Migrate MediatR integration to Mediator

.gitignore

@@ -1,4 +1,4 @@
-## Ignore Visual Studio temporary files, build results, and
+## Ignore Visual Studio temporary files, build results, and
 ## files generated by popular Visual Studio add-ons.
 ##
 ## Get latest from https://github.com/github/gitignore/blob/master/VisualStudio.gitignore
@@ -358,4 +358,5 @@ MigrationBackup/
 .vscode
 
 **/Files/
+.worktrees/
 src/Server.UI/appsettings.development.json

README.md

@@ -59,7 +59,7 @@ Experience the application in action:
 | Layer | Technologies |
 |-------|-------------|
 | **Frontend** | Blazor Server, MudBlazor, SignalR |
-| **Backend** | .NET 10, ASP.NET Core, MediatR, FluentValidation |
+| **Backend** | .NET 10, ASP.NET Core, Mediator, FluentValidation |
 | **Database** | Entity Framework Core, MSSQL/PostgreSQL/SQLite |
 | **Authentication** | ASP.NET Core Identity, OAuth 2.0, JWT |
 | **Caching** | FusionCache, Redis |
@@ -193,7 +193,7 @@ OpenSpec enables spec-driven, reviewable changes with clear proposals, deltas, a
 - Use the patterns in `openspec/project.md`:
   - For data access in handlers use `IApplicationDbContextFactory` and per-operation context lifetime:
     - `await using var db = await _dbContextFactory.CreateAsync(cancellationToken);`
-  - Follow MediatR pipeline behaviors, caching tags, and specification patterns.
+  - Follow mediator pipeline behaviors, caching tags, and specification patterns.
   - Mirror the Contacts module for a new entity's DTOs, commands, queries, specs, security, and UI pages/components.
 
 5) Archive after deployment

docs/superpowers/plans/2026-03-29-migrate-mediatr-to-mediator.md

@@ -0,0 +1,173 @@
+# Migrate MediatR To Mediator Implementation Plan
+
+> **For agentic workers:** REQUIRED SUB-SKILL: Use superpowers:subagent-driven-development. Execute one task at a time with spec review first, then code-quality review.
+
+**Goal:** Remove `MediatR` references from the repository, move shared contracts to `Mediator.Abstractions`, and then reconnect runtime registration to `Mediator.SourceGenerator` in the outer layer.
+
+**Architecture:** This plan no longer preserves a repo-owned `MediatR` facade. Shared projects should reference `Mediator.Abstractions` directly. Temporary compatibility files created during earlier migration attempts must be deleted. Runtime registration belongs in infrastructure or another outer executable-facing layer, not in the shared contract layer.
+
+**Tech Stack:** .NET 10, Blazor Server, NUnit, FluentAssertions, `Mediator.Abstractions`, `Mediator.SourceGenerator`, Microsoft DI
+
+---
+
+## Task 1: Add Migration Safety-Net Tests
+
+Status: completed on branch `migrate-mediatr-to-mediator-main-impl`.
+
+Keep the existing safety-net tests. They intentionally prove that low-level `Mediator` contracts are not fully wired yet.
+
+## Task 2: Replace MediatR Contracts With Direct Mediator.Abstractions Usage
+
+**Intent:** Delete the temporary MediatR compatibility layer and move the shared contract surface to `Mediator.Abstractions` without yet completing the runtime registration rewrite.
+
+**Files:**
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/Contracts.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/Handlers.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/PipelineContracts.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/PreProcessorContracts.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/ExceptionContracts.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/NotificationPublishing.cs`
+- Delete: `src/Domain/Common/MediatorCompatibility/MediatR/ServiceCollectionContracts.cs`
+- Modify: `src/Domain/Domain.csproj`
+- Modify: `src/Application/_Imports.cs`
+- Modify: `src/Domain/Common/DomainEvent.cs`
+- Modify: `tests/Application.UnitTests/Common/MediatorCompatibility/RequestExceptionHandlerStateTests.cs`
+
+- [ ] **Step 1: Write the failing direct-abstractions smoke test**
+
+Rewrite `tests/Application.UnitTests/Common/MediatorCompatibility/RequestExceptionHandlerStateTests.cs` into a direct `Mediator.Abstractions` smoke test. It should prove the project compiles against `Mediator.INotification`, `Mediator.IRequest<TResponse>`, and `Mediator.IPipelineBehavior<TRequest, TResponse>` rather than the deleted MediatR compatibility state type.
+
+Suggested shape:
+
+```csharp
+using Mediator;
+using NUnit.Framework;
+
+namespace CleanArchitecture.Blazor.Application.UnitTests.Common.MediatorCompatibility;
+
+public class MediatorAbstractionsSmokeTests
+{
+    [Test]
+    public void Contracts_ShouldCompileAgainstMediatorAbstractions()
+    {
+        _ = new SmokeNotification();
+        _ = new SmokeRequest();
+        _ = typeof(IPipelineBehavior<SmokeRequest, string>);
+    }
+
+    private sealed record SmokeNotification : INotification;
+    private sealed record SmokeRequest : IRequest<string>;
+}
+```
+
+- [ ] **Step 2: Run the smoke test to confirm it fails**
+
+Run: `dotnet test tests/Application.UnitTests/Application.UnitTests.csproj --filter "FullyQualifiedName~MediatorAbstractionsSmokeTests" -v minimal`
+
+Expected: FAIL because `Mediator.Abstractions` is not referenced yet.
+
+- [ ] **Step 3: Add direct Mediator.Abstractions package support**
+
+Update `src/Domain/Domain.csproj` to reference `Mediator.Abstractions`.
+
+Keep the dependency in the lowest shared layer that exposes `DomainEvent` and shared mediator contracts.
+
+- [ ] **Step 4: Remove the temporary MediatR compatibility files**
+
+Delete all files under `src/Domain/Common/MediatorCompatibility/MediatR/`.
+
+Do not replace them with new repo-owned MediatR shims.
+
+- [ ] **Step 5: Update shared imports and domain event contracts**
+
+Apply the smallest source edits needed so the shared code targets `Mediator` directly:
+
+- `src/Application/_Imports.cs`: replace `global using MediatR;` and `global using MediatR.Pipeline;` with direct `Mediator` imports.
+- `src/Domain/Common/DomainEvent.cs`: replace `global::MediatR` usage with `global::Mediator`.
+
+- [ ] **Step 6: Add the temporary AddMediatR compile shim**
+
+Because the runtime registration rewrite has not happened yet, keep `src/Application/DependencyInjection.cs` compiling by adding the smallest temporary `AddMediatR(...)` shim needed for this stage.
+
+Constraints:
+
+- The shim is transitional only.
+- It must not recreate the deleted MediatR contract surface.
+- It should exist only to let Task 2 land while Task 3 still owns the real DI rewrite.
+
+- [ ] **Step 7: Re-run the smoke test**
+
+Run: `dotnet test tests/Application.UnitTests/Application.UnitTests.csproj --filter "FullyQualifiedName~MediatorAbstractionsSmokeTests" -v minimal`
+
+Expected: PASS, or at worst fail for a known unrelated baseline issue that already existed before this migration work.
+
+- [ ] **Step 8: Run the scoped mediator safety-net test**
+
+Run: `dotnet test tests/Application.UnitTests/Application.UnitTests.csproj --filter "FullyQualifiedName~ScopedMediatorTests" -v minimal`
+
+Expected: The test should move closer to green by compiling against real `Mediator` abstractions. If it still fails, the remaining failure should be due to runtime wiring, not missing MediatR contracts.
+
+- [ ] **Step 9: Commit**
+
+```bash
+git add src/Domain/Domain.csproj src/Application/_Imports.cs src/Domain/Common/DomainEvent.cs tests/Application.UnitTests/Common/MediatorCompatibility/RequestExceptionHandlerStateTests.cs src/Application/DependencyInjection.cs
+git rm -r src/Domain/Common/MediatorCompatibility/MediatR
+git commit -m "refactor: move mediator contracts to abstractions"
+```
+
+## Task 3: Replace DI Registration With Mediator.SourceGenerator Runtime Wiring
+
+**Intent:** Remove the temporary `AddMediatR(...)` bridge, register the real `Mediator` runtime in the outer layer, and reconnect handlers, notifications, behaviors, and scoped mediator execution.
+
+**Files:**
+- Modify: `src/Application/DependencyInjection.cs`
+- Modify: `src/Infrastructure/DependencyInjection.cs`
+- Modify: `src/Infrastructure/Infrastructure.csproj`
+- Modify: `src/Infrastructure/Services/MediatorWrapper/ScopedMediator.cs`
+- Modify: `tests/Application.IntegrationTests/Testing.cs`
+- Modify: `tests/Application.IntegrationTests/Common/MediatorCompatibility/MediatorCompatibilityTests.cs`
+- Modify: `tests/Application.UnitTests/Common/MediatorCompatibility/ParallelNoWaitPublisherTests.cs`
+- Modify: `tests/Application.UnitTests/Infrastructure/MediatorCompatibility/ScopedMediatorTests.cs`
+
+Notes:
+
+- Add `Mediator.SourceGenerator` in the outer layer only.
+- Delete the temporary `AddMediatR(...)` shim as part of this task.
+- Reconnect `ParallelNoWaitPublisher`, scoped mediator resolution, and at least one existing query path through DI.
+- Decide explicitly how current exception-handler behavior maps to `Mediator`. Do not assume a drop-in equivalent exists.
+
+## Task 4: Update UI/Test Imports And Resolve Remaining Runtime Gaps
+
+**Files:**
+- Modify: `src/Server.UI/_Imports.razor`
+- Modify: `src/Server.UI/Services/DialogServiceHelper.cs`
+- Modify: `tests/Application.IntegrationTests/Testing.cs`
+- Modify: any source or test files still importing `MediatR`
+
+Notes:
+
+- Remove leftover `MediatR` namespace imports after runtime wiring is stable.
+- Keep `IScopedMediator` intact as a repository abstraction if it still provides value.
+
+## Task 5: Remove Leftover MediatR References And Update Documentation
+
+**Files:**
+- Modify: `README.md`
+- Modify: `src/Server.UI/Pages/Public/Index.razor`
+- Modify: `src/Server.UI/Pages/AI/Chatbot.razor`
+- Modify: any `.csproj` files still referencing `MediatR`
+
+Verification:
+
+- `rg -n "MediatR" src tests README.md`
+- Update user-facing copy so the app no longer claims it uses MediatR.
+
+## Final Verification
+
+Before claiming the migration complete, run:
+
+- `dotnet test tests/Application.UnitTests/Application.UnitTests.csproj -v minimal`
+- `dotnet test tests/Application.IntegrationTests/Application.IntegrationTests.csproj --filter "FullyQualifiedName~MediatorCompatibilityTests" -v minimal`
+- `rg -n "MediatR" src tests README.md`
+
+If any command fails, report the exact remaining blocker instead of declaring success.

docs/superpowers/specs/2026-03-29-migrate-mediatr-to-mediator-design.md

@@ -0,0 +1,127 @@
+# Migrate MediatR To Mediator Design
+
+## Status
+
+Approved for planning and implementation.
+
+## Summary
+
+Migrate the repository from `MediatR` to `martinothamar/Mediator` by deleting `MediatR` package and namespace dependencies rather than preserving a repository-owned MediatR-compatible facade.
+
+This migration is still conservative about behavior, but it is no longer conservative about API shape:
+
+- Application, domain, infrastructure, UI, and tests should move to `Mediator` / `Mediator.Abstractions` namespaces directly.
+- `Mediator.Abstractions` should be referenced by projects that only need contracts.
+- `Mediator.SourceGenerator` should be referenced only by the outer runtime layer that owns DI wiring and generated handler dispatch.
+- Existing behaviors such as request handling, notification publishing, domain event dispatch, and scoped mediator usage should remain intact or be reconnected with equivalent semantics.
+
+## Goals
+
+- Remove direct `MediatR` references from source, tests, and project files.
+- Move shared contracts to `Mediator.Abstractions`.
+- Preserve current application behavior for request sending, notification publishing, and scoped mediator usage.
+- Prepare the repository for a later runtime registration step that adds `Mediator.SourceGenerator` in the correct outer layer.
+
+## Non-Goals
+
+- Do not keep or expand the temporary repo-owned `MediatR` compatibility layer.
+- Do not redesign the command/query architecture.
+- Do not change feature behavior unless required by the mediator migration.
+- Do not pull `Mediator.SourceGenerator` into low-level shared projects that only need abstractions.
+
+## Current State
+
+The repository currently contains three conflicting mediator shapes:
+
+- Legacy source files still import `MediatR`.
+- Temporary compatibility contracts exist under `src/Domain/Common/MediatorCompatibility/MediatR/*`.
+- Migration safety-net tests already target low-level `Mediator` runtime concepts in a few places.
+
+That mixed state is unstable. The next implementation step must simplify the contract layer instead of adding more compatibility code.
+
+## Approved Architecture
+
+Use direct `Mediator` abstractions throughout the codebase.
+
+### Contract Layer
+
+- `Domain` references `Mediator.Abstractions`.
+- `Application` imports `Mediator` namespaces directly for requests, notifications, handlers, behaviors, preprocessors, and exception handlers.
+- `DomainEvent` implements `Mediator.INotification` directly.
+- UI and integration tests may resolve `Mediator.IMediator` directly once runtime wiring is in place.
+
+### Runtime Layer
+
+- `Infrastructure` will eventually own `Mediator.SourceGenerator` and registration.
+- `Application/DependencyInjection.cs` must stop depending on `AddMediatR(...)`.
+- `IScopedMediator` remains as a repository abstraction, but its implementation should resolve the real `Mediator.IMediator` service from a created scope.
+
+### Temporary Transition Rule
+
+Until the runtime registration task lands:
+
+- Contract-only work may add `Mediator.Abstractions`.
+- Temporary `MediatR` compatibility files should be removed instead of expanded.
+- A minimal compile shim for `AddMediatR(...)` is allowed only as a short-lived bridge while the old DI registration still exists, but it must not become part of the final architecture.
+
+## Behavioral Requirements
+
+The migration must preserve or re-establish these behaviors:
+
+- Existing request handlers still execute for current commands and queries.
+- Existing notification handlers still execute for current notifications and domain events.
+- `ParallelNoWaitPublisher` remains available and keeps its fire-and-forget behavior if the runtime layer still needs that strategy.
+- `DispatchDomainEventsInterceptor` continues to publish domain events through `IScopedMediator`.
+- `ScopedMediator` continues to resolve a fresh scoped `IMediator`.
+
+## File Organization
+
+Expected migration touchpoints:
+
+- `src/Domain/Domain.csproj`
+- `src/Application/_Imports.cs`
+- `src/Application/DependencyInjection.cs`
+- `src/Domain/Common/DomainEvent.cs`
+- `src/Infrastructure/Services/MediatorWrapper/ScopedMediator.cs`
+- `src/Server.UI/_Imports.razor`
+- `src/Server.UI/Services/DialogServiceHelper.cs`
+- `tests/Application.IntegrationTests/Testing.cs`
+- `tests/Application.UnitTests/Common/MediatorCompatibility/*`
+- `tests/Application.IntegrationTests/Common/MediatorCompatibility/*`
+
+Files under `src/Domain/Common/MediatorCompatibility/MediatR/*` are temporary and should be deleted rather than treated as a stable design boundary.
+
+## Migration Sequence
+
+1. Keep the safety-net tests from Task 1.
+2. Remove the temporary MediatR compatibility contracts.
+3. Add `Mediator.Abstractions` where compile-time contracts are required.
+4. Update source imports and contract usage to direct `Mediator` namespaces.
+5. Keep DI compiling with the smallest temporary bridge necessary until runtime registration is replaced.
+6. In a later task, add the real `Mediator.SourceGenerator` runtime registration in the outer layer and reconnect behaviors.
+7. Remove any temporary DI shims before completion.
+
+## Verification Scope
+
+At minimum, verify:
+
+- Contract-layer projects compile against `Mediator.Abstractions`.
+- Safety-net tests that intentionally exercise `Mediator` low-level contracts compile in the expected direction.
+- `IScopedMediator` still resolves `IMediator` from a created scope after runtime wiring is updated.
+- There are no leftover `MediatR` package references or stable source dependencies outside temporary transitional code that is explicitly scheduled for deletion.
+
+## Risks
+
+- `Mediator` does not provide a drop-in equivalent for every MediatR interface, so request exception handling and DI registration need explicit redesign instead of namespace swapping.
+- The temporary compatibility files can hide architectural drift if they are left in place.
+- `AddMediatR(...)` currently anchors application startup, so contract-layer migration and runtime registration need to be staged carefully.
+
+## Success Criteria
+
+The migration is complete when:
+
+- The repository no longer depends on `MediatR`.
+- Shared code compiles against `Mediator.Abstractions` instead of `MediatR`.
+- Runtime registration is owned by `Mediator.SourceGenerator` in the correct outer layer.
+- Scoped mediator, notifications, and domain events still work.
+- Documentation accurately describes the repository as using `Mediator`, not `MediatR`.

src/Application/Application.csproj

@@ -8,6 +8,7 @@
         <LangVersion>default</LangVersion>
     </PropertyGroup>
     <ItemGroup>
+        <PackageReference Include="Mediator.Abstractions" Version="3.0.2" />
 
         <PackageReference Include="Ardalis.Specification" Version="9.3.1" />
         <PackageReference Include="Ardalis.Specification.EntityFrameworkCore" Version="9.3.1" />
@@ -23,10 +24,10 @@
         <PackageReference Include="Riok.Mapperly" Version="5.0.0-next.0" />
         <PackageReference Include="System.Linq.Dynamic.Core" Version="1.7.1" />
         <PackageReference Include="Hangfire.Core" Version="1.8.23" />
-        <PackageReference Include="ZiggyCreatures.FusionCache" Version="2.5.0" />
-           <PackageReference Include="ActualLab.Fusion" Version="12.1.98" />
-        <PackageReference Include="ActualLab.Fusion.Blazor" Version="12.1.98" />
-        <PackageReference Include="ActualLab.Generators" Version="12.1.98">
+        <PackageReference Include="ZiggyCreatures.FusionCache" Version="2.6.0" />
+           <PackageReference Include="ActualLab.Fusion" Version="12.1.125" />
+        <PackageReference Include="ActualLab.Fusion.Blazor" Version="12.1.125" />
+        <PackageReference Include="ActualLab.Generators" Version="12.1.125">
           <PrivateAssets>all</PrivateAssets>
           <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>

src/Application/Common/ExceptionHandlers/DbExceptionHandler.cs

@@ -2,10 +2,9 @@
 
 namespace CleanArchitecture.Blazor.Application.Common.ExceptionHandlers;
 
-public class DbExceptionHandler<TRequest, TResponse, TException> : IRequestExceptionHandler<TRequest, TResponse, TException>
+public class DbExceptionHandler<TRequest, TResponse> : MessageExceptionHandler<TRequest, TResponse>
     where TRequest : IRequest<Result<int>>
     where TResponse : Result<int>
-    where TException : DbUpdateException
 {
     private readonly ILogger _logger;
     private readonly ILoggerFactory _loggerFactory;
@@ -14,14 +13,18 @@
     {
 
         _loggerFactory = loggerFactory;
-        _logger = _loggerFactory.CreateLogger(nameof(DbExceptionHandler<TRequest, TResponse, TException>));
+        _logger = _loggerFactory.CreateLogger(nameof(DbExceptionHandler<TRequest, TResponse>));
     }
 
-    public Task Handle(TRequest request, TException exception, RequestExceptionHandlerState<TResponse> state,
+    protected override ValueTask<ExceptionHandlingResult<TResponse>> Handle(TRequest request, Exception exception,
         CancellationToken cancellationToken)
     {
-        state.SetHandled((TResponse)Result<int>.Failure(GetErrors(exception)));
-        return Task.CompletedTask;
+        if (exception is not DbUpdateException dbUpdateException)
+        {
+            return NotHandled;
+        }
+
+        return Handled((TResponse)Result<int>.Failure(GetErrors(dbUpdateException)));
     }
 
     private  string[] GetErrors(DbUpdateException exception)
@@ -82,4 +85,4 @@
         };
     }
 
-}
+}