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TimeWarp Mediator 14.0: The Rewrite That Pays You Back

13.0.0 corrected the spelling and the license. 14.0.0 is a different dispatcher. The reflection AddMediator() you already call is still here, and it still does not register the source-generated mediator. The generated one is the path that pays the rewrite back: a monomorphic Send, fewer allocated bytes, and a host that can publish trimmed or with NativeAOT.

Ten lines

dotnet add package TimeWarp.Mediator.Contracts --version 14.0.0
dotnet add package TimeWarp.Mediator.Generators --version 14.0.0

public sealed class Ping : IRequest<string> { }

public sealed class PingHandler : IRequestHandler<Ping, string>
{
  public Task<string> Handle(Ping request, CancellationToken cancellationToken) =>
    Task.FromResult("Pong");
}

services.AddGeneratedMediator();
string reply = await provider.GetRequiredService<ISender>().Send(new Ping());

AddGeneratedMediator() is generated as internal. Call it from the host project. A library that only declares messages references TimeWarp.Mediator.Contracts. A library that declares handlers and does not run the generator also references TimeWarp.Mediator.Analyzers and adds [assembly: MediatorAssembly].

What the baseline actually says

comparison-baseline.md was recorded 2026-10-12 at commit d478415 with BenchmarkDotNet 0.15.8 on .NET 10.0.11, an AMD Ryzen 9 7950X3D, Ubuntu. The workload is Ping/Pong with no pipeline behaviors.

Send	Mean	Allocated
Reflection AddMediator	69.0 ns	224 B
Generated monomorphic Send	29.9 ns	96 B
martinothamar generator (same run)	8.8 ns	24 B

The ratio column in that file is 0.43 for time and 0.43 for bytes. Generated Send takes less than half the time and less than half the bytes of this repository's reflection Send. martinothamar's generator is still faster on this microbenchmark (8.8 ns, 24 B). That gap is real. 14.0.0 does not close it. The number to remember is the one against our own reflection path, on this machine, for this Ping.

The reflection entry points carry RequiresUnreferencedCode and RequiresDynamicCode. A trimmed or NativeAOT publish that still calls AddMediator() gets IL2026 / IL3050. The generated host does not. The Aot profile goes further: no IServiceProvider, handlers constructed once with new Handler(). Behaviors are not woven on that profile. Use the Host profile when handlers take constructor dependencies or you need IPipelineBehavior.

What broke

A lot. Read this before you bump a 13.0.0 host.

• net10.0 only for TimeWarp.Mediator and TimeWarp.Mediator.Contracts. netstandard2.0 and net6.0 assets are gone. If you cannot move, stay on 13.0.0.
• AddMediator() is the other stack. It will not start generating code because the package version changed. Call AddGeneratedMediator().
• Streams, pre/post processors, and the exception cascade are reflection-only. The generator reports TWM009 and the generated CreateStream throws. Move that work into a request handler or an IPipelineBehavior, or keep AddMediator().
• Behaviors move to an attribute. cfg.AddOpenBehavior(typeof(LoggingBehavior<,>)) becomes [assembly: MediatorBehavior(typeof(LoggingBehavior<,>))] on the Host profile.
• Some runtime types are gone or internal. ServiceFactory is removed. The handler wrappers and ServiceRegistrar are internal. You did not need them to send a request.
• License expression. The reflection package and Contracts are Unlicense AND Apache-2.0 because they still contain MediatR-derived code. Generators and Analyzers are Unlicense. notice and unlicense ship in every package.

The steps, and the feature matrix, are in migration.md. From MediatR itself, the change is still the 13.x rename (using MediatR to using TimeWarp.Mediator, AddMediatR to AddMediator). That rename does not select the generated mediator.

Named pipelines, if you want them, are a marker type rather than a string: [MediatorScope(typeof(ClientPipeline))] and AddGeneratedMediator<ClientPipeline>(). Diagnostics TWM001–TWM011 are listed in diagnostics.md.

Install

NuGet: https://www.nuget.org/packages/TimeWarp.Mediator/14.0.0

dotnet add package TimeWarp.Mediator.Contracts --version 14.0.0
dotnet add package TimeWarp.Mediator.Generators --version 14.0.0

Repository: https://github.com/TimeWarpEngineering/timewarp-mediator