Message, exception);
+
+    /// <inheritdoc/>
+    public override string ToString()
+    {
+        var result = $"[{Code}] {Message}";
+        if (!string.IsNullOrEmpty(Details))
+        {
+            result += $" Details: {Details}";
+        }
+
+        if (Exception != null)
+        {
+            result += $" Exception: {Exception.GetType().Name}: {Exception.Message}";
+        }
+
+        return result;
+    }
+}

src/common/Common.Search/SearchErrorCode.cs

@@ -0,0 +1,51 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Defines error codes for search operations.
+/// </summary>
+public enum SearchErrorCode
+{
+    /// <summary>
+    /// No error occurred.
+    /// </summary>
+    None = 0,
+
+    /// <summary>
+    /// The search engine failed to initialize.
+    /// </summary>
+    InitializationFailed = 1,
+
+    /// <summary>
+    /// Failed to index content.
+    /// </summary>
+    IndexingFailed = 2,
+
+    /// <summary>
+    /// The search query failed to execute.
+    /// </summary>
+    SearchFailed = 3,
+
+    /// <summary>
+    /// The search engine is not ready to perform the operation.
+    /// </summary>
+    EngineNotReady = 4,
+
+    /// <summary>
+    /// A required capability is not available.
+    /// </summary>
+    CapabilityUnavailable = 5,
+
+    /// <summary>
+    /// The operation timed out.
+    /// </summary>
+    Timeout = 6,
+
+    /// <summary>
+    /// An unexpected error occurred.
+    /// </summary>
+    Unexpected = 99,
+}

src/common/Common.Search/SearchMatchKind.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Specifies the kind of match that produced a search result.
+/// </summary>
+public enum SearchMatchKind
+{
+    /// <summary>
+    /// Exact text match.
+    /// </summary>
+    Exact,
+
+    /// <summary>
+    /// Fuzzy/approximate text match.
+    /// </summary>
+    Fuzzy,
+
+    /// <summary>
+    /// Semantic/AI-based match.
+    /// </summary>
+    Semantic,
+
+    /// <summary>
+    /// Combined match from multiple engines.
+    /// </summary>
+    Composite,
+}

src/common/Common.Search/SearchOperationResult.cs

@@ -0,0 +1,53 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Represents the result of a search operation that may have errors.
+/// </summary>
+public sealed class SearchOperationResult
+{
+    private SearchOperationResult(bool success, SearchError? error = null)
+    {
+        IsSuccess = success;
+        Error = error;
+    }
+
+    /// <summary>
+    /// Gets a value indicating whether the operation was successful.
+    /// </summary>
+    public bool IsSuccess { get; }
+
+    /// <summary>
+    /// Gets a value indicating whether the operation failed.
+    /// </summary>
+    public bool IsFailure => !IsSuccess;
+
+    /// <summary>
+    /// Gets the error if the operation failed, null otherwise.
+    /// </summary>
+    public SearchError? Error { get; }
+
+    /// <summary>
+    /// Creates a successful result.
+    /// </summary>
+    /// <returns>A successful SearchOperationResult.</returns>
+    public static SearchOperationResult Success() => new(true);
+
+    /// <summary>
+    /// Creates a failed result with the specified error.
+    /// </summary>
+    /// <param name="error">The error that caused the failure.</param>
+    /// <returns>A failed SearchOperationResult.</returns>
+    public static SearchOperationResult Failure(SearchError error)
+    {
+        ArgumentNullException.ThrowIfNull(error);
+        return new SearchOperationResult(false, error);
+    }
+
+    /// <inheritdoc/>
+    public override string ToString()
+        => IsSuccess ? "Success" : $"Failure: {Error}";
+}

src/common/Common.Search/SearchOperationResult1.cs

@@ -0,0 +1,87 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics.CodeAnalysis;
+
+#pragma warning disable SA1649 // File name should match first type name - Generic type file naming convention
+
+namespace Common.Search;
+
+/// <summary>
+/// Represents the result of a search operation that returns a value and may have errors.
+/// </summary>
+/// <typeparam name="T">The type of the result value.</typeparam>
+public sealed class SearchOperationResult<T>
+{
+    private SearchOperationResult(bool success, T? value, SearchError? error)
+    {
+        IsSuccess = success;
+        Value = value;
+        Error = error;
+    }
+
+    /// <summary>
+    /// Gets a value indicating whether the operation was successful.
+    /// </summary>
+    public bool IsSuccess { get; }
+
+    /// <summary>
+    /// Gets a value indicating whether the operation failed.
+    /// </summary>
+    public bool IsFailure => !IsSuccess;
+
+    /// <summary>
+    /// Gets the result value if the operation was successful.
+    /// </summary>
+    public T? Value { get; }
+
+    /// <summary>
+    /// Gets the error if the operation failed, null otherwise.
+    /// </summary>
+    public SearchError? Error { get; }
+
+    /// <summary>
+    /// Gets the value or a default if the operation failed.
+    /// </summary>
+    /// <param name="defaultValue">The default value to return if the operation failed.</param>
+    /// <returns>The value if successful, otherwise the default value.</returns>
+    public T GetValueOrDefault(T defaultValue) => IsSuccess && Value is not null ? Value : defaultValue;
+
+    /// <inheritdoc/>
+    public override string ToString()
+        => IsSuccess ? $"Success: {Value}" : $"Failure: {Error}";
+
+    /// <summary>
+    /// Creates a successful result with the specified value.
+    /// </summary>
+    /// <param name="value">The result value.</param>
+    /// <returns>A successful SearchOperationResult.</returns>
+    [SuppressMessage("Design", "CA1000:Do not declare static members on generic types", Justification = "Factory method pattern is the idiomatic way to create instances of generic result types")]
+    public static SearchOperationResult<T> Success(T value) => new(true, value, null);
+
+    /// <summary>
+    /// Creates a failed result with the specified error.
+    /// </summary>
+    /// <param name="error">The error that caused the failure.</param>
+    /// <returns>A failed SearchOperationResult.</returns>
+    [SuppressMessage("Design", "CA1000:Do not declare static members on generic types", Justification = "Factory method pattern is the idiomatic way to create instances of generic result types")]
+    public static SearchOperationResult<T> Failure(SearchError error)
+    {
+        ArgumentNullException.ThrowIfNull(error);
+        return new SearchOperationResult<T>(false, default, error);
+    }
+
+    /// <summary>
+    /// Creates a failed result with the specified error and a fallback value.
+    /// </summary>
+    /// <param name="error">The error that caused the failure.</param>
+    /// <param name="fallbackValue">A fallback value to use despite the failure.</param>
+    /// <returns>A failed SearchOperationResult with a fallback value.</returns>
+    [SuppressMessage("Design", "CA1000:Do not declare static members on generic types", Justification = "Factory method pattern is the idiomatic way to create instances of generic result types")]
+    public static SearchOperationResult<T> FailureWithFallback(SearchError error, T fallbackValue)
+    {
+        ArgumentNullException.ThrowIfNull(error);
+        return new SearchOperationResult<T>(false, fallbackValue, error);
+    }
+}

src/common/Common.Search/SearchOptions.cs

@@ -0,0 +1,35 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Options for configuring search behavior.
+/// </summary>
+public sealed class SearchOptions
+{
+    /// <summary>
+    /// Gets or sets the maximum number of results to return.
+    /// Default is 20.
+    /// </summary>
+    public int MaxResults { get; set; } = 20;
+
+    /// <summary>
+    /// Gets or sets the minimum score threshold.
+    /// Results below this score are filtered out.
+    /// Default is 0.0 (no filtering).
+    /// </summary>
+    public double MinScore { get; set; }
+
+    /// <summary>
+    /// Gets or sets the language hint for the search (e.g., "en-US").
+    /// </summary>
+    public string? Language { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether to include match spans for highlighting.
+    /// Default is false.
+    /// </summary>
+    public bool IncludeMatchSpans { get; set; }
+}

src/common/Common.Search/SearchResult`1.cs

@@ -0,0 +1,33 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search;
+
+/// <summary>
+/// Represents a search result with the matched item and scoring information.
+/// </summary>
+/// <typeparam name="T">The type of the matched item.</typeparam>
+public sealed class SearchResult<T>
+    where T : ISearchable
+{
+    /// <summary>
+    /// Gets the matched item.
+    /// </summary>
+    public required T Item { get; init; }
+
+    /// <summary>
+    /// Gets the relevance score (higher is more relevant).
+    /// </summary>
+    public required double Score { get; init; }
+
+    /// <summary>
+    /// Gets the type of match that produced this result.
+    /// </summary>
+    public required SearchMatchKind MatchKind { get; init; }
+
+    /// <summary>
+    /// Gets the match details for highlighting (optional).
+    /// </summary>
+    public IReadOnlyList<MatchSpan>? MatchSpans { get; init; }
+}

src/common/Common.Search/SemanticSearch/SemanticSearchCapabilities.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Represents the capabilities of the semantic search index.
+/// </summary>
+public class SemanticSearchCapabilities
+{
+    /// <summary>
+    /// Gets or sets a value indicating whether text lexical (keyword) search is available.
+    /// </summary>
+    public bool TextLexicalAvailable { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether text semantic (AI embedding) search is available.
+    /// </summary>
+    public bool TextSemanticAvailable { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether image semantic search is available.
+    /// </summary>
+    public bool ImageSemanticAvailable { get; set; }
+
+    /// <summary>
+    /// Gets or sets a value indicating whether image OCR search is available.
+    /// </summary>
+    public bool ImageOcrAvailable { get; set; }
+
+    /// <summary>
+    /// Gets a value indicating whether any search capability is available.
+    /// </summary>
+    public bool AnyAvailable => TextLexicalAvailable || TextSemanticAvailable || ImageSemanticAvailable || ImageOcrAvailable;
+
+    /// <summary>
+    /// Gets a value indicating whether text search (lexical or semantic) is available.
+    /// </summary>
+    public bool TextSearchAvailable => TextLexicalAvailable || TextSemanticAvailable;
+
+    /// <summary>
+    /// Gets a value indicating whether image search (semantic or OCR) is available.
+    /// </summary>
+    public bool ImageSearchAvailable => ImageSemanticAvailable || ImageOcrAvailable;
+}

src/common/Common.Search/SemanticSearch/SemanticSearchContentKind.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Specifies the kind of content in a semantic search result.
+/// </summary>
+public enum SemanticSearchContentKind
+{
+    /// <summary>
+    /// Text content.
+    /// </summary>
+    Text,
+
+    /// <summary>
+    /// Image content.
+    /// </summary>
+    Image,
+}

src/common/Common.Search/SemanticSearch/SemanticSearchEngine`1.cs

@@ -0,0 +1,406 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using ManagedCommon;
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// A semantic search engine that implements the common search interface.
+/// </summary>
+/// <typeparam name="T">The type of items to search.</typeparam>
+public sealed class SemanticSearchEngine<T> : ISearchEngine<T>
+    where T : ISearchable
+{
+    private readonly SemanticSearchIndex _index;
+    private readonly Dictionary<string, T> _itemsById = new();
+    private readonly object _lockObject = new();
+    private bool _disposed;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SemanticSearchEngine{T}"/> class.
+    /// </summary>
+    /// <param name="indexName">The name of the search index.</param>
+    public SemanticSearchEngine(string indexName)
+    {
+        Logger.LogDebug($"[SemanticSearchEngine] Creating engine. IndexName={indexName}, ItemType={typeof(T).Name}");
+        _index = new SemanticSearchIndex(indexName);
+    }
+
+    /// <inheritdoc/>
+    public bool IsReady => _index.IsInitialized;
+
+    /// <inheritdoc/>
+    public SearchEngineCapabilities Capabilities { get; } = new()
+    {
+        SupportsFuzzyMatch = true,
+        SupportsSemanticSearch = true,
+        PersistsIndex = true,
+        SupportsIncrementalIndex = true,
+        SupportsMatchSpans = false,
+    };
+
+    /// <summary>
+    /// Gets the underlying semantic search capabilities.
+    /// </summary>
+    public SemanticSearchCapabilities? SemanticCapabilities => _index.Capabilities;
+
+    /// <summary>
+    /// Gets the last error that occurred during a search operation, or null if no error occurred.
+    /// </summary>
+    public SearchError? LastError => _index.LastError;
+
+    /// <summary>
+    /// Occurs when the semantic search capabilities change.
+    /// </summary>
+    public event EventHandler<SemanticSearchCapabilities>? CapabilitiesChanged
+    {
+        add => _index.CapabilitiesChanged += value;
+        remove => _index.CapabilitiesChanged -= value;
+    }
+
+    /// <inheritdoc/>
+    public async Task InitializeAsync(CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+        Logger.LogInfo($"[SemanticSearchEngine] InitializeAsync starting. ItemType={typeof(T).Name}");
+        var result = await _index.InitializeAsync().ConfigureAwait(false);
+
+        if (result.IsFailure)
+        {
+            Logger.LogWarning($"[SemanticSearchEngine] InitializeAsync failed. ItemType={typeof(T).Name}, Error={result.Error?.Message}");
+        }
+        else
+        {
+            Logger.LogInfo($"[SemanticSearchEngine] InitializeAsync completed. ItemType={typeof(T).Name}");
+        }
+
+        // Note: We don't throw here to maintain backward compatibility,
+        // but callers can check LastError for details if initialization failed.
+    }
+
+    /// <summary>
+    /// Initializes the search engine and returns the result with error details if any.
+    /// </summary>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public async Task<SearchOperationResult> InitializeWithResultAsync(CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+        return await _index.InitializeAsync().ConfigureAwait(false);
+    }
+
+    /// <inheritdoc/>
+    public Task IndexAsync(T item, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(item);
+        ThrowIfDisposed();
+
+        var text = BuildSearchableText(item);
+        if (string.IsNullOrWhiteSpace(text))
+        {
+            Logger.LogDebug($"[SemanticSearchEngine] IndexAsync skipped (empty text). Id={item.Id}");
+            return Task.CompletedTask;
+        }
+
+        lock (_lockObject)
+        {
+            _itemsById[item.Id] = item;
+        }
+
+        Logger.LogDebug($"[SemanticSearchEngine] IndexAsync. Id={item.Id}, TextLength={text.Length}");
+
+        // Note: Errors are captured in LastError for external logging
+        _ = _index.IndexText(item.Id, text);
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Indexes a single item and returns the result with error details if any.
+    /// </summary>
+    /// <param name="item">The item to index.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public Task<SearchOperationResult> IndexWithResultAsync(T item, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(item);
+        ThrowIfDisposed();
+
+        var text = BuildSearchableText(item);
+        if (string.IsNullOrWhiteSpace(text))
+        {
+            return Task.FromResult(SearchOperationResult.Success());
+        }
+
+        lock (_lockObject)
+        {
+            _itemsById[item.Id] = item;
+        }
+
+        return Task.FromResult(_index.IndexText(item.Id, text));
+    }
+
+    /// <inheritdoc/>
+    public Task IndexBatchAsync(IEnumerable<T> items, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(items);
+        ThrowIfDisposed();
+
+        var batch = new List<(string Id, string Text)>();
+
+        lock (_lockObject)
+        {
+            foreach (var item in items)
+            {
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    Logger.LogDebug($"[SemanticSearchEngine] IndexBatchAsync cancelled. ItemsProcessed={batch.Count}");
+                    break;
+                }
+
+                var text = BuildSearchableText(item);
+                if (!string.IsNullOrWhiteSpace(text))
+                {
+                    _itemsById[item.Id] = item;
+                    batch.Add((item.Id, text));
+                }
+            }
+        }
+
+        Logger.LogInfo($"[SemanticSearchEngine] IndexBatchAsync. BatchSize={batch.Count}");
+
+        // Note: Errors are captured in LastError for external logging
+        _ = _index.IndexTextBatch(batch);
+        return Task.CompletedTask;
+    }
+
+    /// <summary>
+    /// Indexes multiple items in batch and returns the result with error details if any.
+    /// </summary>
+    /// <param name="items">The items to index.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public Task<SearchOperationResult> IndexBatchWithResultAsync(IEnumerable<T> items, CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(items);
+        ThrowIfDisposed();
+
+        var batch = new List<(string Id, string Text)>();
+
+        lock (_lockObject)
+        {
+            foreach (var item in items)
+            {
+                if (cancellationToken.IsCancellationRequested)
+                {
+                    break;
+                }
+
+                var text = BuildSearchableText(item);
+                if (!string.IsNullOrWhiteSpace(text))
+                {
+                    _itemsById[item.Id] = item;
+                    batch.Add((item.Id, text));
+                }
+            }
+        }
+
+        return Task.FromResult(_index.IndexTextBatch(batch));
+    }
+
+    /// <inheritdoc/>
+    public Task RemoveAsync(string id, CancellationToken cancellationToken = default)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(id);
+        ThrowIfDisposed();
+
+        lock (_lockObject)
+        {
+            _itemsById.Remove(id);
+        }
+
+        Logger.LogDebug($"[SemanticSearchEngine] RemoveAsync. Id={id}");
+
+        // Note: Errors are captured in LastError for external logging
+        _ = _index.Remove(id);
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task ClearAsync(CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+
+        int count;
+        lock (_lockObject)
+        {
+            count = _itemsById.Count;
+            _itemsById.Clear();
+        }
+
+        Logger.LogInfo($"[SemanticSearchEngine] ClearAsync. ItemsCleared={count}");
+
+        // Note: Errors are captured in LastError for external logging
+        _ = _index.RemoveAll();
+        return Task.CompletedTask;
+    }
+
+    /// <inheritdoc/>
+    public Task<IReadOnlyList<SearchResult<T>>> SearchAsync(
+        string query,
+        SearchOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+
+        if (string.IsNullOrWhiteSpace(query))
+        {
+            Logger.LogDebug($"[SemanticSearchEngine] SearchAsync skipped (empty query).");
+            return Task.FromResult<IReadOnlyList<SearchResult<T>>>(Array.Empty<SearchResult<T>>());
+        }
+
+        options ??= new SearchOptions();
+        Logger.LogDebug($"[SemanticSearchEngine] SearchAsync starting. Query={query}, MaxResults={options.MaxResults}");
+
+        var semanticOptions = new SemanticSearchOptions
+        {
+            MaxResults = options.MaxResults,
+            Language = options.Language,
+            MatchScope = SemanticSearchMatchScope.Unconstrained,
+            TextMatchType = SemanticSearchTextMatchType.Fuzzy,
+        };
+
+        var searchResult = _index.SearchText(query, semanticOptions);
+
+        // Note: Errors are captured in LastError for external logging
+        var matches = searchResult.Value ?? Array.Empty<SemanticSearchResult>();
+        var results = new List<SearchResult<T>>();
+
+        lock (_lockObject)
+        {
+            foreach (var match in matches)
+            {
+                if (_itemsById.TryGetValue(match.ContentId, out var item))
+                {
+                    results.Add(new SearchResult<T>
+                    {
+                        Item = item,
+                        Score = 100.0, // Semantic search doesn't return scores, use fixed value
+                        MatchKind = SearchMatchKind.Semantic,
+                        MatchSpans = null,
+                    });
+                }
+            }
+        }
+
+        Logger.LogDebug($"[SemanticSearchEngine] SearchAsync completed. Query={query}, Matches={matches.Count}, Results={results.Count}");
+        return Task.FromResult<IReadOnlyList<SearchResult<T>>>(results);
+    }
+
+    /// <summary>
+    /// Searches for items matching the query and returns the result with error details if any.
+    /// </summary>
+    /// <param name="query">The search query.</param>
+    /// <param name="options">Optional search options.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A result containing search results or error details.</returns>
+    public Task<SearchOperationResult<IReadOnlyList<SearchResult<T>>>> SearchWithResultAsync(
+        string query,
+        SearchOptions? options = null,
+        CancellationToken cancellationToken = default)
+    {
+        ThrowIfDisposed();
+
+        if (string.IsNullOrWhiteSpace(query))
+        {
+            return Task.FromResult(SearchOperationResult<IReadOnlyList<SearchResult<T>>>.Success(Array.Empty<SearchResult<T>>()));
+        }
+
+        options ??= new SearchOptions();
+
+        var semanticOptions = new SemanticSearchOptions
+        {
+            MaxResults = options.MaxResults,
+            Language = options.Language,
+            MatchScope = SemanticSearchMatchScope.Unconstrained,
+            TextMatchType = SemanticSearchTextMatchType.Fuzzy,
+        };
+
+        var searchResult = _index.SearchText(query, semanticOptions);
+        var matches = searchResult.Value ?? Array.Empty<SemanticSearchResult>();
+        var results = new List<SearchResult<T>>();
+
+        lock (_lockObject)
+        {
+            foreach (var match in matches)
+            {
+                if (_itemsById.TryGetValue(match.ContentId, out var item))
+                {
+                    results.Add(new SearchResult<T>
+                    {
+                        Item = item,
+                        Score = 100.0,
+                        MatchKind = SearchMatchKind.Semantic,
+                        MatchSpans = null,
+                    });
+                }
+            }
+        }
+
+        if (searchResult.IsFailure)
+        {
+            return Task.FromResult(SearchOperationResult<IReadOnlyList<SearchResult<T>>>.FailureWithFallback(searchResult.Error!, results));
+        }
+
+        return Task.FromResult(SearchOperationResult<IReadOnlyList<SearchResult<T>>>.Success(results));
+    }
+
+    /// <summary>
+    /// Waits for the indexing process to complete.
+    /// </summary>
+    /// <param name="timeout">The maximum time to wait.</param>
+    /// <returns>A task representing the async operation.</returns>
+    public async Task WaitForIndexingCompleteAsync(TimeSpan timeout)
+    {
+        ThrowIfDisposed();
+        await _index.WaitForIndexingCompleteAsync(timeout).ConfigureAwait(false);
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        Logger.LogDebug($"[SemanticSearchEngine] Disposing. ItemType={typeof(T).Name}");
+        _index.Dispose();
+
+        lock (_lockObject)
+        {
+            _itemsById.Clear();
+        }
+
+        _disposed = true;
+    }
+
+    private static string BuildSearchableText(T item)
+    {
+        var primary = item.SearchableText ?? string.Empty;
+        var secondary = item.SecondarySearchableText;
+
+        if (string.IsNullOrWhiteSpace(secondary))
+        {
+            return primary;
+        }
+
+        return $"{primary} {secondary}";
+    }
+
+    private void ThrowIfDisposed()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+    }
+}

src/common/Common.Search/SemanticSearch/SemanticSearchIndex.cs

@@ -0,0 +1,455 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using ManagedCommon;
+using Microsoft.Windows.Search.AppContentIndex;
+using Windows.Graphics.Imaging;
+using SearchOperationResult = Common.Search.SearchOperationResult;
+using SearchOperationResultT = Common.Search.SearchOperationResult<System.Collections.Generic.IReadOnlyList<Common.Search.SemanticSearch.SemanticSearchResult>>;
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// A semantic search engine powered by Windows App SDK AI Search APIs.
+/// Provides text and image indexing with lexical and semantic search capabilities.
+/// </summary>
+public sealed class SemanticSearchIndex : IDisposable
+{
+    private readonly string _indexName;
+    private AppContentIndexer? _indexer;
+    private bool _disposed;
+    private SemanticSearchCapabilities? _capabilities;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SemanticSearchIndex"/> class.
+    /// </summary>
+    /// <param name="indexName">The name of the search index.</param>
+    public SemanticSearchIndex(string indexName)
+    {
+        ArgumentException.ThrowIfNullOrWhiteSpace(indexName);
+        _indexName = indexName;
+    }
+
+    /// <summary>
+    /// Gets the last error that occurred during an operation, or null if no error occurred.
+    /// </summary>
+    public SearchError? LastError { get; private set; }
+
+    /// <summary>
+    /// Occurs when the index capabilities change.
+    /// </summary>
+    public event EventHandler<SemanticSearchCapabilities>? CapabilitiesChanged;
+
+    /// <summary>
+    /// Gets a value indicating whether the search engine is initialized.
+    /// </summary>
+    public bool IsInitialized => _indexer != null;
+
+    /// <summary>
+    /// Gets the current index capabilities, or null if not initialized.
+    /// </summary>
+    public SemanticSearchCapabilities? Capabilities => _capabilities;
+
+    /// <summary>
+    /// Initializes the search engine and creates or opens the index.
+    /// </summary>
+    /// <returns>A task that represents the asynchronous operation. Returns a result indicating success or failure with error details.</returns>
+    public async Task<SearchOperationResult> InitializeAsync()
+    {
+        ThrowIfDisposed();
+        LastError = null;
+
+        if (_indexer != null)
+        {
+            Logger.LogDebug($"[SemanticSearchIndex] Already initialized. IndexName={_indexName}");
+            return SearchOperationResult.Success();
+        }
+
+        Logger.LogInfo($"[SemanticSearchIndex] Initializing. IndexName={_indexName}");
+
+        try
+        {
+            var result = AppContentIndexer.GetOrCreateIndex(_indexName);
+            if (!result.Succeeded)
+            {
+                var errorDetails = $"Succeeded={result.Succeeded}, ExtendedError={result.ExtendedError}";
+                Logger.LogError($"[SemanticSearchIndex] GetOrCreateIndex failed. IndexName={_indexName}, {errorDetails}");
+                LastError = SearchError.InitializationFailed(_indexName, errorDetails);
+                return SearchOperationResult.Failure(LastError);
+            }
+
+            _indexer = result.Indexer;
+
+            // Wait for index capabilities to be ready
+            Logger.LogDebug($"[SemanticSearchIndex] Waiting for index capabilities. IndexName={_indexName}");
+            await _indexer.WaitForIndexCapabilitiesAsync();
+
+            // Load capabilities
+            _capabilities = LoadCapabilities();
+            Logger.LogInfo($"[SemanticSearchIndex] Initialized successfully. IndexName={_indexName}, TextLexical={_capabilities.TextLexicalAvailable}, TextSemantic={_capabilities.TextSemanticAvailable}, ImageSemantic={_capabilities.ImageSemanticAvailable}, ImageOcr={_capabilities.ImageOcrAvailable}");
+
+            // Subscribe to capability changes
+            _indexer.Listener.IndexCapabilitiesChanged += OnIndexCapabilitiesChanged;
+
+            return SearchOperationResult.Success();
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] Initialization failed with exception. IndexName={_indexName}", ex);
+            LastError = SearchError.InitializationFailed(_indexName, ex.Message, ex);
+            return SearchOperationResult.Failure(LastError);
+        }
+    }
+
+    /// <summary>
+    /// Waits for the indexing process to complete.
+    /// </summary>
+    /// <param name="timeout">The maximum time to wait for indexing to complete.</param>
+    /// <returns>A task that represents the asynchronous operation.</returns>
+    public async Task WaitForIndexingCompleteAsync(TimeSpan timeout)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+
+        await _indexer!.WaitForIndexingIdleAsync(timeout);
+    }
+
+    /// <summary>
+    /// Gets the current index capabilities.
+    /// </summary>
+    /// <returns>The current capabilities of the search index.</returns>
+    public SemanticSearchCapabilities GetCapabilities()
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+
+        return _capabilities ?? LoadCapabilities();
+    }
+
+    /// <summary>
+    /// Adds or updates text content in the index.
+    /// </summary>
+    /// <param name="id">The unique identifier for the content.</param>
+    /// <param name="text">The text content to index.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public SearchOperationResult IndexText(string id, string text)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentException.ThrowIfNullOrWhiteSpace(id);
+        ArgumentException.ThrowIfNullOrWhiteSpace(text);
+
+        try
+        {
+            var content = AppManagedIndexableAppContent.CreateFromString(id, text);
+            _indexer!.AddOrUpdate(content);
+            return SearchOperationResult.Success();
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] IndexText failed. Id={id}", ex);
+            LastError = SearchError.IndexingFailed(id, ex.Message, ex);
+            return SearchOperationResult.Failure(LastError);
+        }
+    }
+
+    /// <summary>
+    /// Adds or updates multiple text contents in the index.
+    /// </summary>
+    /// <param name="items">A collection of id-text pairs to index.</param>
+    /// <returns>A result indicating success or failure with error details. Contains the first error encountered if any.</returns>
+    public SearchOperationResult IndexTextBatch(IEnumerable<(string Id, string Text)> items)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentNullException.ThrowIfNull(items);
+
+        SearchError? firstError = null;
+
+        foreach (var (id, text) in items)
+        {
+            if (!string.IsNullOrWhiteSpace(id) && !string.IsNullOrWhiteSpace(text))
+            {
+                try
+                {
+                    var content = AppManagedIndexableAppContent.CreateFromString(id, text);
+                    _indexer!.AddOrUpdate(content);
+                }
+                catch (Exception ex)
+                {
+                    Logger.LogError($"[SemanticSearchIndex] IndexTextBatch item failed. Id={id}", ex);
+                    firstError ??= SearchError.IndexingFailed(id, ex.Message, ex);
+                }
+            }
+        }
+
+        if (firstError != null)
+        {
+            LastError = firstError;
+            return SearchOperationResult.Failure(firstError);
+        }
+
+        return SearchOperationResult.Success();
+    }
+
+    /// <summary>
+    /// Adds or updates image content in the index.
+    /// </summary>
+    /// <param name="id">The unique identifier for the image.</param>
+    /// <param name="bitmap">The image bitmap to index.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public SearchOperationResult IndexImage(string id, SoftwareBitmap bitmap)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentException.ThrowIfNullOrWhiteSpace(id);
+        ArgumentNullException.ThrowIfNull(bitmap);
+
+        try
+        {
+            var content = AppManagedIndexableAppContent.CreateFromBitmap(id, bitmap);
+            _indexer!.AddOrUpdate(content);
+            return SearchOperationResult.Success();
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] IndexImage failed. Id={id}", ex);
+            LastError = SearchError.IndexingFailed(id, ex.Message, ex);
+            return SearchOperationResult.Failure(LastError);
+        }
+    }
+
+    /// <summary>
+    /// Removes content from the index by its identifier.
+    /// </summary>
+    /// <param name="id">The unique identifier of the content to remove.</param>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public SearchOperationResult Remove(string id)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentException.ThrowIfNullOrWhiteSpace(id);
+
+        try
+        {
+            _indexer!.Remove(id);
+            return SearchOperationResult.Success();
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] Remove failed. Id={id}", ex);
+            LastError = SearchError.Unexpected("Remove", ex);
+            return SearchOperationResult.Failure(LastError);
+        }
+    }
+
+    /// <summary>
+    /// Removes all content from the index.
+    /// </summary>
+    /// <returns>A result indicating success or failure with error details.</returns>
+    public SearchOperationResult RemoveAll()
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+
+        try
+        {
+            _indexer!.RemoveAll();
+            return SearchOperationResult.Success();
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] RemoveAll failed.", ex);
+            LastError = SearchError.Unexpected("RemoveAll", ex);
+            return SearchOperationResult.Failure(LastError);
+        }
+    }
+
+    /// <summary>
+    /// Searches for text content in the index.
+    /// </summary>
+    /// <param name="searchText">The text to search for.</param>
+    /// <param name="options">Optional search options.</param>
+    /// <returns>A result containing search results or error details.</returns>
+    public SearchOperationResultT SearchText(string searchText, SemanticSearchOptions? options = null)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentException.ThrowIfNullOrWhiteSpace(searchText);
+
+        options ??= new SemanticSearchOptions();
+
+        try
+        {
+            var queryOptions = new TextQueryOptions
+            {
+                MatchScope = ConvertMatchScope(options.MatchScope),
+                TextMatchType = ConvertTextMatchType(options.TextMatchType),
+            };
+
+            if (!string.IsNullOrEmpty(options.Language))
+            {
+                queryOptions.Language = options.Language;
+            }
+
+            var query = _indexer!.CreateTextQuery(searchText, queryOptions);
+            var matches = query.GetNextMatches(options.MaxResults);
+
+            return SearchOperationResultT.Success(ConvertTextMatches(matches));
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] SearchText failed. Query={searchText}", ex);
+            LastError = SearchError.SearchFailed(searchText, ex.Message, ex);
+            return SearchOperationResultT.FailureWithFallback(LastError, Array.Empty<SemanticSearchResult>());
+        }
+    }
+
+    /// <summary>
+    /// Searches for image content in the index using text.
+    /// </summary>
+    /// <param name="searchText">The text to search for in images.</param>
+    /// <param name="options">Optional search options.</param>
+    /// <returns>A result containing search results or error details.</returns>
+    public SearchOperationResultT SearchImages(string searchText, SemanticSearchOptions? options = null)
+    {
+        ThrowIfDisposed();
+        ThrowIfNotInitialized();
+        ArgumentException.ThrowIfNullOrWhiteSpace(searchText);
+
+        options ??= new SemanticSearchOptions();
+
+        try
+        {
+            var queryOptions = new ImageQueryOptions
+            {
+                MatchScope = ConvertMatchScope(options.MatchScope),
+                ImageOcrTextMatchType = ConvertTextMatchType(options.TextMatchType),
+            };
+
+            var query = _indexer!.CreateImageQuery(searchText, queryOptions);
+            var matches = query.GetNextMatches(options.MaxResults);
+
+            return SearchOperationResultT.Success(ConvertImageMatches(matches));
+        }
+        catch (Exception ex)
+        {
+            Logger.LogError($"[SemanticSearchIndex] SearchImages failed. Query={searchText}", ex);
+            LastError = SearchError.SearchFailed(searchText, ex.Message, ex);
+            return SearchOperationResultT.FailureWithFallback(LastError, Array.Empty<SemanticSearchResult>());
+        }
+    }
+
+    /// <inheritdoc/>
+    public void Dispose()
+    {
+        if (_disposed)
+        {
+            return;
+        }
+
+        if (_indexer != null)
+        {
+            _indexer.Listener.IndexCapabilitiesChanged -= OnIndexCapabilitiesChanged;
+            _indexer.Dispose();
+            _indexer = null;
+        }
+
+        _disposed = true;
+    }
+
+    private SemanticSearchCapabilities LoadCapabilities()
+    {
+        var capabilities = _indexer!.GetIndexCapabilities();
+
+        return new SemanticSearchCapabilities
+        {
+            TextLexicalAvailable = IsCapabilityInitialized(capabilities, IndexCapability.TextLexical),
+            TextSemanticAvailable = IsCapabilityInitialized(capabilities, IndexCapability.TextSemantic),
+            ImageSemanticAvailable = IsCapabilityInitialized(capabilities, IndexCapability.ImageSemantic),
+            ImageOcrAvailable = IsCapabilityInitialized(capabilities, IndexCapability.ImageOcr),
+        };
+    }
+
+    private static bool IsCapabilityInitialized(IndexCapabilities capabilities, IndexCapability capability)
+    {
+        var state = capabilities.GetCapabilityState(capability);
+        return state.InitializationStatus == IndexCapabilityInitializationStatus.Initialized;
+    }
+
+    private void OnIndexCapabilitiesChanged(AppContentIndexer indexer, IndexCapabilities capabilities)
+    {
+        _capabilities = LoadCapabilities();
+        Logger.LogInfo($"[SemanticSearchIndex] Capabilities changed. IndexName={_indexName}, TextLexical={_capabilities.TextLexicalAvailable}, TextSemantic={_capabilities.TextSemanticAvailable}, ImageSemantic={_capabilities.ImageSemanticAvailable}, ImageOcr={_capabilities.ImageOcrAvailable}");
+        CapabilitiesChanged?.Invoke(this, _capabilities);
+    }
+
+    private static QueryMatchScope ConvertMatchScope(SemanticSearchMatchScope scope)
+    {
+        return scope switch
+        {
+            SemanticSearchMatchScope.Unconstrained => QueryMatchScope.Unconstrained,
+            SemanticSearchMatchScope.Region => QueryMatchScope.Region,
+            SemanticSearchMatchScope.ContentItem => QueryMatchScope.ContentItem,
+            _ => QueryMatchScope.Unconstrained,
+        };
+    }
+
+    private static TextLexicalMatchType ConvertTextMatchType(SemanticSearchTextMatchType matchType)
+    {
+        return matchType switch
+        {
+            SemanticSearchTextMatchType.Fuzzy => TextLexicalMatchType.Fuzzy,
+            SemanticSearchTextMatchType.Exact => TextLexicalMatchType.Exact,
+            _ => TextLexicalMatchType.Fuzzy,
+        };
+    }
+
+    private static IReadOnlyList<SemanticSearchResult> ConvertTextMatches(IReadOnlyList<TextQueryMatch> matches)
+    {
+        var results = new List<SemanticSearchResult>();
+
+        foreach (var match in matches)
+        {
+            var result = new SemanticSearchResult(match.ContentId, SemanticSearchContentKind.Text);
+
+            if (match.ContentKind == QueryMatchContentKind.AppManagedText &&
+                match is AppManagedTextQueryMatch textMatch)
+            {
+                result.TextOffset = textMatch.TextOffset;
+                result.TextLength = textMatch.TextLength;
+            }
+
+            results.Add(result);
+        }
+
+        return results;
+    }
+
+    private static IReadOnlyList<SemanticSearchResult> ConvertImageMatches(IReadOnlyList<ImageQueryMatch> matches)
+    {
+        var results = new List<SemanticSearchResult>();
+
+        foreach (var match in matches)
+        {
+            var result = new SemanticSearchResult(match.ContentId, SemanticSearchContentKind.Image);
+            results.Add(result);
+        }
+
+        return results;
+    }
+
+    private void ThrowIfDisposed()
+    {
+        ObjectDisposedException.ThrowIf(_disposed, this);
+    }
+
+    private void ThrowIfNotInitialized()
+    {
+        if (_indexer == null)
+        {
+            throw new InvalidOperationException("Search engine is not initialized. Call InitializeAsync() first.");
+        }
+    }
+}

src/common/Common.Search/SemanticSearch/SemanticSearchMatchScope.cs

@@ -0,0 +1,26 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Specifies the scope for semantic search matching.
+/// </summary>
+public enum SemanticSearchMatchScope
+{
+    /// <summary>
+    /// No constraints, uses both Lexical and Semantic matching.
+    /// </summary>
+    Unconstrained,
+
+    /// <summary>
+    /// Restrict matching to a specific region.
+    /// </summary>
+    Region,
+
+    /// <summary>
+    /// Restrict matching to a single content item.
+    /// </summary>
+    ContentItem,
+}

src/common/Common.Search/SemanticSearch/SemanticSearchOptions.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Options for configuring semantic search queries.
+/// </summary>
+public class SemanticSearchOptions
+{
+    /// <summary>
+    /// Gets or sets the language for the search query (e.g., "en-US").
+    /// </summary>
+    public string? Language { get; set; }
+
+    /// <summary>
+    /// Gets or sets the match scope for the search.
+    /// </summary>
+    public SemanticSearchMatchScope MatchScope { get; set; } = SemanticSearchMatchScope.Unconstrained;
+
+    /// <summary>
+    /// Gets or sets the text match type for lexical matching.
+    /// </summary>
+    public SemanticSearchTextMatchType TextMatchType { get; set; } = SemanticSearchTextMatchType.Fuzzy;
+
+    /// <summary>
+    /// Gets or sets the maximum number of results to return.
+    /// </summary>
+    public int MaxResults { get; set; } = 10;
+}

src/common/Common.Search/SemanticSearch/SemanticSearchResult.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Represents a search result from the semantic search engine.
+/// </summary>
+public class SemanticSearchResult
+{
+    /// <summary>
+    /// Initializes a new instance of the <see cref="SemanticSearchResult"/> class.
+    /// </summary>
+    /// <param name="contentId">The unique identifier of the matched content.</param>
+    /// <param name="contentKind">The kind of content matched (text or image).</param>
+    public SemanticSearchResult(string contentId, SemanticSearchContentKind contentKind)
+    {
+        ContentId = contentId;
+        ContentKind = contentKind;
+    }
+
+    /// <summary>
+    /// Gets the unique identifier of the matched content.
+    /// </summary>
+    public string ContentId { get; }
+
+    /// <summary>
+    /// Gets the kind of content that was matched.
+    /// </summary>
+    public SemanticSearchContentKind ContentKind { get; }
+
+    /// <summary>
+    /// Gets or sets the text offset where the match was found (for text matches only).
+    /// </summary>
+    public int TextOffset { get; set; }
+
+    /// <summary>
+    /// Gets or sets the length of the matched text (for text matches only).
+    /// </summary>
+    public int TextLength { get; set; }
+}

src/common/Common.Search/SemanticSearch/SemanticSearchTextMatchType.cs

@@ -0,0 +1,21 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+namespace Common.Search.SemanticSearch;
+
+/// <summary>
+/// Specifies the type of text matching for lexical searches.
+/// </summary>
+public enum SemanticSearchTextMatchType
+{
+    /// <summary>
+    /// Fuzzy matching allows spelling errors and approximate words.
+    /// </summary>
+    Fuzzy,
+
+    /// <summary>
+    /// Exact matching requires exact text matches.
+    /// </summary>
+    Exact,
+}

src/modules/alwaysontop/AlwaysOnTop/AlwaysOnTop.cpp

@@ -153,9 +153,21 @@ LRESULT AlwaysOnTop::WndProc(HWND window, UINT message, WPARAM wparam, LPARAM lp
 {
     if (message == WM_HOTKEY)
     {
+        int hotkeyId = static_cast<int>(wparam);
         if (HWND fw{ GetForegroundWindow() })
         {
-            ProcessCommand(fw);
+            if (hotkeyId == static_cast<int>(HotkeyId::Pin))
+            {
+                ProcessCommand(fw);
+            }
+            else if (hotkeyId == static_cast<int>(HotkeyId::IncreaseOpacity))
+            {
+                AdjustTransparency(fw, Settings::transparencyStep);
+            }
+            else if (hotkeyId == static_cast<int>(HotkeyId::DecreaseOpacity))
+            {
+                AdjustTransparency(fw, -Settings::transparencyStep);
+            }
         }
     }
     else if (message == WM_PRIV_SETTINGS_CHANGED)
@@ -191,6 +203,11 @@ void AlwaysOnTop::ProcessCommand(HWND window)
                 m_topmostWindows.erase(iter);
             }
 
+            // Restore transparency when unpinning
+            RemoveTransparency(window);
+            m_windowOriginalLayeredState.erase(window);
+            m_windowTransparency.erase(window);
+
             Trace::AlwaysOnTop::UnpinWindow();
         }
     }
@@ -200,6 +217,7 @@ void AlwaysOnTop::ProcessCommand(HWND window)
         {
             soundType = Sound::Type::On;
             AssignBorder(window);
+            
             Trace::AlwaysOnTop::PinWindow();
         }
     }
@@ -269,11 +287,22 @@ void AlwaysOnTop::RegisterHotkey() const
 {
     if (m_useCentralizedLLKH)
     {
+        // All hotkeys are handled by centralized LLKH
         return;
     }
 
+    // Register hotkeys only when not using centralized LLKH
     UnregisterHotKey(m_window, static_cast<int>(HotkeyId::Pin));
+    UnregisterHotKey(m_window, static_cast<int>(HotkeyId::IncreaseOpacity));
+    UnregisterHotKey(m_window, static_cast<int>(HotkeyId::DecreaseOpacity));
+
+    // Register pin hotkey
     RegisterHotKey(m_window, static_cast<int>(HotkeyId::Pin), AlwaysOnTopSettings::settings().hotkey.get_modifiers(), AlwaysOnTopSettings::settings().hotkey.get_code());
+
+    // Register transparency hotkeys using the same modifiers as the pin hotkey
+    UINT modifiers = AlwaysOnTopSettings::settings().hotkey.get_modifiers();
+    RegisterHotKey(m_window, static_cast<int>(HotkeyId::IncreaseOpacity), modifiers, VK_OEM_PLUS);
+    RegisterHotKey(m_window, static_cast<int>(HotkeyId::DecreaseOpacity), modifiers, VK_OEM_MINUS);
 }
 
 void AlwaysOnTop::RegisterLLKH()
@@ -285,6 +314,8 @@ void AlwaysOnTop::RegisterLLKH()
 	
     m_hPinEvent = CreateEventW(nullptr, false, false, CommonSharedConstants::ALWAYS_ON_TOP_PIN_EVENT);
     m_hTerminateEvent = CreateEventW(nullptr, false, false, CommonSharedConstants::ALWAYS_ON_TOP_TERMINATE_EVENT);
+    m_hIncreaseOpacityEvent = CreateEventW(nullptr, false, false, CommonSharedConstants::ALWAYS_ON_TOP_INCREASE_OPACITY_EVENT);
+    m_hDecreaseOpacityEvent = CreateEventW(nullptr, false, false, CommonSharedConstants::ALWAYS_ON_TOP_DECREASE_OPACITY_EVENT);
 
     if (!m_hPinEvent)
     {
@@ -298,30 +329,54 @@ void AlwaysOnTop::RegisterLLKH()
         return;
     }
 
-    HANDLE handles[2] = { m_hPinEvent,
-                          m_hTerminateEvent };
+    if (!m_hIncreaseOpacityEvent)
+    {
+        Logger::warn(L"Failed to create increaseOpacityEvent. {}", get_last_error_or_default(GetLastError()));
+    }
+
+    if (!m_hDecreaseOpacityEvent)
+    {
+        Logger::warn(L"Failed to create decreaseOpacityEvent. {}", get_last_error_or_default(GetLastError()));
+    }
+
+    HANDLE handles[4] = { m_hPinEvent,
+                          m_hTerminateEvent,
+                          m_hIncreaseOpacityEvent,
+                          m_hDecreaseOpacityEvent };
 
     m_thread = std::thread([this, handles]() {
         MSG msg;
         while (m_running)
         {
-            DWORD dwEvt = MsgWaitForMultipleObjects(2, handles, false, INFINITE, QS_ALLINPUT);
+            DWORD dwEvt = MsgWaitForMultipleObjects(4, handles, false, INFINITE, QS_ALLINPUT);
             if (!m_running)
             {
                 break;
             }
             switch (dwEvt)
             {
-            case WAIT_OBJECT_0:
+            case WAIT_OBJECT_0: // Pin event
                 if (HWND fw{ GetForegroundWindow() })
                 {
                     ProcessCommand(fw);
                 }
                 break;
-            case WAIT_OBJECT_0 + 1:
+            case WAIT_OBJECT_0 + 1: // Terminate event
                 PostThreadMessage(m_mainThreadId, WM_QUIT, 0, 0);
                 break;
-            case WAIT_OBJECT_0 + 2:
+            case WAIT_OBJECT_0 + 2: // Increase opacity event
+                if (HWND fw{ GetForegroundWindow() })
+                {
+                    AdjustTransparency(fw, Settings::transparencyStep);
+                }
+                break;
+            case WAIT_OBJECT_0 + 3: // Decrease opacity event
+                if (HWND fw{ GetForegroundWindow() })
+                {
+                    AdjustTransparency(fw, -Settings::transparencyStep);
+                }
+                break;
+            case WAIT_OBJECT_0 + 4: // Message queue
                 if (PeekMessageW(&msg, nullptr, 0, 0, PM_REMOVE))
                 {
                     TranslateMessage(&msg);
@@ -370,9 +425,13 @@ void AlwaysOnTop::UnpinAll()
         {
             Logger::error(L"Unpinning topmost window failed");
         }
+        // Restore transparency when unpinning all
+        RemoveTransparency(topWindow);
     }
 
     m_topmostWindows.clear();
+    m_windowTransparency.clear();
+    m_windowOriginalLayeredState.clear();
 }
 
 void AlwaysOnTop::CleanUp()
@@ -456,6 +515,8 @@ void AlwaysOnTop::HandleWinHookEvent(WinHookEvent* data) noexcept
     for (const auto window : toErase)
     {
         m_topmostWindows.erase(window);
+        m_windowTransparency.erase(window);
+        m_windowOriginalLayeredState.erase(window);
     }
 
     switch (data->event)
@@ -556,4 +617,182 @@ void AlwaysOnTop::RefreshBorders()
             }
         }
     }
+}
+
+// Transparency adjustment methods
+HWND AlwaysOnTop::GetTransparencyTarget(HWND window)
+{
+    if (!window || !IsWindow(window))
+    {
+        return nullptr;
+    }
+
+    // Only allow transparency adjustment on tracked/pinned windows
+    if (!IsTracked(window) && !IsPinned(window))
+    {
+        return nullptr;
+    }
+
+    // Use GA_ROOTOWNER to get the root owner window
+    HWND targetWindow = GetAncestor(window, GA_ROOTOWNER);
+    if (!targetWindow)
+    {
+        targetWindow = window;
+    }
+
+    // Filter out desktop, shell, invisible windows
+    if (targetWindow == GetDesktopWindow() || targetWindow == GetShellWindow())
+    {
+        return nullptr;
+    }
+    if (!IsWindowVisible(targetWindow))
+    {
+        return nullptr;
+    }
+
+    return targetWindow;
+}
+
+void AlwaysOnTop::AdjustTransparency(HWND window, int delta)
+{
+    HWND targetWindow = GetTransparencyTarget(window);
+    if (!targetWindow)
+    {
+        return;
+    }
+
+    auto it = m_windowTransparency.find(targetWindow);
+    int currentTransparency = (it != m_windowTransparency.end()) ? it->second : Settings::maxTransparencyPercentage;
+    int newTransparency = (std::max)(Settings::minTransparencyPercentage, 
+                                     (std::min)(Settings::maxTransparencyPercentage, currentTransparency + delta));
+
+    if (newTransparency != currentTransparency)
+    {
+        SetTransparency(targetWindow, newTransparency);
+
+        if (AlwaysOnTopSettings::settings().enableSound)
+        {
+            m_sound.Play(delta > 0 ? Sound::Type::IncreaseOpacity : Sound::Type::DecreaseOpacity);
+        }
+
+        Logger::trace(L"Transparency adjusted to {}%", newTransparency);
+    }
+}
+
+void AlwaysOnTop::SetTransparency(HWND window, int percentage)
+{
+    if (!window || !IsWindow(window))
+    {
+        return;
+    }
+    
+    percentage = (std::max)(Settings::minTransparencyPercentage, 
+                            (std::min)(Settings::maxTransparencyPercentage, percentage));
+
+    m_windowTransparency[window] = percentage;
+
+    if (percentage == Settings::maxTransparencyPercentage)
+    {
+        RemoveTransparency(window);
+        return;
+    }
+
+    LONG exStyle = GetWindowLong(window, GWL_EXSTYLE);
+    bool isCurrentlyLayered = (exStyle & WS_EX_LAYERED) != 0;
+
+    // Cache original state on first transparency application
+    if (m_windowOriginalLayeredState.find(window) == m_windowOriginalLayeredState.end())
+    {
+        WindowLayeredState state;
+        state.hadLayeredStyle = isCurrentlyLayered;
+        
+        if (isCurrentlyLayered)
+        {
+            BYTE alpha = 255;
+            COLORREF colorKey = 0;
+            DWORD flags = 0;
+            if (GetLayeredWindowAttributes(window, &colorKey, &alpha, &flags))
+            {
+                state.originalAlpha = alpha;
+                state.usedColorKey = (flags & LWA_COLORKEY) != 0;
+                state.colorKey = colorKey;
+            }
+            else
+            {
+                Logger::warn(L"GetLayeredWindowAttributes failed for layered window, skipping");
+                return;
+            }
+        }
+        m_windowOriginalLayeredState[window] = state;
+    }
+
+    // Clear WS_EX_LAYERED first to ensure SetLayeredWindowAttributes works
+    if (isCurrentlyLayered)
+    {
+        SetWindowLong(window, GWL_EXSTYLE, exStyle & ~WS_EX_LAYERED);
+        SetWindowPos(window, nullptr, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
+        exStyle = GetWindowLong(window, GWL_EXSTYLE);
+    }
+
+    BYTE alphaValue = static_cast<BYTE>((255 * percentage) / 100);
+    SetWindowLong(window, GWL_EXSTYLE, exStyle | WS_EX_LAYERED);
+    SetLayeredWindowAttributes(window, 0, alphaValue, LWA_ALPHA);
+}
+
+void AlwaysOnTop::RemoveTransparency(HWND window)
+{
+    if (!window || !IsWindow(window))
+    {
+        return;
+    }
+
+    LONG exStyle = GetWindowLong(window, GWL_EXSTYLE);
+    auto it = m_windowOriginalLayeredState.find(window);
+    
+    if (it != m_windowOriginalLayeredState.end())
+    {
+        const auto& originalState = it->second;
+        
+        if (originalState.hadLayeredStyle)
+        {
+            // Window originally had WS_EX_LAYERED - restore original attributes
+            // Clear and re-add to ensure clean state
+            if (exStyle & WS_EX_LAYERED)
+            {
+                SetWindowLong(window, GWL_EXSTYLE, exStyle & ~WS_EX_LAYERED);
+                exStyle = GetWindowLong(window, GWL_EXSTYLE);
+            }
+            SetWindowLong(window, GWL_EXSTYLE, exStyle | WS_EX_LAYERED);
+            
+            // Restore original alpha and/or color key
+            DWORD flags = LWA_ALPHA;
+            if (originalState.usedColorKey)
+            {
+                flags |= LWA_COLORKEY;
+            }
+            SetLayeredWindowAttributes(window, originalState.colorKey, originalState.originalAlpha, flags);
+            SetWindowPos(window, nullptr, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
+        }
+        else
+        {
+            // Window originally didn't have WS_EX_LAYERED - remove it completely
+            if (exStyle & WS_EX_LAYERED)
+            {
+                SetLayeredWindowAttributes(window, 0, 255, LWA_ALPHA);
+                SetWindowLong(window, GWL_EXSTYLE, exStyle & ~WS_EX_LAYERED);
+                SetWindowPos(window, nullptr, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED);
+            }
+        }
+        
+        m_windowOriginalLayeredState.erase(it);
+    }
+    else
+    {
+        // Fallback: no cached state, just remove layered style
+        if (exStyle & WS_EX_LAYERED)
+        {
+            SetLayeredWindowAttributes(window, 0, 255, LWA_ALPHA);
+            SetWindowLong(window, GWL_EXSTYLE, exStyle & ~WS_EX_LAYERED);
+        }
+    }
 }

src/modules/alwaysontop/AlwaysOnTop/AlwaysOnTop.h

@@ -10,6 +10,7 @@
 
 #include <common/hooks/WinHookEvent.h>
 #include <common/notifications/NotificationUtil.h>
+#include <common/utils/window.h>
 
 class AlwaysOnTop : public SettingsObserver
 {
@@ -38,6 +39,8 @@ private:
     enum class HotkeyId : int
     {
         Pin = 1,
+        IncreaseOpacity = 2,
+        DecreaseOpacity = 3,
     };
 
     static inline AlwaysOnTop* s_instance = nullptr;
@@ -48,8 +51,21 @@ private:
     HWND m_window{ nullptr };
     HINSTANCE m_hinstance;
     std::map<HWND, std::unique_ptr<WindowBorder>> m_topmostWindows{};
+    std::map<HWND, int> m_windowTransparency{}; // Track transparency per window (20-100)
+    
+    // Store original window layered state for proper restoration
+    struct WindowLayeredState {
+        bool hadLayeredStyle = false;
+        BYTE originalAlpha = 255;
+        bool usedColorKey = false;
+        COLORREF colorKey = 0;
+    };
+    std::map<HWND, WindowLayeredState> m_windowOriginalLayeredState{};
+    
     HANDLE m_hPinEvent;
     HANDLE m_hTerminateEvent;
+    HANDLE m_hIncreaseOpacityEvent;
+    HANDLE m_hDecreaseOpacityEvent;
     DWORD m_mainThreadId;
     std::thread m_thread;
     const bool m_useCentralizedLLKH;
@@ -78,6 +94,12 @@ private:
     bool AssignBorder(HWND window);
     void RefreshBorders();
 
+    // Transparency methods
+    HWND GetTransparencyTarget(HWND window);
+    void AdjustTransparency(HWND window, int delta);
+    void SetTransparency(HWND window, int percentage);
+    void RemoveTransparency(HWND window);
+
     virtual void SettingsUpdate(SettingId type) override;
 
     static void CALLBACK WinHookProc(HWINEVENTHOOK winEventHook,

src/modules/cmdpal/ExtensionTemplate/TemplateCmdPalExtension/Directory.Packages.props

@@ -5,12 +5,12 @@
   <ItemGroup>
     <PackageVersion Include="Microsoft.CommandPalette.Extensions" Version="0.5.250829002" />
     <PackageVersion Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="9.0.0-preview.24508.2" />
-    <PackageVersion Include="Microsoft.Web.WebView2" Version="1.0.2903.40" />
+    <PackageVersion Include="Microsoft.Web.WebView2" Version="1.0.3405.78" />
     <PackageVersion Include="Microsoft.Windows.CsWin32" Version="0.3.183" />
     <PackageVersion Include="Microsoft.Windows.CsWinRT" Version="2.2.0" />
     <PackageVersion Include="Microsoft.Windows.SDK.BuildTools" Version="10.0.26100.4188" />
     <PackageVersion Include="Microsoft.Windows.SDK.BuildTools.MSIX" Version="1.7.20250829.1" />
-    <PackageVersion Include="Microsoft.WindowsAppSDK" Version="1.8.250907003" />
+    <PackageVersion Include="Microsoft.WindowsAppSDK" Version="2.0.0-experimental3" />
     <PackageVersion Include="Shmuelie.WinRTServer" Version="2.1.1" />
     <PackageVersion Include="StyleCop.Analyzers" Version="1.2.0-beta.556" />
     <PackageVersion Include="System.Text.Json" Version="9.0.8" />

src/modules/peek/Peek.UI/PeekXAML/MainWindow.xaml.cs

@@ -197,10 +197,16 @@ namespace Peek.UI
 
             ViewModel.Initialize(selectedItem);
 
-            // If no files were found (e.g., user is typing in rename/search box, or in virtual folders),
-            // don't show anything - just return silently to avoid stealing focus
+            // If no files were found (e.g., in virtual folders like Home/Recent), show an error
             if (ViewModel.CurrentItem == null)
             {
+                Logger.LogInfo("Peek: No files found to preview, showing error.");
+                var errorMessage = ResourceLoaderInstance.ResourceLoader.GetString("NoFilesSelected");
+                ViewModel.ShowError(errorMessage);
+
+                // Still show the window so user can see the warning
+                this.Show();
+                WindowHelpers.BringToForeground(this.GetWindowHandle());
                 return;
             }
 

src/modules/powerrename/lib/PowerRenameRegEx.cpp

@@ -33,27 +33,23 @@ static std::wstring SanitizeAndNormalize(const std::wstring& input)
 
     // Normalize to NFC (Precomposed).
     // Get the size needed for the normalized string, including null terminator.
-    int sizeEstimate = NormalizeString(NormalizationC, sanitized.c_str(), -1, nullptr, 0);
-    if (sizeEstimate <= 0)
+    int size = NormalizeString(NormalizationC, sanitized.c_str(), -1, nullptr, 0);
+    if (size <= 0)
     {
         return sanitized; // Return unaltered if normalization fails.
     }
 
     // Perform the normalization.
     std::wstring normalized;
-    normalized.resize(sizeEstimate);
-    int actualSize = NormalizeString(NormalizationC, sanitized.c_str(), -1, &normalized[0], sizeEstimate);
+    normalized.resize(size);
+    NormalizeString(NormalizationC, sanitized.c_str(), -1, &normalized[0], size);
 
-    if (actualSize <= 0)
+    // Remove the explicit null terminator added by NormalizeString.
+    if (!normalized.empty() && normalized.back() == L'\0')
     {
-        // Normalization failed, return sanitized string.
-        return sanitized;
+        normalized.pop_back();
     }
 
-    // Resize to actual size minus the null terminator.
-    // actualSize includes the null terminator when input length is -1.
-    normalized.resize(static_cast<size_t>(actualSize) - 1);
-
     return normalized;
 }
 

src/modules/powerrename/unittests/CommonRegExTests.h

@@ -695,38 +695,6 @@ TEST_METHOD(VerifyUnicodeAndWhitespaceNormalizationRegex)
     VerifyNormalizationHelper(UseRegularExpressions);
 }
 
-TEST_METHOD(VerifyRegexMetacharacterDollarSign)
-{
-    CComPtr<IPowerRenameRegEx> renameRegEx;
-    Assert::IsTrue(CPowerRenameRegEx::s_CreateInstance(&renameRegEx) == S_OK);
-    DWORD flags = UseRegularExpressions;
-    Assert::IsTrue(renameRegEx->PutFlags(flags) == S_OK);
-
-    PWSTR result = nullptr;
-    Assert::IsTrue(renameRegEx->PutSearchTerm(L"$") == S_OK);
-    Assert::IsTrue(renameRegEx->PutReplaceTerm(L"_end") == S_OK);
-    unsigned long index = {};
-    Assert::IsTrue(renameRegEx->Replace(L"test.txt", &result, index) == S_OK);
-    Assert::AreEqual(L"test.txt_end", result);
-    CoTaskMemFree(result);
-}
-
-TEST_METHOD(VerifyRegexMetacharacterCaret)
-{
-    CComPtr<IPowerRenameRegEx> renameRegEx;
-    Assert::IsTrue(CPowerRenameRegEx::s_CreateInstance(&renameRegEx) == S_OK);
-    DWORD flags = UseRegularExpressions;
-    Assert::IsTrue(renameRegEx->PutFlags(flags) == S_OK);
-
-    PWSTR result = nullptr;
-    Assert::IsTrue(renameRegEx->PutSearchTerm(L"^") == S_OK);
-    Assert::IsTrue(renameRegEx->PutReplaceTerm(L"start_") == S_OK);
-    unsigned long index = {};
-    Assert::IsTrue(renameRegEx->Replace(L"test.txt", &result, index) == S_OK);
-    Assert::AreEqual(L"start_test.txt", result);
-    CoTaskMemFree(result);
-}
-
 #ifndef TESTS_PARTIAL
 };
 }

src/runner/Resources.resx

@@ -173,10 +173,6 @@
     <value>Settings\tDouble-click</value>
     <comment>Don't localize "\t" as that is what separates the click portion to be right aligned in the menu.</comment>
   </data>
-  <data name="SETTINGS_MENU_TEXT_LEFTCLICK" xml:space="preserve">
-    <value>Settings\tLeft-click</value>
-    <comment>Don't localize "\t" as that is what separates the click portion to be right aligned in the menu. This is shown when Quick Access is disabled.</comment>
-  </data>
   <data name="DOCUMENTATION_MENU_TEXT" xml:space="preserve">
     <value>Documentation</value>
   </data>

src/runner/settings_window.cpp

@@ -3,6 +3,7 @@
 #include <Sddl.h>
 #include <sstream>
 #include <aclapi.h>
+#include <shobjidl.h>
 
 #include "powertoy_module.h"
 #include <common/interop/two_way_pipe_message_ipc.h>
@@ -64,6 +65,74 @@ json::JsonObject get_all_settings()
     return result;
 }
 
+namespace
+{
+    constexpr wchar_t SettingsApplicationId[] = L"PowerToys.SettingsUI";
+    constexpr wchar_t SparseAppFamilyDev[] = L"Microsoft.PowerToys.SparseApp_djwsxzxb4ksa8";
+    constexpr wchar_t SparseAppFamilyStore[] = L"Microsoft.PowerToys.SparseApp_8wekyb3d8bbwe";
+
+    bool try_activate_settings_with_identity(const std::wstring& arguments, PROCESS_INFORMATION& process_info)
+    {
+        HRESULT hr = CoInitializeEx(nullptr, COINIT_APARTMENTTHREADED);
+        const bool should_uninit = SUCCEEDED(hr);
+        if (hr == RPC_E_CHANGED_MODE)
+        {
+            hr = S_OK;
+        }
+
+        if (FAILED(hr))
+        {
+            Logger::warn(L"Settings: CoInitializeEx failed. hr=0x{:x}", hr);
+            return false;
+        }
+
+        IApplicationActivationManager* activation_manager = nullptr;
+        hr = CoCreateInstance(CLSID_ApplicationActivationManager,
+                              nullptr,
+                              CLSCTX_INPROC_SERVER,
+                              IID_PPV_ARGS(&activation_manager));
+        if (FAILED(hr))
+        {
+            Logger::warn(L"Settings: CoCreateInstance(ApplicationActivationManager) failed. hr=0x{:x}", hr);
+            if (should_uninit)
+            {
+                CoUninitialize();
+            }
+            return false;
+        }
+
+        auto try_activate = [&](const wchar_t* family) -> bool {
+            std::wstring aumid = std::wstring(family) + L"!" + SettingsApplicationId;
+            DWORD pid = 0;
+            HRESULT hr_activate = activation_manager->ActivateApplication(aumid.c_str(),
+                                                                          arguments.c_str(),
+                                                                          AO_NONE,
+                                                                          &pid);
+            if (SUCCEEDED(hr_activate) && pid != 0)
+            {
+                process_info = {};
+                process_info.dwProcessId = pid;
+                process_info.hProcess = OpenProcess(SYNCHRONIZE | PROCESS_QUERY_LIMITED_INFORMATION, FALSE, pid);
+                Logger::info(L"Settings: Activated via AUMID {} (pid {}).", aumid, pid);
+                return true;
+            }
+
+            Logger::warn(L"Settings: ActivateApplication failed for {}. hr=0x{:x}", aumid, hr_activate);
+            return false;
+        };
+
+        const bool activated = try_activate(SparseAppFamilyDev) || try_activate(SparseAppFamilyStore);
+
+        activation_manager->Release();
+        if (should_uninit)
+        {
+            CoUninitialize();
+        }
+
+        return activated;
+    }
+}
+
 std::optional<std::wstring> dispatch_json_action_to_module(const json::JsonObject& powertoys_configs)
 {
     std::optional<std::wstring> result;
@@ -522,15 +591,34 @@ void run_settings_window(bool show_oobe_window, bool show_scoobe_window, std::op
                                                settings_showOobe,
                                                settings_showScoobe,
                                                settings_containsSettingsWindow);
+    std::wstring activation_args = fmt::format(L"{} {} {} {} {} {} {} {} {}",
+                                               powertoys_pipe_name,
+                                               settings_pipe_name,
+                                               std::to_wstring(powertoys_pid),
+                                               settings_theme,
+                                               settings_elevatedStatus,
+                                               settings_isUserAnAdmin,
+                                               settings_showOobe,
+                                               settings_showScoobe,
+                                               settings_containsSettingsWindow);
 
     if (settings_window.has_value())
     {
         executable_args.append(L" ");
         executable_args.append(settings_window.value());
+        activation_args.append(L" ");
+        activation_args.append(settings_window.value());
     }
 
     BOOL process_created = false;
 
+    // Prefer activating via package identity so the package graph (framework deps) is applied.
+    if (try_activate_settings_with_identity(activation_args, process_info))
+    {
+        process_created = true;
+        g_isLaunchInProgress = false;
+    }
+
     // Commented out to fix #22659
     // Running settings non-elevated and modules elevated when PowerToys is running elevated results
     // in settings making changes in one file (non-elevated user dir) and modules are reading settings

src/runner/tray_icon.cpp

@@ -40,7 +40,6 @@ namespace
     bool double_click_timer_running = false;
     bool double_clicked = false;
     POINT tray_icon_click_point;
-    std::optional<bool> last_quick_access_state; // Track the last known Quick Access state
 
     static ThemeListener theme_listener;
     static bool theme_adaptive_enabled = false;
@@ -196,18 +195,6 @@ LRESULT __stdcall tray_icon_window_proc(HWND window, UINT message, WPARAM wparam
             case WM_RBUTTONUP:
             case WM_CONTEXTMENU:
             {
-                bool quick_access_enabled = get_general_settings().enableQuickAccess;
-
-                // Reload menu if Quick Access state has changed or is first time
-                if (h_menu && (!last_quick_access_state.has_value() || quick_access_enabled != last_quick_access_state.value()))
-                {
-                    DestroyMenu(h_menu);
-                    h_menu = nullptr;
-                    h_sub_menu = nullptr;
-                }
-
-                last_quick_access_state = quick_access_enabled;
-
                 if (!h_menu)
                 {
                     h_menu = LoadMenu(reinterpret_cast<HINSTANCE>(&__ImageBase), MAKEINTRESOURCE(ID_TRAY_MENU));
@@ -215,39 +202,17 @@ LRESULT __stdcall tray_icon_window_proc(HWND window, UINT message, WPARAM wparam
                 if (h_menu)
                 {
                     static std::wstring settings_menuitem_label = GET_RESOURCE_STRING(IDS_SETTINGS_MENU_TEXT);
-                    static std::wstring settings_menuitem_label_leftclick = GET_RESOURCE_STRING(IDS_SETTINGS_MENU_TEXT_LEFTCLICK);
                     static std::wstring close_menuitem_label = GET_RESOURCE_STRING(IDS_CLOSE_MENU_TEXT);
                     static std::wstring submit_bug_menuitem_label = GET_RESOURCE_STRING(IDS_SUBMIT_BUG_TEXT);
                     static std::wstring documentation_menuitem_label = GET_RESOURCE_STRING(IDS_DOCUMENTATION_MENU_TEXT);
                     static std::wstring quick_access_menuitem_label = GET_RESOURCE_STRING(IDS_QUICK_ACCESS_MENU_TEXT);
-
-                    // Update Settings menu text based on Quick Access state
-                    if (quick_access_enabled)
-                    {
-                        change_menu_item_text(ID_SETTINGS_MENU_COMMAND, settings_menuitem_label.data());
-                    }
-                    else
-                    {
-                        change_menu_item_text(ID_SETTINGS_MENU_COMMAND, settings_menuitem_label_leftclick.data());
-                    }
-
+                    change_menu_item_text(ID_SETTINGS_MENU_COMMAND, settings_menuitem_label.data());
                     change_menu_item_text(ID_CLOSE_MENU_COMMAND, close_menuitem_label.data());
                     change_menu_item_text(ID_REPORT_BUG_COMMAND, submit_bug_menuitem_label.data());
                     bool bug_report_disabled = is_bug_report_running();
                     EnableMenuItem(h_sub_menu, ID_REPORT_BUG_COMMAND, MF_BYCOMMAND | (bug_report_disabled ? MF_GRAYED : MF_ENABLED));
                     change_menu_item_text(ID_DOCUMENTATION_MENU_COMMAND, documentation_menuitem_label.data());
                     change_menu_item_text(ID_QUICK_ACCESS_MENU_COMMAND, quick_access_menuitem_label.data());
-
-                    // Hide or show Quick Access menu item based on setting
-                    if (!h_sub_menu)
-                    {
-                        h_sub_menu = GetSubMenu(h_menu, 0);
-                    }
-                    if (!quick_access_enabled)
-                    {
-                        // Remove Quick Access menu item when disabled
-                        DeleteMenu(h_sub_menu, ID_QUICK_ACCESS_MENU_COMMAND, MF_BYCOMMAND);
-                    }
                 }
                 if (!h_sub_menu)
                 {

src/settings-ui/Settings.UI.Library/SettingEntry.cs

@@ -2,6 +2,10 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
+using Common.Search;
+
 namespace Settings.UI.Library
 {
     public enum EntryType
@@ -11,7 +15,7 @@ namespace Settings.UI.Library
         SettingsExpander,
     }
 
-    public struct SettingEntry
+    public struct SettingEntry : ISearchable
     {
         public EntryType Type { get; set; }
 
@@ -29,16 +33,23 @@ namespace Settings.UI.Library
 
         public string Icon { get; set; }
 
-        public SettingEntry(EntryType type, string header, string pageTypeName, string elementName, string elementUid, string parentElementName = null, string description = null, string icon = null)
+        public SettingEntry(EntryType type, string header, string pageTypeName, string elementName, string elementUid, string? parentElementName = null, string? description = null, string? icon = null)
         {
             Type = type;
             Header = header;
             PageTypeName = pageTypeName;
             ElementName = elementName;
             ElementUid = elementUid;
-            ParentElementName = parentElementName;
-            Description = description;
-            Icon = icon;
+            ParentElementName = parentElementName ?? string.Empty;
+            Description = description ?? string.Empty;
+            Icon = icon ?? string.Empty;
         }
+
+        // ISearchable implementation
+        public readonly string Id => ElementUid ?? $"{PageTypeName}|{ElementName}";
+
+        public readonly string SearchableText => Header ?? string.Empty;
+
+        public readonly string? SecondarySearchableText => Description;
     }
 }

src/settings-ui/Settings.UI.Library/SettingSearchResult.cs

@@ -0,0 +1,25 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+#nullable enable
+
+using System.Collections.Generic;
+using Common.Search;
+
+namespace Settings.UI.Library
+{
+    /// <summary>
+    /// Represents a search result for a settings entry with scoring metadata.
+    /// </summary>
+    public sealed class SettingSearchResult
+    {
+        public required SettingEntry Entry { get; init; }
+
+        public required double Score { get; init; }
+
+        public required SearchMatchKind MatchKind { get; init; }
+
+        public IReadOnlyList<MatchSpan>? MatchSpans { get; init; }
+    }
+}

src/settings-ui/Settings.UI.Library/Settings.UI.Library.csproj

@@ -23,6 +23,7 @@
         <ProjectReference Include="..\..\common\ManagedCommon\ManagedCommon.csproj" />
         <ProjectReference Include="..\..\common\ManagedTelemetry\Telemetry\ManagedTelemetry.csproj" />
         <ProjectReference Include="..\..\modules\MouseUtils\MouseJump.Common\MouseJump.Common.csproj" />
+        <ProjectReference Include="..\..\common\Common.Search\Common.Search.csproj" />
     </ItemGroup>
 
     <ItemGroup>

src/settings-ui/Settings.UI.UnitTests/Services/SettingsSearchTests.cs

@@ -0,0 +1,76 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.Threading.Tasks;
+using Common.Search.FuzzSearch;
+using Microsoft.PowerToys.Settings.UI.Services;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Settings.UI.Library;
+
+namespace Microsoft.PowerToys.Settings.UI.UnitTests.Services
+{
+    [TestClass]
+    [DoNotParallelize]
+    public class SettingsSearchTests
+    {
+        [TestMethod]
+        public void LoadIndexFromJson_ReturnsEntries()
+        {
+            const string json = @"
+[
+  {
+    ""type"": 0,
+    ""header"": ""General"",
+    ""pageTypeName"": ""GeneralPage"",
+    ""elementName"": """",
+    ""elementUid"": ""General_Page"",
+    ""parentElementName"": """",
+    ""description"": ""General settings"",
+    ""icon"": """"
+  },
+  {
+    ""type"": 1,
+    ""header"": ""Mouse Utilities"",
+    ""pageTypeName"": ""MouseUtilsPage"",
+    ""elementName"": ""MouseUtilsSetting"",
+    ""elementUid"": ""MouseUtils_Setting"",
+    ""parentElementName"": """",
+    ""description"": ""Adjust mouse settings"",
+    ""icon"": """"
+  }
+]
+";
+
+            var entries = SettingsSearch.LoadIndexFromJson(json);
+
+            Assert.AreEqual(2, entries.Count);
+            Assert.AreEqual(EntryType.SettingsPage, entries[0].Type);
+            Assert.AreEqual("GeneralPage", entries[0].PageTypeName);
+            Assert.AreEqual("MouseUtilsPage", entries[1].PageTypeName);
+        }
+
+        [TestMethod]
+        public async Task InitializeIndexAsync_InitializesSearchAndReturnsResults()
+        {
+            var entries = new List<SettingEntry>
+            {
+                new(EntryType.SettingsPage, "General", "GeneralPage", string.Empty, "General_Page"),
+                new(EntryType.SettingsCard, "Mouse Utilities", "MouseUtilsPage", "MouseUtilsSetting", "MouseUtils_Setting", description: "Adjust mouse settings"),
+            };
+
+            using var search = new SettingsSearch(new FuzzSearchEngine<SettingEntry>());
+            await search.InitializeIndexAsync(entries);
+
+            Assert.IsTrue(search.IsReady);
+
+            var results = await search.SearchAsync("mouse", options: null);
+
+            Assert.IsTrue(results.Count > 0);
+            Assert.AreEqual("Mouse Utilities", results[0].Entry.Header);
+            Assert.IsTrue(results[0].Score > 0);
+            Assert.IsNotNull(results[0].MatchSpans);
+        }
+    }
+}

src/settings-ui/Settings.UI/PowerToys.Settings.csproj

@@ -215,4 +215,4 @@
 		<Message Importance="high" Text="[Settings] Building XamlIndexBuilder prior to compile. Views='$(MSBuildProjectDirectory)\SettingsXAML\Views' Out='$(GeneratedJsonFile)'" />
 		<MSBuild Projects="..\Settings.UI.XamlIndexBuilder\Settings.UI.XamlIndexBuilder.csproj" Targets="Build" Properties="Configuration=$(Configuration);Platform=Any CPU;TargetFramework=net9.0;XamlViewsDir=$(MSBuildProjectDirectory)\SettingsXAML\Views;GeneratedJsonFile=$(GeneratedJsonFile)" />
 	</Target>
-</Project>
+</Project>

src/settings-ui/Settings.UI/Services/SearchIndexService.cs

@@ -1,338 +0,0 @@
-// Copyright (c) Microsoft Corporation
-// The Microsoft Corporation licenses this file to you under the MIT license.
-// See the LICENSE file in the project root for more information.
-
-using System;
-using System.Collections.Concurrent;
-using System.Collections.Generic;
-using System.Collections.Immutable;
-using System.Diagnostics;
-using System.Globalization;
-using System.IO;
-using System.Linq;
-using System.Reflection;
-using System.Text;
-using System.Text.Json;
-using System.Threading;
-using System.Threading.Tasks;
-using Common.Search.FuzzSearch;
-using Microsoft.PowerToys.Settings.UI.Helpers;
-using Microsoft.PowerToys.Settings.UI.Views;
-using Microsoft.Windows.ApplicationModel.Resources;
-using Settings.UI.Library;
-
-namespace Microsoft.PowerToys.Settings.UI.Services
-{
-    public static class SearchIndexService
-    {
-        private static readonly object _lockObject = new();
-        private static readonly Dictionary<string, string> _pageNameCache = [];
-        private static readonly Dictionary<string, (string HeaderNorm, string DescNorm)> _normalizedTextCache = new();
-        private static readonly Dictionary<string, Type> _pageTypeCache = new();
-        private static ImmutableArray<SettingEntry> _index = [];
-        private static bool _isIndexBuilt;
-        private static bool _isIndexBuilding;
-        private const string PrebuiltIndexResourceName = "Microsoft.PowerToys.Settings.UI.Assets.search.index.json";
-        private static JsonSerializerOptions _serializerOptions = new() { PropertyNameCaseInsensitive = true };
-
-        public static ImmutableArray<SettingEntry> Index
-        {
-            get
-            {
-                lock (_lockObject)
-                {
-                    return _index;
-                }
-            }
-        }
-
-        public static bool IsIndexReady
-        {
-            get
-            {
-                lock (_lockObject)
-                {
-                    return _isIndexBuilt;
-                }
-            }
-        }
-
-        public static void BuildIndex()
-        {
-            lock (_lockObject)
-            {
-                if (_isIndexBuilt || _isIndexBuilding)
-                {
-                    return;
-                }
-
-                _isIndexBuilding = true;
-
-                // Clear caches on rebuild
-                _normalizedTextCache.Clear();
-                _pageTypeCache.Clear();
-            }
-
-            try
-            {
-                var builder = ImmutableArray.CreateBuilder<SettingEntry>();
-                LoadIndexFromPrebuiltData(builder);
-
-                lock (_lockObject)
-                {
-                    _index = builder.ToImmutable();
-                    _isIndexBuilt = true;
-                    _isIndexBuilding = false;
-                }
-            }
-            catch (Exception ex)
-            {
-                Debug.WriteLine($"[SearchIndexService] CRITICAL ERROR building search index: {ex.Message}\n{ex.StackTrace}");
-                lock (_lockObject)
-                {
-                    _isIndexBuilding = false;
-                    _isIndexBuilt = false;
-                }
-            }
-        }
-
-        private static void LoadIndexFromPrebuiltData(ImmutableArray<SettingEntry>.Builder builder)
-        {
-            var assembly = Assembly.GetExecutingAssembly();
-            var resourceLoader = ResourceLoaderInstance.ResourceLoader;
-            SettingEntry[] metadataList;
-
-            Debug.WriteLine($"[SearchIndexService] Attempting to load prebuilt index from: {PrebuiltIndexResourceName}");
-
-            try
-            {
-                using Stream stream = assembly.GetManifestResourceStream(PrebuiltIndexResourceName);
-                if (stream == null)
-                {
-                    Debug.WriteLine($"[SearchIndexService] ERROR: Embedded resource '{PrebuiltIndexResourceName}' not found. Ensure it's correctly embedded and the name matches.");
-                    return;
-                }
-
-                using StreamReader reader = new(stream);
-                string json = reader.ReadToEnd();
-                if (string.IsNullOrWhiteSpace(json))
-                {
-                    Debug.WriteLine("[SearchIndexService] ERROR: Embedded resource was empty.");
-                    return;
-                }
-
-                metadataList = JsonSerializer.Deserialize<SettingEntry[]>(json, _serializerOptions);
-            }
-            catch (Exception ex)
-            {
-                Debug.WriteLine($"[SearchIndexService] ERROR: Failed to load or deserialize prebuilt index: {ex.Message}");
-                return;
-            }
-
-            if (metadataList == null || metadataList.Length == 0)
-            {
-                Debug.WriteLine("[SearchIndexService] Prebuilt index is empty or deserialization failed.");
-                return;
-            }
-
-            foreach (ref var metadata in metadataList.AsSpan())
-            {
-                if (metadata.Type == EntryType.SettingsPage)
-                {
-                    (metadata.Header, metadata.Description) = GetLocalizedModuleTitleAndDescription(resourceLoader, metadata.ElementUid);
-                }
-                else
-                {
-                    (metadata.Header, metadata.Description) = GetLocalizedSettingHeaderAndDescription(resourceLoader, metadata.ElementUid);
-                }
-
-                if (string.IsNullOrEmpty(metadata.Header))
-                {
-                    continue;
-                }
-
-                builder.Add(metadata);
-
-                // Cache the page name mapping for SettingsPage entries
-                if (metadata.Type == EntryType.SettingsPage && !string.IsNullOrEmpty(metadata.Header))
-                {
-                    _pageNameCache[metadata.PageTypeName] = metadata.Header;
-                }
-            }
-
-            Debug.WriteLine($"[SearchIndexService] Finished loading index. Total entries: {builder.Count}");
-        }
-
-        private static (string Header, string Description) GetLocalizedSettingHeaderAndDescription(ResourceLoader resourceLoader, string elementUid)
-        {
-            string header = GetString(resourceLoader, $"{elementUid}/Header");
-            string description = GetString(resourceLoader, $"{elementUid}/Description");
-
-            if (string.IsNullOrEmpty(header))
-            {
-                header = GetString(resourceLoader, $"{elementUid}/Content");
-            }
-
-            return (header, description);
-        }
-
-        private static (string Title, string Description) GetLocalizedModuleTitleAndDescription(ResourceLoader resourceLoader, string elementUid)
-        {
-            string title = GetString(resourceLoader, $"{elementUid}/ModuleTitle");
-            string description = GetString(resourceLoader, $"{elementUid}/ModuleDescription");
-
-            return (title, description);
-        }
-
-        private static string GetString(ResourceLoader rl, string key)
-        {
-            try
-            {
-                string value = rl.GetString(key);
-                return string.IsNullOrWhiteSpace(value) ? string.Empty : value;
-            }
-            catch (Exception)
-            {
-                return string.Empty;
-            }
-        }
-
-        public static List<SettingEntry> Search(string query)
-        {
-            return Search(query, CancellationToken.None);
-        }
-
-        public static List<SettingEntry> Search(string query, CancellationToken token)
-        {
-            if (string.IsNullOrWhiteSpace(query))
-            {
-                return [];
-            }
-
-            var currentIndex = Index;
-            if (currentIndex.IsEmpty)
-            {
-                Debug.WriteLine("[SearchIndexService] Search called but index is empty.");
-                return [];
-            }
-
-            var normalizedQuery = NormalizeString(query);
-            var bag = new ConcurrentBag<(SettingEntry Hit, double Score)>();
-            var po = new ParallelOptions
-            {
-                CancellationToken = token,
-                MaxDegreeOfParallelism = Math.Max(1, Environment.ProcessorCount - 1),
-            };
-
-            try
-            {
-                Parallel.ForEach(currentIndex, po, entry =>
-                {
-                    var (headerNorm, descNorm) = GetNormalizedTexts(entry);
-                    var captionScoreResult = StringMatcher.FuzzyMatch(normalizedQuery, headerNorm);
-                    double score = captionScoreResult.Score;
-
-                    if (!string.IsNullOrEmpty(descNorm))
-                    {
-                        var descriptionScoreResult = StringMatcher.FuzzyMatch(normalizedQuery, descNorm);
-                        if (descriptionScoreResult.Success)
-                        {
-                            score = Math.Max(score, descriptionScoreResult.Score * 0.8);
-                        }
-                    }
-
-                    if (score > 0)
-                    {
-                        var pageType = GetPageTypeFromName(entry.PageTypeName);
-                        if (pageType != null)
-                        {
-                            bag.Add((entry, score));
-                        }
-                    }
-                });
-            }
-            catch (OperationCanceledException)
-            {
-                return [];
-            }
-
-            return bag
-                .OrderByDescending(r => r.Score)
-                .Select(r => r.Hit)
-                .ToList();
-        }
-
-        private static Type GetPageTypeFromName(string pageTypeName)
-        {
-            if (string.IsNullOrEmpty(pageTypeName))
-            {
-                return null;
-            }
-
-            lock (_lockObject)
-            {
-                if (_pageTypeCache.TryGetValue(pageTypeName, out var cached))
-                {
-                    return cached;
-                }
-
-                var assembly = typeof(GeneralPage).Assembly;
-                var type = assembly.GetType($"Microsoft.PowerToys.Settings.UI.Views.{pageTypeName}");
-                _pageTypeCache[pageTypeName] = type;
-                return type;
-            }
-        }
-
-        private static (string HeaderNorm, string DescNorm) GetNormalizedTexts(SettingEntry entry)
-        {
-            if (entry.ElementUid == null && entry.Header == null)
-            {
-                return (NormalizeString(entry.Header), NormalizeString(entry.Description));
-            }
-
-            var key = entry.ElementUid ?? $"{entry.PageTypeName}|{entry.ElementName}";
-            lock (_lockObject)
-            {
-                if (_normalizedTextCache.TryGetValue(key, out var cached))
-                {
-                    return cached;
-                }
-            }
-
-            var headerNorm = NormalizeString(entry.Header);
-            var descNorm = NormalizeString(entry.Description);
-            lock (_lockObject)
-            {
-                _normalizedTextCache[key] = (headerNorm, descNorm);
-            }
-
-            return (headerNorm, descNorm);
-        }
-
-        private static string NormalizeString(string input)
-        {
-            if (string.IsNullOrEmpty(input))
-            {
-                return string.Empty;
-            }
-
-            var normalized = input.ToLowerInvariant().Normalize(NormalizationForm.FormKD);
-            var stringBuilder = new StringBuilder();
-            foreach (var c in normalized)
-            {
-                var unicodeCategory = CharUnicodeInfo.GetUnicodeCategory(c);
-                if (unicodeCategory != UnicodeCategory.NonSpacingMark)
-                {
-                    stringBuilder.Append(c);
-                }
-            }
-
-            return stringBuilder.ToString();
-        }
-
-        public static string GetLocalizedPageName(string pageTypeName)
-        {
-            return _pageNameCache.TryGetValue(pageTypeName, out string cachedName) ? cachedName : string.Empty;
-        }
-    }
-}

src/settings-ui/Settings.UI/Services/SettingsSearch.cs

@@ -0,0 +1,434 @@
+// Copyright (c) Microsoft Corporation
+// The Microsoft Corporation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Diagnostics;
+using System.IO;
+using System.Reflection;
+using System.Text.Json;
+using System.Threading;
+using System.Threading.Tasks;
+using Common.Search;
+using Common.Search.SemanticSearch;
+using ManagedCommon;
+using Microsoft.PowerToys.Settings.UI.Helpers;
+using Microsoft.PowerToys.Settings.UI.Views;
+using Microsoft.Windows.ApplicationModel.Resources;
+using Settings.UI.Library;
+
+namespace Microsoft.PowerToys.Settings.UI.Services
+{
+    public sealed class SettingsSearch : IDisposable
+    {
+        private static readonly Lazy<SettingsSearch> DefaultInstance = new(() => new SettingsSearch());
+
+        private readonly object _lockObject = new();
+        private readonly Dictionary<string, string> _pageNameCache = [];
+        private readonly Dictionary<string, Type> _pageTypeCache = new();
+        private readonly ISearchEngine<SettingEntry> _searchEngine;
+        private ImmutableArray<SettingEntry> _index = [];
+        private bool _isIndexBuilt;
+        private bool _isIndexBuilding;
+        private bool _disposed;
+        private Task _buildTask;
+
+        private const string PrebuiltIndexResourceName = "Microsoft.PowerToys.Settings.UI.Assets.search.index.json";
+        private static readonly JsonSerializerOptions SerializerOptions = new() { PropertyNameCaseInsensitive = true };
+
+        private const string DefaultIndexName = "PowerToys.Settings";
+
+        public SettingsSearch()
+            : this(new SemanticSearchEngine<SettingEntry>(DefaultIndexName))
+        {
+        }
+
+        public SettingsSearch(ISearchEngine<SettingEntry> searchEngine)
+        {
+            ArgumentNullException.ThrowIfNull(searchEngine);
+            _searchEngine = searchEngine;
+        }
+
+        public static SettingsSearch Default => DefaultInstance.Value;
+
+        public ImmutableArray<SettingEntry> Index
+        {
+            get
+            {
+                lock (_lockObject)
+                {
+                    return _index;
+                }
+            }
+        }
+
+        public bool IsReady
+        {
+            get
+            {
+                lock (_lockObject)
+                {
+                    return _isIndexBuilt && _searchEngine.IsReady;
+                }
+            }
+        }
+
+        public Task BuildIndexAsync(CancellationToken cancellationToken = default)
+        {
+            ThrowIfDisposed();
+
+            lock (_lockObject)
+            {
+                if (_isIndexBuilt)
+                {
+                    Logger.LogDebug("[SettingsSearch] BuildIndexAsync skipped: index already built.");
+                    return Task.CompletedTask;
+                }
+
+                if (_isIndexBuilding)
+                {
+                    Logger.LogDebug("[SettingsSearch] BuildIndexAsync skipped: index build already in progress.");
+                    return _buildTask ?? Task.CompletedTask;
+                }
+
+                if (_buildTask != null)
+                {
+                    Logger.LogDebug("[SettingsSearch] BuildIndexAsync skipped: build task already scheduled.");
+                    return _buildTask;
+                }
+
+                Logger.LogInfo("[SettingsSearch] BuildIndexAsync started.");
+                _buildTask = BuildIndexInternalAsync(cancellationToken);
+                return _buildTask;
+            }
+        }
+
+        public async Task InitializeIndexAsync(IEnumerable<SettingEntry> entries, CancellationToken cancellationToken = default)
+        {
+            ArgumentNullException.ThrowIfNull(entries);
+            ThrowIfDisposed();
+
+            var builtIndex = entries is ImmutableArray<SettingEntry> immutableEntries
+                ? immutableEntries
+                : ImmutableArray.CreateRange(entries);
+
+            lock (_lockObject)
+            {
+                _isIndexBuilding = true;
+                _isIndexBuilt = false;
+                _index = builtIndex;
+                _pageNameCache.Clear();
+                _pageTypeCache.Clear();
+            }
+
+            Logger.LogInfo($"[SettingsSearch] Initializing index. Entries={builtIndex.Length}, Engine={_searchEngine.GetType().Name}.");
+            CachePageNames(builtIndex);
+
+            try
+            {
+                if (_searchEngine.IsReady)
+                {
+                    Logger.LogDebug("[SettingsSearch] Clearing existing search engine index.");
+                    await _searchEngine.ClearAsync(cancellationToken).ConfigureAwait(false);
+                }
+                else
+                {
+                    Logger.LogDebug("[SettingsSearch] Initializing search engine.");
+                    await _searchEngine.InitializeAsync(cancellationToken).ConfigureAwait(false);
+                }
+
+                if (!_searchEngine.IsReady)
+                {
+                    Logger.LogWarning("[SettingsSearch] Search engine not ready after initialization. Skipping indexing.");
+                    return;
+                }
+
+                await _searchEngine.IndexBatchAsync(builtIndex, cancellationToken).ConfigureAwait(false);
+
+                lock (_lockObject)
+                {
+                    _isIndexBuilt = true;
+                }
+
+                Logger.LogInfo($"[SettingsSearch] Index initialized. Entries={builtIndex.Length}, EngineReady={_searchEngine.IsReady}.");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[SettingsSearch] CRITICAL ERROR initializing search engine: {ex.Message}", ex);
+            }
+            finally
+            {
+                lock (_lockObject)
+                {
+                    _isIndexBuilding = false;
+                }
+            }
+        }
+
+        public async Task<IReadOnlyList<SettingSearchResult>> SearchAsync(
+            string query,
+            SearchOptions options = null,
+            CancellationToken token = default)
+        {
+            ThrowIfDisposed();
+
+            if (string.IsNullOrWhiteSpace(query))
+            {
+                return Array.Empty<SettingSearchResult>();
+            }
+
+            if (!IsReady)
+            {
+                Logger.LogWarning("[SettingsSearch] Search called but index is not ready.");
+                return Array.Empty<SettingSearchResult>();
+            }
+
+            var effectiveOptions = options ?? new SearchOptions
+            {
+                MaxResults = Index.Length,
+                IncludeMatchSpans = true,
+            };
+
+            try
+            {
+                var sw = Stopwatch.StartNew();
+                Logger.LogDebug($"[SettingsSearch] Search start. QueryLength={query.Length}, MaxResults={effectiveOptions.MaxResults}.");
+                var results = await Task.Run(
+                    () => _searchEngine.SearchAsync(query, effectiveOptions, token),
+                    token).ConfigureAwait(false);
+                var filtered = FilterValidPageTypes(results);
+                sw.Stop();
+                Logger.LogDebug($"[SettingsSearch] Search complete. Results={filtered.Count}, ElapsedMs={sw.ElapsedMilliseconds}.");
+                return filtered;
+            }
+            catch (OperationCanceledException)
+            {
+                Logger.LogDebug("[SettingsSearch] Search canceled.");
+                return Array.Empty<SettingSearchResult>();
+            }
+        }
+
+        public static IReadOnlyList<SettingEntry> LoadIndexFromJson(string json)
+        {
+            if (string.IsNullOrWhiteSpace(json))
+            {
+                return Array.Empty<SettingEntry>();
+            }
+
+            try
+            {
+                return JsonSerializer.Deserialize<SettingEntry[]>(json, SerializerOptions) ?? Array.Empty<SettingEntry>();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[SettingsSearch] ERROR: Failed to load index from json: {ex.Message}", ex);
+                return Array.Empty<SettingEntry>();
+            }
+        }
+
+        public string GetLocalizedPageName(string pageTypeName)
+        {
+            lock (_lockObject)
+            {
+                return _pageNameCache.TryGetValue(pageTypeName, out string cachedName) ? cachedName : string.Empty;
+            }
+        }
+
+        public void Dispose()
+        {
+            if (_disposed)
+            {
+                return;
+            }
+
+            _searchEngine.Dispose();
+            _disposed = true;
+        }
+
+        private async Task BuildIndexInternalAsync(CancellationToken cancellationToken)
+        {
+            try
+            {
+                var sw = Stopwatch.StartNew();
+                var entries = LoadIndexFromPrebuiltData();
+                Logger.LogInfo($"[SettingsSearch] Prebuilt index loaded. Entries={entries.Length}.");
+                await InitializeIndexAsync(entries, cancellationToken).ConfigureAwait(false);
+                sw.Stop();
+                Logger.LogInfo($"[SettingsSearch] BuildIndexAsync finished. ElapsedMs={sw.ElapsedMilliseconds}, Ready={IsReady}.");
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[SettingsSearch] CRITICAL ERROR building search index: {ex.Message}", ex);
+            }
+            finally
+            {
+                lock (_lockObject)
+                {
+                    _buildTask = null;
+                }
+            }
+        }
+
+        private void CachePageNames(ImmutableArray<SettingEntry> entries)
+        {
+            lock (_lockObject)
+            {
+                foreach (var entry in entries)
+                {
+                    if (entry.Type == EntryType.SettingsPage && !string.IsNullOrEmpty(entry.Header))
+                    {
+                        _pageNameCache[entry.PageTypeName] = entry.Header;
+                    }
+                }
+            }
+        }
+
+        private ImmutableArray<SettingEntry> LoadIndexFromPrebuiltData()
+        {
+            var assembly = Assembly.GetExecutingAssembly();
+            var resourceLoader = ResourceLoaderInstance.ResourceLoader;
+
+            Logger.LogInfo($"[SettingsSearch] Attempting to load prebuilt index from: {PrebuiltIndexResourceName}");
+
+            string json;
+            try
+            {
+                using Stream stream = assembly.GetManifestResourceStream(PrebuiltIndexResourceName);
+                if (stream == null)
+                {
+                    Logger.LogError($"[SettingsSearch] ERROR: Embedded resource '{PrebuiltIndexResourceName}' not found. Ensure it's correctly embedded and the name matches.");
+                    return ImmutableArray<SettingEntry>.Empty;
+                }
+
+                using StreamReader reader = new(stream);
+                json = reader.ReadToEnd();
+            }
+            catch (Exception ex)
+            {
+                Logger.LogError($"[SettingsSearch] ERROR: Failed to read prebuilt index: {ex.Message}", ex);
+                return ImmutableArray<SettingEntry>.Empty;
+            }
+
+            if (string.IsNullOrWhiteSpace(json))
+            {
+                Logger.LogError("[SettingsSearch] ERROR: Embedded resource was empty.");
+                return ImmutableArray<SettingEntry>.Empty;
+            }
+
+            var metadataList = LoadIndexFromJson(json);
+            if (metadataList == null || metadataList.Count == 0)
+            {
+                Logger.LogWarning("[SettingsSearch] Prebuilt index is empty or deserialization failed.");
+                return ImmutableArray<SettingEntry>.Empty;
+            }
+
+            var builder = ImmutableArray.CreateBuilder<SettingEntry>(metadataList.Count);
+
+            foreach (var metadata in metadataList)
+            {
+                var entry = metadata;
+                if (entry.Type == EntryType.SettingsPage)
+                {
+                    (entry.Header, entry.Description) = GetLocalizedModuleTitleAndDescription(resourceLoader, entry.ElementUid);
+                }
+                else
+                {
+                    (entry.Header, entry.Description) = GetLocalizedSettingHeaderAndDescription(resourceLoader, entry.ElementUid);
+                }
+
+                if (string.IsNullOrEmpty(entry.Header))
+                {
+                    continue;
+                }
+
+                builder.Add(entry);
+            }
+
+            Logger.LogInfo($"[SettingsSearch] Finished loading index. Total entries: {builder.Count}");
+            return builder.ToImmutable();
+        }
+
+        private static (string Header, string Description) GetLocalizedSettingHeaderAndDescription(ResourceLoader resourceLoader, string elementUid)
+        {
+            string header = GetString(resourceLoader, $"{elementUid}/Header");
+            string description = GetString(resourceLoader, $"{elementUid}/Description");
+
+            if (string.IsNullOrEmpty(header))
+            {
+                header = GetString(resourceLoader, $"{elementUid}/Content");
+            }
+
+            return (header, description);
+        }
+
+        private static (string Title, string Description) GetLocalizedModuleTitleAndDescription(ResourceLoader resourceLoader, string elementUid)
+        {
+            string title = GetString(resourceLoader, $"{elementUid}/ModuleTitle");
+            string description = GetString(resourceLoader, $"{elementUid}/ModuleDescription");
+
+            return (title, description);
+        }
+
+        private static string GetString(ResourceLoader rl, string key)
+        {
+            try
+            {
+                string value = rl.GetString(key);
+                return string.IsNullOrWhiteSpace(value) ? string.Empty : value;
+            }
+            catch (Exception)
+            {
+                return string.Empty;
+            }
+        }
+
+        private IReadOnlyList<SettingSearchResult> FilterValidPageTypes(IReadOnlyList<SearchResult<SettingEntry>> results)
+        {
+            var filtered = new List<SettingSearchResult>(results.Count);
+            foreach (var result in results)
+            {
+                var entry = result.Item;
+                if (GetPageTypeFromName(entry.PageTypeName) != null)
+                {
+                    filtered.Add(new SettingSearchResult
+                    {
+                        Entry = entry,
+                        Score = result.Score,
+                        MatchKind = result.MatchKind,
+                        MatchSpans = result.MatchSpans,
+                    });
+                }
+            }
+
+            return filtered;
+        }
+
+        private Type GetPageTypeFromName(string pageTypeName)
+        {
+            if (string.IsNullOrEmpty(pageTypeName))
+            {
+                return null;
+            }
+
+            lock (_lockObject)
+            {
+                if (_pageTypeCache.TryGetValue(pageTypeName, out var cached))
+                {
+                    return cached;
+                }
+
+                var assembly = typeof(GeneralPage).Assembly;
+                var type = assembly.GetType($"Microsoft.PowerToys.Settings.UI.Views.{pageTypeName}");
+                _pageTypeCache[pageTypeName] = type;
+                return type;
+            }
+        }
+
+        private void ThrowIfDisposed()
+        {
+            ObjectDisposedException.ThrowIf(_disposed, this);
+        }
+    }
+}

src/settings-ui/Settings.UI/SettingsXAML/Views/SearchResultsPage.xaml

@@ -32,12 +32,12 @@
                         IsTabStop="False"
                         ItemsSource="{x:Bind ViewModel.ModuleResults, Mode=OneWay}">
                         <ItemsControl.ItemTemplate>
-                            <DataTemplate x:DataType="models:SettingEntry">
+                            <DataTemplate x:DataType="models:SettingSearchResult">
                                 <tkcontrols:SettingsCard
                                     Margin="0,0,0,2"
                                     Click="ModuleButton_Click"
-                                    Header="{x:Bind Header}"
-                                    HeaderIcon="{x:Bind Icon, Converter={StaticResource IconConverter}, ConverterParameter=&#xE8B7;}"
+                                    Header="{x:Bind Entry.Header}"
+                                    HeaderIcon="{x:Bind Entry.Icon, Converter={StaticResource IconConverter}, ConverterParameter=&#xE8B7;}"
                                     IsClickEnabled="True" />
                             </DataTemplate>
                         </ItemsControl.ItemTemplate>
@@ -52,19 +52,19 @@
                     <ItemsControl.ItemTemplate>
                         <DataTemplate x:DataType="vm:SettingsGroup">
                             <controls:SettingsGroup Header="{x:Bind GroupName}">
-                                <ItemsControl IsTabStop="False" ItemsSource="{x:Bind Settings}">
-                                    <ItemsControl.ItemTemplate>
-                                        <DataTemplate x:DataType="models:SettingEntry">
-                                            <tkcontrols:SettingsCard
-                                                Margin="0,0,0,2"
-                                                Click="SettingButton_Click"
-                                                Description="{x:Bind Description}"
-                                                Header="{x:Bind Header}"
-                                                HeaderIcon="{x:Bind Icon, Converter={StaticResource IconConverter}, ConverterParameter=&#xE713;}"
-                                                IsClickEnabled="True" />
-                                        </DataTemplate>
-                                    </ItemsControl.ItemTemplate>
-                                </ItemsControl>
+                                    <ItemsControl IsTabStop="False" ItemsSource="{x:Bind Settings}">
+                                        <ItemsControl.ItemTemplate>
+                                            <DataTemplate x:DataType="models:SettingSearchResult">
+                                                <tkcontrols:SettingsCard
+                                                    Margin="0,0,0,2"
+                                                    Click="SettingButton_Click"
+                                                    Description="{x:Bind Entry.Description}"
+                                                    Header="{x:Bind Entry.Header}"
+                                                    HeaderIcon="{x:Bind Entry.Icon, Converter={StaticResource IconConverter}, ConverterParameter=&#xE713;}"
+                                                    IsClickEnabled="True" />
+                                            </DataTemplate>
+                                        </ItemsControl.ItemTemplate>
+                                    </ItemsControl>
                             </controls:SettingsGroup>
                         </DataTemplate>
                     </ItemsControl.ItemTemplate>

src/settings-ui/Settings.UI/SettingsXAML/Views/SearchResultsPage.xaml.cs

@@ -44,17 +44,17 @@ namespace Microsoft.PowerToys.Settings.UI.Views
 
         private void ModuleButton_Click(object sender, RoutedEventArgs e)
         {
-            if (sender is SettingsCard card && card.DataContext is SettingEntry tagEntry)
+            if (sender is SettingsCard card && card.DataContext is SettingSearchResult tagResult)
             {
-                NavigateToModule(tagEntry);
+                NavigateToModule(tagResult.Entry);
             }
         }
 
         private void SettingButton_Click(object sender, RoutedEventArgs e)
         {
-            if (sender is SettingsCard card && card.DataContext is SettingEntry tagEntry)
+            if (sender is SettingsCard card && card.DataContext is SettingSearchResult tagResult)
             {
-                NavigateToSetting(tagEntry);
+                NavigateToSetting(tagResult.Entry);
             }
         }
 
@@ -98,9 +98,9 @@ namespace Microsoft.PowerToys.Settings.UI.Views
     {
         public string Query { get; set; }
 
-        public List<SettingEntry> Results { get; set; }
+        public List<SettingSearchResult> Results { get; set; }
 
-        public SearchResultsNavigationParams(string query, List<SettingEntry> results)
+        public SearchResultsNavigationParams(string query, List<SettingSearchResult> results)
         {
             Query = query;
             Results = results;

src/settings-ui/Settings.UI/SettingsXAML/Views/ShellPage.xaml.cs

@@ -8,7 +8,6 @@ using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
 using Common.Search;
-using Common.Search.FuzzSearch;
 using ManagedCommon;
 using Microsoft.PowerToys.Settings.UI.Controls;
 using Microsoft.PowerToys.Settings.UI.Helpers;
@@ -385,11 +384,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
 
         private void ShellPage_Loaded(object sender, RoutedEventArgs e)
         {
-            Task.Run(() =>
-            {
-                SearchIndexService.BuildIndex();
-            })
-            .ContinueWith(_ => { });
+            _ = Task.Run(() => SettingsSearch.Default.BuildIndexAsync());
         }
 
         private void NavigationView_DisplayModeChanged(NavigationView sender, NavigationViewDisplayModeChangedEventArgs args)
@@ -427,7 +422,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
             NativeMethods.SendMessage(hWnd, NativeMethods.WM_COMMAND, ID_CLOSE_MENU_COMMAND, 0);
         }
 
-        private List<SettingEntry> _lastSearchResults = new();
+        private List<SettingSearchResult> _lastSearchResults = new();
         private string _lastQueryText = string.Empty;
 
         private async void SearchBox_TextChanged(AutoSuggestBox sender, AutoSuggestBoxTextChangedEventArgs args)
@@ -470,11 +465,10 @@ namespace Microsoft.PowerToys.Settings.UI.Views
             }
 
             // Query the index on a background thread to avoid blocking UI
-            List<SettingEntry> results = null;
+            List<SettingSearchResult> results = null;
             try
             {
-                // If the token is already canceled before scheduling, the task won't start.
-                results = await Task.Run(() => SearchIndexService.Search(query, token), token);
+                results = (await SettingsSearch.Default.SearchAsync(query, options: null, token)).ToList();
             }
             catch (OperationCanceledException)
             {
@@ -578,7 +572,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
         }
 
         // Centralized suggestion projection logic used by TextChanged & GotFocus restore.
-        private List<SuggestionItem> BuildSuggestionItems(string query, List<SettingEntry> results)
+        private List<SuggestionItem> BuildSuggestionItems(string query, List<SettingSearchResult> results)
         {
             results ??= new();
             if (results.Count == 0)
@@ -601,16 +595,17 @@ namespace Microsoft.PowerToys.Settings.UI.Views
                 };
             }
 
-            var list = results.Take(5).Select(e =>
+            var list = results.Take(5).Select(result =>
             {
+                var entry = result.Entry;
                 string subtitle = string.Empty;
-                if (e.Type != EntryType.SettingsPage)
+                if (entry.Type != EntryType.SettingsPage)
                 {
-                    subtitle = SearchIndexService.GetLocalizedPageName(e.PageTypeName);
+                    subtitle = SettingsSearch.Default.GetLocalizedPageName(entry.PageTypeName);
                     if (string.IsNullOrEmpty(subtitle))
                     {
-                        subtitle = SearchIndexService.Index
-                            .Where(x => x.Type == EntryType.SettingsPage && x.PageTypeName == e.PageTypeName)
+                        subtitle = SettingsSearch.Default.Index
+                            .Where(x => x.Type == EntryType.SettingsPage && x.PageTypeName == entry.PageTypeName)
                             .Select(x => x.Header)
                             .FirstOrDefault() ?? string.Empty;
                     }
@@ -618,12 +613,15 @@ namespace Microsoft.PowerToys.Settings.UI.Views
 
                 return new SuggestionItem
                 {
-                    Header = e.Header,
-                    Icon = e.Icon,
-                    PageTypeName = e.PageTypeName,
-                    ElementName = e.ElementName,
-                    ParentElementName = e.ParentElementName,
+                    Header = entry.Header,
+                    Icon = entry.Icon,
+                    PageTypeName = entry.PageTypeName,
+                    ElementName = entry.ElementName,
+                    ParentElementName = entry.ParentElementName,
                     Subtitle = subtitle,
+                    Score = result.Score,
+                    MatchKind = result.MatchKind,
+                    MatchSpans = result.MatchSpans ?? Array.Empty<MatchSpan>(),
                     IsShowAll = false,
                 };
             }).ToList();
@@ -655,7 +653,7 @@ namespace Microsoft.PowerToys.Settings.UI.Views
             // Prefer cached results (from live search); if empty, perform a fresh search
             var matched = _lastSearchResults?.Count > 0 && string.Equals(_lastQueryText, queryText, StringComparison.Ordinal)
                 ? _lastSearchResults
-                : await Task.Run(() => SearchIndexService.Search(queryText));
+                : (await SettingsSearch.Default.SearchAsync(queryText, options: null)).ToList();
 
             var searchParams = new SearchResultsNavigationParams(queryText, matched);
             NavigationService.Navigate<SearchResultsPage>(searchParams);

src/settings-ui/Settings.UI/ViewModels/SearchResultsViewModel.cs

@@ -14,11 +14,11 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 {
     public class SearchResultsViewModel : INotifyPropertyChanged
     {
-        private ObservableCollection<SettingEntry> _moduleResults = new();
+        private ObservableCollection<SettingSearchResult> _moduleResults = new();
         private ObservableCollection<SettingsGroup> _groupedSettingsResults = new();
         private bool _hasNoResults;
 
-        public ObservableCollection<SettingEntry> ModuleResults
+        public ObservableCollection<SettingSearchResult> ModuleResults
         {
             get => _moduleResults;
             set
@@ -48,7 +48,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
             }
         }
 
-        public void SetSearchResults(string query, List<SettingEntry> results)
+        public void SetSearchResults(string query, List<SettingSearchResult> results)
         {
             if (results == null || results.Count == 0)
             {
@@ -61,8 +61,8 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
             HasNoResults = false;
 
             // Separate modules and settings
-            var modules = results.Where(r => r.Type == EntryType.SettingsPage).ToList();
-            var settings = results.Where(r => r.Type == EntryType.SettingsCard).ToList();
+            var modules = results.Where(r => r.Entry.Type == EntryType.SettingsPage).ToList();
+            var settings = results.Where(r => r.Entry.Type == EntryType.SettingsCard).ToList();
 
             // Update module results
             ModuleResults.Clear();
@@ -73,11 +73,11 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 
             // Group settings by their page/module
             var groupedSettings = settings
-                .GroupBy(s => SearchIndexService.GetLocalizedPageName(s.PageTypeName))
+                .GroupBy(s => SettingsSearch.Default.GetLocalizedPageName(s.Entry.PageTypeName))
                 .Select(g => new SettingsGroup
                 {
                     GroupName = g.Key,
-                    Settings = new ObservableCollection<SettingEntry>(g),
+                    Settings = new ObservableCollection<SettingSearchResult>(g),
                 })
                 .ToList();
 
@@ -101,7 +101,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 #pragma warning restore SA1402 // File may only contain a single type
     {
         private string _groupName;
-        private ObservableCollection<SettingEntry> _settings;
+        private ObservableCollection<SettingSearchResult> _settings;
 
         public string GroupName
         {
@@ -113,7 +113,7 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
             }
         }
 
-        public ObservableCollection<SettingEntry> Settings
+        public ObservableCollection<SettingSearchResult> Settings
         {
             get => _settings;
             set

src/settings-ui/Settings.UI/ViewModels/SuggestionItem.cs

@@ -2,6 +2,9 @@
 // The Microsoft Corporation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+using System.Collections.Generic;
+using Common.Search;
+
 namespace Microsoft.PowerToys.Settings.UI.ViewModels
 {
     public sealed partial class SuggestionItem
@@ -18,6 +21,12 @@ namespace Microsoft.PowerToys.Settings.UI.ViewModels
 
         public string Subtitle { get; init; }
 
+        public double Score { get; init; }
+
+        public SearchMatchKind? MatchKind { get; init; }
+
+        public IReadOnlyList<MatchSpan> MatchSpans { get; init; }
+
         public bool IsShowAll { get; init; }
 
         public bool IsNoResults { get; init; }

src/settings-ui/Settings.UI/app.manifest

@@ -2,6 +2,11 @@
 <assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
   <assemblyIdentity version="1.0.0.0" name="PowerToys.Settings.app"/>
 
+  <msix xmlns="urn:schemas-microsoft-com:msix.v1"
+        packageName="Microsoft.PowerToys.SparseApp"
+        applicationId="PowerToys.SettingsUI"
+        publisher="CN=PowerToys Dev, O=PowerToys, L=Redmond, S=Washington, C=US" />
+
   <application xmlns="urn:schemas-microsoft-com:asm.v3">
     <windowsSettings>
       <!-- The combination of below two tags have the following effect:

tools/build/build-essentials.ps1

@@ -63,7 +63,7 @@ if (-not $Platform -or $Platform -eq '') {
 }
 
 # Ensure solution packages are restored
-RestoreThenBuild 'PowerToys.slnx' '' $Platform $Configuration $true
+RestoreThenBuild 'PowerToys.slnx' '' $Platform $Confi.guration $true
 
 # Build both runner and settings
 $ProjectsToBuild = @(".\src\runner\runner.vcxproj", ".\src\settings-ui\Settings.UI\PowerToys.Settings.csproj")