There are a lot of optimizations that we plan to add to this path. The intent of this preview was getting a functional version of `dotnet run app.cs` out the door. Items like startup optimization are going to be coming soon.

I’m not really into the whole dotnet space. Except during the beta early on BSD ‘00.

It’s good that it allows scripts to run, and does packages. Simple is good

I was just curious and then surprised that it already caches compiled binaries, but that the time remained the same.

I opened an issue since I couldn't find docs that indicate what they were working on to improve the start time, and they replied:

https://github.com/dotnet/sdk/issues/49197

Ah, I didn't managed to find something that talked about what was planned for this, so I opened an issue asking for that. Is there a doc somewhere talking about it ?

maybe it's worth adding that info to the blog post :)

thanks Jared and team, keep up the great work.

If you're trying things like that in a Mac, watch out for the notary check delay https://eclecticlight.co/2025/04/30/why-some-apps-sometimes-...

It can easily add hundreds of milliseconds in various situations you can't easily control.

This is nuts. More than a decade ago Microsoft made a big deal of startup optimisations they had made in the .Net framework.

I had some Windows command-line apps written in C# that always took at least 0.5s to run. It was an annoying distraction. After Microsoft's improvements the same code was running in 0.2s. Still perceptible, but a great improvement. This was on a cheap laptop bought in 2009.

I'm aware that .Net is using a different runtime now, but I'm amazed that it so slow on a high-end modern laptop.

To be fair, this is timing early bits of a preview feature. Compiled .NET apps have much better startup perf.

This is also a preview feature at the moment. They mention in the embedded video that it is not optimized or ready for production scenarios. They release these features very early in preview to start getting some feedback as they prepare for final release in November.

They are not on Windows. As someone else pointed out, there are very likely Apple-specific shenanigans going on.

For comparison, skipping dotnet run and running the compiled program directly:

  time "/Users/bouke/Library/Application Support/dotnet/runfile/hello-world-fc604c4e7d71b490ccde5271268569273873cc7ab51f5ef7dee6fb34372e89a2/bin/debug/hello-world" > /dev/null

  real 0m0.051s
  user 0m0.029s
  sys 0m0.017s

So yeah the overhead of dotnet run is pretty high in this preview version.