feat(HotReload): IHotReloadAware + MetadataUpdateHandler (aligns with dotnet/maui#35229)

.github/workflows/ci-hotreload.yml

@@ -0,0 +1,34 @@
+name: CI - HotReload
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - 'src/HotReload/**'
+      - 'eng/**'
+      - 'Directory.Build.props'
+      - 'Directory.Build.targets'
+      - 'Directory.Packages.props'
+      - 'global.json'
+      - 'NuGet.config'
+  pull_request:
+    types: [opened, synchronize, reopened, edited]
+    branches: [main]
+    paths:
+      - 'src/HotReload/**'
+      - 'eng/**'
+      - 'Directory.Build.props'
+      - 'Directory.Build.targets'
+      - 'Directory.Packages.props'
+      - 'global.json'
+      - 'NuGet.config'
+
+jobs:
+  build:
+    uses: ./.github/workflows/_build.yml
+    with:
+      project-path: src/HotReload/HotReload.slnf
+      project-name: hotreload
+      run-tests: false
+      pack: true
+      install-workloads: false

AGENTS.md

@@ -13,6 +13,7 @@ This repository hosts experimental .NET MAUI packages. It is a **multi-product m
 | **Cli** | `Microsoft.Maui.Cli` (global tool: `maui`) | Unified MAUI command-line tool: environment diagnostics (`maui doctor`), Android SDK/JDK/emulator management, Apple platform management, device listing, `maui go` for rapid prototyping, `maui profile startup` for performance tracing, and the `maui devflow` automation surface. |
 | **DevFlow** | `Microsoft.Maui.DevFlow.*` packages plus the unified `maui devflow` CLI surface | Runtime MAUI automation toolkit. In-app agent with HTTP API, visual tree inspection, CDP bridge for Blazor WebViews, MCP server for AI agents, cross-platform driver library. |
 | **Comet** | `Comet`, `Comet.SourceGenerator`, `Comet.Layout.Yoga` | Experimental MVU UI framework for .NET MAUI — C# fluent UI, signals/reactive state, Yoga layout. |
+| **HotReload** | `Microsoft.Maui.HotReload` | MetadataUpdateHandler for .NET MAUI hot reload — `IHotReloadable` interface with per-instance `OnHotReload()` callbacks, backed by a Roslyn source generator. |
 | **Go** | `Microsoft.Maui.Go.Server` + Comet Go companion app | Single-file Comet apps server and companion app for rapid prototyping (alpha; sister to Comet). |
 | **Essentials.AI** | `Microsoft.Maui.Essentials.AI` | On-device AI for .NET MAUI — semantic search, chat completion, embeddings, and tool use against local models. |
 | **AIExtensions** | `Microsoft.Maui.AI.Attributes` | Source-generated AI tool bindings — turns decorated C# methods into `Microsoft.Extensions.AI`-callable tools using Roslyn, with DI parameter binding and AOT support. |
@@ -128,6 +129,11 @@ maui-labs/
 │   ├── Linux.Gtk4/                       # Linux GTK4 platform backend
 │   ├── MacOS/                            # macOS AppKit platform backend
 │   └── Windows.WPF/                      # WPF platform backend
+├── src/
+│   └── HotReload/                        # HotReload product
+│       ├── Microsoft.Maui.HotReload/     # Shipping package (IHotReloadable, registry, handler)
+│       ├── Microsoft.Maui.HotReload.SourceGen/ # Roslyn source generator (bundled as analyzer)
+│       └── HotReload.slnf               # Solution filter
 ├── samples/                              # Sample MAUI apps (not shipped)
 ├── playground/                           # Manual test/scratch apps
 ├── eng/                                  # Shared build infrastructure

MauiLabs.slnx

@@ -17,6 +17,10 @@
     <Project Path="samples/EssentialsAISample/EssentialsAISample.csproj" />
   </Folder>
   <Folder Name="/src/" />
+  <Folder Name="/src/HotReload/">
+    <Project Path="src/HotReload/Microsoft.Maui.HotReload/Microsoft.Maui.HotReload.csproj" />
+    <Project Path="src/HotReload/Microsoft.Maui.HotReload.SourceGen/Microsoft.Maui.HotReload.SourceGen.csproj" />
+  </Folder>
   <Folder Name="/src/AI/">
     <Project Path="src/AI/Microsoft.Maui.Essentials.AI/Microsoft.Maui.Essentials.AI.csproj" />
   </Folder>

README.md

@@ -140,6 +140,14 @@ Built artifacts are exposed as `@(MauiAppArtifact)` items with `ArtifactType`, `
 |---------|-------------|
 | `Microsoft.Maui.Build.AppProjectReference` | Build-time app project reference with artifact discovery |
 
+### HotReload
+
+A `MetadataUpdateHandler` for .NET MAUI that delivers per-instance hot reload callbacks via the `IHotReloadable` interface, backed by a Roslyn source generator.
+
+| Package | Description |
+|---------|-------------|
+| `Microsoft.Maui.HotReload` | MetadataUpdateHandler for .NET MAUI hot reload with `IHotReloadable` callbacks |
+
 ## Agent Skills
 
 This repository is also a marketplace for distributable agent skills for .NET MAUI development. Skills are organized as plugins compatible with Copilot CLI, Claude Code, and VS Code.

eng/pipelines/devflow-official.yml

@@ -44,6 +44,10 @@ parameters:
   displayName: 'Publish EssentialsAI packages to NuGet.org'
   type: boolean
   default: false
+- name: publishHotReloadNuget
+  displayName: 'Publish HotReload packages to NuGet.org'
+  type: boolean
+  default: false
 
 variables:
 - template: /eng/pipelines/common-variables.yml@self
@@ -387,7 +391,33 @@ extends:
                 -projects $(Build.SourcesDirectory)\platforms\MacOS\MacOS-libs.slnf
                 $(_OfficialBuildArgs)
               displayName: Build, Test and Pack macOS AppKit
-
+
+          # HotReload targets netstandard2.0 + net10.0 with no MAUI workloads.
+          # Builds and packs on Windows for MicroBuild/ESRP signing.
+          - job: HotReload
+            displayName: HotReload - Windows
+            pool:
+              name: NetCore1ESPool-Internal
+              demands: ImageOverride -equals windows.vs2026preview.scout.amd64
+            strategy:
+              matrix:
+                Release:
+                  _BuildConfig: Release
+                  _OfficialBuildArgs: /p:DotNetSignType=$(_SignType)
+                    /p:TeamName=$(_TeamName)
+                    /p:OfficialBuildId=$(BUILD.BUILDNUMBER)
+            steps:
+            - task: UseDotNet@2
+              displayName: Install .NET SDK
+              inputs:
+                version: 10.0.105
+            - script: eng\common\cibuild.cmd
+                -configuration $(_BuildConfig)
+                -prepareMachine
+                -projects $(Build.SourcesDirectory)\src\HotReload\HotReload.slnf
+                $(_OfficialBuildArgs)
+              displayName: Build and Pack HotReload
+
     - template: /eng/common/templates-official/post-build/post-build.yml@self
       parameters:
         enableSourceLinkValidation: false
@@ -834,3 +864,58 @@ extends:
               packageParentPath: '$(Pipeline.Workspace)/MacOSPackages'
               nuGetFeedType: external
               publishFeedCredentials: 'nuget.org (dotnetframework)'
+
+    # Publish HotReload packages to NuGet.org
+    - ${{ if eq(parameters.publishHotReloadNuget, true) }}:
+      - stage: publish_hotreload_nuget
+        displayName: 'Publish HotReload to NuGet.org'
+        dependsOn:
+        - Validate
+        - publish_using_darc
+        jobs:
+        - job: PrepareArtifacts
+          displayName: 'Prepare HotReload Artifacts'
+          timeoutInMinutes: 15
+          pool:
+            name: NetCore1ESPool-Internal
+            image: windows.vs2026preview.scout.amd64
+            os: windows
+          templateContext:
+            outputs:
+            - output: pipelineArtifact
+              displayName: Publish HotReload Packages
+              targetPath: '$(Pipeline.Workspace)/HotReloadPackages'
+              artifactName: HotReloadPackagesForNuGet
+          steps:
+          - download: current
+            artifact: PackageArtifacts
+            displayName: Download PackageArtifacts
+          - powershell: |
+              New-Item -ItemType Directory -Force -Path '$(Pipeline.Workspace)/HotReloadPackages'
+              Copy-Item '$(Pipeline.Workspace)/PackageArtifacts/Microsoft.Maui.HotReload.*.nupkg' '$(Pipeline.Workspace)/HotReloadPackages/' -Verbose
+            displayName: Filter HotReload packages
+
+        - job: PublishNuGet
+          displayName: 'Push HotReload to NuGet.org'
+          dependsOn: PrepareArtifacts
+          timeoutInMinutes: 30
+          pool:
+            name: NetCore1ESPool-Internal
+            image: windows.vs2026preview.scout.amd64
+            os: windows
+          templateContext:
+            type: releaseJob
+            isProduction: true
+            inputs:
+            - input: pipelineArtifact
+              artifactName: HotReloadPackagesForNuGet
+              targetPath: '$(Pipeline.Workspace)/HotReloadPackages'
+          steps:
+          - task: 1ES.PublishNuget@1
+            displayName: 'Push HotReload to NuGet.org'
+            inputs:
+              useDotNetTask: false
+              packagesToPush: '$(Pipeline.Workspace)/HotReloadPackages/*.nupkg'
+              packageParentPath: '$(Pipeline.Workspace)/HotReloadPackages'
+              nuGetFeedType: external
+              publishFeedCredentials: 'nuget.org (dotnetframework)'

src/HotReload/HotReload.slnf

@@ -0,0 +1,9 @@
+{
+  "solution": {
+    "path": "../../MauiLabs.slnx",
+    "projects": [
+      "src\\HotReload\\Microsoft.Maui.HotReload\\Microsoft.Maui.HotReload.csproj",
+      "src\\HotReload\\Microsoft.Maui.HotReload.SourceGen\\Microsoft.Maui.HotReload.SourceGen.csproj"
+    ]
+  }
+}

src/HotReload/Microsoft.Maui.HotReload.SourceGen/AnalyzerReleases.Shipped.md

@@ -0,0 +1,3 @@
+; Shipped analyzer releases
+; https://github.com/dotnet/roslyn-analyzers/blob/master/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md
+

src/HotReload/Microsoft.Maui.HotReload.SourceGen/AnalyzerReleases.Unshipped.md

@@ -0,0 +1,8 @@
+; Unshipped analyzer release
+; https://github.com/dotnet/roslyn-analyzers/blob/master/src/Microsoft.CodeAnalysis.Analyzers/ReleaseTrackingAnalyzers.Help.md
+
+### New Rules
+
+Rule ID | Category | Severity | Notes
+--------|----------|----------|-------
+MUH0001 | HotReload | Info | HotReloadInitialize not called in constructor