dotnet: Inconsistent uptime when InProcess after Windows Server 2025 upgrade

[Eric1243123]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

After upgrading to Windows Server 2025, I've been having several issues with my IIS Website. URL Rewrite got unistalled, but more importantly, my old configuration is now (seemingly) randomly crashing. Previously, I was running something like this:

<aspNetCore processPath="./Program.exe" arguments="" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout" hostingModel="InProcess">

after doing some research, realized that the hostingModel could switch to OutOfProcess, which works, or I could target the DLL being output instead. InProcess seems much better in the long term due to speed and reliability. However, having the program in InProcess, even after the changes, has yielded inconsistent results.

Sometimes the application will start up, but an IISReset or server restart will cause it to stay down, sometimes it starts out down, then randomly comes up 10 minutes later. Whenever it's down, it results in a 503 page.

I've:

• Made sure all .NET runtimes were installed and on the project version
• AppPool permissions were properly set-up
• Application runs (OutOfProcess working)
• Retried making the AppPool and pointing the site there
• Repairing all of the .NET runtimes and uninstalling old versions
• Setting the shutdown delay to 0 for the app pool
• Increasing the stack size from default (1MB) to 4MB

None of which yielded consistent results with InProcess mode

Expected Behavior

Consistent execution for the same settings within InProcess mode despite being IISReset or Server Restarts

Steps To Reproduce

Create an IIS (Version 10.0.26100.1) Application pool with the following settings and host an InProcess .NET 8 app on it

Exceptions (if any)

This is part of the problem; there are no errors within the Application or System parts of Event Viewer. Even a crash dump simply shows w3wp crashing with only low-level system DLLs

.NET Version

8.0.20

Anything else?

No response